Merge remote-tracking branch 'linus/master' into testing

[mirror_ubuntu-artful-kernel.git] / fs / ceph / mds_client.c

#include <linux/ceph/ceph_debug.h>

#include <linux/fs.h>
#include <linux/wait.h>
#include <linux/slab.h>
#include <linux/sched.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>

#include "super.h"
#include "mds_client.h"

#include <linux/ceph/ceph_features.h>
#include <linux/ceph/messenger.h>
#include <linux/ceph/decode.h>
#include <linux/ceph/pagelist.h>
#include <linux/ceph/auth.h>
#include <linux/ceph/debugfs.h>

/*
 * A cluster of MDS (metadata server) daemons is responsible for
 * managing the file system namespace (the directory hierarchy and
 * inodes) and for coordinating shared access to storage.  Metadata is
 * partitioning hierarchically across a number of servers, and that
 * partition varies over time as the cluster adjusts the distribution
 * in order to balance load.
 *
 * The MDS client is primarily responsible to managing synchronous
 * metadata requests for operations like open, unlink, and so forth.
 * If there is a MDS failure, we find out about it when we (possibly
 * request and) receive a new MDS map, and can resubmit affected
 * requests.
 *
 * For the most part, though, we take advantage of a lossless
 * communications channel to the MDS, and do not need to worry about
 * timing out or resubmitting requests.
 *
 * We maintain a stateful "session" with each MDS we interact with.
 * Within each session, we sent periodic heartbeat messages to ensure
 * any capabilities or leases we have been issues remain valid.  If
 * the session times out and goes stale, our leases and capabilities
 * are no longer valid.
 */

struct ceph_reconnect_state {
        struct ceph_pagelist *pagelist;
        bool flock;
};

static void __wake_requests(struct ceph_mds_client *mdsc,
                            struct list_head *head);

static const struct ceph_connection_operations mds_con_ops;


/*
 * mds reply parsing
 */

/*
 * parse individual inode info
 */
static int parse_reply_info_in(void **p, void *end,
                               struct ceph_mds_reply_info_in *info,
                               int features)
{
        int err = -EIO;

        info->in = *p;
        *p += sizeof(struct ceph_mds_reply_inode) +
                sizeof(*info->in->fragtree.splits) *
                le32_to_cpu(info->in->fragtree.nsplits);

        ceph_decode_32_safe(p, end, info->symlink_len, bad);
        ceph_decode_need(p, end, info->symlink_len, bad);
        info->symlink = *p;
        *p += info->symlink_len;

        if (features & CEPH_FEATURE_DIRLAYOUTHASH)
                ceph_decode_copy_safe(p, end, &info->dir_layout,
                                      sizeof(info->dir_layout), bad);
        else
                memset(&info->dir_layout, 0, sizeof(info->dir_layout));

        ceph_decode_32_safe(p, end, info->xattr_len, bad);
        ceph_decode_need(p, end, info->xattr_len, bad);
        info->xattr_data = *p;
        *p += info->xattr_len;
        return 0;
bad:
        return err;
}

/*
 * parse a normal reply, which may contain a (dir+)dentry and/or a
 * target inode.
 */
static int parse_reply_info_trace(void **p, void *end,
                                  struct ceph_mds_reply_info_parsed *info,
                                  int features)
{
        int err;

        if (info->head->is_dentry) {
                err = parse_reply_info_in(p, end, &info->diri, features);
                if (err < 0)
                        goto out_bad;

                if (unlikely(*p + sizeof(*info->dirfrag) > end))
                        goto bad;
                info->dirfrag = *p;
                *p += sizeof(*info->dirfrag) +
                        sizeof(u32)*le32_to_cpu(info->dirfrag->ndist);
                if (unlikely(*p > end))
                        goto bad;

                ceph_decode_32_safe(p, end, info->dname_len, bad);
                ceph_decode_need(p, end, info->dname_len, bad);
                info->dname = *p;
                *p += info->dname_len;
                info->dlease = *p;
                *p += sizeof(*info->dlease);
        }

        if (info->head->is_target) {
                err = parse_reply_info_in(p, end, &info->targeti, features);
                if (err < 0)
                        goto out_bad;
        }

        if (unlikely(*p != end))
                goto bad;
        return 0;

bad:
        err = -EIO;
out_bad:
        pr_err("problem parsing mds trace %d\n", err);
        return err;
}

/*
 * parse readdir results
 */
static int parse_reply_info_dir(void **p, void *end,
                                struct ceph_mds_reply_info_parsed *info,
                                int features)
{
        u32 num, i = 0;
        int err;

        info->dir_dir = *p;
        if (*p + sizeof(*info->dir_dir) > end)
                goto bad;
        *p += sizeof(*info->dir_dir) +
                sizeof(u32)*le32_to_cpu(info->dir_dir->ndist);
        if (*p > end)
                goto bad;

        ceph_decode_need(p, end, sizeof(num) + 2, bad);
        num = ceph_decode_32(p);
        info->dir_end = ceph_decode_8(p);
        info->dir_complete = ceph_decode_8(p);
        if (num == 0)
                goto done;

        /* alloc large array */
        info->dir_nr = num;
        info->dir_in = kcalloc(num, sizeof(*info->dir_in) +
                               sizeof(*info->dir_dname) +
                               sizeof(*info->dir_dname_len) +
                               sizeof(*info->dir_dlease),
                               GFP_NOFS);
        if (info->dir_in == NULL) {
                err = -ENOMEM;
                goto out_bad;
        }
        info->dir_dname = (void *)(info->dir_in + num);
        info->dir_dname_len = (void *)(info->dir_dname + num);
        info->dir_dlease = (void *)(info->dir_dname_len + num);

        while (num) {
                /* dentry */
                ceph_decode_need(p, end, sizeof(u32)*2, bad);
                info->dir_dname_len[i] = ceph_decode_32(p);
                ceph_decode_need(p, end, info->dir_dname_len[i], bad);
                info->dir_dname[i] = *p;
                *p += info->dir_dname_len[i];
                dout("parsed dir dname '%.*s'\n", info->dir_dname_len[i],
                     info->dir_dname[i]);
                info->dir_dlease[i] = *p;
                *p += sizeof(struct ceph_mds_reply_lease);

                /* inode */
                err = parse_reply_info_in(p, end, &info->dir_in[i], features);
                if (err < 0)
                        goto out_bad;
                i++;
                num--;
        }

done:
        if (*p != end)
                goto bad;
        return 0;

bad:
        err = -EIO;
out_bad:
        pr_err("problem parsing dir contents %d\n", err);
        return err;
}

