[mirror_lxcfs.git] / bindings.c

/* lxcfs
 *
 * Copyright © 2014-2016 Canonical, Inc
 * Author: Serge Hallyn <serge.hallyn@ubuntu.com>
 *
 * See COPYING file for details.
 */

#define FUSE_USE_VERSION 26

#define __STDC_FORMAT_MACROS
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <fuse.h>
#include <inttypes.h>
#include <libgen.h>
#include <pthread.h>
#include <sched.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <wait.h>
#include <linux/magic.h>
#include <linux/sched.h>
#include <sys/epoll.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/param.h>
#include <sys/socket.h>
#include <sys/syscall.h>
#include <sys/sysinfo.h>
#include <sys/vfs.h>

#include "bindings.h"
#include "config.h" // for VERSION

/* Maximum number for 64 bit integer is a string with 21 digits: 2^64 - 1 = 21 */
#define LXCFS_NUMSTRLEN64 21

/* Define pivot_root() if missing from the C library */
#ifndef HAVE_PIVOT_ROOT
static int pivot_root(const char * new_root, const char * put_old)
{
#ifdef __NR_pivot_root
return syscall(__NR_pivot_root, new_root, put_old);
#else
errno = ENOSYS;
return -1;
#endif
}
#else
extern int pivot_root(const char * new_root, const char * put_old);
#endif

enum {
        LXC_TYPE_CGDIR,
        LXC_TYPE_CGFILE,
        LXC_TYPE_PROC_MEMINFO,
        LXC_TYPE_PROC_CPUINFO,
        LXC_TYPE_PROC_UPTIME,
        LXC_TYPE_PROC_STAT,
        LXC_TYPE_PROC_DISKSTATS,
        LXC_TYPE_PROC_SWAPS,
        LXC_TYPE_PROC_LOADAVG,
};

struct file_info {
        char *controller;
        char *cgroup;
        char *file;
        int type;
        char *buf;  // unused as of yet
        int buflen;
        int size; //actual data size
        int cached;
};

/* The function of hash table.*/
#define LOAD_SIZE 100 /*the size of hash_table */
#define FLUSH_TIME 5  /*the flush rate */
#define DEPTH_DIR 3   /*the depth of per cgroup */
/* The function of calculate loadavg .*/
#define FSHIFT          11              /* nr of bits of precision */
#define FIXED_1         (1<<FSHIFT)     /* 1.0 as fixed-point */
#define EXP_1           1884            /* 1/exp(5sec/1min) as fixed-point */
#define EXP_5           2014            /* 1/exp(5sec/5min) */
#define EXP_15          2037            /* 1/exp(5sec/15min) */
#define LOAD_INT(x) ((x) >> FSHIFT)
#define LOAD_FRAC(x) LOAD_INT(((x) & (FIXED_1-1)) * 100)
/* 
 * This parameter is used for proc_loadavg_read().
 * 1 means use loadavg, 0 means not use.
 */
static int loadavg = 0;
static int calc_hash(char *name)
{
        unsigned int hash = 0;
        unsigned int x = 0;
        /* ELFHash algorithm. */
        while (*name) {
                hash = (hash << 4) + *name++;
                x = hash & 0xf0000000;
                if (x != 0)
                        hash ^= (x >> 24);
                hash &= ~x;
        }
        return ((hash & 0x7fffffff) % LOAD_SIZE);
}

struct load_node {
        char *cg;  /*cg */
        unsigned long avenrun[3];               /* Load averages */
        unsigned int run_pid;
        unsigned int total_pid;
        unsigned int last_pid;
        int cfd; /* The file descriptor of the mounted cgroup */
        struct  load_node *next;
        struct  load_node **pre;
};

struct load_head {
        /*
         * The lock is about insert load_node and refresh load_node.To the first
         * load_node of each hash bucket, insert and refresh in this hash bucket is
         * mutually exclusive.
         */
        pthread_mutex_t lock;
        /*
         * The rdlock is about read loadavg and delete load_node.To each hash
         * bucket, read and delete is mutually exclusive. But at the same time, we
         * allow paratactic read operation. This rdlock is at list level.
         */
        pthread_rwlock_t rdlock;
        /*
         * The rilock is about read loadavg and insert load_node.To the first
         * load_node of each hash bucket, read and insert is mutually exclusive.
         * But at the same time, we allow paratactic read operation.
         */
        pthread_rwlock_t rilock;
        struct load_node *next;
};

static struct load_head load_hash[LOAD_SIZE]; /* hash table */
/*
 * init_load initialize the hash table.
 * Return 0 on success, return -1 on failure.
 */
static int init_load(void)
{
        int i;
        int ret;

        for (i = 0; i < LOAD_SIZE; i++) {
                load_hash[i].next = NULL;
                ret = pthread_mutex_init(&load_hash[i].lock, NULL);
                if (ret != 0) {
                        lxcfs_error("%s\n", "Failed to initialize lock");
                        goto out3;
                }
                ret = pthread_rwlock_init(&load_hash[i].rdlock, NULL);
                if (ret != 0) {
                        lxcfs_error("%s\n", "Failed to initialize rdlock");
                        goto out2;
                }
                ret = pthread_rwlock_init(&load_hash[i].rilock, NULL);
                if (ret != 0) {
                        lxcfs_error("%s\n", "Failed to initialize rilock");
                        goto out1;
                }
        }
        return 0;
out1:
        pthread_rwlock_destroy(&load_hash[i].rdlock);
out2:
        pthread_mutex_destroy(&load_hash[i].lock);
out3:
        while (i > 0) {
                i--;
                pthread_mutex_destroy(&load_hash[i].lock);
                pthread_rwlock_destroy(&load_hash[i].rdlock);
                pthread_rwlock_destroy(&load_hash[i].rilock);
        }
        return -1;
}

static void insert_node(struct load_node **n, int locate)
{
        struct load_node *f;

        pthread_mutex_lock(&load_hash[locate].lock);
        pthread_rwlock_wrlock(&load_hash[locate].rilock);
        f = load_hash[locate].next;
        load_hash[locate].next = *n;

        (*n)->pre = &(load_hash[locate].next);
        if (f)
                f->pre = &((*n)->next);
        (*n)->next = f;
        pthread_mutex_unlock(&load_hash[locate].lock);
        pthread_rwlock_unlock(&load_hash[locate].rilock);
}
/*
 * locate_node() finds special node. Not return NULL means success.
 * It should be noted that rdlock isn't unlocked at the end of code
 * because this function is used to read special node. Delete is not
 * allowed before read has ended.
 * unlock rdlock only in proc_loadavg_read().
 */
static struct load_node *locate_node(char *cg, int locate)
{
        struct load_node *f = NULL;
        int i = 0;

        pthread_rwlock_rdlock(&load_hash[locate].rilock);
        pthread_rwlock_rdlock(&load_hash[locate].rdlock);
        if (load_hash[locate].next == NULL) {
                pthread_rwlock_unlock(&load_hash[locate].rilock);
                return f;
        }
        f = load_hash[locate].next;
        pthread_rwlock_unlock(&load_hash[locate].rilock);
        while (f && ((i = strcmp(f->cg, cg)) != 0))
                f = f->next;
        return f;
}
/* Delete the load_node n and return the next node of it. */
static struct load_node *del_node(struct load_node *n, int locate)
{
        struct load_node *g;

        pthread_rwlock_wrlock(&load_hash[locate].rdlock);
        if (n->next == NULL) {
                *(n->pre) = NULL;
        } else {
                *(n->pre) = n->next;
                n->next->pre = n->pre;
        }
        g = n->next;
        free(n->cg);
        free(n);
        pthread_rwlock_unlock(&load_hash[locate].rdlock);
        return g;
}

/* Reserve buffer size to account for file size changes. */
#define BUF_RESERVE_SIZE 512

/*
 * A table caching which pid is init for a pid namespace.
 * When looking up which pid is init for $qpid, we first
 * 1. Stat /proc/$qpid/ns/pid.
 * 2. Check whether the ino_t is in our store.
 *   a. if not, fork a child in qpid's ns to send us
 *       ucred.pid = 1, and read the initpid.  Cache
 *       initpid and creation time for /proc/initpid
 *       in a new store entry.
 *   b. if so, verify that /proc/initpid still matches
 *       what we have saved.  If not, clear the store
 *       entry and go back to a.  If so, return the
 *       cached initpid.
 */
struct pidns_init_store {
        ino_t ino;          // inode number for /proc/$pid/ns/pid
        pid_t initpid;      // the pid of nit in that ns
        long int ctime;     // the time at which /proc/$initpid was created
        struct pidns_init_store *next;
        long int lastcheck;
};

/* lol - look at how they are allocated in the kernel */
#define PIDNS_HASH_SIZE 4096
#define HASH(x) ((x) % PIDNS_HASH_SIZE)

static struct pidns_init_store *pidns_hash_table[PIDNS_HASH_SIZE];
static pthread_mutex_t pidns_store_mutex = PTHREAD_MUTEX_INITIALIZER;
static void lock_mutex(pthread_mutex_t *l)
{
        int ret;

        if ((ret = pthread_mutex_lock(l)) != 0) {
                lxcfs_error("returned:%d %s\n", ret, strerror(ret));
                exit(1);
        }
}

/* READ-ONLY after __constructor__ collect_and_mount_subsystems() has run.
 * Number of hierarchies mounted. */
static int num_hierarchies;

/* READ-ONLY after __constructor__ collect_and_mount_subsystems() has run.
 * Hierachies mounted {cpuset, blkio, ...}:
 * Initialized via __constructor__ collect_and_mount_subsystems(). */
static char **hierarchies;

/* READ-ONLY after __constructor__ collect_and_mount_subsystems() has run.
 * Open file descriptors:
 * @fd_hierarchies[i] refers to cgroup @hierarchies[i]. They are mounted in a
 * private mount namespace.
 * Initialized via __constructor__ collect_and_mount_subsystems().
 * @fd_hierarchies[i] can be used to perform file operations on the cgroup
 * mounts and respective files in the private namespace even when located in
 * another namespace using the *at() family of functions
 * {openat(), fchownat(), ...}. */
static int *fd_hierarchies;
static int cgroup_mount_ns_fd = -1;

static void unlock_mutex(pthread_mutex_t *l)
{
        int ret;

        if ((ret = pthread_mutex_unlock(l)) != 0) {
                lxcfs_error("returned:%d %s\n", ret, strerror(ret));
                exit(1);
        }
}

static void store_lock(void)
{
        lock_mutex(&pidns_store_mutex);
}

static void store_unlock(void)
{
        unlock_mutex(&pidns_store_mutex);
}

/* Must be called under store_lock */
static bool initpid_still_valid(struct pidns_init_store *e, struct stat *nsfdsb)
{
        struct stat initsb;
        char fnam[100];

        snprintf(fnam, 100, "/proc/%d", e->initpid);
        if (stat(fnam, &initsb) < 0)
                return false;

        lxcfs_debug("Comparing ctime %ld == %ld for pid %d.\n", e->ctime,
                    initsb.st_ctime, e->initpid);

        if (e->ctime != initsb.st_ctime)
                return false;
        return true;
}

/* Must be called under store_lock */
static void remove_initpid(struct pidns_init_store *e)
{
        struct pidns_init_store *tmp;
        int h;

        lxcfs_debug("Remove_initpid: removing entry for %d.\n", e->initpid);

        h = HASH(e->ino);
        if (pidns_hash_table[h] == e) {
                pidns_hash_table[h] = e->next;
                free(e);
                return;
        }

        tmp = pidns_hash_table[h];
        while (tmp) {
                if (tmp->next == e) {
                        tmp->next = e->next;
                        free(e);
                        return;
                }
                tmp = tmp->next;
        }
}

#define PURGE_SECS 5
/* Must be called under store_lock */
static void prune_initpid_store(void)
{
        static long int last_prune = 0;
        struct pidns_init_store *e, *prev, *delme;
        long int now, threshold;
        int i;

        if (!last_prune) {
                last_prune = time(NULL);
                return;
        }
        now = time(NULL);
        if (now < last_prune + PURGE_SECS)
                return;

        lxcfs_debug("%s\n", "Pruning.");

        last_prune = now;
        threshold = now - 2 * PURGE_SECS;

        for (i = 0; i < PIDNS_HASH_SIZE; i++) {
                for (prev = NULL, e = pidns_hash_table[i]; e; ) {
                        if (e->lastcheck < threshold) {

                                lxcfs_debug("Removing cached entry for %d.\n", e->initpid);

                                delme = e;
                                if (prev)
                                        prev->next = e->next;
                                else
                                        pidns_hash_table[i] = e->next;
                                e = e->next;
                                free(delme);
                        } else {
                                prev = e;
                                e = e->next;
                        }
                }
        }
}

/* Must be called under store_lock */
static void save_initpid(struct stat *sb, pid_t pid)
{
        struct pidns_init_store *e;
        char fpath[100];
        struct stat procsb;
        int h;

        lxcfs_debug("Save_initpid: adding entry for %d.\n", pid);

        snprintf(fpath, 100, "/proc/%d", pid);
        if (stat(fpath, &procsb) < 0)
                return;
        do {
                e = malloc(sizeof(*e));
        } while (!e);
        e->ino = sb->st_ino;
        e->initpid = pid;
        e->ctime = procsb.st_ctime;
        h = HASH(e->ino);
        e->next = pidns_hash_table[h];
        e->lastcheck = time(NULL);
        pidns_hash_table[h] = e;
}

/*
 * Given the stat(2) info for a nsfd pid inode, lookup the init_pid_store
 * entry for the inode number and creation time.  Verify that the init pid
 * is still valid.  If not, remove it.  Return the entry if valid, NULL
 * otherwise.
 * Must be called under store_lock
 */
static struct pidns_init_store *lookup_verify_initpid(struct stat *sb)
{
        int h = HASH(sb->st_ino);
        struct pidns_init_store *e = pidns_hash_table[h];

        while (e) {
                if (e->ino == sb->st_ino) {
                        if (initpid_still_valid(e, sb)) {
                                e->lastcheck = time(NULL);
                                return e;
                        }
                        remove_initpid(e);
                        return NULL;
                }
                e = e->next;
        }

        return NULL;
}

static int is_dir(const char *path, int fd)
{
        struct stat statbuf;
        int ret = fstatat(fd, path, &statbuf, fd);
        if (ret == 0 && S_ISDIR(statbuf.st_mode))
                return 1;
        return 0;
}

static char *must_copy_string(const char *str)
{
        char *dup = NULL;
        if (!str)
                return NULL;
        do {
                dup = strdup(str);
        } while (!dup);

        return dup;
}

static inline void drop_trailing_newlines(char *s)
{
        int l;

        for (l=strlen(s); l>0 && s[l-1] == '\n'; l--)
                s[l-1] = '\0';
}

#define BATCH_SIZE 50
static void dorealloc(char **mem, size_t oldlen, size_t newlen)
{
        int newbatches = (newlen / BATCH_SIZE) + 1;
        int oldbatches = (oldlen / BATCH_SIZE) + 1;

        if (!*mem || newbatches > oldbatches) {
                char *tmp;
                do {
                        tmp = realloc(*mem, newbatches * BATCH_SIZE);
                } while (!tmp);
                *mem = tmp;
        }
}
static void append_line(char **contents, size_t *len, char *line, ssize_t linelen)
{
        size_t newlen = *len + linelen;
        dorealloc(contents, *len, newlen + 1);
        memcpy(*contents + *len, line, linelen+1);
        *len = newlen;
}

static char *slurp_file(const char *from, int fd)
{
        char *line = NULL;
        char *contents = NULL;
        FILE *f = fdopen(fd, "r");
        size_t len = 0, fulllen = 0;
        ssize_t linelen;

        if (!f)
                return NULL;

        while ((linelen = getline(&line, &len, f)) != -1) {
                append_line(&contents, &fulllen, line, linelen);
        }
        fclose(f);

        if (contents)
                drop_trailing_newlines(contents);
        free(line);
        return contents;
}

static bool write_string(const char *fnam, const char *string, int fd)
{
        FILE *f;
        size_t len, ret;

        if (!(f = fdopen(fd, "w")))
                return false;
        len = strlen(string);
        ret = fwrite(string, 1, len, f);
        if (ret != len) {
                lxcfs_error("Error writing to file: %s\n", strerror(errno));
                fclose(f);
                return false;
        }
        if (fclose(f) < 0) {
                lxcfs_error("Error writing to file: %s\n", strerror(errno));
                return false;
        }
        return true;
}

struct cgfs_files {
        char *name;
        uint32_t uid, gid;
        uint32_t mode;
};

#define ALLOC_NUM 20
static bool store_hierarchy(char *stridx, char *h)
{
        if (num_hierarchies % ALLOC_NUM == 0) {
                size_t n = (num_hierarchies / ALLOC_NUM) + 1;
                n *= ALLOC_NUM;
                char **tmp = realloc(hierarchies, n * sizeof(char *));
                if (!tmp) {
                        lxcfs_error("%s\n", strerror(errno));
                        exit(1);
                }
                hierarchies = tmp;
        }

        hierarchies[num_hierarchies++] = must_copy_string(h);
        return true;
}

static void print_subsystems(void)
{
        int i;

        fprintf(stderr, "mount namespace: %d\n", cgroup_mount_ns_fd);
        fprintf(stderr, "hierarchies:\n");
        for (i = 0; i < num_hierarchies; i++) {
                if (hierarchies[i])
                        fprintf(stderr, " %2d: fd: %3d: %s\n", i,
                                fd_hierarchies[i], hierarchies[i]);
        }
}

static bool in_comma_list(const char *needle, const char *haystack)
{
        const char *s = haystack, *e;
        size_t nlen = strlen(needle);

        while (*s && (e = strchr(s, ','))) {
                if (nlen != e - s) {
                        s = e + 1;
                        continue;
                }
                if (strncmp(needle, s, nlen) == 0)
                        return true;
                s = e + 1;
        }
        if (strcmp(needle, s) == 0)
                return true;
        return false;
}

/* do we need to do any massaging here?  I'm not sure... */
/* Return the mounted controller and store the corresponding open file descriptor
 * referring to the controller mountpoint in the private lxcfs namespace in
 * @cfd.
 */
static char *find_mounted_controller(const char *controller, int *cfd)
{
        int i;

        for (i = 0; i < num_hierarchies; i++) {
                if (!hierarchies[i])
                        continue;
                if (strcmp(hierarchies[i], controller) == 0) {
                        *cfd = fd_hierarchies[i];
                        return hierarchies[i];
                }
                if (in_comma_list(controller, hierarchies[i])) {
                        *cfd = fd_hierarchies[i];
                        return hierarchies[i];
                }
        }

        return NULL;
}

bool cgfs_set_value(const char *controller, const char *cgroup, const char *file,
                const char *value)
{
        int ret, fd, cfd;
        size_t len;
        char *fnam, *tmpc;

        tmpc = find_mounted_controller(controller, &cfd);
        if (!tmpc)
                return false;