/*
 * parse fcntl F_GETLK results
 */
static int parse_reply_info_filelock(void **p, void *end,
                                     struct ceph_mds_reply_info_parsed *info,
                                     int features)
{
        if (*p + sizeof(*info->filelock_reply) > end)
                goto bad;

        info->filelock_reply = *p;
        *p += sizeof(*info->filelock_reply);

        if (unlikely(*p != end))
                goto bad;
        return 0;

bad:
        return -EIO;
}

/*
 * parse create results
 */
static int parse_reply_info_create(void **p, void *end,
                                  struct ceph_mds_reply_info_parsed *info,
                                  int features)
{
        if (features & CEPH_FEATURE_REPLY_CREATE_INODE) {
                if (*p == end) {
                        info->has_create_ino = false;
                } else {
                        info->has_create_ino = true;
                        info->ino = ceph_decode_64(p);
                }
        }

        if (unlikely(*p != end))
                goto bad;
        return 0;

bad:
        return -EIO;
}

/*
 * parse extra results
 */
static int parse_reply_info_extra(void **p, void *end,
                                  struct ceph_mds_reply_info_parsed *info,
                                  int features)
{
        if (info->head->op == CEPH_MDS_OP_GETFILELOCK)
                return parse_reply_info_filelock(p, end, info, features);
        else if (info->head->op == CEPH_MDS_OP_READDIR ||
                 info->head->op == CEPH_MDS_OP_LSSNAP)
                return parse_reply_info_dir(p, end, info, features);
        else if (info->head->op == CEPH_MDS_OP_CREATE)
                return parse_reply_info_create(p, end, info, features);
        else
                return -EIO;
}

/*
 * parse entire mds reply
 */
static int parse_reply_info(struct ceph_msg *msg,
                            struct ceph_mds_reply_info_parsed *info,
                            int features)
{
        void *p, *end;
        u32 len;
        int err;

        info->head = msg->front.iov_base;
        p = msg->front.iov_base + sizeof(struct ceph_mds_reply_head);
        end = p + msg->front.iov_len - sizeof(struct ceph_mds_reply_head);

        /* trace */
        ceph_decode_32_safe(&p, end, len, bad);
        if (len > 0) {
                ceph_decode_need(&p, end, len, bad);
                err = parse_reply_info_trace(&p, p+len, info, features);
                if (err < 0)
                        goto out_bad;
        }

        /* extra */
        ceph_decode_32_safe(&p, end, len, bad);
        if (len > 0) {
                ceph_decode_need(&p, end, len, bad);
                err = parse_reply_info_extra(&p, p+len, info, features);
                if (err < 0)
                        goto out_bad;
        }

        /* snap blob */
        ceph_decode_32_safe(&p, end, len, bad);
        info->snapblob_len = len;
        info->snapblob = p;
        p += len;

        if (p != end)
                goto bad;
        return 0;

bad:
        err = -EIO;
out_bad:
        pr_err("mds parse_reply err %d\n", err);
        return err;
}

static void destroy_reply_info(struct ceph_mds_reply_info_parsed *info)
{
        kfree(info->dir_in);
}


/*
 * sessions
 */
static const char *session_state_name(int s)
{
        switch (s) {
        case CEPH_MDS_SESSION_NEW: return "new";
        case CEPH_MDS_SESSION_OPENING: return "opening";
        case CEPH_MDS_SESSION_OPEN: return "open";
        case CEPH_MDS_SESSION_HUNG: return "hung";
        case CEPH_MDS_SESSION_CLOSING: return "closing";
        case CEPH_MDS_SESSION_RESTARTING: return "restarting";
        case CEPH_MDS_SESSION_RECONNECTING: return "reconnecting";
        default: return "???";
        }
}

static struct ceph_mds_session *get_session(struct ceph_mds_session *s)
{
        if (atomic_inc_not_zero(&s->s_ref)) {
                dout("mdsc get_session %p %d -> %d\n", s,
                     atomic_read(&s->s_ref)-1, atomic_read(&s->s_ref));
                return s;
        } else {
                dout("mdsc get_session %p 0 -- FAIL", s);
                return NULL;
        }
}

void ceph_put_mds_session(struct ceph_mds_session *s)
{
        dout("mdsc put_session %p %d -> %d\n", s,
             atomic_read(&s->s_ref), atomic_read(&s->s_ref)-1);
        if (atomic_dec_and_test(&s->s_ref)) {
                if (s->s_auth.authorizer)
                        ceph_auth_destroy_authorizer(
                                s->s_mdsc->fsc->client->monc.auth,
                                s->s_auth.authorizer);
                kfree(s);
        }
}

/*
 * called under mdsc->mutex
 */
struct ceph_mds_session *__ceph_lookup_mds_session(struct ceph_mds_client *mdsc,
                                                   int mds)
{
        struct ceph_mds_session *session;

        if (mds >= mdsc->max_sessions || mdsc->sessions[mds] == NULL)
                return NULL;
        session = mdsc->sessions[mds];
        dout("lookup_mds_session %p %d\n", session,
             atomic_read(&session->s_ref));
        get_session(session);
        return session;
}

static bool __have_session(struct ceph_mds_client *mdsc, int mds)
{
        if (mds >= mdsc->max_sessions)
                return false;
        return mdsc->sessions[mds];
}

static int __verify_registered_session(struct ceph_mds_client *mdsc,
                                       struct ceph_mds_session *s)
{
        if (s->s_mds >= mdsc->max_sessions ||
            mdsc->sessions[s->s_mds] != s)
                return -ENOENT;
        return 0;
}

/*
 * create+register a new session for given mds.
 * called under mdsc->mutex.
 */
static struct ceph_mds_session *register_session(struct ceph_mds_client *mdsc,
                                                 int mds)
{
        struct ceph_mds_session *s;

        if (mds >= mdsc->mdsmap->m_max_mds)
                return ERR_PTR(-EINVAL);

        s = kzalloc(sizeof(*s), GFP_NOFS);
        if (!s)
                return ERR_PTR(-ENOMEM);
        s->s_mdsc = mdsc;
        s->s_mds = mds;
        s->s_state = CEPH_MDS_SESSION_NEW;
        s->s_ttl = 0;
        s->s_seq = 0;
        mutex_init(&s->s_mutex);

        ceph_con_init(&s->s_con, s, &mds_con_ops, &mdsc->fsc->client->msgr);

        spin_lock_init(&s->s_gen_ttl_lock);
        s->s_cap_gen = 0;
        s->s_cap_ttl = jiffies - 1;

        spin_lock_init(&s->s_cap_lock);
        s->s_renew_requested = 0;
        s->s_renew_seq = 0;
        INIT_LIST_HEAD(&s->s_caps);
        s->s_nr_caps = 0;
        s->s_trim_caps = 0;
        atomic_set(&s->s_ref, 1);
        INIT_LIST_HEAD(&s->s_waiting);
        INIT_LIST_HEAD(&s->s_unsafe);
        s->s_num_cap_releases = 0;
        s->s_cap_iterator = NULL;
        INIT_LIST_HEAD(&s->s_cap_releases);
        INIT_LIST_HEAD(&s->s_cap_releases_done);
        INIT_LIST_HEAD(&s->s_cap_flushing);
        INIT_LIST_HEAD(&s->s_cap_snaps_flushing);

        dout("register_session mds%d\n", mds);
        if (mds >= mdsc->max_sessions) {
                int newmax = 1 << get_count_order(mds+1);
                struct ceph_mds_session **sa;

                dout("register_session realloc to %d\n", newmax);
                sa = kcalloc(newmax, sizeof(void *), GFP_NOFS);
                if (sa == NULL)
                        goto fail_realloc;
                if (mdsc->sessions) {
                        memcpy(sa, mdsc->sessions,
                               mdsc->max_sessions * sizeof(void *));
                        kfree(mdsc->sessions);
                }
                mdsc->sessions = sa;
                mdsc->max_sessions = newmax;
        }
        mdsc->sessions[mds] = s;
        atomic_inc(&s->s_ref);  /* one ref to sessions[], one to caller */

        ceph_con_open(&s->s_con, CEPH_ENTITY_TYPE_MDS, mds,
                      ceph_mdsmap_get_addr(mdsc->mdsmap, mds));

        return s;

fail_realloc:
        kfree(s);
        return ERR_PTR(-ENOMEM);
}

/*
 * called under mdsc->mutex
 */
static void __unregister_session(struct ceph_mds_client *mdsc,
                               struct ceph_mds_session *s)
{
        dout("__unregister_session mds%d %p\n", s->s_mds, s);
        BUG_ON(mdsc->sessions[s->s_mds] != s);
        mdsc->sessions[s->s_mds] = NULL;
        ceph_con_close(&s->s_con);
        ceph_put_mds_session(s);
}

/*
 * drop session refs in request.
 *
 * should be last request ref, or hold mdsc->mutex
 */
static void put_request_session(struct ceph_mds_request *req)
{
        if (req->r_session) {
                ceph_put_mds_session(req->r_session);
                req->r_session = NULL;
        }
}

void ceph_mdsc_release_request(struct kref *kref)
{
        struct ceph_mds_request *req = container_of(kref,
                                                    struct ceph_mds_request,
                                                    r_kref);
        if (req->r_request)
                ceph_msg_put(req->r_request);
        if (req->r_reply) {
                ceph_msg_put(req->r_reply);
                destroy_reply_info(&req->r_reply_info);
        }
        if (req->r_inode) {
                ceph_put_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
                iput(req->r_inode);
        }
        if (req->r_locked_dir)
                ceph_put_cap_refs(ceph_inode(req->r_locked_dir), CEPH_CAP_PIN);
        if (req->r_target_inode)
                iput(req->r_target_inode);
        if (req->r_dentry)
                dput(req->r_dentry);
        if (req->r_old_dentry) {
                /*
                 * track (and drop pins for) r_old_dentry_dir
                 * separately, since r_old_dentry's d_parent may have
                 * changed between the dir mutex being dropped and
                 * this request being freed.
                 */
                ceph_put_cap_refs(ceph_inode(req->r_old_dentry_dir),
                                  CEPH_CAP_PIN);
                dput(req->r_old_dentry);
                iput(req->r_old_dentry_dir);
        }
        kfree(req->r_path1);
        kfree(req->r_path2);
        put_request_session(req);
        ceph_unreserve_caps(req->r_mdsc, &req->r_caps_reservation);
        kfree(req);
}

/*
 * lookup session, bump ref if found.
 *
 * called under mdsc->mutex.
 */
static struct ceph_mds_request *__lookup_request(struct ceph_mds_client *mdsc,
                                             u64 tid)
{
        struct ceph_mds_request *req;
        struct rb_node *n = mdsc->request_tree.rb_node;

        while (n) {
                req = rb_entry(n, struct ceph_mds_request, r_node);
                if (tid < req->r_tid)
                        n = n->rb_left;
                else if (tid > req->r_tid)
                        n = n->rb_right;
                else {
                        ceph_mdsc_get_request(req);
                        return req;
                }
        }
        return NULL;
}

static void __insert_request(struct ceph_mds_client *mdsc,
                             struct ceph_mds_request *new)
{
        struct rb_node **p = &mdsc->request_tree.rb_node;
        struct rb_node *parent = NULL;
        struct ceph_mds_request *req = NULL;

        while (*p) {
                parent = *p;
                req = rb_entry(parent, struct ceph_mds_request, r_node);
                if (new->r_tid < req->r_tid)
                        p = &(*p)->rb_left;
                else if (new->r_tid > req->r_tid)
                        p = &(*p)->rb_right;
                else
                        BUG();
        }

        rb_link_node(&new->r_node, parent, p);
        rb_insert_color(&new->r_node, &mdsc->request_tree);
}

/*
 * Register an in-flight request, and assign a tid.  Link to directory
 * are modifying (if any).
 *
 * Called under mdsc->mutex.
 */
static void __register_request(struct ceph_mds_client *mdsc,
                               struct ceph_mds_request *req,
                               struct inode *dir)
{
        req->r_tid = ++mdsc->last_tid;
        if (req->r_num_caps)
                ceph_reserve_caps(mdsc, &req->r_caps_reservation,
                                  req->r_num_caps);
        dout("__register_request %p tid %lld\n", req, req->r_tid);
        ceph_mdsc_get_request(req);
        __insert_request(mdsc, req);

        req->r_uid = current_fsuid();
        req->r_gid = current_fsgid();

        if (dir) {
                struct ceph_inode_info *ci = ceph_inode(dir);

                ihold(dir);
                spin_lock(&ci->i_unsafe_lock);
                req->r_unsafe_dir = dir;
                list_add_tail(&req->r_unsafe_dir_item, &ci->i_unsafe_dirops);
                spin_unlock(&ci->i_unsafe_lock);
        }
}

static void __unregister_request(struct ceph_mds_client *mdsc,
                                 struct ceph_mds_request *req)
{
        dout("__unregister_request %p tid %lld\n", req, req->r_tid);
        rb_erase(&req->r_node, &mdsc->request_tree);
        RB_CLEAR_NODE(&req->r_node);

        if (req->r_unsafe_dir) {
                struct ceph_inode_info *ci = ceph_inode(req->r_unsafe_dir);

                spin_lock(&ci->i_unsafe_lock);
                list_del_init(&req->r_unsafe_dir_item);
                spin_unlock(&ci->i_unsafe_lock);

                iput(req->r_unsafe_dir);
                req->r_unsafe_dir = NULL;
        }

        ceph_mdsc_put_request(req);
}

/*
 * Choose mds to send request to next.  If there is a hint set in the
 * request (e.g., due to a prior forward hint from the mds), use that.
 * Otherwise, consult frag tree and/or caps to identify the
 * appropriate mds.  If all else fails, choose randomly.
 *
 * Called under mdsc->mutex.
 */
static struct dentry *get_nonsnap_parent(struct dentry *dentry)
{
        /*
         * we don't need to worry about protecting the d_parent access
         * here because we never renaming inside the snapped namespace
         * except to resplice to another snapdir, and either the old or new
         * result is a valid result.
         */
        while (!IS_ROOT(dentry) && ceph_snap(dentry->d_inode) != CEPH_NOSNAP)
                dentry = dentry->d_parent;
        return dentry;
}

static int __choose_mds(struct ceph_mds_client *mdsc,
                        struct ceph_mds_request *req)
{
        struct inode *inode;
        struct ceph_inode_info *ci;
        struct ceph_cap *cap;
        int mode = req->r_direct_mode;
        int mds = -1;
        u32 hash = req->r_direct_hash;
        bool is_hash = req->r_direct_is_hash;