        /* Make sure we pass a relative path to *at() family of functions.
         * . + /cgroup + / + file + \0
         */
        len = strlen(cgroup) + strlen(file) + 3;
        fnam = alloca(len);
        ret = snprintf(fnam, len, "%s%s/%s", *cgroup == '/' ? "." : "", cgroup, file);
        if (ret < 0 || (size_t)ret >= len)
                return false;

        fd = openat(cfd, fnam, O_WRONLY);
        if (fd < 0)
                return false;

        return write_string(fnam, value, fd);
}

// Chown all the files in the cgroup directory.  We do this when we create
// a cgroup on behalf of a user.
static void chown_all_cgroup_files(const char *dirname, uid_t uid, gid_t gid, int fd)
{
        struct dirent *direntp;
        char path[MAXPATHLEN];
        size_t len;
        DIR *d;
        int fd1, ret;

        len = strlen(dirname);
        if (len >= MAXPATHLEN) {
                lxcfs_error("Pathname too long: %s\n", dirname);
                return;
        }

        fd1 = openat(fd, dirname, O_DIRECTORY);
        if (fd1 < 0)
                return;

        d = fdopendir(fd1);
        if (!d) {
                lxcfs_error("Failed to open %s\n", dirname);
                return;
        }

        while ((direntp = readdir(d))) {
                if (!strcmp(direntp->d_name, ".") || !strcmp(direntp->d_name, ".."))
                        continue;
                ret = snprintf(path, MAXPATHLEN, "%s/%s", dirname, direntp->d_name);
                if (ret < 0 || ret >= MAXPATHLEN) {
                        lxcfs_error("Pathname too long under %s\n", dirname);
                        continue;
                }
                if (fchownat(fd, path, uid, gid, 0) < 0)
                        lxcfs_error("Failed to chown file %s to %u:%u", path, uid, gid);
        }
        closedir(d);
}

int cgfs_create(const char *controller, const char *cg, uid_t uid, gid_t gid)
{
        int cfd;
        size_t len;
        char *dirnam, *tmpc;

        tmpc = find_mounted_controller(controller, &cfd);
        if (!tmpc)
                return -EINVAL;

        /* Make sure we pass a relative path to *at() family of functions.
         * . + /cg + \0
         */
        len = strlen(cg) + 2;
        dirnam = alloca(len);
        snprintf(dirnam, len, "%s%s", *cg == '/' ? "." : "", cg);

        if (mkdirat(cfd, dirnam, 0755) < 0)
                return -errno;

        if (uid == 0 && gid == 0)
                return 0;

        if (fchownat(cfd, dirnam, uid, gid, 0) < 0)
                return -errno;

        chown_all_cgroup_files(dirnam, uid, gid, cfd);

        return 0;
}

static bool recursive_rmdir(const char *dirname, int fd, const int cfd)
{
        struct dirent *direntp;
        DIR *dir;
        bool ret = false;
        char pathname[MAXPATHLEN];
        int dupfd;

        dupfd = dup(fd); // fdopendir() does bad things once it uses an fd.
        if (dupfd < 0)
                return false;

        dir = fdopendir(dupfd);
        if (!dir) {
                lxcfs_debug("Failed to open %s: %s.\n", dirname, strerror(errno));
                close(dupfd);
                return false;
        }

        while ((direntp = readdir(dir))) {
                struct stat mystat;
                int rc;

                if (!strcmp(direntp->d_name, ".") ||
                    !strcmp(direntp->d_name, ".."))
                        continue;

                rc = snprintf(pathname, MAXPATHLEN, "%s/%s", dirname, direntp->d_name);
                if (rc < 0 || rc >= MAXPATHLEN) {
                        lxcfs_error("%s\n", "Pathname too long.");
                        continue;
                }

                rc = fstatat(cfd, pathname, &mystat, AT_SYMLINK_NOFOLLOW);
                if (rc) {
                        lxcfs_debug("Failed to stat %s: %s.\n", pathname, strerror(errno));
                        continue;
                }
                if (S_ISDIR(mystat.st_mode))
                        if (!recursive_rmdir(pathname, fd, cfd))
                                lxcfs_debug("Error removing %s.\n", pathname);
        }

        ret = true;
        if (closedir(dir) < 0) {
                lxcfs_error("Failed to close directory %s: %s\n", dirname, strerror(errno));
                ret = false;
        }

        if (unlinkat(cfd, dirname, AT_REMOVEDIR) < 0) {
                lxcfs_debug("Failed to delete %s: %s.\n", dirname, strerror(errno));
                ret = false;
        }

        close(dupfd);

        return ret;
}

bool cgfs_remove(const char *controller, const char *cg)
{
        int fd, cfd;
        size_t len;
        char *dirnam, *tmpc;
        bool bret;

        tmpc = find_mounted_controller(controller, &cfd);
        if (!tmpc)
                return false;

        /* Make sure we pass a relative path to *at() family of functions.
         * . +  /cg + \0
         */
        len = strlen(cg) + 2;
        dirnam = alloca(len);
        snprintf(dirnam, len, "%s%s", *cg == '/' ? "." : "", cg);

        fd = openat(cfd, dirnam, O_DIRECTORY);
        if (fd < 0)
                return false;

        bret = recursive_rmdir(dirnam, fd, cfd);
        close(fd);
        return bret;
}

bool cgfs_chmod_file(const char *controller, const char *file, mode_t mode)
{
        int cfd;
        size_t len;
        char *pathname, *tmpc;

        tmpc = find_mounted_controller(controller, &cfd);
        if (!tmpc)
                return false;

        /* Make sure we pass a relative path to *at() family of functions.
         * . + /file + \0
         */
        len = strlen(file) + 2;
        pathname = alloca(len);
        snprintf(pathname, len, "%s%s", *file == '/' ? "." : "", file);
        if (fchmodat(cfd, pathname, mode, 0) < 0)
                return false;
        return true;
}

static int chown_tasks_files(const char *dirname, uid_t uid, gid_t gid, int fd)
{
        size_t len;
        char *fname;

        len = strlen(dirname) + strlen("/cgroup.procs") + 1;
        fname = alloca(len);
        snprintf(fname, len, "%s/tasks", dirname);
        if (fchownat(fd, fname, uid, gid, 0) != 0)
                return -errno;
        snprintf(fname, len, "%s/cgroup.procs", dirname);
        if (fchownat(fd, fname, uid, gid, 0) != 0)
                return -errno;
        return 0;
}

int cgfs_chown_file(const char *controller, const char *file, uid_t uid, gid_t gid)
{
        int cfd;
        size_t len;
        char *pathname, *tmpc;

        tmpc = find_mounted_controller(controller, &cfd);
        if (!tmpc)
                return -EINVAL;

        /* Make sure we pass a relative path to *at() family of functions.
         * . + /file + \0
         */
        len = strlen(file) + 2;
        pathname = alloca(len);
        snprintf(pathname, len, "%s%s", *file == '/' ? "." : "", file);
        if (fchownat(cfd, pathname, uid, gid, 0) < 0)
                return -errno;

        if (is_dir(pathname, cfd))
                // like cgmanager did, we want to chown the tasks file as well
                return chown_tasks_files(pathname, uid, gid, cfd);

        return 0;
}

FILE *open_pids_file(const char *controller, const char *cgroup)
{
        int fd, cfd;
        size_t len;
        char *pathname, *tmpc;

        tmpc = find_mounted_controller(controller, &cfd);
        if (!tmpc)
                return NULL;

        /* Make sure we pass a relative path to *at() family of functions.
         * . + /cgroup + / "cgroup.procs" + \0
         */
        len = strlen(cgroup) + strlen("cgroup.procs") + 3;
        pathname = alloca(len);
        snprintf(pathname, len, "%s%s/cgroup.procs", *cgroup == '/' ? "." : "", cgroup);

        fd = openat(cfd, pathname, O_WRONLY);
        if (fd < 0)
                return NULL;

        return fdopen(fd, "w");
}

static bool cgfs_iterate_cgroup(const char *controller, const char *cgroup, bool directories,
                                void ***list, size_t typesize,
                                void* (*iterator)(const char*, const char*, const char*))
{
        int cfd, fd, ret;
        size_t len;
        char *cg, *tmpc;
        char pathname[MAXPATHLEN];
        size_t sz = 0, asz = 0;
        struct dirent *dirent;
        DIR *dir;

        tmpc = find_mounted_controller(controller, &cfd);
        *list = NULL;
        if (!tmpc)
                return false;

        /* Make sure we pass a relative path to *at() family of functions. */
        len = strlen(cgroup) + 1 /* . */ + 1 /* \0 */;
        cg = alloca(len);
        ret = snprintf(cg, len, "%s%s", *cgroup == '/' ? "." : "", cgroup);
        if (ret < 0 || (size_t)ret >= len) {
                lxcfs_error("Pathname too long under %s\n", cgroup);
                return false;
        }

        fd = openat(cfd, cg, O_DIRECTORY);
        if (fd < 0)
                return false;

        dir = fdopendir(fd);
        if (!dir)
                return false;

        while ((dirent = readdir(dir))) {
                struct stat mystat;

                if (!strcmp(dirent->d_name, ".") ||
                    !strcmp(dirent->d_name, ".."))
                        continue;

                ret = snprintf(pathname, MAXPATHLEN, "%s/%s", cg, dirent->d_name);
                if (ret < 0 || ret >= MAXPATHLEN) {
                        lxcfs_error("Pathname too long under %s\n", cg);
                        continue;
                }

                ret = fstatat(cfd, pathname, &mystat, AT_SYMLINK_NOFOLLOW);
                if (ret) {
                        lxcfs_error("Failed to stat %s: %s\n", pathname, strerror(errno));
                        continue;
                }
                if ((!directories && !S_ISREG(mystat.st_mode)) ||
                    (directories && !S_ISDIR(mystat.st_mode)))
                        continue;

                if (sz+2 >= asz) {
                        void **tmp;
                        asz += BATCH_SIZE;
                        do {
                                tmp = realloc(*list, asz * typesize);
                        } while  (!tmp);
                        *list = tmp;
                }
                (*list)[sz] = (*iterator)(controller, cg, dirent->d_name);
                (*list)[sz+1] = NULL;
                sz++;
        }
        if (closedir(dir) < 0) {
                lxcfs_error("Failed closedir for %s: %s\n", cgroup, strerror(errno));
                return false;
        }
        return true;
}

static void *make_children_list_entry(const char *controller, const char *cgroup, const char *dir_entry)
{
        char *dup;
        do {
                dup = strdup(dir_entry);
        } while (!dup);
        return dup;
}

bool cgfs_list_children(const char *controller, const char *cgroup, char ***list)
{
        return cgfs_iterate_cgroup(controller, cgroup, true, (void***)list, sizeof(*list), &make_children_list_entry);
}

void free_key(struct cgfs_files *k)
{
        if (!k)
                return;
        free(k->name);
        free(k);
}

void free_keys(struct cgfs_files **keys)
{
        int i;

        if (!keys)
                return;
        for (i = 0; keys[i]; i++) {
                free_key(keys[i]);
        }
        free(keys);
}

bool cgfs_get_value(const char *controller, const char *cgroup, const char *file, char **value)
{
        int ret, fd, cfd;
        size_t len;
        char *fnam, *tmpc;

        tmpc = find_mounted_controller(controller, &cfd);
        if (!tmpc)
                return false;

        /* Make sure we pass a relative path to *at() family of functions.
         * . + /cgroup + / + file + \0
         */
        len = strlen(cgroup) + strlen(file) + 3;
        fnam = alloca(len);
        ret = snprintf(fnam, len, "%s%s/%s", *cgroup == '/' ? "." : "", cgroup, file);
        if (ret < 0 || (size_t)ret >= len)
                return false;

        fd = openat(cfd, fnam, O_RDONLY);
        if (fd < 0)
                return false;

        *value = slurp_file(fnam, fd);
        return *value != NULL;
}

struct cgfs_files *cgfs_get_key(const char *controller, const char *cgroup, const char *file)
{
        int ret, cfd;
        size_t len;
        char *fnam, *tmpc;
        struct stat sb;
        struct cgfs_files *newkey;

        tmpc = find_mounted_controller(controller, &cfd);
        if (!tmpc)
                return false;

        if (file && *file == '/')
                file++;

        if (file && strchr(file, '/'))
                return NULL;

        /* Make sure we pass a relative path to *at() family of functions.
         * . + /cgroup + / + file + \0
         */
        len = strlen(cgroup) + 3;
        if (file)
                len += strlen(file) + 1;
        fnam = alloca(len);
        snprintf(fnam, len, "%s%s%s%s", *cgroup == '/' ? "." : "", cgroup,
                 file ? "/" : "", file ? file : "");

        ret = fstatat(cfd, fnam, &sb, 0);
        if (ret < 0)
                return NULL;

        do {
                newkey = malloc(sizeof(struct cgfs_files));
        } while (!newkey);
        if (file)
                newkey->name = must_copy_string(file);
        else if (strrchr(cgroup, '/'))
                newkey->name = must_copy_string(strrchr(cgroup, '/'));
        else
                newkey->name = must_copy_string(cgroup);
        newkey->uid = sb.st_uid;
        newkey->gid = sb.st_gid;
        newkey->mode = sb.st_mode;

        return newkey;
}

static void *make_key_list_entry(const char *controller, const char *cgroup, const char *dir_entry)
{
        struct cgfs_files *entry = cgfs_get_key(controller, cgroup, dir_entry);
        if (!entry) {
                lxcfs_error("Error getting files under %s:%s\n", controller,
                             cgroup);
        }
        return entry;
}

bool cgfs_list_keys(const char *controller, const char *cgroup, struct cgfs_files ***keys)
{
        return cgfs_iterate_cgroup(controller, cgroup, false, (void***)keys, sizeof(*keys), &make_key_list_entry);
}

bool is_child_cgroup(const char *controller, const char *cgroup, const char *f)
{
        int cfd;
        size_t len;
        char *fnam, *tmpc;
        int ret;
        struct stat sb;

        tmpc = find_mounted_controller(controller, &cfd);
        if (!tmpc)
                return false;

        /* Make sure we pass a relative path to *at() family of functions.
         * . + /cgroup + / + f + \0
         */
        len = strlen(cgroup) + strlen(f) + 3;
        fnam = alloca(len);
        ret = snprintf(fnam, len, "%s%s/%s", *cgroup == '/' ? "." : "", cgroup, f);
        if (ret < 0 || (size_t)ret >= len)
                return false;

        ret = fstatat(cfd, fnam, &sb, 0);
        if (ret < 0 || !S_ISDIR(sb.st_mode))
                return false;

        return true;
}

#define SEND_CREDS_OK 0
#define SEND_CREDS_NOTSK 1
#define SEND_CREDS_FAIL 2
static bool recv_creds(int sock, struct ucred *cred, char *v);
static int wait_for_pid(pid_t pid);
static int send_creds(int sock, struct ucred *cred, char v, bool pingfirst);
static int send_creds_clone_wrapper(void *arg);

/*
 * clone a task which switches to @task's namespace and writes '1'.
 * over a unix sock so we can read the task's reaper's pid in our
 * namespace
 *
 * Note: glibc's fork() does not respect pidns, which can lead to failed
 * assertions inside glibc (and thus failed forks) if the child's pid in
 * the pidns and the parent pid outside are identical. Using clone prevents
 * this issue.
 */
static void write_task_init_pid_exit(int sock, pid_t target)
{
        char fnam[100];
        pid_t pid;
        int fd, ret;
        size_t stack_size = sysconf(_SC_PAGESIZE);
        void *stack = alloca(stack_size);

        ret = snprintf(fnam, sizeof(fnam), "/proc/%d/ns/pid", (int)target);
        if (ret < 0 || ret >= sizeof(fnam))
                _exit(1);

        fd = open(fnam, O_RDONLY);
        if (fd < 0) {
                perror("write_task_init_pid_exit open of ns/pid");
                _exit(1);
        }
        if (setns(fd, 0)) {
                perror("write_task_init_pid_exit setns 1");
                close(fd);
                _exit(1);
        }
        pid = clone(send_creds_clone_wrapper, stack + stack_size, SIGCHLD, &sock);
        if (pid < 0)
                _exit(1);
        if (pid != 0) {
                if (!wait_for_pid(pid))
                        _exit(1);
                _exit(0);
        }
}

static int send_creds_clone_wrapper(void *arg) {
        struct ucred cred;
        char v;
        int sock = *(int *)arg;

        /* we are the child */
        cred.uid = 0;
        cred.gid = 0;
        cred.pid = 1;
        v = '1';
        if (send_creds(sock, &cred, v, true) != SEND_CREDS_OK)
                return 1;
        return 0;
}

static pid_t get_init_pid_for_task(pid_t task)
{
        int sock[2];
        pid_t pid;
        pid_t ret = -1;
        char v = '0';
        struct ucred cred;

        if (socketpair(AF_UNIX, SOCK_DGRAM, 0, sock) < 0) {
                perror("socketpair");
                return -1;
        }

        pid = fork();
        if (pid < 0)
                goto out;
        if (!pid) {
                close(sock[1]);
                write_task_init_pid_exit(sock[0], task);
                _exit(0);
        }

        if (!recv_creds(sock[1], &cred, &v))
                goto out;
        ret = cred.pid;

out:
        close(sock[0]);
        close(sock[1]);
        if (pid > 0)
                wait_for_pid(pid);
        return ret;
}

static pid_t lookup_initpid_in_store(pid_t qpid)
{
        pid_t answer = 0;
        struct stat sb;
        struct pidns_init_store *e;
        char fnam[100];

        snprintf(fnam, 100, "/proc/%d/ns/pid", qpid);
        store_lock();
        if (stat(fnam, &sb) < 0)
                goto out;
        e = lookup_verify_initpid(&sb);
        if (e) {
                answer = e->initpid;
                goto out;
        }
        answer = get_init_pid_for_task(qpid);
        if (answer > 0)
                save_initpid(&sb, answer);

out:
        /* we prune at end in case we are returning
         * the value we were about to return */
        prune_initpid_store();
        store_unlock();
        return answer;
}

static int wait_for_pid(pid_t pid)
{
        int status, ret;

        if (pid <= 0)
                return -1;

again:
        ret = waitpid(pid, &status, 0);
        if (ret == -1) {
                if (errno == EINTR)
                        goto again;
                return -1;
        }
        if (ret != pid)
                goto again;
        if (!WIFEXITED(status) || WEXITSTATUS(status) != 0)
                return -1;
        return 0;
}


/*
 * append pid to *src.
 * src: a pointer to a char* in which ot append the pid.
 * sz: the number of characters printed so far, minus trailing \0.
 * asz: the allocated size so far
 * pid: the pid to append
 */
static void must_strcat_pid(char **src, size_t *sz, size_t *asz, pid_t pid)
{
        char tmp[30];

        int tmplen = sprintf(tmp, "%d\n", (int)pid);

        if (!*src || tmplen + *sz + 1 >= *asz) {
                char *tmp;
                do {
                        tmp = realloc(*src, *asz + BUF_RESERVE_SIZE);
                } while (!tmp);
                *src = tmp;
                *asz += BUF_RESERVE_SIZE;
        }
        memcpy((*src) +*sz , tmp, tmplen+1); /* include the \0 */
        *sz += tmplen;
}