        /*
         * is there a specific mds we should try?  ignore hint if we have
         * no session and the mds is not up (active or recovering).
         */
        if (req->r_resend_mds >= 0 &&
            (__have_session(mdsc, req->r_resend_mds) ||
             ceph_mdsmap_get_state(mdsc->mdsmap, req->r_resend_mds) > 0)) {
                dout("choose_mds using resend_mds mds%d\n",
                     req->r_resend_mds);
                return req->r_resend_mds;
        }

        if (mode == USE_RANDOM_MDS)
                goto random;

        inode = NULL;
        if (req->r_inode) {
                inode = req->r_inode;
        } else if (req->r_dentry) {
                /* ignore race with rename; old or new d_parent is okay */
                struct dentry *parent = req->r_dentry->d_parent;
                struct inode *dir = parent->d_inode;

                if (dir->i_sb != mdsc->fsc->sb) {
                        /* not this fs! */
                        inode = req->r_dentry->d_inode;
                } else if (ceph_snap(dir) != CEPH_NOSNAP) {
                        /* direct snapped/virtual snapdir requests
                         * based on parent dir inode */
                        struct dentry *dn = get_nonsnap_parent(parent);
                        inode = dn->d_inode;
                        dout("__choose_mds using nonsnap parent %p\n", inode);
                } else if (req->r_dentry->d_inode) {
                        /* dentry target */
                        inode = req->r_dentry->d_inode;
                } else {
                        /* dir + name */
                        inode = dir;
                        hash = ceph_dentry_hash(dir, req->r_dentry);
                        is_hash = true;
                }
        }

        dout("__choose_mds %p is_hash=%d (%d) mode %d\n", inode, (int)is_hash,
             (int)hash, mode);
        if (!inode)
                goto random;
        ci = ceph_inode(inode);

        if (is_hash && S_ISDIR(inode->i_mode)) {
                struct ceph_inode_frag frag;
                int found;

                ceph_choose_frag(ci, hash, &frag, &found);
                if (found) {
                        if (mode == USE_ANY_MDS && frag.ndist > 0) {
                                u8 r;

                                /* choose a random replica */
                                get_random_bytes(&r, 1);
                                r %= frag.ndist;
                                mds = frag.dist[r];
                                dout("choose_mds %p %llx.%llx "
                                     "frag %u mds%d (%d/%d)\n",
                                     inode, ceph_vinop(inode),
                                     frag.frag, mds,
                                     (int)r, frag.ndist);
                                if (ceph_mdsmap_get_state(mdsc->mdsmap, mds) >=
                                    CEPH_MDS_STATE_ACTIVE)
                                        return mds;
                        }

                        /* since this file/dir wasn't known to be
                         * replicated, then we want to look for the
                         * authoritative mds. */
                        mode = USE_AUTH_MDS;
                        if (frag.mds >= 0) {
                                /* choose auth mds */
                                mds = frag.mds;
                                dout("choose_mds %p %llx.%llx "
                                     "frag %u mds%d (auth)\n",
                                     inode, ceph_vinop(inode), frag.frag, mds);
                                if (ceph_mdsmap_get_state(mdsc->mdsmap, mds) >=
                                    CEPH_MDS_STATE_ACTIVE)
                                        return mds;
                        }
                }
        }

        spin_lock(&ci->i_ceph_lock);
        cap = NULL;
        if (mode == USE_AUTH_MDS)
                cap = ci->i_auth_cap;
        if (!cap && !RB_EMPTY_ROOT(&ci->i_caps))
                cap = rb_entry(rb_first(&ci->i_caps), struct ceph_cap, ci_node);
        if (!cap) {
                spin_unlock(&ci->i_ceph_lock);
                goto random;
        }
        mds = cap->session->s_mds;
        dout("choose_mds %p %llx.%llx mds%d (%scap %p)\n",
             inode, ceph_vinop(inode), mds,
             cap == ci->i_auth_cap ? "auth " : "", cap);
        spin_unlock(&ci->i_ceph_lock);
        return mds;

random:
        mds = ceph_mdsmap_get_random_mds(mdsc->mdsmap);
        dout("choose_mds chose random mds%d\n", mds);
        return mds;
}


/*
 * session messages
 */
static struct ceph_msg *create_session_msg(u32 op, u64 seq)
{
        struct ceph_msg *msg;
        struct ceph_mds_session_head *h;

        msg = ceph_msg_new(CEPH_MSG_CLIENT_SESSION, sizeof(*h), GFP_NOFS,
                           false);
        if (!msg) {
                pr_err("create_session_msg ENOMEM creating msg\n");
                return NULL;
        }
        h = msg->front.iov_base;
        h->op = cpu_to_le32(op);
        h->seq = cpu_to_le64(seq);
        return msg;
}

/*
 * send session open request.
 *
 * called under mdsc->mutex
 */
static int __open_session(struct ceph_mds_client *mdsc,
                          struct ceph_mds_session *session)
{
        struct ceph_msg *msg;
        int mstate;
        int mds = session->s_mds;

        /* wait for mds to go active? */
        mstate = ceph_mdsmap_get_state(mdsc->mdsmap, mds);
        dout("open_session to mds%d (%s)\n", mds,
             ceph_mds_state_name(mstate));
        session->s_state = CEPH_MDS_SESSION_OPENING;
        session->s_renew_requested = jiffies;

        /* send connect message */
        msg = create_session_msg(CEPH_SESSION_REQUEST_OPEN, session->s_seq);
        if (!msg)
                return -ENOMEM;
        ceph_con_send(&session->s_con, msg);
        return 0;
}

/*
 * open sessions for any export targets for the given mds
 *
 * called under mdsc->mutex
 */
static void __open_export_target_sessions(struct ceph_mds_client *mdsc,
                                          struct ceph_mds_session *session)
{
        struct ceph_mds_info *mi;
        struct ceph_mds_session *ts;
        int i, mds = session->s_mds;
        int target;

        if (mds >= mdsc->mdsmap->m_max_mds)
                return;
        mi = &mdsc->mdsmap->m_info[mds];
        dout("open_export_target_sessions for mds%d (%d targets)\n",
             session->s_mds, mi->num_export_targets);

        for (i = 0; i < mi->num_export_targets; i++) {
                target = mi->export_targets[i];
                ts = __ceph_lookup_mds_session(mdsc, target);
                if (!ts) {
                        ts = register_session(mdsc, target);
                        if (IS_ERR(ts))
                                return;
                }
                if (session->s_state == CEPH_MDS_SESSION_NEW ||
                    session->s_state == CEPH_MDS_SESSION_CLOSING)
                        __open_session(mdsc, session);
                else
                        dout(" mds%d target mds%d %p is %s\n", session->s_mds,
                             i, ts, session_state_name(ts->s_state));
                ceph_put_mds_session(ts);
        }
}

void ceph_mdsc_open_export_target_sessions(struct ceph_mds_client *mdsc,
                                           struct ceph_mds_session *session)
{
        mutex_lock(&mdsc->mutex);
        __open_export_target_sessions(mdsc, session);
        mutex_unlock(&mdsc->mutex);
}