/*
 * Given a open file * to /proc/pid/{u,g}id_map, and an id
 * valid in the caller's namespace, return the id mapped into
 * pid's namespace.
 * Returns the mapped id, or -1 on error.
 */
unsigned int
convert_id_to_ns(FILE *idfile, unsigned int in_id)
{
        unsigned int nsuid,   // base id for a range in the idfile's namespace
                     hostuid, // base id for a range in the caller's namespace
                     count;   // number of ids in this range
        char line[400];
        int ret;

        fseek(idfile, 0L, SEEK_SET);
        while (fgets(line, 400, idfile)) {
                ret = sscanf(line, "%u %u %u\n", &nsuid, &hostuid, &count);
                if (ret != 3)
                        continue;
                if (hostuid + count < hostuid || nsuid + count < nsuid) {
                        /*
                         * uids wrapped around - unexpected as this is a procfile,
                         * so just bail.
                         */
                        lxcfs_error("pid wrapparound at entry %u %u %u in %s\n",
                                nsuid, hostuid, count, line);
                        return -1;
                }
                if (hostuid <= in_id && hostuid+count > in_id) {
                        /*
                         * now since hostuid <= in_id < hostuid+count, and
                         * hostuid+count and nsuid+count do not wrap around,
                         * we know that nsuid+(in_id-hostuid) which must be
                         * less that nsuid+(count) must not wrap around
                         */
                        return (in_id - hostuid) + nsuid;
                }
        }

        // no answer found
        return -1;
}

/*
 * for is_privileged_over,
 * specify whether we require the calling uid to be root in his
 * namespace
 */
#define NS_ROOT_REQD true
#define NS_ROOT_OPT false

#define PROCLEN 100

static bool is_privileged_over(pid_t pid, uid_t uid, uid_t victim, bool req_ns_root)
{
        char fpath[PROCLEN];
        int ret;
        bool answer = false;
        uid_t nsuid;

        if (victim == -1 || uid == -1)
                return false;

        /*
         * If the request is one not requiring root in the namespace,
         * then having the same uid suffices.  (i.e. uid 1000 has write
         * access to files owned by uid 1000
         */
        if (!req_ns_root && uid == victim)
                return true;

        ret = snprintf(fpath, PROCLEN, "/proc/%d/uid_map", pid);
        if (ret < 0 || ret >= PROCLEN)
                return false;
        FILE *f = fopen(fpath, "r");
        if (!f)
                return false;

        /* if caller's not root in his namespace, reject */
        nsuid = convert_id_to_ns(f, uid);
        if (nsuid)
                goto out;

        /*
         * If victim is not mapped into caller's ns, reject.
         * XXX I'm not sure this check is needed given that fuse
         * will be sending requests where the vfs has converted
         */
        nsuid = convert_id_to_ns(f, victim);
        if (nsuid == -1)
                goto out;

        answer = true;

out:
        fclose(f);
        return answer;
}

static bool perms_include(int fmode, mode_t req_mode)
{
        mode_t r;

        switch (req_mode & O_ACCMODE) {
        case O_RDONLY:
                r = S_IROTH;
                break;
        case O_WRONLY:
                r = S_IWOTH;
                break;
        case O_RDWR:
                r = S_IROTH | S_IWOTH;
                break;
        default:
                return false;
        }
        return ((fmode & r) == r);
}


/*
 * taskcg is  a/b/c
 * querycg is /a/b/c/d/e
 * we return 'd'
 */
static char *get_next_cgroup_dir(const char *taskcg, const char *querycg)
{
        char *start, *end;

        if (strlen(taskcg) <= strlen(querycg)) {
                lxcfs_error("%s\n", "I was fed bad input.");
                return NULL;
        }

        if ((strcmp(querycg, "/") == 0) || (strcmp(querycg, "./") == 0))
                start =  strdup(taskcg + 1);
        else
                start = strdup(taskcg + strlen(querycg) + 1);
        if (!start)
                return NULL;
        end = strchr(start, '/');
        if (end)
                *end = '\0';
        return start;
}

static void stripnewline(char *x)
{
        size_t l = strlen(x);
        if (l && x[l-1] == '\n')
                x[l-1] = '\0';
}

static char *get_pid_cgroup(pid_t pid, const char *contrl)
{
        int cfd;
        char fnam[PROCLEN];
        FILE *f;
        char *answer = NULL;
        char *line = NULL;
        size_t len = 0;
        int ret;
        const char *h = find_mounted_controller(contrl, &cfd);
        if (!h)
                return NULL;

        ret = snprintf(fnam, PROCLEN, "/proc/%d/cgroup", pid);
        if (ret < 0 || ret >= PROCLEN)
                return NULL;
        if (!(f = fopen(fnam, "r")))
                return NULL;

        while (getline(&line, &len, f) != -1) {
                char *c1, *c2;
                if (!line[0])
                        continue;
                c1 = strchr(line, ':');
                if (!c1)
                        goto out;
                c1++;
                c2 = strchr(c1, ':');
                if (!c2)
                        goto out;
                *c2 = '\0';
                if (strcmp(c1, h) != 0)
                        continue;
                c2++;
                stripnewline(c2);
                do {
                        answer = strdup(c2);
                } while (!answer);
                break;
        }

out:
        fclose(f);
        free(line);
        return answer;
}

/*
 * check whether a fuse context may access a cgroup dir or file
 *
 * If file is not null, it is a cgroup file to check under cg.
 * If file is null, then we are checking perms on cg itself.
 *
 * For files we can check the mode of the list_keys result.
 * For cgroups, we must make assumptions based on the files under the
 * cgroup, because cgmanager doesn't tell us ownership/perms of cgroups
 * yet.
 */
static bool fc_may_access(struct fuse_context *fc, const char *contrl, const char *cg, const char *file, mode_t mode)
{
        struct cgfs_files *k = NULL;
        bool ret = false;

        k = cgfs_get_key(contrl, cg, file);
        if (!k)
                return false;

        if (is_privileged_over(fc->pid, fc->uid, k->uid, NS_ROOT_OPT)) {
                if (perms_include(k->mode >> 6, mode)) {
                        ret = true;
                        goto out;
                }
        }
        if (fc->gid == k->gid) {
                if (perms_include(k->mode >> 3, mode)) {
                        ret = true;
                        goto out;
                }
        }
        ret = perms_include(k->mode, mode);

out:
        free_key(k);
        return ret;
}

#define INITSCOPE "/init.scope"
static void prune_init_slice(char *cg)
{
        char *point;
        size_t cg_len = strlen(cg), initscope_len = strlen(INITSCOPE);

        if (cg_len < initscope_len)
                return;

        point = cg + cg_len - initscope_len;
        if (strcmp(point, INITSCOPE) == 0) {
                if (point == cg)
                        *(point+1) = '\0';
                else
                        *point = '\0';
        }
}

/*
 * If pid is in /a/b/c/d, he may only act on things under cg=/a/b/c/d.
 * If pid is in /a, he may act on /a/b, but not on /b.
 * if the answer is false and nextcg is not NULL, then *nextcg will point
 * to a string containing the next cgroup directory under cg, which must be
 * freed by the caller.
 */
static bool caller_is_in_ancestor(pid_t pid, const char *contrl, const char *cg, char **nextcg)
{
        bool answer = false;
        char *c2 = get_pid_cgroup(pid, contrl);
        char *linecmp;

        if (!c2)
                return false;
        prune_init_slice(c2);

        /*
         * callers pass in '/' or './' (openat()) for root cgroup, otherwise
         * they pass in a cgroup without leading '/'
         *
         * The original line here was:
         *      linecmp = *cg == '/' ? c2 : c2+1;
         * TODO: I'm not sure why you'd want to increment when *cg != '/'?
         *       Serge, do you know?
         */
        if (*cg == '/' || !strncmp(cg, "./", 2))
                linecmp = c2;
        else
                linecmp = c2 + 1;
        if (strncmp(linecmp, cg, strlen(linecmp)) != 0) {
                if (nextcg) {
                        *nextcg = get_next_cgroup_dir(linecmp, cg);
                }
                goto out;
        }
        answer = true;

out:
        free(c2);
        return answer;
}

/*
 * If pid is in /a/b/c, he may see that /a exists, but not /b or /a/c.
 */
static bool caller_may_see_dir(pid_t pid, const char *contrl, const char *cg)
{
        bool answer = false;
        char *c2, *task_cg;
        size_t target_len, task_len;

        if (strcmp(cg, "/") == 0 || strcmp(cg, "./") == 0)
                return true;

        c2 = get_pid_cgroup(pid, contrl);
        if (!c2)
                return false;
        prune_init_slice(c2);

        task_cg = c2 + 1;
        target_len = strlen(cg);
        task_len = strlen(task_cg);
        if (task_len == 0) {
                /* Task is in the root cg, it can see everything. This case is
                 * not handled by the strmcps below, since they test for the
                 * last /, but that is the first / that we've chopped off
                 * above.
                 */
                answer = true;
                goto out;
        }
        if (strcmp(cg, task_cg) == 0) {
                answer = true;
                goto out;
        }
        if (target_len < task_len) {
                /* looking up a parent dir */
                if (strncmp(task_cg, cg, target_len) == 0 && task_cg[target_len] == '/')
                        answer = true;
                goto out;
        }
        if (target_len > task_len) {
                /* looking up a child dir */
                if (strncmp(task_cg, cg, task_len) == 0 && cg[task_len] == '/')
                        answer = true;
                goto out;
        }

out:
        free(c2);
        return answer;
}

/*
 * given /cgroup/freezer/a/b, return "freezer".
 * the returned char* should NOT be freed.
 */
static char *pick_controller_from_path(struct fuse_context *fc, const char *path)
{
        const char *p1;
        char *contr, *slash;

        if (strlen(path) < 9) {
                errno = EACCES;
                return NULL;
        }
        if (*(path + 7) != '/') {
                errno = EINVAL;
                return NULL;
        }
        p1 = path + 8;
        contr = strdupa(p1);
        if (!contr) {
                errno = ENOMEM;
                return NULL;
        }
        slash = strstr(contr, "/");
        if (slash)
                *slash = '\0';

        int i;
        for (i = 0; i < num_hierarchies; i++) {
                if (hierarchies[i] && strcmp(hierarchies[i], contr) == 0)
                        return hierarchies[i];
        }
        errno = ENOENT;
        return NULL;
}

/*
 * Find the start of cgroup in /cgroup/controller/the/cgroup/path
 * Note that the returned value may include files (keynames) etc
 */
static const char *find_cgroup_in_path(const char *path)
{
        const char *p1;

        if (strlen(path) < 9) {
                errno = EACCES;
                return NULL;
        }
        p1 = strstr(path + 8, "/");
        if (!p1) {
                errno = EINVAL;
                return NULL;
        }
        errno = 0;
        return p1 + 1;
}

/*
 * split the last path element from the path in @cg.
 * @dir is newly allocated and should be freed, @last not
*/
static void get_cgdir_and_path(const char *cg, char **dir, char **last)
{
        char *p;

        do {
                *dir = strdup(cg);
        } while (!*dir);
        *last = strrchr(cg, '/');
        if (!*last) {
                *last = NULL;
                return;
        }
        p = strrchr(*dir, '/');
        *p = '\0';
}

/*
 * FUSE ops for /cgroup
 */

int cg_getattr(const char *path, struct stat *sb)
{
        struct timespec now;
        struct fuse_context *fc = fuse_get_context();
        char * cgdir = NULL;
        char *last = NULL, *path1, *path2;
        struct cgfs_files *k = NULL;
        const char *cgroup;
        const char *controller = NULL;
        int ret = -ENOENT;


        if (!fc)
                return -EIO;

        memset(sb, 0, sizeof(struct stat));

        if (clock_gettime(CLOCK_REALTIME, &now) < 0)
                return -EINVAL;

        sb->st_uid = sb->st_gid = 0;
        sb->st_atim = sb->st_mtim = sb->st_ctim = now;
        sb->st_size = 0;

        if (strcmp(path, "/cgroup") == 0) {
                sb->st_mode = S_IFDIR | 00755;
                sb->st_nlink = 2;
                return 0;
        }

        controller = pick_controller_from_path(fc, path);
        if (!controller)
                return -errno;
        cgroup = find_cgroup_in_path(path);
        if (!cgroup) {
                /* this is just /cgroup/controller, return it as a dir */
                sb->st_mode = S_IFDIR | 00755;
                sb->st_nlink = 2;
                return 0;
        }

        get_cgdir_and_path(cgroup, &cgdir, &last);

        if (!last) {
                path1 = "/";
                path2 = cgdir;
        } else {
                path1 = cgdir;
                path2 = last;
        }

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        /* check that cgcopy is either a child cgroup of cgdir, or listed in its keys.
         * Then check that caller's cgroup is under path if last is a child
         * cgroup, or cgdir if last is a file */

        if (is_child_cgroup(controller, path1, path2)) {
                if (!caller_may_see_dir(initpid, controller, cgroup)) {
                        ret = -ENOENT;
                        goto out;
                }
                if (!caller_is_in_ancestor(initpid, controller, cgroup, NULL)) {
                        /* this is just /cgroup/controller, return it as a dir */
                        sb->st_mode = S_IFDIR | 00555;
                        sb->st_nlink = 2;
                        ret = 0;
                        goto out;
                }
                if (!fc_may_access(fc, controller, cgroup, NULL, O_RDONLY)) {
                        ret = -EACCES;
                        goto out;
                }

                // get uid, gid, from '/tasks' file and make up a mode
                // That is a hack, until cgmanager gains a GetCgroupPerms fn.
                sb->st_mode = S_IFDIR | 00755;
                k = cgfs_get_key(controller, cgroup, NULL);
                if (!k) {
                        sb->st_uid = sb->st_gid = 0;
                } else {
                        sb->st_uid = k->uid;
                        sb->st_gid = k->gid;
                }
                free_key(k);
                sb->st_nlink = 2;
                ret = 0;
                goto out;
        }

        if ((k = cgfs_get_key(controller, path1, path2)) != NULL) {
                sb->st_mode = S_IFREG | k->mode;
                sb->st_nlink = 1;
                sb->st_uid = k->uid;
                sb->st_gid = k->gid;
                sb->st_size = 0;
                free_key(k);
                if (!caller_is_in_ancestor(initpid, controller, path1, NULL)) {
                        ret = -ENOENT;
                        goto out;
                }
                ret = 0;
        }

out:
        free(cgdir);
        return ret;
}

int cg_opendir(const char *path, struct fuse_file_info *fi)
{
        struct fuse_context *fc = fuse_get_context();
        const char *cgroup;
        struct file_info *dir_info;
        char *controller = NULL;

        if (!fc)
                return -EIO;

        if (strcmp(path, "/cgroup") == 0) {
                cgroup = NULL;
                controller = NULL;
        } else {
                // return list of keys for the controller, and list of child cgroups
                controller = pick_controller_from_path(fc, path);
                if (!controller)
                        return -errno;

                cgroup = find_cgroup_in_path(path);
                if (!cgroup) {
                        /* this is just /cgroup/controller, return its contents */
                        cgroup = "/";
                }
        }

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        if (cgroup) {
                if (!caller_may_see_dir(initpid, controller, cgroup))
                        return -ENOENT;
                if (!fc_may_access(fc, controller, cgroup, NULL, O_RDONLY))
                        return -EACCES;
        }

        /* we'll free this at cg_releasedir */
        dir_info = malloc(sizeof(*dir_info));
        if (!dir_info)
                return -ENOMEM;
        dir_info->controller = must_copy_string(controller);
        dir_info->cgroup = must_copy_string(cgroup);
        dir_info->type = LXC_TYPE_CGDIR;
        dir_info->buf = NULL;
        dir_info->file = NULL;
        dir_info->buflen = 0;

        fi->fh = (unsigned long)dir_info;
        return 0;
}

int cg_readdir(const char *path, void *buf, fuse_fill_dir_t filler, off_t offset,
                struct fuse_file_info *fi)
{
        struct file_info *d = (struct file_info *)fi->fh;
        struct cgfs_files **list = NULL;
        int i, ret;
        char *nextcg = NULL;
        struct fuse_context *fc = fuse_get_context();
        char **clist = NULL;

        if (filler(buf, ".", NULL, 0) != 0 || filler(buf, "..", NULL, 0) != 0)
                return -EIO;

        if (d->type != LXC_TYPE_CGDIR) {
                lxcfs_error("%s\n", "Internal error: file cache info used in readdir.");
                return -EIO;
        }
        if (!d->cgroup && !d->controller) {
                // ls /var/lib/lxcfs/cgroup - just show list of controllers
                int i;

                for (i = 0;  i < num_hierarchies; i++) {
                        if (hierarchies[i] && filler(buf, hierarchies[i], NULL, 0) != 0) {
                                return -EIO;
                        }
                }
                return 0;
        }

        if (!cgfs_list_keys(d->controller, d->cgroup, &list)) {
                // not a valid cgroup
                ret = -EINVAL;
                goto out;
        }

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        if (!caller_is_in_ancestor(initpid, d->controller, d->cgroup, &nextcg)) {
                if (nextcg) {
                        ret = filler(buf, nextcg,  NULL, 0);
                        free(nextcg);
                        if (ret != 0) {
                                ret = -EIO;
                                goto out;
                        }
                }
                ret = 0;
                goto out;
        }

        for (i = 0; list[i]; i++) {
                if (filler(buf, list[i]->name, NULL, 0) != 0) {
                        ret = -EIO;
                        goto out;
                }
        }

        // now get the list of child cgroups

        if (!cgfs_list_children(d->controller, d->cgroup, &clist)) {
                ret = 0;
                goto out;
        }
        if (clist) {
                for (i = 0; clist[i]; i++) {
                        if (filler(buf, clist[i], NULL, 0) != 0) {
                                ret = -EIO;
                                goto out;
                        }
                }
        }
        ret = 0;

out:
        free_keys(list);
        if (clist) {
                for (i = 0; clist[i]; i++)
                        free(clist[i]);
                free(clist);
        }
        return ret;
}

static void do_release_file_info(struct fuse_file_info *fi)
{
        struct file_info *f = (struct file_info *)fi->fh;

        if (!f)
                return;

        fi->fh = 0;

        free(f->controller);
        f->controller = NULL;
        free(f->cgroup);
        f->cgroup = NULL;
        free(f->file);
        f->file = NULL;
        free(f->buf);
        f->buf = NULL;
        free(f);
}

int cg_releasedir(const char *path, struct fuse_file_info *fi)
{
        do_release_file_info(fi);
        return 0;
}

int cg_open(const char *path, struct fuse_file_info *fi)
{
        const char *cgroup;
        char *last = NULL, *path1, *path2, * cgdir = NULL, *controller;
        struct cgfs_files *k = NULL;
        struct file_info *file_info;
        struct fuse_context *fc = fuse_get_context();
        int ret;

        if (!fc)
                return -EIO;

        controller = pick_controller_from_path(fc, path);
        if (!controller)
                return -errno;
        cgroup = find_cgroup_in_path(path);
        if (!cgroup)
                return -errno;

        get_cgdir_and_path(cgroup, &cgdir, &last);
        if (!last) {
                path1 = "/";
                path2 = cgdir;
        } else {
                path1 = cgdir;
                path2 = last;
        }

        k = cgfs_get_key(controller, path1, path2);
        if (!k) {
                ret = -EINVAL;
                goto out;
        }
        free_key(k);