/*
 * session caps
 */

/*
 * Free preallocated cap messages assigned to this session
 */
static void cleanup_cap_releases(struct ceph_mds_session *session)
{
        struct ceph_msg *msg;

        spin_lock(&session->s_cap_lock);
        while (!list_empty(&session->s_cap_releases)) {
                msg = list_first_entry(&session->s_cap_releases,
                                       struct ceph_msg, list_head);
                list_del_init(&msg->list_head);
                ceph_msg_put(msg);
        }
        while (!list_empty(&session->s_cap_releases_done)) {
                msg = list_first_entry(&session->s_cap_releases_done,
                                       struct ceph_msg, list_head);
                list_del_init(&msg->list_head);
                ceph_msg_put(msg);
        }
        spin_unlock(&session->s_cap_lock);
}

/*
 * Helper to safely iterate over all caps associated with a session, with
 * special care taken to handle a racing __ceph_remove_cap().
 *
 * Caller must hold session s_mutex.
 */
static int iterate_session_caps(struct ceph_mds_session *session,
                                 int (*cb)(struct inode *, struct ceph_cap *,
                                            void *), void *arg)
{
        struct list_head *p;
        struct ceph_cap *cap;
        struct inode *inode, *last_inode = NULL;
        struct ceph_cap *old_cap = NULL;
        int ret;

        dout("iterate_session_caps %p mds%d\n", session, session->s_mds);
        spin_lock(&session->s_cap_lock);
        p = session->s_caps.next;
        while (p != &session->s_caps) {
                cap = list_entry(p, struct ceph_cap, session_caps);
                inode = igrab(&cap->ci->vfs_inode);
                if (!inode) {
                        p = p->next;
                        continue;
                }
                session->s_cap_iterator = cap;
                spin_unlock(&session->s_cap_lock);

                if (last_inode) {
                        iput(last_inode);
                        last_inode = NULL;
                }
                if (old_cap) {
                        ceph_put_cap(session->s_mdsc, old_cap);
                        old_cap = NULL;
                }

                ret = cb(inode, cap, arg);
                last_inode = inode;

                spin_lock(&session->s_cap_lock);
                p = p->next;
                if (cap->ci == NULL) {
                        dout("iterate_session_caps  finishing cap %p removal\n",
                             cap);
                        BUG_ON(cap->session != session);
                        list_del_init(&cap->session_caps);
                        session->s_nr_caps--;
                        cap->session = NULL;
                        old_cap = cap;  /* put_cap it w/o locks held */
                }
                if (ret < 0)
                        goto out;
        }
        ret = 0;
out:
        session->s_cap_iterator = NULL;
        spin_unlock(&session->s_cap_lock);

        if (last_inode)
                iput(last_inode);
        if (old_cap)
                ceph_put_cap(session->s_mdsc, old_cap);

        return ret;
}

static int remove_session_caps_cb(struct inode *inode, struct ceph_cap *cap,
                                  void *arg)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        int drop = 0;

        dout("removing cap %p, ci is %p, inode is %p\n",
             cap, ci, &ci->vfs_inode);
        spin_lock(&ci->i_ceph_lock);
        __ceph_remove_cap(cap);
        if (!__ceph_is_any_real_caps(ci)) {
                struct ceph_mds_client *mdsc =
                        ceph_sb_to_client(inode->i_sb)->mdsc;

                spin_lock(&mdsc->cap_dirty_lock);
                if (!list_empty(&ci->i_dirty_item)) {
                        pr_info(" dropping dirty %s state for %p %lld\n",
                                ceph_cap_string(ci->i_dirty_caps),
                                inode, ceph_ino(inode));
                        ci->i_dirty_caps = 0;
                        list_del_init(&ci->i_dirty_item);
                        drop = 1;
                }
                if (!list_empty(&ci->i_flushing_item)) {
                        pr_info(" dropping dirty+flushing %s state for %p %lld\n",
                                ceph_cap_string(ci->i_flushing_caps),
                                inode, ceph_ino(inode));
                        ci->i_flushing_caps = 0;
                        list_del_init(&ci->i_flushing_item);
                        mdsc->num_cap_flushing--;
                        drop = 1;
                }
                if (drop && ci->i_wrbuffer_ref) {
                        pr_info(" dropping dirty data for %p %lld\n",
                                inode, ceph_ino(inode));
                        ci->i_wrbuffer_ref = 0;
                        ci->i_wrbuffer_ref_head = 0;
                        drop++;
                }
                spin_unlock(&mdsc->cap_dirty_lock);
        }
        spin_unlock(&ci->i_ceph_lock);
        while (drop--)
                iput(inode);
        return 0;
}

/*
 * caller must hold session s_mutex
 */
static void remove_session_caps(struct ceph_mds_session *session)
{
        dout("remove_session_caps on %p\n", session);
        iterate_session_caps(session, remove_session_caps_cb, NULL);

        spin_lock(&session->s_cap_lock);
        if (session->s_nr_caps > 0) {
                struct super_block *sb = session->s_mdsc->fsc->sb;
                struct inode *inode;
                struct ceph_cap *cap, *prev = NULL;
                struct ceph_vino vino;
                /*
                 * iterate_session_caps() skips inodes that are being
                 * deleted, we need to wait until deletions are complete.
                 * __wait_on_freeing_inode() is designed for the job,
                 * but it is not exported, so use lookup inode function
                 * to access it.
                 */
                while (!list_empty(&session->s_caps)) {
                        cap = list_entry(session->s_caps.next,
                                         struct ceph_cap, session_caps);
                        if (cap == prev)
                                break;
                        prev = cap;
                        vino = cap->ci->i_vino;
                        spin_unlock(&session->s_cap_lock);

                        inode = ceph_lookup_inode(sb, vino);
                        iput(inode);

                        spin_lock(&session->s_cap_lock);
                }
        }
        spin_unlock(&session->s_cap_lock);

        BUG_ON(session->s_nr_caps > 0);
        BUG_ON(!list_empty(&session->s_cap_flushing));
        cleanup_cap_releases(session);
}

/*
 * wake up any threads waiting on this session's caps.  if the cap is
 * old (didn't get renewed on the client reconnect), remove it now.
 *
 * caller must hold s_mutex.
 */
static int wake_up_session_cb(struct inode *inode, struct ceph_cap *cap,
                              void *arg)
{
        struct ceph_inode_info *ci = ceph_inode(inode);

        wake_up_all(&ci->i_cap_wq);
        if (arg) {
                spin_lock(&ci->i_ceph_lock);
                ci->i_wanted_max_size = 0;
                ci->i_requested_max_size = 0;
                spin_unlock(&ci->i_ceph_lock);
        }
        return 0;
}

static void wake_up_session_caps(struct ceph_mds_session *session,
                                 int reconnect)
{
        dout("wake_up_session_caps %p mds%d\n", session, session->s_mds);
        iterate_session_caps(session, wake_up_session_cb,
                             (void *)(unsigned long)reconnect);
}