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        if (!caller_may_see_dir(initpid, controller, path1)) {
                ret = -ENOENT;
                goto out;
        }
        if (!fc_may_access(fc, controller, path1, path2, fi->flags)) {
                ret = -EACCES;
                goto out;
        }

        /* we'll free this at cg_release */
        file_info = malloc(sizeof(*file_info));
        if (!file_info) {
                ret = -ENOMEM;
                goto out;
        }
        file_info->controller = must_copy_string(controller);
        file_info->cgroup = must_copy_string(path1);
        file_info->file = must_copy_string(path2);
        file_info->type = LXC_TYPE_CGFILE;
        file_info->buf = NULL;
        file_info->buflen = 0;

        fi->fh = (unsigned long)file_info;
        ret = 0;

out:
        free(cgdir);
        return ret;
}

int cg_access(const char *path, int mode)
{
        int ret;
        const char *cgroup;
        char *path1, *path2, *controller;
        char *last = NULL, *cgdir = NULL;
        struct cgfs_files *k = NULL;
        struct fuse_context *fc = fuse_get_context();

        if (strcmp(path, "/cgroup") == 0)
                return 0;

        if (!fc)
                return -EIO;

        controller = pick_controller_from_path(fc, path);
        if (!controller)
                return -errno;
        cgroup = find_cgroup_in_path(path);
        if (!cgroup) {
                // access("/sys/fs/cgroup/systemd", mode) - rx allowed, w not
                if ((mode & W_OK) == 0)
                        return 0;
                return -EACCES;
        }

        get_cgdir_and_path(cgroup, &cgdir, &last);
        if (!last) {
                path1 = "/";
                path2 = cgdir;
        } else {
                path1 = cgdir;
                path2 = last;
        }

        k = cgfs_get_key(controller, path1, path2);
        if (!k) {
                if ((mode & W_OK) == 0)
                        ret = 0;
                else
                        ret = -EACCES;
                goto out;
        }
        free_key(k);

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        if (!caller_may_see_dir(initpid, controller, path1)) {
                ret = -ENOENT;
                goto out;
        }
        if (!fc_may_access(fc, controller, path1, path2, mode)) {
                ret = -EACCES;
                goto out;
        }

        ret = 0;

out:
        free(cgdir);
        return ret;
}

int cg_release(const char *path, struct fuse_file_info *fi)
{
        do_release_file_info(fi);
        return 0;
}

#define POLLIN_SET ( EPOLLIN | EPOLLHUP | EPOLLRDHUP )

static bool wait_for_sock(int sock, int timeout)
{
        struct epoll_event ev;
        int epfd, ret, now, starttime, deltatime, saved_errno;

        if ((starttime = time(NULL)) < 0)
                return false;

        if ((epfd = epoll_create(1)) < 0) {
                lxcfs_error("%s\n", "Failed to create epoll socket: %m.");
                return false;
        }

        ev.events = POLLIN_SET;
        ev.data.fd = sock;
        if (epoll_ctl(epfd, EPOLL_CTL_ADD, sock, &ev) < 0) {
                lxcfs_error("%s\n", "Failed adding socket to epoll: %m.");
                close(epfd);
                return false;
        }

again:
        if ((now = time(NULL)) < 0) {
                close(epfd);
                return false;
        }

        deltatime = (starttime + timeout) - now;
        if (deltatime < 0) { // timeout
                errno = 0;
                close(epfd);
                return false;
        }
        ret = epoll_wait(epfd, &ev, 1, 1000*deltatime + 1);
        if (ret < 0 && errno == EINTR)
                goto again;
        saved_errno = errno;
        close(epfd);

        if (ret <= 0) {
                errno = saved_errno;
                return false;
        }
        return true;
}

static int msgrecv(int sockfd, void *buf, size_t len)
{
        if (!wait_for_sock(sockfd, 2))
                return -1;
        return recv(sockfd, buf, len, MSG_DONTWAIT);
}

static int send_creds(int sock, struct ucred *cred, char v, bool pingfirst)
{
        struct msghdr msg = { 0 };
        struct iovec iov;
        struct cmsghdr *cmsg;
        char cmsgbuf[CMSG_SPACE(sizeof(*cred))];
        char buf[1];
        buf[0] = 'p';

        if (pingfirst) {
                if (msgrecv(sock, buf, 1) != 1) {
                        lxcfs_error("%s\n", "Error getting reply from server over socketpair.");
                        return SEND_CREDS_FAIL;
                }
        }

        msg.msg_control = cmsgbuf;
        msg.msg_controllen = sizeof(cmsgbuf);

        cmsg = CMSG_FIRSTHDR(&msg);
        cmsg->cmsg_len = CMSG_LEN(sizeof(struct ucred));
        cmsg->cmsg_level = SOL_SOCKET;
        cmsg->cmsg_type = SCM_CREDENTIALS;
        memcpy(CMSG_DATA(cmsg), cred, sizeof(*cred));

        msg.msg_name = NULL;
        msg.msg_namelen = 0;

        buf[0] = v;
        iov.iov_base = buf;
        iov.iov_len = sizeof(buf);
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;

        if (sendmsg(sock, &msg, 0) < 0) {
                lxcfs_error("Failed at sendmsg: %s.\n",strerror(errno));
                if (errno == 3)
                        return SEND_CREDS_NOTSK;
                return SEND_CREDS_FAIL;
        }

        return SEND_CREDS_OK;
}

static bool recv_creds(int sock, struct ucred *cred, char *v)
{
        struct msghdr msg = { 0 };
        struct iovec iov;
        struct cmsghdr *cmsg;
        char cmsgbuf[CMSG_SPACE(sizeof(*cred))];
        char buf[1];
        int ret;
        int optval = 1;

        *v = '1';

        cred->pid = -1;
        cred->uid = -1;
        cred->gid = -1;

        if (setsockopt(sock, SOL_SOCKET, SO_PASSCRED, &optval, sizeof(optval)) == -1) {
                lxcfs_error("Failed to set passcred: %s\n", strerror(errno));
                return false;
        }
        buf[0] = '1';
        if (write(sock, buf, 1) != 1) {
                lxcfs_error("Failed to start write on scm fd: %s\n", strerror(errno));
                return false;
        }

        msg.msg_name = NULL;
        msg.msg_namelen = 0;
        msg.msg_control = cmsgbuf;
        msg.msg_controllen = sizeof(cmsgbuf);

        iov.iov_base = buf;
        iov.iov_len = sizeof(buf);
        msg.msg_iov = &iov;
        msg.msg_iovlen = 1;

        if (!wait_for_sock(sock, 2)) {
                lxcfs_error("Timed out waiting for scm_cred: %s\n", strerror(errno));
                return false;
        }
        ret = recvmsg(sock, &msg, MSG_DONTWAIT);
        if (ret < 0) {
                lxcfs_error("Failed to receive scm_cred: %s\n", strerror(errno));
                return false;
        }

        cmsg = CMSG_FIRSTHDR(&msg);

        if (cmsg && cmsg->cmsg_len == CMSG_LEN(sizeof(struct ucred)) &&
                        cmsg->cmsg_level == SOL_SOCKET &&
                        cmsg->cmsg_type == SCM_CREDENTIALS) {
                memcpy(cred, CMSG_DATA(cmsg), sizeof(*cred));
        }
        *v = buf[0];

        return true;
}

struct pid_ns_clone_args {
        int *cpipe;
        int sock;
        pid_t tpid;
        int (*wrapped) (int, pid_t); // pid_from_ns or pid_to_ns
};

/*
 * pid_ns_clone_wrapper - wraps pid_to_ns or pid_from_ns for usage
 * with clone(). This simply writes '1' as ACK back to the parent
 * before calling the actual wrapped function.
 */
static int pid_ns_clone_wrapper(void *arg) {
        struct pid_ns_clone_args* args = (struct pid_ns_clone_args *) arg;
        char b = '1';

        close(args->cpipe[0]);
        if (write(args->cpipe[1], &b, sizeof(char)) < 0)
                lxcfs_error("(child): error on write: %s.\n", strerror(errno));
        close(args->cpipe[1]);
        return args->wrapped(args->sock, args->tpid);
}

/*
 * pid_to_ns - reads pids from a ucred over a socket, then writes the
 * int value back over the socket.  This shifts the pid from the
 * sender's pidns into tpid's pidns.
 */
static int pid_to_ns(int sock, pid_t tpid)
{
        char v = '0';
        struct ucred cred;

        while (recv_creds(sock, &cred, &v)) {
                if (v == '1')
                        return 0;
                if (write(sock, &cred.pid, sizeof(pid_t)) != sizeof(pid_t))
                        return 1;
        }
        return 0;
}


/*
 * pid_to_ns_wrapper: when you setns into a pidns, you yourself remain
 * in your old pidns.  Only children which you clone will be in the target
 * pidns.  So the pid_to_ns_wrapper does the setns, then clones a child to
 * actually convert pids.
 *
 * Note: glibc's fork() does not respect pidns, which can lead to failed
 * assertions inside glibc (and thus failed forks) if the child's pid in
 * the pidns and the parent pid outside are identical. Using clone prevents
 * this issue.
 */
static void pid_to_ns_wrapper(int sock, pid_t tpid)
{
        int newnsfd = -1, ret, cpipe[2];
        char fnam[100];
        pid_t cpid;
        char v;

        ret = snprintf(fnam, sizeof(fnam), "/proc/%d/ns/pid", tpid);
        if (ret < 0 || ret >= sizeof(fnam))
                _exit(1);
        newnsfd = open(fnam, O_RDONLY);
        if (newnsfd < 0)
                _exit(1);
        if (setns(newnsfd, 0) < 0)
                _exit(1);
        close(newnsfd);

        if (pipe(cpipe) < 0)
                _exit(1);

        struct pid_ns_clone_args args = {
                .cpipe = cpipe,
                .sock = sock,
                .tpid = tpid,
                .wrapped = &pid_to_ns
        };
        size_t stack_size = sysconf(_SC_PAGESIZE);
        void *stack = alloca(stack_size);

        cpid = clone(pid_ns_clone_wrapper, stack + stack_size, SIGCHLD, &args);
        if (cpid < 0)
                _exit(1);

        // give the child 1 second to be done forking and
        // write its ack
        if (!wait_for_sock(cpipe[0], 1))
                _exit(1);
        ret = read(cpipe[0], &v, 1);
        if (ret != sizeof(char) || v != '1')
                _exit(1);

        if (!wait_for_pid(cpid))
                _exit(1);
        _exit(0);
}

/*
 * To read cgroup files with a particular pid, we will setns into the child
 * pidns, open a pipe, fork a child - which will be the first to really be in
 * the child ns - which does the cgfs_get_value and writes the data to the pipe.
 */
bool do_read_pids(pid_t tpid, const char *contrl, const char *cg, const char *file, char **d)
{
        int sock[2] = {-1, -1};
        char *tmpdata = NULL;
        int ret;
        pid_t qpid, cpid = -1;
        bool answer = false;
        char v = '0';
        struct ucred cred;
        size_t sz = 0, asz = 0;

        if (!cgfs_get_value(contrl, cg, file, &tmpdata))
                return false;

        /*
         * Now we read the pids from returned data one by one, pass
         * them into a child in the target namespace, read back the
         * translated pids, and put them into our to-return data
         */

        if (socketpair(AF_UNIX, SOCK_DGRAM, 0, sock) < 0) {
                perror("socketpair");
                free(tmpdata);
                return false;
        }

        cpid = fork();
        if (cpid == -1)
                goto out;

        if (!cpid) // child - exits when done
                pid_to_ns_wrapper(sock[1], tpid);

        char *ptr = tmpdata;
        cred.uid = 0;
        cred.gid = 0;
        while (sscanf(ptr, "%d\n", &qpid) == 1) {
                cred.pid = qpid;
                ret = send_creds(sock[0], &cred, v, true);

                if (ret == SEND_CREDS_NOTSK)
                        goto next;
                if (ret == SEND_CREDS_FAIL)
                        goto out;

                // read converted results
                if (!wait_for_sock(sock[0], 2)) {
                        lxcfs_error("Timed out waiting for pid from child: %s.\n", strerror(errno));
                        goto out;
                }
                if (read(sock[0], &qpid, sizeof(qpid)) != sizeof(qpid)) {
                        lxcfs_error("Error reading pid from child: %s.\n", strerror(errno));
                        goto out;
                }
                must_strcat_pid(d, &sz, &asz, qpid);
next:
                ptr = strchr(ptr, '\n');
                if (!ptr)
                        break;
                ptr++;
        }

        cred.pid = getpid();
        v = '1';
        if (send_creds(sock[0], &cred, v, true) != SEND_CREDS_OK) {
                // failed to ask child to exit
                lxcfs_error("Failed to ask child to exit: %s.\n", strerror(errno));
                goto out;
        }

        answer = true;

out:
        free(tmpdata);
        if (cpid != -1)
                wait_for_pid(cpid);
        if (sock[0] != -1) {
                close(sock[0]);
                close(sock[1]);
        }
        return answer;
}

int cg_read(const char *path, char *buf, size_t size, off_t offset,
                struct fuse_file_info *fi)
{
        struct fuse_context *fc = fuse_get_context();
        struct file_info *f = (struct file_info *)fi->fh;
        struct cgfs_files *k = NULL;
        char *data = NULL;
        int ret, s;
        bool r;

        if (f->type != LXC_TYPE_CGFILE) {
                lxcfs_error("%s\n", "Internal error: directory cache info used in cg_read.");
                return -EIO;
        }

        if (offset)
                return 0;

        if (!fc)
                return -EIO;

        if (!f->controller)
                return -EINVAL;

        if ((k = cgfs_get_key(f->controller, f->cgroup, f->file)) == NULL) {
                return -EINVAL;
        }
        free_key(k);


        if (!fc_may_access(fc, f->controller, f->cgroup, f->file, O_RDONLY)) {
                ret = -EACCES;
                goto out;
        }

        if (strcmp(f->file, "tasks") == 0 ||
                        strcmp(f->file, "/tasks") == 0 ||
                        strcmp(f->file, "/cgroup.procs") == 0 ||
                        strcmp(f->file, "cgroup.procs") == 0)
                // special case - we have to translate the pids
                r = do_read_pids(fc->pid, f->controller, f->cgroup, f->file, &data);
        else
                r = cgfs_get_value(f->controller, f->cgroup, f->file, &data);

        if (!r) {
                ret = -EINVAL;
                goto out;
        }

        if (!data) {
                ret = 0;
                goto out;
        }
        s = strlen(data);
        if (s > size)
                s = size;
        memcpy(buf, data, s);
        if (s > 0 && s < size && data[s-1] != '\n')
                buf[s++] = '\n';

        ret = s;

out:
        free(data);
        return ret;
}

static int pid_from_ns(int sock, pid_t tpid)
{
        pid_t vpid;
        struct ucred cred;
        char v;
        int ret;

        cred.uid = 0;
        cred.gid = 0;
        while (1) {
                if (!wait_for_sock(sock, 2)) {
                        lxcfs_error("%s\n", "Timeout reading from parent.");
                        return 1;
                }
                if ((ret = read(sock, &vpid, sizeof(pid_t))) != sizeof(pid_t)) {
                        lxcfs_error("Bad read from parent: %s.\n", strerror(errno));
                        return 1;
                }
                if (vpid == -1) // done
                        break;
                v = '0';
                cred.pid = vpid;
                if (send_creds(sock, &cred, v, true) != SEND_CREDS_OK) {
                        v = '1';
                        cred.pid = getpid();
                        if (send_creds(sock, &cred, v, false) != SEND_CREDS_OK)
                                return 1;
                }
        }
        return 0;
}

static void pid_from_ns_wrapper(int sock, pid_t tpid)
{
        int newnsfd = -1, ret, cpipe[2];
        char fnam[100];
        pid_t cpid;
        char v;

        ret = snprintf(fnam, sizeof(fnam), "/proc/%d/ns/pid", tpid);
        if (ret < 0 || ret >= sizeof(fnam))
                _exit(1);
        newnsfd = open(fnam, O_RDONLY);
        if (newnsfd < 0)
                _exit(1);
        if (setns(newnsfd, 0) < 0)
                _exit(1);
        close(newnsfd);

        if (pipe(cpipe) < 0)
                _exit(1);

        struct pid_ns_clone_args args = {
                .cpipe = cpipe,
                .sock = sock,
                .tpid = tpid,
                .wrapped = &pid_from_ns
        };
        size_t stack_size = sysconf(_SC_PAGESIZE);
        void *stack = alloca(stack_size);

        cpid = clone(pid_ns_clone_wrapper, stack + stack_size, SIGCHLD, &args);
        if (cpid < 0)
                _exit(1);

        // give the child 1 second to be done forking and
        // write its ack
        if (!wait_for_sock(cpipe[0], 1))
                _exit(1);
        ret = read(cpipe[0], &v, 1);
        if (ret != sizeof(char) || v != '1')
                _exit(1);

        if (!wait_for_pid(cpid))
                _exit(1);
        _exit(0);
}

/*
 * Given host @uid, return the uid to which it maps in
 * @pid's user namespace, or -1 if none.
 */
bool hostuid_to_ns(uid_t uid, pid_t pid, uid_t *answer)
{
        FILE *f;
        char line[400];

        sprintf(line, "/proc/%d/uid_map", pid);
        if ((f = fopen(line, "r")) == NULL) {
                return false;
        }

        *answer = convert_id_to_ns(f, uid);
        fclose(f);

        if (*answer == -1)
                return false;
        return true;
}

/*
 * get_pid_creds: get the real uid and gid of @pid from
 * /proc/$$/status
 * (XXX should we use euid here?)
 */
void get_pid_creds(pid_t pid, uid_t *uid, gid_t *gid)
{
        char line[400];
        uid_t u;
        gid_t g;
        FILE *f;

        *uid = -1;
        *gid = -1;
        sprintf(line, "/proc/%d/status", pid);
        if ((f = fopen(line, "r")) == NULL) {
                lxcfs_error("Error opening %s: %s\n", line, strerror(errno));
                return;
        }
        while (fgets(line, 400, f)) {
                if (strncmp(line, "Uid:", 4) == 0) {
                        if (sscanf(line+4, "%u", &u) != 1) {
                                lxcfs_error("bad uid line for pid %u\n", pid);
                                fclose(f);
                                return;
                        }
                        *uid = u;
                } else if (strncmp(line, "Gid:", 4) == 0) {
                        if (sscanf(line+4, "%u", &g) != 1) {
                                lxcfs_error("bad gid line for pid %u\n", pid);
                                fclose(f);
                                return;
                        }
                        *gid = g;
                }
        }
        fclose(f);
}