/*
 * Send periodic message to MDS renewing all currently held caps.  The
 * ack will reset the expiration for all caps from this session.
 *
 * caller holds s_mutex
 */
static int send_renew_caps(struct ceph_mds_client *mdsc,
                           struct ceph_mds_session *session)
{
        struct ceph_msg *msg;
        int state;

        if (time_after_eq(jiffies, session->s_cap_ttl) &&
            time_after_eq(session->s_cap_ttl, session->s_renew_requested))
                pr_info("mds%d caps stale\n", session->s_mds);
        session->s_renew_requested = jiffies;

        /* do not try to renew caps until a recovering mds has reconnected
         * with its clients. */
        state = ceph_mdsmap_get_state(mdsc->mdsmap, session->s_mds);
        if (state < CEPH_MDS_STATE_RECONNECT) {
                dout("send_renew_caps ignoring mds%d (%s)\n",
                     session->s_mds, ceph_mds_state_name(state));
                return 0;
        }

        dout("send_renew_caps to mds%d (%s)\n", session->s_mds,
                ceph_mds_state_name(state));
        msg = create_session_msg(CEPH_SESSION_REQUEST_RENEWCAPS,
                                 ++session->s_renew_seq);
        if (!msg)
                return -ENOMEM;
        ceph_con_send(&session->s_con, msg);
        return 0;
}

/*
 * Note new cap ttl, and any transition from stale -> not stale (fresh?).
 *
 * Called under session->s_mutex
 */
static void renewed_caps(struct ceph_mds_client *mdsc,
                         struct ceph_mds_session *session, int is_renew)
{
        int was_stale;
        int wake = 0;

        spin_lock(&session->s_cap_lock);
        was_stale = is_renew && time_after_eq(jiffies, session->s_cap_ttl);

        session->s_cap_ttl = session->s_renew_requested +
                mdsc->mdsmap->m_session_timeout*HZ;

        if (was_stale) {
                if (time_before(jiffies, session->s_cap_ttl)) {
                        pr_info("mds%d caps renewed\n", session->s_mds);
                        wake = 1;
                } else {
                        pr_info("mds%d caps still stale\n", session->s_mds);
                }
        }
        dout("renewed_caps mds%d ttl now %lu, was %s, now %s\n",
             session->s_mds, session->s_cap_ttl, was_stale ? "stale" : "fresh",
             time_before(jiffies, session->s_cap_ttl) ? "stale" : "fresh");
        spin_unlock(&session->s_cap_lock);

        if (wake)
                wake_up_session_caps(session, 0);
}

/*
 * send a session close request
 */
static int request_close_session(struct ceph_mds_client *mdsc,
                                 struct ceph_mds_session *session)
{
        struct ceph_msg *msg;

        dout("request_close_session mds%d state %s seq %lld\n",
             session->s_mds, session_state_name(session->s_state),
             session->s_seq);
        msg = create_session_msg(CEPH_SESSION_REQUEST_CLOSE, session->s_seq);
        if (!msg)
                return -ENOMEM;
        ceph_con_send(&session->s_con, msg);
        return 0;
}

/*
 * Called with s_mutex held.
 */
static int __close_session(struct ceph_mds_client *mdsc,
                         struct ceph_mds_session *session)
{
        if (session->s_state >= CEPH_MDS_SESSION_CLOSING)
                return 0;
        session->s_state = CEPH_MDS_SESSION_CLOSING;
        return request_close_session(mdsc, session);
}

/*
 * Trim old(er) caps.
 *
 * Because we can't cache an inode without one or more caps, we do
 * this indirectly: if a cap is unused, we prune its aliases, at which
 * point the inode will hopefully get dropped to.
 *
 * Yes, this is a bit sloppy.  Our only real goal here is to respond to
 * memory pressure from the MDS, though, so it needn't be perfect.
 */
static int trim_caps_cb(struct inode *inode, struct ceph_cap *cap, void *arg)
{
        struct ceph_mds_session *session = arg;
        struct ceph_inode_info *ci = ceph_inode(inode);
        int used, oissued, mine;

        if (session->s_trim_caps <= 0)
                return -1;

        spin_lock(&ci->i_ceph_lock);
        mine = cap->issued | cap->implemented;
        used = __ceph_caps_used(ci);
        oissued = __ceph_caps_issued_other(ci, cap);

        dout("trim_caps_cb %p cap %p mine %s oissued %s used %s\n",
             inode, cap, ceph_cap_string(mine), ceph_cap_string(oissued),
             ceph_cap_string(used));
        if (ci->i_dirty_caps)
                goto out;   /* dirty caps */
        if ((used & ~oissued) & mine)
                goto out;   /* we need these caps */

        session->s_trim_caps--;
        if (oissued) {
                /* we aren't the only cap.. just remove us */
                __queue_cap_release(session, ceph_ino(inode), cap->cap_id,
                                    cap->mseq, cap->issue_seq);
                __ceph_remove_cap(cap);
        } else {
                /* try to drop referring dentries */
                spin_unlock(&ci->i_ceph_lock);
                d_prune_aliases(inode);
                dout("trim_caps_cb %p cap %p  pruned, count now %d\n",
                     inode, cap, atomic_read(&inode->i_count));
                return 0;
        }

out:
        spin_unlock(&ci->i_ceph_lock);
        return 0;
}

/*
 * Trim session cap count down to some max number.
 */
static int trim_caps(struct ceph_mds_client *mdsc,
                     struct ceph_mds_session *session,
                     int max_caps)
{
        int trim_caps = session->s_nr_caps - max_caps;

        dout("trim_caps mds%d start: %d / %d, trim %d\n",
             session->s_mds, session->s_nr_caps, max_caps, trim_caps);
        if (trim_caps > 0) {
                session->s_trim_caps = trim_caps;
                iterate_session_caps(session, trim_caps_cb, session);
                dout("trim_caps mds%d done: %d / %d, trimmed %d\n",
                     session->s_mds, session->s_nr_caps, max_caps,
                        trim_caps - session->s_trim_caps);
                session->s_trim_caps = 0;
        }
        return 0;
}

/*
 * Allocate cap_release messages.  If there is a partially full message
 * in the queue, try to allocate enough to cover it's remainder, so that
 * we can send it immediately.
 *
 * Called under s_mutex.
 */
int ceph_add_cap_releases(struct ceph_mds_client *mdsc,
                          struct ceph_mds_session *session)
{
        struct ceph_msg *msg, *partial = NULL;
        struct ceph_mds_cap_release *head;
        int err = -ENOMEM;
        int extra = mdsc->fsc->mount_options->cap_release_safety;
        int num;

        dout("add_cap_releases %p mds%d extra %d\n", session, session->s_mds,
             extra);

        spin_lock(&session->s_cap_lock);