/*
 * May the requestor @r move victim @v to a new cgroup?
 * This is allowed if
 *   . they are the same task
 *   . they are ownedy by the same uid
 *   . @r is root on the host, or
 *   . @v's uid is mapped into @r's where @r is root.
 */
bool may_move_pid(pid_t r, uid_t r_uid, pid_t v)
{
        uid_t v_uid, tmpuid;
        gid_t v_gid;

        if (r == v)
                return true;
        if (r_uid == 0)
                return true;
        get_pid_creds(v, &v_uid, &v_gid);
        if (r_uid == v_uid)
                return true;
        if (hostuid_to_ns(r_uid, r, &tmpuid) && tmpuid == 0
                        && hostuid_to_ns(v_uid, r, &tmpuid))
                return true;
        return false;
}

static bool do_write_pids(pid_t tpid, uid_t tuid, const char *contrl, const char *cg,
                const char *file, const char *buf)
{
        int sock[2] = {-1, -1};
        pid_t qpid, cpid = -1;
        FILE *pids_file = NULL;
        bool answer = false, fail = false;

        pids_file = open_pids_file(contrl, cg);
        if (!pids_file)
                return false;

        /*
         * write the pids to a socket, have helper in writer's pidns
         * call movepid for us
         */
        if (socketpair(AF_UNIX, SOCK_DGRAM, 0, sock) < 0) {
                perror("socketpair");
                goto out;
        }

        cpid = fork();
        if (cpid == -1)
                goto out;

        if (!cpid) { // child
                fclose(pids_file);
                pid_from_ns_wrapper(sock[1], tpid);
        }

        const char *ptr = buf;
        while (sscanf(ptr, "%d", &qpid) == 1) {
                struct ucred cred;
                char v;

                if (write(sock[0], &qpid, sizeof(qpid)) != sizeof(qpid)) {
                        lxcfs_error("Error writing pid to child: %s.\n", strerror(errno));
                        goto out;
                }

                if (recv_creds(sock[0], &cred, &v)) {
                        if (v == '0') {
                                if (!may_move_pid(tpid, tuid, cred.pid)) {
                                        fail = true;
                                        break;
                                }
                                if (fprintf(pids_file, "%d", (int) cred.pid) < 0)
                                        fail = true;
                        }
                }

                ptr = strchr(ptr, '\n');
                if (!ptr)
                        break;
                ptr++;
        }

        /* All good, write the value */
        qpid = -1;
        if (write(sock[0], &qpid ,sizeof(qpid)) != sizeof(qpid))
                lxcfs_error("%s\n", "Warning: failed to ask child to exit.");

        if (!fail)
                answer = true;

out:
        if (cpid != -1)
                wait_for_pid(cpid);
        if (sock[0] != -1) {
                close(sock[0]);
                close(sock[1]);
        }
        if (pids_file) {
                if (fclose(pids_file) != 0)
                        answer = false;
        }
        return answer;
}

int cg_write(const char *path, const char *buf, size_t size, off_t offset,
             struct fuse_file_info *fi)
{
        struct fuse_context *fc = fuse_get_context();
        char *localbuf = NULL;
        struct cgfs_files *k = NULL;
        struct file_info *f = (struct file_info *)fi->fh;
        bool r;

        if (f->type != LXC_TYPE_CGFILE) {
                lxcfs_error("%s\n", "Internal error: directory cache info used in cg_write.");
                return -EIO;
        }

        if (offset)
                return 0;

        if (!fc)
                return -EIO;

        localbuf = alloca(size+1);
        localbuf[size] = '\0';
        memcpy(localbuf, buf, size);

        if ((k = cgfs_get_key(f->controller, f->cgroup, f->file)) == NULL) {
                size = -EINVAL;
                goto out;
        }

        if (!fc_may_access(fc, f->controller, f->cgroup, f->file, O_WRONLY)) {
                size = -EACCES;
                goto out;
        }

        if (strcmp(f->file, "tasks") == 0 ||
                        strcmp(f->file, "/tasks") == 0 ||
                        strcmp(f->file, "/cgroup.procs") == 0 ||
                        strcmp(f->file, "cgroup.procs") == 0)
                // special case - we have to translate the pids
                r = do_write_pids(fc->pid, fc->uid, f->controller, f->cgroup, f->file, localbuf);
        else
                r = cgfs_set_value(f->controller, f->cgroup, f->file, localbuf);

        if (!r)
                size = -EINVAL;

out:
        free_key(k);
        return size;
}

int cg_chown(const char *path, uid_t uid, gid_t gid)
{
        struct fuse_context *fc = fuse_get_context();
        char *cgdir = NULL, *last = NULL, *path1, *path2, *controller;
        struct cgfs_files *k = NULL;
        const char *cgroup;
        int ret;

        if (!fc)
                return -EIO;

        if (strcmp(path, "/cgroup") == 0)
                return -EPERM;

        controller = pick_controller_from_path(fc, path);
        if (!controller)
                return errno == ENOENT ? -EPERM : -errno;

        cgroup = find_cgroup_in_path(path);
        if (!cgroup)
                /* this is just /cgroup/controller */
                return -EPERM;

        get_cgdir_and_path(cgroup, &cgdir, &last);

        if (!last) {
                path1 = "/";
                path2 = cgdir;
        } else {
                path1 = cgdir;
                path2 = last;
        }

        if (is_child_cgroup(controller, path1, path2)) {
                // get uid, gid, from '/tasks' file and make up a mode
                // That is a hack, until cgmanager gains a GetCgroupPerms fn.
                k = cgfs_get_key(controller, cgroup, "tasks");

        } else
                k = cgfs_get_key(controller, path1, path2);

        if (!k) {
                ret = -EINVAL;
                goto out;
        }

        /*
         * This being a fuse request, the uid and gid must be valid
         * in the caller's namespace.  So we can just check to make
         * sure that the caller is root in his uid, and privileged
         * over the file's current owner.
         */
        if (!is_privileged_over(fc->pid, fc->uid, k->uid, NS_ROOT_REQD)) {
                ret = -EACCES;
                goto out;
        }

        ret = cgfs_chown_file(controller, cgroup, uid, gid);

out:
        free_key(k);
        free(cgdir);

        return ret;
}

int cg_chmod(const char *path, mode_t mode)
{
        struct fuse_context *fc = fuse_get_context();
        char * cgdir = NULL, *last = NULL, *path1, *path2, *controller;
        struct cgfs_files *k = NULL;
        const char *cgroup;
        int ret;

        if (!fc)
                return -EIO;

        if (strcmp(path, "/cgroup") == 0)
                return -EPERM;

        controller = pick_controller_from_path(fc, path);
        if (!controller)
                return errno == ENOENT ? -EPERM : -errno;

        cgroup = find_cgroup_in_path(path);
        if (!cgroup)
                /* this is just /cgroup/controller */
                return -EPERM;

        get_cgdir_and_path(cgroup, &cgdir, &last);

        if (!last) {
                path1 = "/";
                path2 = cgdir;
        } else {
                path1 = cgdir;
                path2 = last;
        }

        if (is_child_cgroup(controller, path1, path2)) {
                // get uid, gid, from '/tasks' file and make up a mode
                // That is a hack, until cgmanager gains a GetCgroupPerms fn.
                k = cgfs_get_key(controller, cgroup, "tasks");

        } else
                k = cgfs_get_key(controller, path1, path2);

        if (!k) {
                ret = -EINVAL;
                goto out;
        }

        /*
         * This being a fuse request, the uid and gid must be valid
         * in the caller's namespace.  So we can just check to make
         * sure that the caller is root in his uid, and privileged
         * over the file's current owner.
         */
        if (!is_privileged_over(fc->pid, fc->uid, k->uid, NS_ROOT_OPT)) {
                ret = -EPERM;
                goto out;
        }

        if (!cgfs_chmod_file(controller, cgroup, mode)) {
                ret = -EINVAL;
                goto out;
        }

        ret = 0;
out:
        free_key(k);
        free(cgdir);
        return ret;
}

int cg_mkdir(const char *path, mode_t mode)
{
        struct fuse_context *fc = fuse_get_context();
        char *last = NULL, *path1, *cgdir = NULL, *controller, *next = NULL;
        const char *cgroup;
        int ret;

        if (!fc)
                return -EIO;

        controller = pick_controller_from_path(fc, path);
        if (!controller)
                return errno == ENOENT ? -EPERM : -errno;

        cgroup = find_cgroup_in_path(path);
        if (!cgroup)
                return -errno;

        get_cgdir_and_path(cgroup, &cgdir, &last);
        if (!last)
                path1 = "/";
        else
                path1 = cgdir;

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        if (!caller_is_in_ancestor(initpid, controller, path1, &next)) {
                if (!next)
                        ret = -EINVAL;
                else if (last && strcmp(next, last) == 0)
                        ret = -EEXIST;
                else
                        ret = -EPERM;
                goto out;
        }

        if (!fc_may_access(fc, controller, path1, NULL, O_RDWR)) {
                ret = -EACCES;
                goto out;
        }
        if (!caller_is_in_ancestor(initpid, controller, path1, NULL)) {
                ret = -EACCES;
                goto out;
        }

        ret = cgfs_create(controller, cgroup, fc->uid, fc->gid);

out:
        free(cgdir);
        free(next);
        return ret;
}

int cg_rmdir(const char *path)
{
        struct fuse_context *fc = fuse_get_context();
        char *last = NULL, *cgdir = NULL, *controller, *next = NULL;
        const char *cgroup;
        int ret;

        if (!fc)
                return -EIO;

        controller = pick_controller_from_path(fc, path);
        if (!controller) /* Someone's trying to delete "/cgroup". */
                return -EPERM;

        cgroup = find_cgroup_in_path(path);
        if (!cgroup) /* Someone's trying to delete a controller e.g. "/blkio". */
                return -EPERM;

        get_cgdir_and_path(cgroup, &cgdir, &last);
        if (!last) {
                /* Someone's trying to delete a cgroup on the same level as the
                 * "/lxc" cgroup e.g. rmdir "/cgroup/blkio/lxc" or
                 * rmdir "/cgroup/blkio/init.slice".
                 */
                ret = -EPERM;
                goto out;
        }

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        if (!caller_is_in_ancestor(initpid, controller, cgroup, &next)) {
                if (!last || (next && (strcmp(next, last) == 0)))
                        ret = -EBUSY;
                else
                        ret = -ENOENT;
                goto out;
        }

        if (!fc_may_access(fc, controller, cgdir, NULL, O_WRONLY)) {
                ret = -EACCES;
                goto out;
        }
        if (!caller_is_in_ancestor(initpid, controller, cgroup, NULL)) {
                ret = -EACCES;
                goto out;
        }

        if (!cgfs_remove(controller, cgroup)) {
                ret = -EINVAL;
                goto out;
        }

        ret = 0;

out:
        free(cgdir);
        free(next);
        return ret;
}

static bool startswith(const char *line, const char *pref)
{
        if (strncmp(line, pref, strlen(pref)) == 0)
                return true;
        return false;
}

static void parse_memstat(char *memstat, unsigned long *cached,
                unsigned long *active_anon, unsigned long *inactive_anon,
                unsigned long *active_file, unsigned long *inactive_file,
                unsigned long *unevictable)
{
        char *eol;

        while (*memstat) {
                if (startswith(memstat, "total_cache")) {
                        sscanf(memstat + 11, "%lu", cached);
                        *cached /= 1024;
                } else if (startswith(memstat, "total_active_anon")) {
                        sscanf(memstat + 17, "%lu", active_anon);
                        *active_anon /= 1024;
                } else if (startswith(memstat, "total_inactive_anon")) {
                        sscanf(memstat + 19, "%lu", inactive_anon);
                        *inactive_anon /= 1024;
                } else if (startswith(memstat, "total_active_file")) {
                        sscanf(memstat + 17, "%lu", active_file);
                        *active_file /= 1024;
                } else if (startswith(memstat, "total_inactive_file")) {
                        sscanf(memstat + 19, "%lu", inactive_file);
                        *inactive_file /= 1024;
                } else if (startswith(memstat, "total_unevictable")) {
                        sscanf(memstat + 17, "%lu", unevictable);
                        *unevictable /= 1024;
                }
                eol = strchr(memstat, '\n');
                if (!eol)
                        return;
                memstat = eol+1;
        }
}

static void get_blkio_io_value(char *str, unsigned major, unsigned minor, char *iotype, unsigned long *v)
{
        char *eol;
        char key[32];

        memset(key, 0, 32);
        snprintf(key, 32, "%u:%u %s", major, minor, iotype);

        size_t len = strlen(key);
        *v = 0;

        while (*str) {
                if (startswith(str, key)) {
                        sscanf(str + len, "%lu", v);
                        return;
                }
                eol = strchr(str, '\n');
                if (!eol)
                        return;
                str = eol+1;
        }
}

static int read_file(const char *path, char *buf, size_t size,
                     struct file_info *d)
{
        size_t linelen = 0, total_len = 0, rv = 0;
        char *line = NULL;
        char *cache = d->buf;
        size_t cache_size = d->buflen;
        FILE *f = fopen(path, "r");
        if (!f)
                return 0;

        while (getline(&line, &linelen, f) != -1) {
                ssize_t l = snprintf(cache, cache_size, "%s", line);
                if (l < 0) {
                        perror("Error writing to cache");
                        rv = 0;
                        goto err;
                }
                if (l >= cache_size) {
                        lxcfs_error("%s\n", "Internal error: truncated write to cache.");
                        rv = 0;
                        goto err;
                }
                cache += l;
                cache_size -= l;
                total_len += l;
        }

        d->size = total_len;
        if (total_len > size)
                total_len = size;

        /* read from off 0 */
        memcpy(buf, d->buf, total_len);
        rv = total_len;
  err:
        fclose(f);
        free(line);
        return rv;
}

/*
 * FUSE ops for /proc
 */

static unsigned long get_memlimit(const char *cgroup, const char *file)
{
        char *memlimit_str = NULL;
        unsigned long memlimit = -1;

        if (cgfs_get_value("memory", cgroup, file, &memlimit_str))
                memlimit = strtoul(memlimit_str, NULL, 10);

        free(memlimit_str);

        return memlimit;
}

static unsigned long get_min_memlimit(const char *cgroup, const char *file)
{
        char *copy = strdupa(cgroup);
        unsigned long memlimit = 0, retlimit;

        retlimit = get_memlimit(copy, file);

        while (strcmp(copy, "/") != 0) {
                copy = dirname(copy);
                memlimit = get_memlimit(copy, file);
                if (memlimit != -1 && memlimit < retlimit)
                        retlimit = memlimit;
        };

        return retlimit;
}

static int proc_meminfo_read(char *buf, size_t size, off_t offset,
                struct fuse_file_info *fi)
{
        struct fuse_context *fc = fuse_get_context();
        struct file_info *d = (struct file_info *)fi->fh;
        char *cg;
        char *memusage_str = NULL, *memstat_str = NULL,
                *memswlimit_str = NULL, *memswusage_str = NULL;
        unsigned long memlimit = 0, memusage = 0, memswlimit = 0, memswusage = 0,
                cached = 0, hosttotal = 0, active_anon = 0, inactive_anon = 0,
                active_file = 0, inactive_file = 0, unevictable = 0,
                hostswtotal = 0;
        char *line = NULL;
        size_t linelen = 0, total_len = 0, rv = 0;
        char *cache = d->buf;
        size_t cache_size = d->buflen;
        FILE *f = NULL;

        if (offset){
                if (offset > d->size)
                        return -EINVAL;
                if (!d->cached)
                        return 0;
                int left = d->size - offset;
                total_len = left > size ? size: left;
                memcpy(buf, cache + offset, total_len);
                return total_len;
        }

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        cg = get_pid_cgroup(initpid, "memory");
        if (!cg)
                return read_file("/proc/meminfo", buf, size, d);
        prune_init_slice(cg);

        memlimit = get_min_memlimit(cg, "memory.limit_in_bytes");
        if (!cgfs_get_value("memory", cg, "memory.usage_in_bytes", &memusage_str))
                goto err;
        if (!cgfs_get_value("memory", cg, "memory.stat", &memstat_str))
                goto err;

        // Following values are allowed to fail, because swapaccount might be turned
        // off for current kernel
        if(cgfs_get_value("memory", cg, "memory.memsw.limit_in_bytes", &memswlimit_str) &&
                cgfs_get_value("memory", cg, "memory.memsw.usage_in_bytes", &memswusage_str))
        {
                memswlimit = get_min_memlimit(cg, "memory.memsw.limit_in_bytes");
                memswusage = strtoul(memswusage_str, NULL, 10);

                memswlimit = memswlimit / 1024;
                memswusage = memswusage / 1024;
        }

        memusage = strtoul(memusage_str, NULL, 10);
        memlimit /= 1024;
        memusage /= 1024;

        parse_memstat(memstat_str, &cached, &active_anon,
                        &inactive_anon, &active_file, &inactive_file,
                        &unevictable);

        f = fopen("/proc/meminfo", "r");
        if (!f)
                goto err;

        while (getline(&line, &linelen, f) != -1) {
                ssize_t l;
                char *printme, lbuf[100];

                memset(lbuf, 0, 100);
                if (startswith(line, "MemTotal:")) {
                        sscanf(line+sizeof("MemTotal:")-1, "%lu", &hosttotal);
                        if (hosttotal < memlimit)
                                memlimit = hosttotal;
                        snprintf(lbuf, 100, "MemTotal:       %8lu kB\n", memlimit);
                        printme = lbuf;
                } else if (startswith(line, "MemFree:")) {
                        snprintf(lbuf, 100, "MemFree:        %8lu kB\n", memlimit - memusage);
                        printme = lbuf;
                } else if (startswith(line, "MemAvailable:")) {
                        snprintf(lbuf, 100, "MemAvailable:   %8lu kB\n", memlimit - memusage + cached);
                        printme = lbuf;
                } else if (startswith(line, "SwapTotal:") && memswlimit > 0) {
                        sscanf(line+sizeof("SwapTotal:")-1, "%lu", &hostswtotal);
                        if (hostswtotal < memswlimit)
                                memswlimit = hostswtotal;
                        snprintf(lbuf, 100, "SwapTotal:      %8lu kB\n", memswlimit);
                        printme = lbuf;
                } else if (startswith(line, "SwapFree:") && memswlimit > 0 && memswusage > 0) {
                        unsigned long swaptotal = memswlimit,
                                        swapusage = memswusage - memusage,
                                        swapfree = swapusage < swaptotal ? swaptotal - swapusage : 0;
                        snprintf(lbuf, 100, "SwapFree:       %8lu kB\n", swapfree);
                        printme = lbuf;
                } else if (startswith(line, "Slab:")) {
                        snprintf(lbuf, 100, "Slab:        %8lu kB\n", 0UL);
                        printme = lbuf;
                } else if (startswith(line, "Buffers:")) {
                        snprintf(lbuf, 100, "Buffers:        %8lu kB\n", 0UL);
                        printme = lbuf;
                } else if (startswith(line, "Cached:")) {
                        snprintf(lbuf, 100, "Cached:         %8lu kB\n", cached);
                        printme = lbuf;
                } else if (startswith(line, "SwapCached:")) {
                        snprintf(lbuf, 100, "SwapCached:     %8lu kB\n", 0UL);
                        printme = lbuf;
                } else if (startswith(line, "Active:")) {
                        snprintf(lbuf, 100, "Active:         %8lu kB\n",
                                        active_anon + active_file);
                        printme = lbuf;
                } else if (startswith(line, "Inactive:")) {
                        snprintf(lbuf, 100, "Inactive:       %8lu kB\n",
                                        inactive_anon + inactive_file);
                        printme = lbuf;
                } else if (startswith(line, "Active(anon)")) {
                        snprintf(lbuf, 100, "Active(anon):   %8lu kB\n", active_anon);
                        printme = lbuf;
                } else if (startswith(line, "Inactive(anon)")) {
                        snprintf(lbuf, 100, "Inactive(anon): %8lu kB\n", inactive_anon);
                        printme = lbuf;
                } else if (startswith(line, "Active(file)")) {
                        snprintf(lbuf, 100, "Active(file):   %8lu kB\n", active_file);
                        printme = lbuf;
                } else if (startswith(line, "Inactive(file)")) {
                        snprintf(lbuf, 100, "Inactive(file): %8lu kB\n", inactive_file);
                        printme = lbuf;
                } else if (startswith(line, "Unevictable")) {
                        snprintf(lbuf, 100, "Unevictable:    %8lu kB\n", unevictable);
                        printme = lbuf;
                } else if (startswith(line, "SReclaimable")) {
                        snprintf(lbuf, 100, "SReclaimable:   %8lu kB\n", 0UL);
                        printme = lbuf;
                } else if (startswith(line, "SUnreclaim")) {
                        snprintf(lbuf, 100, "SUnreclaim:     %8lu kB\n", 0UL);
                        printme = lbuf;
                } else
                        printme = line;

                l = snprintf(cache, cache_size, "%s", printme);
                if (l < 0) {
                        perror("Error writing to cache");
                        rv = 0;
                        goto err;

                }
                if (l >= cache_size) {
                        lxcfs_error("%s\n", "Internal error: truncated write to cache.");
                        rv = 0;
                        goto err;
                }

                cache += l;
                cache_size -= l;
                total_len += l;
        }

        d->cached = 1;
        d->size = total_len;
        if (total_len > size ) total_len = size;
        memcpy(buf, d->buf, total_len);

        rv = total_len;
err:
        if (f)
                fclose(f);
        free(line);
        free(cg);
        free(memusage_str);
        free(memswlimit_str);
        free(memswusage_str);
        free(memstat_str);
        return rv;
}

/*
 * Read the cpuset.cpus for cg
 * Return the answer in a newly allocated string which must be freed
 */
static char *get_cpuset(const char *cg)
{
        char *answer;

        if (!cgfs_get_value("cpuset", cg, "cpuset.cpus", &answer))
                return NULL;
        return answer;
}

bool cpu_in_cpuset(int cpu, const char *cpuset);

static bool cpuline_in_cpuset(const char *line, const char *cpuset)
{
        int cpu;

        if (sscanf(line, "processor       : %d", &cpu) != 1)
                return false;
        return cpu_in_cpuset(cpu, cpuset);
}

/*
 * check whether this is a '^processor" line in /proc/cpuinfo
 */
static bool is_processor_line(const char *line)
{
        int cpu;

        if (sscanf(line, "processor       : %d", &cpu) == 1)
                return true;
        return false;
}

static int proc_cpuinfo_read(char *buf, size_t size, off_t offset,
                struct fuse_file_info *fi)
{
        struct fuse_context *fc = fuse_get_context();
        struct file_info *d = (struct file_info *)fi->fh;
        char *cg;
        char *cpuset = NULL;
        char *line = NULL;
        size_t linelen = 0, total_len = 0, rv = 0;
        bool am_printing = false, firstline = true, is_s390x = false;
        int curcpu = -1, cpu;
        char *cache = d->buf;
        size_t cache_size = d->buflen;
        FILE *f = NULL;

        if (offset){
                if (offset > d->size)
                        return -EINVAL;
                if (!d->cached)
                        return 0;
                int left = d->size - offset;
                total_len = left > size ? size: left;
                memcpy(buf, cache + offset, total_len);
                return total_len;
        }

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        cg = get_pid_cgroup(initpid, "cpuset");
        if (!cg)
                return read_file("proc/cpuinfo", buf, size, d);
        prune_init_slice(cg);

        cpuset = get_cpuset(cg);
        if (!cpuset)
                goto err;

        f = fopen("/proc/cpuinfo", "r");
        if (!f)
                goto err;

        while (getline(&line, &linelen, f) != -1) {
                ssize_t l;
                if (firstline) {
                        firstline = false;
                        if (strstr(line, "IBM/S390") != NULL) {
                                is_s390x = true;
                                am_printing = true;
                                continue;
                        }
                }
                if (strncmp(line, "# processors:", 12) == 0)
                        continue;
                if (is_processor_line(line)) {
                        am_printing = cpuline_in_cpuset(line, cpuset);
                        if (am_printing) {
                                curcpu ++;
                                l = snprintf(cache, cache_size, "processor      : %d\n", curcpu);
                                if (l < 0) {
                                        perror("Error writing to cache");
                                        rv = 0;
                                        goto err;
                                }
                                if (l >= cache_size) {
                                        lxcfs_error("%s\n", "Internal error: truncated write to cache.");
                                        rv = 0;
                                        goto err;
                                }
                                cache += l;
                                cache_size -= l;
                                total_len += l;
                        }
                        continue;
                } else if (is_s390x && sscanf(line, "processor %d:", &cpu) == 1) {
                        char *p;
                        if (!cpu_in_cpuset(cpu, cpuset))
                                continue;
                        curcpu ++;
                        p = strchr(line, ':');
                        if (!p || !*p)
                                goto err;
                        p++;
                        l = snprintf(cache, cache_size, "processor %d:%s", curcpu, p);
                        if (l < 0) {
                                perror("Error writing to cache");
                                rv = 0;
                                goto err;
                        }
                        if (l >= cache_size) {
                                lxcfs_error("%s\n", "Internal error: truncated write to cache.");
                                rv = 0;
                                goto err;
                        }
                        cache += l;
                        cache_size -= l;
                        total_len += l;
                        continue;

                }
                if (am_printing) {
                        l = snprintf(cache, cache_size, "%s", line);
                        if (l < 0) {
                                perror("Error writing to cache");
                                rv = 0;
                                goto err;
                        }
                        if (l >= cache_size) {
                                lxcfs_error("%s\n", "Internal error: truncated write to cache.");
                                rv = 0;
                                goto err;
                        }
                        cache += l;
                        cache_size -= l;
                        total_len += l;
                }
        }

        if (is_s390x) {
                char *origcache = d->buf;
                ssize_t l;
                do {
                        d->buf = malloc(d->buflen);
                } while (!d->buf);
                cache = d->buf;
                cache_size = d->buflen;
                total_len = 0;
                l = snprintf(cache, cache_size, "vendor_id       : IBM/S390\n");
                if (l < 0 || l >= cache_size) {
                        free(origcache);
                        goto err;
                }
                cache_size -= l;
                cache += l;
                total_len += l;
                l = snprintf(cache, cache_size, "# processors    : %d\n", curcpu + 1);
                if (l < 0 || l >= cache_size) {
                        free(origcache);
                        goto err;
                }
                cache_size -= l;
                cache += l;
                total_len += l;
                l = snprintf(cache, cache_size, "%s", origcache);
                free(origcache);
                if (l < 0 || l >= cache_size)
                        goto err;
                total_len += l;
        }

        d->cached = 1;
        d->size = total_len;
        if (total_len > size ) total_len = size;

        /* read from off 0 */
        memcpy(buf, d->buf, total_len);
        rv = total_len;
err:
        if (f)
                fclose(f);
        free(line);
        free(cpuset);
        free(cg);
        return rv;
}

static uint64_t get_reaper_start_time(pid_t pid)
{
        int ret;
        FILE *f;
        uint64_t starttime;
        /* strlen("/proc/") = 6
         * +
         * LXCFS_NUMSTRLEN64
         * +
         * strlen("/stat") = 5
         * +
         * \0 = 1
         * */
#define __PROC_PID_STAT_LEN (6 + LXCFS_NUMSTRLEN64 + 5 + 1)
        char path[__PROC_PID_STAT_LEN];
        pid_t qpid;

        qpid = lookup_initpid_in_store(pid);
        if (qpid <= 0) {
                /* Caller can check for EINVAL on 0. */
                errno = EINVAL;
                return 0;
        }

        ret = snprintf(path, __PROC_PID_STAT_LEN, "/proc/%d/stat", qpid);
        if (ret < 0 || ret >= __PROC_PID_STAT_LEN) {
                /* Caller can check for EINVAL on 0. */
                errno = EINVAL;
                return 0;
        }

        f = fopen(path, "r");
        if (!f) {
                /* Caller can check for EINVAL on 0. */
                errno = EINVAL;
                return 0;
        }

        /* Note that the *scanf() argument supression requires that length
         * modifiers such as "l" are omitted. Otherwise some compilers will yell
         * at us. It's like telling someone you're not married and then asking
         * if you can bring your wife to the party.
         */
        ret = fscanf(f, "%*d "      /* (1)  pid         %d   */
                        "%*s "      /* (2)  comm        %s   */
                        "%*c "      /* (3)  state       %c   */
                        "%*d "      /* (4)  ppid        %d   */
                        "%*d "      /* (5)  pgrp        %d   */
                        "%*d "      /* (6)  session     %d   */
                        "%*d "      /* (7)  tty_nr      %d   */
                        "%*d "      /* (8)  tpgid       %d   */
                        "%*u "      /* (9)  flags       %u   */
                        "%*u "      /* (10) minflt      %lu  */
                        "%*u "      /* (11) cminflt     %lu  */
                        "%*u "      /* (12) majflt      %lu  */
                        "%*u "      /* (13) cmajflt     %lu  */
                        "%*u "      /* (14) utime       %lu  */
                        "%*u "      /* (15) stime       %lu  */
                        "%*d "      /* (16) cutime      %ld  */
                        "%*d "      /* (17) cstime      %ld  */
                        "%*d "      /* (18) priority    %ld  */
                        "%*d "      /* (19) nice        %ld  */
                        "%*d "      /* (20) num_threads %ld  */
                        "%*d "      /* (21) itrealvalue %ld  */
                        "%" PRIu64, /* (22) starttime   %llu */
                     &starttime);
        if (ret != 1) {
                fclose(f);
                /* Caller can check for EINVAL on 0. */
                errno = EINVAL;
                return 0;
        }

        fclose(f);

        errno = 0;
        return starttime;
}

static uint64_t get_reaper_start_time_in_sec(pid_t pid)
{
        uint64_t clockticks;
        int64_t ticks_per_sec;

        clockticks = get_reaper_start_time(pid);
        if (clockticks == 0 && errno == EINVAL) {
                lxcfs_debug("failed to retrieve start time of pid %d\n", pid);
                return 0;
        }

        ticks_per_sec = sysconf(_SC_CLK_TCK);
        if (ticks_per_sec < 0 && errno == EINVAL) {
                lxcfs_debug(
                    "%s\n",
                    "failed to determine number of clock ticks in a second");
                return 0;
        }

        return (clockticks /= ticks_per_sec);
}

static uint64_t get_reaper_age(pid_t pid)
{
        uint64_t procstart, uptime, procage;

        /* We need to substract the time the process has started since system
         * boot minus the time when the system has started to get the actual
         * reaper age.
         */
        procstart = get_reaper_start_time_in_sec(pid);
        procage = procstart;
        if (procstart > 0) {
                int ret;
                struct timespec spec;

                ret = clock_gettime(CLOCK_BOOTTIME, &spec);
                if (ret < 0)
                        return 0;
                /* We could make this more precise here by using the tv_nsec
                 * field in the timespec struct and convert it to milliseconds
                 * and then create a double for the seconds and milliseconds but
                 * that seems more work than it is worth.
                 */
                uptime = spec.tv_sec;
                procage = uptime - procstart;
        }

        return procage;
}

#define CPUALL_MAX_SIZE (BUF_RESERVE_SIZE / 2)
static int proc_stat_read(char *buf, size_t size, off_t offset,
                struct fuse_file_info *fi)
{
        struct fuse_context *fc = fuse_get_context();
        struct file_info *d = (struct file_info *)fi->fh;
        char *cg;
        char *cpuset = NULL;
        char *line = NULL;
        size_t linelen = 0, total_len = 0, rv = 0;
        int curcpu = -1; /* cpu numbering starts at 0 */
        unsigned long user = 0, nice = 0, system = 0, idle = 0, iowait = 0, irq = 0, softirq = 0, steal = 0, guest = 0, guest_nice = 0;
        unsigned long user_sum = 0, nice_sum = 0, system_sum = 0, idle_sum = 0, iowait_sum = 0,
                                        irq_sum = 0, softirq_sum = 0, steal_sum = 0, guest_sum = 0, guest_nice_sum = 0;
        char cpuall[CPUALL_MAX_SIZE];
        /* reserve for cpu all */
        char *cache = d->buf + CPUALL_MAX_SIZE;
        size_t cache_size = d->buflen - CPUALL_MAX_SIZE;
        FILE *f = NULL;

        if (offset){
                if (offset > d->size)
                        return -EINVAL;
                if (!d->cached)
                        return 0;
                int left = d->size - offset;
                total_len = left > size ? size: left;
                memcpy(buf, d->buf + offset, total_len);
                return total_len;
        }

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        cg = get_pid_cgroup(initpid, "cpuset");
        if (!cg)
                return read_file("/proc/stat", buf, size, d);
        prune_init_slice(cg);

        cpuset = get_cpuset(cg);
        if (!cpuset)
                goto err;

        f = fopen("/proc/stat", "r");
        if (!f)
                goto err;

        //skip first line
        if (getline(&line, &linelen, f) < 0) {
                lxcfs_error("%s\n", "proc_stat_read read first line failed.");
                goto err;
        }

        while (getline(&line, &linelen, f) != -1) {
                ssize_t l;
                int cpu;
                char cpu_char[10]; /* That's a lot of cores */
                char *c;

                if (strlen(line) == 0)
                        continue;
                if (sscanf(line, "cpu%9[^ ]", cpu_char) != 1) {
                        /* not a ^cpuN line containing a number N, just print it */
                        l = snprintf(cache, cache_size, "%s", line);
                        if (l < 0) {
                                perror("Error writing to cache");
                                rv = 0;
                                goto err;
                        }
                        if (l >= cache_size) {
                                lxcfs_error("%s\n", "Internal error: truncated write to cache.");
                                rv = 0;
                                goto err;
                        }
                        cache += l;
                        cache_size -= l;
                        total_len += l;
                        continue;
                }

                if (sscanf(cpu_char, "%d", &cpu) != 1)
                        continue;
                if (!cpu_in_cpuset(cpu, cpuset))
                        continue;
                curcpu ++;

                c = strchr(line, ' ');
                if (!c)
                        continue;
                l = snprintf(cache, cache_size, "cpu%d%s", curcpu, c);
                if (l < 0) {
                        perror("Error writing to cache");
                        rv = 0;
                        goto err;

                }
                if (l >= cache_size) {
                        lxcfs_error("%s\n", "Internal error: truncated write to cache.");
                        rv = 0;
                        goto err;
                }

                cache += l;
                cache_size -= l;
                total_len += l;

                if (sscanf(line, "%*s %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu",
                           &user,
                           &nice,
                           &system,
                           &idle,
                           &iowait,
                           &irq,
                           &softirq,
                           &steal,
                           &guest,
                           &guest_nice) != 10)
                        continue;
                user_sum += user;
                nice_sum += nice;
                system_sum += system;
                idle_sum += idle;
                iowait_sum += iowait;
                irq_sum += irq;
                softirq_sum += softirq;
                steal_sum += steal;
                guest_sum += guest;
                guest_nice_sum += guest_nice;
        }

        cache = d->buf;

        int cpuall_len = snprintf(cpuall, CPUALL_MAX_SIZE, "cpu  %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu\n",
                        user_sum,
                        nice_sum,
                        system_sum,
                        idle_sum,
                        iowait_sum,
                        irq_sum,
                        softirq_sum,
                        steal_sum,
                        guest_sum,
                        guest_nice_sum);
        if (cpuall_len > 0 && cpuall_len < CPUALL_MAX_SIZE) {
                memcpy(cache, cpuall, cpuall_len);
                cache += cpuall_len;
        } else {
                /* shouldn't happen */
                lxcfs_error("proc_stat_read copy cpuall failed, cpuall_len=%d.", cpuall_len);
                cpuall_len = 0;
        }

        memmove(cache, d->buf + CPUALL_MAX_SIZE, total_len);
        total_len += cpuall_len;
        d->cached = 1;
        d->size = total_len;
        if (total_len > size)
                total_len = size;

        memcpy(buf, d->buf, total_len);
        rv = total_len;

err:
        if (f)
                fclose(f);
        free(line);
        free(cpuset);
        free(cg);
        return rv;
}

/* This function retrieves the busy time of a group of tasks by looking at
 * cpuacct.usage. Unfortunately, this only makes sense when the container has
 * been given it's own cpuacct cgroup. If not, this function will take the busy
 * time of all other taks that do not actually belong to the container into
 * account as well. If someone has a clever solution for this please send a
 * patch!
 */
static unsigned long get_reaper_busy(pid_t task)
{
        pid_t initpid = lookup_initpid_in_store(task);
        char *cgroup = NULL, *usage_str = NULL;
        unsigned long usage = 0;

        if (initpid <= 0)
                return 0;

        cgroup = get_pid_cgroup(initpid, "cpuacct");
        if (!cgroup)
                goto out;
        prune_init_slice(cgroup);
        if (!cgfs_get_value("cpuacct", cgroup, "cpuacct.usage", &usage_str))
                goto out;
        usage = strtoul(usage_str, NULL, 10);
        usage /= 1000000000;

out:
        free(cgroup);
        free(usage_str);
        return usage;
}

#if RELOADTEST
void iwashere(void)
{
        int fd;

        fd = creat("/tmp/lxcfs-iwashere", 0644);
        if (fd >= 0)
                close(fd);
}
#endif

/*
 * We read /proc/uptime and reuse its second field.
 * For the first field, we use the mtime for the reaper for
 * the calling pid as returned by getreaperage
 */
static int proc_uptime_read(char *buf, size_t size, off_t offset,
                struct fuse_file_info *fi)
{
        struct fuse_context *fc = fuse_get_context();
        struct file_info *d = (struct file_info *)fi->fh;
        unsigned long int busytime = get_reaper_busy(fc->pid);
        char *cache = d->buf;
        ssize_t total_len = 0;
        uint64_t idletime, reaperage;