        if (!list_empty(&session->s_cap_releases)) {
                msg = list_first_entry(&session->s_cap_releases,
                                       struct ceph_msg,
                                 list_head);
                head = msg->front.iov_base;
                num = le32_to_cpu(head->num);
                if (num) {
                        dout(" partial %p with (%d/%d)\n", msg, num,
                             (int)CEPH_CAPS_PER_RELEASE);
                        extra += CEPH_CAPS_PER_RELEASE - num;
                        partial = msg;
                }
        }
        while (session->s_num_cap_releases < session->s_nr_caps + extra) {
                spin_unlock(&session->s_cap_lock);
                msg = ceph_msg_new(CEPH_MSG_CLIENT_CAPRELEASE, PAGE_CACHE_SIZE,
                                   GFP_NOFS, false);
                if (!msg)
                        goto out_unlocked;
                dout("add_cap_releases %p msg %p now %d\n", session, msg,
                     (int)msg->front.iov_len);
                head = msg->front.iov_base;
                head->num = cpu_to_le32(0);
                msg->front.iov_len = sizeof(*head);
                spin_lock(&session->s_cap_lock);
                list_add(&msg->list_head, &session->s_cap_releases);
                session->s_num_cap_releases += CEPH_CAPS_PER_RELEASE;
        }

        if (partial) {
                head = partial->front.iov_base;
                num = le32_to_cpu(head->num);
                dout(" queueing partial %p with %d/%d\n", partial, num,
                     (int)CEPH_CAPS_PER_RELEASE);
                list_move_tail(&partial->list_head,
                               &session->s_cap_releases_done);
                session->s_num_cap_releases -= CEPH_CAPS_PER_RELEASE - num;
        }
        err = 0;
        spin_unlock(&session->s_cap_lock);
out_unlocked:
        return err;
}

/*
 * flush all dirty inode data to disk.
 *
 * returns true if we've flushed through want_flush_seq
 */
static int check_cap_flush(struct ceph_mds_client *mdsc, u64 want_flush_seq)
{
        int mds, ret = 1;

        dout("check_cap_flush want %lld\n", want_flush_seq);
        mutex_lock(&mdsc->mutex);
        for (mds = 0; ret && mds < mdsc->max_sessions; mds++) {
                struct ceph_mds_session *session = mdsc->sessions[mds];

                if (!session)
                        continue;
                get_session(session);
                mutex_unlock(&mdsc->mutex);

                mutex_lock(&session->s_mutex);
                if (!list_empty(&session->s_cap_flushing)) {
                        struct ceph_inode_info *ci =
                                list_entry(session->s_cap_flushing.next,
                                           struct ceph_inode_info,
                                           i_flushing_item);
                        struct inode *inode = &ci->vfs_inode;

                        spin_lock(&ci->i_ceph_lock);
                        if (ci->i_cap_flush_seq <= want_flush_seq) {
                                dout("check_cap_flush still flushing %p "
                                     "seq %lld <= %lld to mds%d\n", inode,
                                     ci->i_cap_flush_seq, want_flush_seq,
                                     session->s_mds);
                                ret = 0;
                        }
                        spin_unlock(&ci->i_ceph_lock);
                }
                mutex_unlock(&session->s_mutex);
                ceph_put_mds_session(session);

                if (!ret)
                        return ret;
                mutex_lock(&mdsc->mutex);
        }

        mutex_unlock(&mdsc->mutex);
        dout("check_cap_flush ok, flushed thru %lld\n", want_flush_seq);
        return ret;
}

/*
 * called under s_mutex
 */
void ceph_send_cap_releases(struct ceph_mds_client *mdsc,
                            struct ceph_mds_session *session)
{
        struct ceph_msg *msg;

        dout("send_cap_releases mds%d\n", session->s_mds);
        spin_lock(&session->s_cap_lock);
        while (!list_empty(&session->s_cap_releases_done)) {
                msg = list_first_entry(&session->s_cap_releases_done,
                                 struct ceph_msg, list_head);
                list_del_init(&msg->list_head);
                spin_unlock(&session->s_cap_lock);
                msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);
                dout("send_cap_releases mds%d %p\n", session->s_mds, msg);
                ceph_con_send(&session->s_con, msg);
                spin_lock(&session->s_cap_lock);
        }
        spin_unlock(&session->s_cap_lock);
}

static void discard_cap_releases(struct ceph_mds_client *mdsc,
                                 struct ceph_mds_session *session)
{
        struct ceph_msg *msg;
        struct ceph_mds_cap_release *head;
        unsigned num;

        dout("discard_cap_releases mds%d\n", session->s_mds);
        spin_lock(&session->s_cap_lock);

        /* zero out the in-progress message */
        msg = list_first_entry(&session->s_cap_releases,
                               struct ceph_msg, list_head);
        head = msg->front.iov_base;
        num = le32_to_cpu(head->num);
        dout("discard_cap_releases mds%d %p %u\n", session->s_mds, msg, num);
        head->num = cpu_to_le32(0);
        msg->front.iov_len = sizeof(*head);
        session->s_num_cap_releases += num;

        /* requeue completed messages */
        while (!list_empty(&session->s_cap_releases_done)) {
                msg = list_first_entry(&session->s_cap_releases_done,
                                 struct ceph_msg, list_head);
                list_del_init(&msg->list_head);

                head = msg->front.iov_base;
                num = le32_to_cpu(head->num);
                dout("discard_cap_releases mds%d %p %u\n", session->s_mds, msg,
                     num);
                session->s_num_cap_releases += num;
                head->num = cpu_to_le32(0);
                msg->front.iov_len = sizeof(*head);
                list_add(&msg->list_head, &session->s_cap_releases);
        }

        spin_unlock(&session->s_cap_lock);
}

/*
 * requests
 */

/*
 * Create an mds request.
 */
struct ceph_mds_request *
ceph_mdsc_create_request(struct ceph_mds_client *mdsc, int op, int mode)
{
        struct ceph_mds_request *req = kzalloc(sizeof(*req), GFP_NOFS);

        if (!req)
                return ERR_PTR(-ENOMEM);

        mutex_init(&req->r_fill_mutex);
        req->r_mdsc = mdsc;
        req->r_started = jiffies;
        req->r_resend_mds = -1;
        INIT_LIST_HEAD(&req->r_unsafe_dir_item);
        req->r_fmode = -1;
        kref_init(&req->r_kref);
        INIT_LIST_HEAD(&req->r_wait);
        init_completion(&req->r_completion);
        init_completion(&req->r_safe_completion);
        INIT_LIST_HEAD(&req->r_unsafe_item);

        req->r_op = op;
        req->r_direct_mode = mode;
        return req;
}

/*
 * return oldest (lowest) request, tid in request tree, 0 if none.
 *
 * called under mdsc->mutex.
 */
static struct ceph_mds_request *__get_oldest_req(struct ceph_mds_client *mdsc)
{
        if (RB_EMPTY_ROOT(&mdsc->request_tree))
                return NULL;
        return rb_entry(rb_first(&mdsc->request_tree),
                        struct ceph_mds_request, r_node);
}

static u64 __get_oldest_tid(struct ceph_mds_client *mdsc)
{
        struct ceph_mds_request *req = __get_oldest_req(mdsc);