#if RELOADTEST
        iwashere();
#endif

        if (offset){
                if (!d->cached)
                        return 0;
                if (offset > d->size)
                        return -EINVAL;
                int left = d->size - offset;
                total_len = left > size ? size: left;
                memcpy(buf, cache + offset, total_len);
                return total_len;
        }

        reaperage = get_reaper_age(fc->pid);
        /* To understand why this is done, please read the comment to the
         * get_reaper_busy() function.
         */
        idletime = reaperage;
        if (reaperage >= busytime)
                idletime = reaperage - busytime;

        total_len = snprintf(d->buf, d->buflen, "%"PRIu64".00 %"PRIu64".00\n", reaperage, idletime);
        if (total_len < 0 || total_len >=  d->buflen){
                lxcfs_error("%s\n", "failed to write to cache");
                return 0;
        }

        d->size = (int)total_len;
        d->cached = 1;

        if (total_len > size) total_len = size;

        memcpy(buf, d->buf, total_len);
        return total_len;
}

static int proc_diskstats_read(char *buf, size_t size, off_t offset,
                struct fuse_file_info *fi)
{
        char dev_name[72];
        struct fuse_context *fc = fuse_get_context();
        struct file_info *d = (struct file_info *)fi->fh;
        char *cg;
        char *io_serviced_str = NULL, *io_merged_str = NULL, *io_service_bytes_str = NULL,
                        *io_wait_time_str = NULL, *io_service_time_str = NULL;
        unsigned long read = 0, write = 0;
        unsigned long read_merged = 0, write_merged = 0;
        unsigned long read_sectors = 0, write_sectors = 0;
        unsigned long read_ticks = 0, write_ticks = 0;
        unsigned long ios_pgr = 0, tot_ticks = 0, rq_ticks = 0;
        unsigned long rd_svctm = 0, wr_svctm = 0, rd_wait = 0, wr_wait = 0;
        char *cache = d->buf;
        size_t cache_size = d->buflen;
        char *line = NULL;
        size_t linelen = 0, total_len = 0, rv = 0;
        unsigned int major = 0, minor = 0;
        int i = 0;
        FILE *f = NULL;

        if (offset){
                if (offset > d->size)
                        return -EINVAL;
                if (!d->cached)
                        return 0;
                int left = d->size - offset;
                total_len = left > size ? size: left;
                memcpy(buf, cache + offset, total_len);
                return total_len;
        }

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        cg = get_pid_cgroup(initpid, "blkio");
        if (!cg)
                return read_file("/proc/diskstats", buf, size, d);
        prune_init_slice(cg);

        if (!cgfs_get_value("blkio", cg, "blkio.io_serviced_recursive", &io_serviced_str))
                goto err;
        if (!cgfs_get_value("blkio", cg, "blkio.io_merged_recursive", &io_merged_str))
                goto err;
        if (!cgfs_get_value("blkio", cg, "blkio.io_service_bytes_recursive", &io_service_bytes_str))
                goto err;
        if (!cgfs_get_value("blkio", cg, "blkio.io_wait_time_recursive", &io_wait_time_str))
                goto err;
        if (!cgfs_get_value("blkio", cg, "blkio.io_service_time_recursive", &io_service_time_str))
                goto err;


        f = fopen("/proc/diskstats", "r");
        if (!f)
                goto err;

        while (getline(&line, &linelen, f) != -1) {
                ssize_t l;
                char lbuf[256];

                i = sscanf(line, "%u %u %71s", &major, &minor, dev_name);
                if (i != 3)
                        continue;

                get_blkio_io_value(io_serviced_str, major, minor, "Read", &read);
                get_blkio_io_value(io_serviced_str, major, minor, "Write", &write);
                get_blkio_io_value(io_merged_str, major, minor, "Read", &read_merged);
                get_blkio_io_value(io_merged_str, major, minor, "Write", &write_merged);
                get_blkio_io_value(io_service_bytes_str, major, minor, "Read", &read_sectors);
                read_sectors = read_sectors/512;
                get_blkio_io_value(io_service_bytes_str, major, minor, "Write", &write_sectors);
                write_sectors = write_sectors/512;

                get_blkio_io_value(io_service_time_str, major, minor, "Read", &rd_svctm);
                rd_svctm = rd_svctm/1000000;
                get_blkio_io_value(io_wait_time_str, major, minor, "Read", &rd_wait);
                rd_wait = rd_wait/1000000;
                read_ticks = rd_svctm + rd_wait;

                get_blkio_io_value(io_service_time_str, major, minor, "Write", &wr_svctm);
                wr_svctm =  wr_svctm/1000000;
                get_blkio_io_value(io_wait_time_str, major, minor, "Write", &wr_wait);
                wr_wait =  wr_wait/1000000;
                write_ticks = wr_svctm + wr_wait;

                get_blkio_io_value(io_service_time_str, major, minor, "Total", &tot_ticks);
                tot_ticks =  tot_ticks/1000000;

                memset(lbuf, 0, 256);
                if (read || write || read_merged || write_merged || read_sectors || write_sectors || read_ticks || write_ticks)
                        snprintf(lbuf, 256, "%u       %u %s %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu %lu\n",
                                major, minor, dev_name, read, read_merged, read_sectors, read_ticks,
                                write, write_merged, write_sectors, write_ticks, ios_pgr, tot_ticks, rq_ticks);
                else
                        continue;

                l = snprintf(cache, cache_size, "%s", lbuf);
                if (l < 0) {
                        perror("Error writing to fuse buf");
                        rv = 0;
                        goto err;
                }
                if (l >= cache_size) {
                        lxcfs_error("%s\n", "Internal error: truncated write to cache.");
                        rv = 0;
                        goto err;
                }
                cache += l;
                cache_size -= l;
                total_len += l;
        }

        d->cached = 1;
        d->size = total_len;
        if (total_len > size ) total_len = size;
        memcpy(buf, d->buf, total_len);

        rv = total_len;
err:
        free(cg);
        if (f)
                fclose(f);
        free(line);
        free(io_serviced_str);
        free(io_merged_str);
        free(io_service_bytes_str);
        free(io_wait_time_str);
        free(io_service_time_str);
        return rv;
}

static int proc_swaps_read(char *buf, size_t size, off_t offset,
                struct fuse_file_info *fi)
{
        struct fuse_context *fc = fuse_get_context();
        struct file_info *d = (struct file_info *)fi->fh;
        char *cg = NULL;
        char *memswlimit_str = NULL, *memlimit_str = NULL, *memusage_str = NULL, *memswusage_str = NULL;
        unsigned long memswlimit = 0, memlimit = 0, memusage = 0, memswusage = 0, swap_total = 0, swap_free = 0;
        ssize_t total_len = 0, rv = 0;
        ssize_t l = 0;
        char *cache = d->buf;

        if (offset) {
                if (offset > d->size)
                        return -EINVAL;
                if (!d->cached)
                        return 0;
                int left = d->size - offset;
                total_len = left > size ? size: left;
                memcpy(buf, cache + offset, total_len);
                return total_len;
        }

        pid_t initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        cg = get_pid_cgroup(initpid, "memory");
        if (!cg)
                return read_file("/proc/swaps", buf, size, d);
        prune_init_slice(cg);

        memlimit = get_min_memlimit(cg, "memory.limit_in_bytes");

        if (!cgfs_get_value("memory", cg, "memory.usage_in_bytes", &memusage_str))
                goto err;

        memusage = strtoul(memusage_str, NULL, 10);

        if (cgfs_get_value("memory", cg, "memory.memsw.usage_in_bytes", &memswusage_str) &&
            cgfs_get_value("memory", cg, "memory.memsw.limit_in_bytes", &memswlimit_str)) {

                memswlimit = get_min_memlimit(cg, "memory.memsw.limit_in_bytes");
                memswusage = strtoul(memswusage_str, NULL, 10);

                swap_total = (memswlimit - memlimit) / 1024;
                swap_free = (memswusage - memusage) / 1024;
        }

        total_len = snprintf(d->buf, d->size, "Filename\t\t\t\tType\t\tSize\tUsed\tPriority\n");

        /* When no mem + swap limit is specified or swapaccount=0*/
        if (!memswlimit) {
                char *line = NULL;
                size_t linelen = 0;
                FILE *f = fopen("/proc/meminfo", "r");

                if (!f)
                        goto err;

                while (getline(&line, &linelen, f) != -1) {
                        if (startswith(line, "SwapTotal:")) {
                                sscanf(line, "SwapTotal:      %8lu kB", &swap_total);
                        } else if (startswith(line, "SwapFree:")) {
                                sscanf(line, "SwapFree:      %8lu kB", &swap_free);
                        }
                }

                free(line);
                fclose(f);
        }

        if (swap_total > 0) {
                l = snprintf(d->buf + total_len, d->size - total_len,
                                "none%*svirtual\t\t%lu\t%lu\t0\n", 36, " ",
                                swap_total, swap_free);
                total_len += l;
        }

        if (total_len < 0 || l < 0) {
                perror("Error writing to cache");
                rv = 0;
                goto err;
        }

        d->cached = 1;
        d->size = (int)total_len;

        if (total_len > size) total_len = size;
        memcpy(buf, d->buf, total_len);
        rv = total_len;

err:
        free(cg);
        free(memswlimit_str);
        free(memlimit_str);
        free(memusage_str);
        free(memswusage_str);
        return rv;
}
/*
 * Find the process pid from cgroup path.
 * eg:from /sys/fs/cgroup/cpu/docker/containerid/cgroup.procs to find the process pid.
 * @pid_buf : put pid to pid_buf.
 * @dpath : the path of cgroup. eg: /docker/containerid or /docker/containerid/child-cgroup ...
 * @depth : the depth of cgroup in container.
 * @sum : return the number of pid.
 * @cfd : the file descriptor of the mounted cgroup. eg: /sys/fs/cgroup/cpu
 */
static int calc_pid(char ***pid_buf, char *dpath, int depth, int sum, int cfd)
{
        DIR *dir;
        int fd;
        struct dirent *file;
        FILE *f = NULL;
        size_t linelen = 0;
        char *line = NULL;
        int pd;
        char *path_dir, *path;
        char **pid;

        /* path = dpath + "/cgroup.procs" + /0 */
        do {
                path = malloc(strlen(dpath) + 20);
        } while (!path);

        strcpy(path, dpath);
        fd = openat(cfd, path, O_RDONLY);
        if (fd < 0)
                goto out;

        dir = fdopendir(fd);
        if (dir == NULL) {
                close(fd);
                goto out;
        }

        while (((file = readdir(dir)) != NULL) && depth > 0) {
                if (strncmp(file->d_name, ".", 1) == 0)
                        continue;
                if (strncmp(file->d_name, "..", 1) == 0)
                        continue;
                if (file->d_type == DT_DIR) {
                        /* path + '/' + d_name +/0 */
                        do {
                                path_dir = malloc(strlen(path) + 2 + sizeof(file->d_name));
                        } while (!path_dir);
                        strcpy(path_dir, path);
                        strcat(path_dir, "/");
                        strcat(path_dir, file->d_name);
                        pd = depth - 1;
                        sum = calc_pid(pid_buf, path_dir, pd, sum, cfd);
                        free(path_dir);
                }
        }
        closedir(dir);

        strcat(path, "/cgroup.procs");
        fd = openat(cfd, path, O_RDONLY);
        if (fd < 0)
                goto out;

        f = fdopen(fd, "r");
        if (!f) {
                close(fd);
                goto out;
        }

        while (getline(&line, &linelen, f) != -1) {
                do {
                        pid = realloc(*pid_buf, sizeof(char *) * (sum + 1));
                } while (!pid);
                *pid_buf = pid;
                do {
                        *(*pid_buf + sum) = malloc(strlen(line) + 1);
                } while (*(*pid_buf + sum) == NULL);
                strcpy(*(*pid_buf + sum), line);
                sum++;
        }
        fclose(f);
out:
        free(path);
        return sum;
}
/*
 * calc_load calculates the load according to the following formula:
 * load1 = load0 * exp + active * (1 - exp)
 *
 * @load1: the new loadavg.
 * @load0: the former loadavg.
 * @active: the total number of running pid at this moment.
 * @exp: the fixed-point defined in the beginning.
 */
static unsigned long
calc_load(unsigned long load, unsigned long exp, unsigned long active)
{
        unsigned long newload;

        active = active > 0 ? active * FIXED_1 : 0;
        newload = load * exp + active * (FIXED_1 - exp);
        if (active >= load)
                newload += FIXED_1 - 1;

        return newload / FIXED_1;
}

/*
 * Return 0 means that container p->cg is closed.
 * Return -1 means that error occurred in refresh.
 * Positive num equals the total number of pid.
 */
static int refresh_load(struct load_node *p, char *path)
{
        FILE *f = NULL;
        char **idbuf;
        char proc_path[256];
        int i, ret, run_pid = 0, total_pid = 0, last_pid = 0;
        char *line = NULL;
        size_t linelen = 0;
        int sum, length;
        DIR *dp;
        struct dirent *file;

        do {
                idbuf = malloc(sizeof(char *));
        } while (!idbuf);
        sum = calc_pid(&idbuf, path, DEPTH_DIR, 0, p->cfd);
        /*  normal exit  */
        if (sum == 0)
                goto out;

        for (i = 0; i < sum; i++) {
                /*clean up '\n' */
                length = strlen(idbuf[i])-1;
                idbuf[i][length] = '\0';
                ret = snprintf(proc_path, 256, "/proc/%s/task", idbuf[i]);
                if (ret < 0 || ret > 255) {
                        lxcfs_error("%s\n", "snprintf() failed in refresh_load.");
                        i = sum;
                        sum = -1;
                        goto err_out;
                }

                dp = opendir(proc_path);
                if (!dp) {
                        lxcfs_error("%s\n", "Open proc_path failed in refresh_load.");
                        continue;
                }
                while ((file = readdir(dp)) != NULL) {
                        if (strncmp(file->d_name, ".", 1) == 0)
                                continue;
                        if (strncmp(file->d_name, "..", 1) == 0)
                                continue;
                        total_pid++;
                        /* We make the biggest pid become last_pid.*/
                        ret = atof(file->d_name);
                        last_pid = (ret > last_pid) ? ret : last_pid;

                        ret = snprintf(proc_path, 256, "/proc/%s/task/%s/status", idbuf[i], file->d_name);
                        if (ret < 0 || ret > 255) {
                                lxcfs_error("%s\n", "snprintf() failed in refresh_load.");
                                i = sum;
                                sum = -1;
                                closedir(dp);
                                goto err_out;
                        }
                        f = fopen(proc_path, "r");
                        if (f != NULL) {
                                while (getline(&line, &linelen, f) != -1) {
                                        /* Find State */
                                        if ((line[0] == 'S') && (line[1] == 't'))
                                                break;
                                }
                        if ((line[7] == 'R') || (line[7] == 'D'))
                                run_pid++;
                        fclose(f);
                        }
                }
                closedir(dp);
        }
        /*Calculate the loadavg.*/
        p->avenrun[0] = calc_load(p->avenrun[0], EXP_1, run_pid);
        p->avenrun[1] = calc_load(p->avenrun[1], EXP_5, run_pid);
        p->avenrun[2] = calc_load(p->avenrun[2], EXP_15, run_pid);
        p->run_pid = run_pid;
        p->total_pid = total_pid;
        p->last_pid = last_pid;

        free(line);
err_out:        
        for (; i > 0; i--)
                free(idbuf[i-1]);
out:
        free(idbuf);
        return sum;
}
/*
 * Traverse the hash table and update it.
 */
void *load_begin(void *arg)
{

        char *path = NULL;
        int i, sum, length, ret;
        struct load_node *f;
        int first_node;
        clock_t time1, time2;

        while (1) {
                time1 = clock();
                for (i = 0; i < LOAD_SIZE; i++) {
                        pthread_mutex_lock(&load_hash[i].lock);
                        if (load_hash[i].next == NULL) {
                                pthread_mutex_unlock(&load_hash[i].lock);
                                continue;
                        }
                        f = load_hash[i].next;
                        first_node = 1;
                        while (f) {
                                length = strlen(f->cg) + 2;
                                do {
                                        /* strlen(f->cg) + '.' or '' + \0 */
                                        path = malloc(length);
                                } while (!path);

                                ret = snprintf(path, length, "%s%s", *(f->cg) == '/' ? "." : "", f->cg);
                                if (ret < 0 || ret > length - 1) {
                                        /* snprintf failed, ignore the node.*/
                                        lxcfs_error("Refresh node %s failed for snprintf().\n", f->cg);
                                        goto out;
                                }
                                sum = refresh_load(f, path);
                                if (sum == 0) {
                                        f = del_node(f, i);
                                } else {
out:                                    f = f->next;
                                }
                                free(path);
                                /* load_hash[i].lock locks only on the first node.*/
                                if (first_node == 1) {
                                        first_node = 0;
                                        pthread_mutex_unlock(&load_hash[i].lock);
                                }
                        }
                }
                time2 = clock();
                usleep(FLUSH_TIME * 1000000 - (int)((time2 - time1) * 1000000 / CLOCKS_PER_SEC));
        }
}

static int proc_loadavg_read(char *buf, size_t size, off_t offset,
                struct fuse_file_info *fi)
{
        struct fuse_context *fc = fuse_get_context();
        struct file_info *d = (struct file_info *)fi->fh;
        pid_t initpid;
        char *cg;
        size_t total_len = 0;
        char *cache = d->buf;
        struct load_node *n;
        int hash;
        int cfd;
        unsigned long a, b, c;

        if (offset) {
                if (offset > d->size)
                        return -EINVAL;
                if (!d->cached)
                        return 0;
                int left = d->size - offset;
                total_len = left > size ? size : left;
                memcpy(buf, cache + offset, total_len);
                return total_len;
        }
        if (!loadavg)
                return read_file("/proc/loadavg", buf, size, d);

        initpid = lookup_initpid_in_store(fc->pid);
        if (initpid <= 0)
                initpid = fc->pid;
        cg = get_pid_cgroup(initpid, "cpu");
        if (!cg)
                return read_file("/proc/loadavg", buf, size, d);

        prune_init_slice(cg);
        hash = calc_hash(cg);
        n = locate_node(cg, hash);

        /* First time */
        if (n == NULL) {
                if (!find_mounted_controller("cpu", &cfd)) {
                        /*
                         * In locate_node() above, pthread_rwlock_unlock() isn't used
                         * because delete is not allowed before read has ended.
                         */
                        pthread_rwlock_unlock(&load_hash[hash].rdlock);
                        return 0;
                }
                do {
                        n = malloc(sizeof(struct load_node));
                } while (!n);

                do {
                        n->cg = malloc(strlen(cg)+1);
                } while (!n->cg);
                strcpy(n->cg, cg);
                n->avenrun[0] = 0;
                n->avenrun[1] = 0;
                n->avenrun[2] = 0;
                n->run_pid = 0;
                n->total_pid = 1;
                n->last_pid = initpid;
                n->cfd = cfd;
                insert_node(&n, hash);
        }
        a = n->avenrun[0] + (FIXED_1/200);
        b = n->avenrun[1] + (FIXED_1/200);
        c = n->avenrun[2] + (FIXED_1/200);
        total_len = snprintf(d->buf, d->buflen, "%lu.%02lu %lu.%02lu %lu.%02lu %d/%d %d\n",
                LOAD_INT(a), LOAD_FRAC(a),
                LOAD_INT(b), LOAD_FRAC(b),
                LOAD_INT(c), LOAD_FRAC(c),
                n->run_pid, n->total_pid, n->last_pid);
        pthread_rwlock_unlock(&load_hash[hash].rdlock);
        if (total_len < 0 || total_len >=  d->buflen) {
                lxcfs_error("%s\n", "Failed to write to cache");
                return 0;
        }
        d->size = (int)total_len;
        d->cached = 1;

        if (total_len > size)
                total_len = size;
        memcpy(buf, d->buf, total_len);
        return total_len;
}
/* Return a positive number on success, return 0 on failure.*/
pthread_t load_daemon(int load_use)
{
        int ret;
        pthread_t pid;

        ret = init_load();
        if (ret == -1) {
                lxcfs_error("%s\n", "Initialize hash_table fails in load_daemon!");
                return 0;
        }
        ret = pthread_create(&pid, NULL, load_begin, NULL);
        if (ret != 0) {
                lxcfs_error("%s\n", "Create pthread fails in load_daemon!");
                load_free();
                return 0;
        }
        /* use loadavg, here loadavg = 1*/
        loadavg = load_use;
        return pid;
}

static off_t get_procfile_size(const char *which)
{
        FILE *f = fopen(which, "r");
        char *line = NULL;
        size_t len = 0;
        ssize_t sz, answer = 0;
        if (!f)
                return 0;

        while ((sz = getline(&line, &len, f)) != -1)
                answer += sz;
        fclose (f);
        free(line);

        return answer;
}

int proc_getattr(const char *path, struct stat *sb)
{
        struct timespec now;

        memset(sb, 0, sizeof(struct stat));
        if (clock_gettime(CLOCK_REALTIME, &now) < 0)
                return -EINVAL;
        sb->st_uid = sb->st_gid = 0;
        sb->st_atim = sb->st_mtim = sb->st_ctim = now;
        if (strcmp(path, "/proc") == 0) {
                sb->st_mode = S_IFDIR | 00555;
                sb->st_nlink = 2;
                return 0;
        }
        if (strcmp(path, "/proc/meminfo") == 0 ||
                        strcmp(path, "/proc/cpuinfo") == 0 ||
                        strcmp(path, "/proc/uptime") == 0 ||
                        strcmp(path, "/proc/stat") == 0 ||
                        strcmp(path, "/proc/diskstats") == 0 ||
                        strcmp(path, "/proc/swaps") == 0 ||
                        strcmp(path, "/proc/loadavg") == 0) {
                sb->st_size = 0;
                sb->st_mode = S_IFREG | 00444;
                sb->st_nlink = 1;
                return 0;
        }

        return -ENOENT;
}

int proc_readdir(const char *path, void *buf, fuse_fill_dir_t filler, off_t offset,
                struct fuse_file_info *fi)
{
        if (filler(buf, ".", NULL, 0) != 0 ||
            filler(buf, "..", NULL, 0) != 0 ||
            filler(buf, "cpuinfo", NULL, 0) != 0 ||
            filler(buf, "meminfo", NULL, 0) != 0 ||
            filler(buf, "stat", NULL, 0) != 0 ||
            filler(buf, "uptime", NULL, 0) != 0 ||
            filler(buf, "diskstats", NULL, 0) != 0 ||
            filler(buf, "swaps", NULL, 0) != 0   ||
            filler(buf, "loadavg", NULL, 0) != 0)
                return -EINVAL;
        return 0;
}

int proc_open(const char *path, struct fuse_file_info *fi)
{
        int type = -1;
        struct file_info *info;

        if (strcmp(path, "/proc/meminfo") == 0)
                type = LXC_TYPE_PROC_MEMINFO;
        else if (strcmp(path, "/proc/cpuinfo") == 0)
                type = LXC_TYPE_PROC_CPUINFO;
        else if (strcmp(path, "/proc/uptime") == 0)
                type = LXC_TYPE_PROC_UPTIME;
        else if (strcmp(path, "/proc/stat") == 0)
                type = LXC_TYPE_PROC_STAT;
        else if (strcmp(path, "/proc/diskstats") == 0)
                type = LXC_TYPE_PROC_DISKSTATS;
        else if (strcmp(path, "/proc/swaps") == 0)
                type = LXC_TYPE_PROC_SWAPS;
        else if (strcmp(path, "/proc/loadavg") == 0)
                type = LXC_TYPE_PROC_LOADAVG;
        if (type == -1)
                return -ENOENT;

        info = malloc(sizeof(*info));
        if (!info)
                return -ENOMEM;

        memset(info, 0, sizeof(*info));
        info->type = type;

        info->buflen = get_procfile_size(path) + BUF_RESERVE_SIZE;
        do {
                info->buf = malloc(info->buflen);
        } while (!info->buf);
        memset(info->buf, 0, info->buflen);
        /* set actual size to buffer size */
        info->size = info->buflen;

        fi->fh = (unsigned long)info;
        return 0;
}

int proc_access(const char *path, int mask)
{
        if (strcmp(path, "/proc") == 0 && access(path, R_OK) == 0)
                return 0;

        /* these are all read-only */
        if ((mask & ~R_OK) != 0)
                return -EACCES;
        return 0;
}

int proc_release(const char *path, struct fuse_file_info *fi)
{
        do_release_file_info(fi);
        return 0;
}

int proc_read(const char *path, char *buf, size_t size, off_t offset,
                struct fuse_file_info *fi)
{
        struct file_info *f = (struct file_info *) fi->fh;

        switch (f->type) {
        case LXC_TYPE_PROC_MEMINFO:
                return proc_meminfo_read(buf, size, offset, fi);
        case LXC_TYPE_PROC_CPUINFO:
                return proc_cpuinfo_read(buf, size, offset, fi);
        case LXC_TYPE_PROC_UPTIME:
                return proc_uptime_read(buf, size, offset, fi);
        case LXC_TYPE_PROC_STAT:
                return proc_stat_read(buf, size, offset, fi);
        case LXC_TYPE_PROC_DISKSTATS:
                return proc_diskstats_read(buf, size, offset, fi);
        case LXC_TYPE_PROC_SWAPS:
                return proc_swaps_read(buf, size, offset, fi);
        case LXC_TYPE_PROC_LOADAVG:
                return proc_loadavg_read(buf, size, offset, fi);
        default:
                return -EINVAL;
        }
}

/*
 * Functions needed to setup cgroups in the __constructor__.
 */

static bool mkdir_p(const char *dir, mode_t mode)
{
        const char *tmp = dir;
        const char *orig = dir;
        char *makeme;

        do {
                dir = tmp + strspn(tmp, "/");
                tmp = dir + strcspn(dir, "/");
                makeme = strndup(orig, dir - orig);
                if (!makeme)
                        return false;
                if (mkdir(makeme, mode) && errno != EEXIST) {
                        lxcfs_error("Failed to create directory '%s': %s.\n",
                                makeme, strerror(errno));
                        free(makeme);
                        return false;
                }
                free(makeme);
        } while(tmp != dir);

        return true;
}

static bool umount_if_mounted(void)
{
        if (umount2(BASEDIR, MNT_DETACH) < 0 && errno != EINVAL) {
                lxcfs_error("Failed to unmount %s: %s.\n", BASEDIR, strerror(errno));
                return false;
        }
        return true;
}

/* __typeof__ should be safe to use with all compilers. */
typedef __typeof__(((struct statfs *)NULL)->f_type) fs_type_magic;
static bool has_fs_type(const struct statfs *fs, fs_type_magic magic_val)
{
        return (fs->f_type == (fs_type_magic)magic_val);
}

/*
 * looking at fs/proc_namespace.c, it appears we can
 * actually expect the rootfs entry to very specifically contain
 * " - rootfs rootfs "
 * IIUC, so long as we've chrooted so that rootfs is not our root,
 * the rootfs entry should always be skipped in mountinfo contents.
 */
static bool is_on_ramfs(void)
{
        FILE *f;
        char *p, *p2;
        char *line = NULL;
        size_t len = 0;
        int i;

        f = fopen("/proc/self/mountinfo", "r");
        if (!f)
                return false;

        while (getline(&line, &len, f) != -1) {
                for (p = line, i = 0; p && i < 4; i++)
                        p = strchr(p + 1, ' ');
                if (!p)
                        continue;
                p2 = strchr(p + 1, ' ');
                if (!p2)
                        continue;
                *p2 = '\0';
                if (strcmp(p + 1, "/") == 0) {
                        // this is '/'.  is it the ramfs?
                        p = strchr(p2 + 1, '-');
                        if (p && strncmp(p, "- rootfs rootfs ", 16) == 0) {
                                free(line);
                                fclose(f);
                                return true;
                        }
                }
        }
        free(line);
        fclose(f);
        return false;
}

static int pivot_enter()
{
        int ret = -1, oldroot = -1, newroot = -1;

        oldroot = open("/", O_DIRECTORY | O_RDONLY);
        if (oldroot < 0) {
                lxcfs_error("%s\n", "Failed to open old root for fchdir.");
                return ret;
        }

        newroot = open(ROOTDIR, O_DIRECTORY | O_RDONLY);
        if (newroot < 0) {
                lxcfs_error("%s\n", "Failed to open new root for fchdir.");
                goto err;
        }

        /* change into new root fs */
        if (fchdir(newroot) < 0) {
                lxcfs_error("Failed to change directory to new rootfs: %s.\n", ROOTDIR);
                goto err;
        }

        /* pivot_root into our new root fs */
        if (pivot_root(".", ".") < 0) {
                lxcfs_error("pivot_root() syscall failed: %s.\n", strerror(errno));
                goto err;
        }

        /*
         * At this point the old-root is mounted on top of our new-root.
         * To unmounted it we must not be chdir'd into it, so escape back
         * to the old-root.
         */
        if (fchdir(oldroot) < 0) {
                lxcfs_error("%s\n", "Failed to enter old root.");
                goto err;
        }

        if (umount2(".", MNT_DETACH) < 0) {
                lxcfs_error("%s\n", "Failed to detach old root.");
                goto err;
        }

        if (fchdir(newroot) < 0) {
                lxcfs_error("%s\n", "Failed to re-enter new root.");
                goto err;
        }

        ret = 0;

err:
        if (oldroot > 0)
                close(oldroot);
        if (newroot > 0)
                close(newroot);

        return ret;
}

static int chroot_enter()
{
        if (mount(ROOTDIR, "/", NULL, MS_REC | MS_BIND, NULL)) {
                lxcfs_error("Failed to recursively bind-mount %s into /.", ROOTDIR);
                return -1;
        }

        if (chroot(".") < 0) {
                lxcfs_error("Call to chroot() failed: %s.\n", strerror(errno));
                return -1;
        }

        if (chdir("/") < 0) {
                lxcfs_error("Failed to change directory: %s.\n", strerror(errno));
                return -1;
        }

        return 0;
}

static int permute_and_enter(void)
{
        struct statfs sb;

        if (statfs("/", &sb) < 0) {
                lxcfs_error("%s\n", "Could not stat / mountpoint.");
                return -1;
        }

        /* has_fs_type() is not reliable. When the ramfs is a tmpfs it will
         * likely report TMPFS_MAGIC. Hence, when it reports no we still check
         * /proc/1/mountinfo. */
        if (has_fs_type(&sb, RAMFS_MAGIC) || is_on_ramfs())
                return chroot_enter();

        if (pivot_enter() < 0) {
                lxcfs_error("%s\n", "Could not perform pivot root.");
                return -1;
        }

        return 0;
}

/* Prepare our new clean root. */
static int permute_prepare(void)
{
        if (mkdir(ROOTDIR, 0700) < 0 && errno != EEXIST) {
                lxcfs_error("%s\n", "Failed to create directory for new root.");
                return -1;
        }

        if (mount("/", ROOTDIR, NULL, MS_BIND, 0) < 0) {
                lxcfs_error("Failed to bind-mount / for new root: %s.\n", strerror(errno));
                return -1;
        }

        if (mount(RUNTIME_PATH, ROOTDIR RUNTIME_PATH, NULL, MS_BIND, 0) < 0) {
                lxcfs_error("Failed to bind-mount /run into new root: %s.\n", strerror(errno));
                return -1;
        }

        if (mount(BASEDIR, ROOTDIR BASEDIR, NULL, MS_REC | MS_MOVE, 0) < 0) {
                printf("Failed to move " BASEDIR " into new root: %s.\n", strerror(errno));
                return -1;
        }

        return 0;
}

/* Calls chroot() on ramfs, pivot_root() in all other cases. */
static bool permute_root(void)
{
        /* Prepare new root. */
        if (permute_prepare() < 0)
                return false;

        /* Pivot into new root. */
        if (permute_and_enter() < 0)
                return false;

        return true;
}

static int preserve_mnt_ns(int pid)
{
        int ret;
        size_t len = sizeof("/proc/") + 21 + sizeof("/ns/mnt");
        char path[len];

        ret = snprintf(path, len, "/proc/%d/ns/mnt", pid);
        if (ret < 0 || (size_t)ret >= len)
                return -1;

        return open(path, O_RDONLY | O_CLOEXEC);
}

static bool cgfs_prepare_mounts(void)
{
        if (!mkdir_p(BASEDIR, 0700)) {
                lxcfs_error("%s\n", "Failed to create lxcfs cgroup mountpoint.");
                return false;
        }

        if (!umount_if_mounted()) {
                lxcfs_error("%s\n", "Failed to clean up old lxcfs cgroup mountpoint.");
                return false;
        }

        if (unshare(CLONE_NEWNS) < 0) {
                lxcfs_error("Failed to unshare mount namespace: %s.\n", strerror(errno));
                return false;
        }

        cgroup_mount_ns_fd = preserve_mnt_ns(getpid());
        if (cgroup_mount_ns_fd < 0) {
                lxcfs_error("Failed to preserve mount namespace: %s.\n", strerror(errno));
                return false;
        }

        if (mount(NULL, "/", NULL, MS_REC | MS_PRIVATE, 0) < 0) {
                lxcfs_error("Failed to remount / private: %s.\n", strerror(errno));
                return false;
        }

        if (mount("tmpfs", BASEDIR, "tmpfs", 0, "size=100000,mode=700") < 0) {
                lxcfs_error("%s\n", "Failed to mount tmpfs over lxcfs cgroup mountpoint.");
                return false;
        }

        return true;
}

static bool cgfs_mount_hierarchies(void)
{
        char *target;
        size_t clen, len;
        int i, ret;

        for (i = 0; i < num_hierarchies; i++) {
                char *controller = hierarchies[i];

                clen = strlen(controller);
                len = strlen(BASEDIR) + clen + 2;
                target = malloc(len);
                if (!target)
                        return false;

                ret = snprintf(target, len, "%s/%s", BASEDIR, controller);
                if (ret < 0 || ret >= len) {
                        free(target);
                        return false;
                }
                if (mkdir(target, 0755) < 0 && errno != EEXIST) {
                        free(target);
                        return false;
                }
                if (!strcmp(controller, "unified"))
                        ret = mount("none", target, "cgroup2", 0, NULL);
                else
                        ret = mount(controller, target, "cgroup", 0, controller);
                if (ret < 0) {
                        lxcfs_error("Failed mounting cgroup %s: %s\n", controller, strerror(errno));
                        free(target);
                        return false;
                }

                fd_hierarchies[i] = open(target, O_DIRECTORY);
                if (fd_hierarchies[i] < 0) {
                        free(target);
                        return false;
                }
                free(target);
        }
        return true;
}

static bool cgfs_setup_controllers(void)
{
        if (!cgfs_prepare_mounts())
                return false;

        if (!cgfs_mount_hierarchies()) {
                lxcfs_error("%s\n", "Failed to set up private lxcfs cgroup mounts.");
                return false;
        }

        if (!permute_root())
                return false;

        return true;
}

static void __attribute__((constructor)) collect_and_mount_subsystems(void)
{
        FILE *f;
        char *cret, *line = NULL;
        char cwd[MAXPATHLEN];
        size_t len = 0;
        int i, init_ns = -1;
        bool found_unified = false;

        if ((f = fopen("/proc/self/cgroup", "r")) == NULL) {
                lxcfs_error("Error opening /proc/self/cgroup: %s\n", strerror(errno));
                return;
        }

        while (getline(&line, &len, f) != -1) {
                char *idx, *p, *p2;

                p = strchr(line, ':');
                if (!p)
                        goto out;
                idx = line;
                *(p++) = '\0';

                p2 = strrchr(p, ':');
                if (!p2)
                        goto out;
                *p2 = '\0';

                /* With cgroupv2 /proc/self/cgroup can contain entries of the
                 * form: 0::/ This will cause lxcfs to fail the cgroup mounts
                 * because it parses out the empty string "" and later on passes
                 * it to mount(). Let's skip such entries.
                 */
                if (!strcmp(p, "") && !strcmp(idx, "0") && !found_unified) {
                        found_unified = true;
                        p = "unified";
                }

                if (!store_hierarchy(line, p))
                        goto out;
        }

        /* Preserve initial namespace. */
        init_ns = preserve_mnt_ns(getpid());
        if (init_ns < 0) {
                lxcfs_error("%s\n", "Failed to preserve initial mount namespace.");
                goto out;
        }

        fd_hierarchies = malloc(sizeof(int) * num_hierarchies);
        if (!fd_hierarchies) {
                lxcfs_error("%s\n", strerror(errno));
                goto out;
        }

        for (i = 0; i < num_hierarchies; i++)
                fd_hierarchies[i] = -1;

        cret = getcwd(cwd, MAXPATHLEN);
        if (!cret)
                lxcfs_debug("Could not retrieve current working directory: %s.\n", strerror(errno));

        /* This function calls unshare(CLONE_NEWNS) our initial mount namespace
         * to privately mount lxcfs cgroups. */
        if (!cgfs_setup_controllers()) {
                lxcfs_error("%s\n", "Failed to setup private cgroup mounts for lxcfs.");
                goto out;
        }

        if (setns(init_ns, 0) < 0) {
                lxcfs_error("Failed to switch back to initial mount namespace: %s.\n", strerror(errno));
                goto out;
        }

        if (!cret || chdir(cwd) < 0)
                lxcfs_debug("Could not change back to original working directory: %s.\n", strerror(errno));

        print_subsystems();

out:
        free(line);
        fclose(f);
        if (init_ns >= 0)
                close(init_ns);
}

static void __attribute__((destructor)) free_subsystems(void)
{
        int i;

        lxcfs_debug("%s\n", "Running destructor for liblxcfs.");

        for (i = 0; i < num_hierarchies; i++) {
                if (hierarchies[i])
                        free(hierarchies[i]);
                if (fd_hierarchies && fd_hierarchies[i] >= 0)
                        close(fd_hierarchies[i]);
        }
        free(hierarchies);
        free(fd_hierarchies);

        if (cgroup_mount_ns_fd >= 0)
                close(cgroup_mount_ns_fd);
}