        if (req)
                return req->r_tid;
        return 0;
}

/*
 * Build a dentry's path.  Allocate on heap; caller must kfree.  Based
 * on build_path_from_dentry in fs/cifs/dir.c.
 *
 * If @stop_on_nosnap, generate path relative to the first non-snapped
 * inode.
 *
 * Encode hidden .snap dirs as a double /, i.e.
 *   foo/.snap/bar -> foo//bar
 */
char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *base,
                           int stop_on_nosnap)
{
        struct dentry *temp;
        char *path;
        int len, pos;
        unsigned seq;

        if (dentry == NULL)
                return ERR_PTR(-EINVAL);

retry:
        len = 0;
        seq = read_seqbegin(&rename_lock);
        rcu_read_lock();
        for (temp = dentry; !IS_ROOT(temp);) {
                struct inode *inode = temp->d_inode;
                if (inode && ceph_snap(inode) == CEPH_SNAPDIR)
                        len++;  /* slash only */
                else if (stop_on_nosnap && inode &&
                         ceph_snap(inode) == CEPH_NOSNAP)
                        break;
                else
                        len += 1 + temp->d_name.len;
                temp = temp->d_parent;
        }
        rcu_read_unlock();
        if (len)
                len--;  /* no leading '/' */

        path = kmalloc(len+1, GFP_NOFS);
        if (path == NULL)
                return ERR_PTR(-ENOMEM);
        pos = len;
        path[pos] = 0;  /* trailing null */
        rcu_read_lock();
        for (temp = dentry; !IS_ROOT(temp) && pos != 0; ) {
                struct inode *inode;

                spin_lock(&temp->d_lock);
                inode = temp->d_inode;
                if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {
                        dout("build_path path+%d: %p SNAPDIR\n",
                             pos, temp);
                } else if (stop_on_nosnap && inode &&
                           ceph_snap(inode) == CEPH_NOSNAP) {
                        spin_unlock(&temp->d_lock);
                        break;
                } else {
                        pos -= temp->d_name.len;
                        if (pos < 0) {
                                spin_unlock(&temp->d_lock);
                                break;
                        }
                        strncpy(path + pos, temp->d_name.name,
                                temp->d_name.len);
                }
                spin_unlock(&temp->d_lock);
                if (pos)
                        path[--pos] = '/';
                temp = temp->d_parent;
        }
        rcu_read_unlock();
        if (pos != 0 || read_seqretry(&rename_lock, seq)) {
                pr_err("build_path did not end path lookup where "
                       "expected, namelen is %d, pos is %d\n", len, pos);
                /* presumably this is only possible if racing with a
                   rename of one of the parent directories (we can not
                   lock the dentries above us to prevent this, but
                   retrying should be harmless) */
                kfree(path);
                goto retry;
        }

        *base = ceph_ino(temp->d_inode);
        *plen = len;
        dout("build_path on %p %d built %llx '%.*s'\n",
             dentry, d_count(dentry), *base, len, path);
        return path;
}

static int build_dentry_path(struct dentry *dentry,
                             const char **ppath, int *ppathlen, u64 *pino,
                             int *pfreepath)
{
        char *path;

        if (ceph_snap(dentry->d_parent->d_inode) == CEPH_NOSNAP) {
                *pino = ceph_ino(dentry->d_parent->d_inode);
                *ppath = dentry->d_name.name;
                *ppathlen = dentry->d_name.len;
                return 0;
        }
        path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
        if (IS_ERR(path))
                return PTR_ERR(path);
        *ppath = path;
        *pfreepath = 1;
        return 0;
}

static int build_inode_path(struct inode *inode,
                            const char **ppath, int *ppathlen, u64 *pino,
                            int *pfreepath)
{
        struct dentry *dentry;
        char *path;

        if (ceph_snap(inode) == CEPH_NOSNAP) {
                *pino = ceph_ino(inode);
                *ppathlen = 0;
                return 0;
        }
        dentry = d_find_alias(inode);
        path = ceph_mdsc_build_path(dentry, ppathlen, pino, 1);
        dput(dentry);
        if (IS_ERR(path))
                return PTR_ERR(path);
        *ppath = path;
        *pfreepath = 1;
        return 0;
}

/*
 * request arguments may be specified via an inode *, a dentry *, or
 * an explicit ino+path.
 */
static int set_request_path_attr(struct inode *rinode, struct dentry *rdentry,
                                  const char *rpath, u64 rino,
                                  const char **ppath, int *pathlen,
                                  u64 *ino, int *freepath)
{
        int r = 0;

        if (rinode) {
                r = build_inode_path(rinode, ppath, pathlen, ino, freepath);
                dout(" inode %p %llx.%llx\n", rinode, ceph_ino(rinode),
                     ceph_snap(rinode));
        } else if (rdentry) {
                r = build_dentry_path(rdentry, ppath, pathlen, ino, freepath);
                dout(" dentry %p %llx/%.*s\n", rdentry, *ino, *pathlen,
                     *ppath);
        } else if (rpath || rino) {
                *ino = rino;
                *ppath = rpath;
                *pathlen = rpath ? strlen(rpath) : 0;
                dout(" path %.*s\n", *pathlen, rpath);
        }

        return r;
}

/*
 * called under mdsc->mutex
 */
static struct ceph_msg *create_request_message(struct ceph_mds_client *mdsc,
                                               struct ceph_mds_request *req,
                                               int mds)
{
        struct ceph_msg *msg;
        struct ceph_mds_request_head *head;
        const char *path1 = NULL;
        const char *path2 = NULL;
        u64 ino1 = 0, ino2 = 0;
        int pathlen1 = 0, pathlen2 = 0;
        int freepath1 = 0, freepath2 = 0;
        int len;
        u16 releases;
        void *p, *end;
        int ret;

        ret = set_request_path_attr(req->r_inode, req->r_dentry,
                              req->r_path1, req->r_ino1.ino,
                              &path1, &pathlen1, &ino1, &freepath1);
        if (ret < 0) {
                msg = ERR_PTR(ret);
                goto out;
        }

        ret = set_request_path_attr(NULL, req->r_old_dentry,
                              req->r_path2, req->r_ino2.ino,
                              &path2, &pathlen2, &ino2, &freepath2);
        if (ret < 0) {
                msg = ERR_PTR(ret);
                goto out_free1;
        }

        len = sizeof(*head) +
                pathlen1 + pathlen2 + 2*(1 + sizeof(u32) + sizeof(u64));

        /* calculate (max) length for cap releases */
        len += sizeof(struct ceph_mds_request_release) *
                (!!req->r_inode_drop + !!req->r_dentry_drop +
                 !!req->r_old_inode_drop + !!req->r_old_dentry_drop);
        if (req->r_dentry_drop)
                len += req->r_dentry->d_name.len;
        if (req->r_old_dentry_drop)
                len += req->r_old_dentry->d_name.len;

        msg = ceph_msg_new(CEPH_MSG_CLIENT_REQUEST, len, GFP_NOFS, false);
        if (!msg) {
                msg = ERR_PTR(-ENOMEM);
                goto out_free2;
        }

        msg->hdr.tid = cpu_to_le64(req->r_tid);

        head = msg->front.iov_base;
        p = msg->front.iov_base + sizeof(*head);
        end = msg->front.iov_base + msg->front.iov_len;

        head->mdsmap_epoch = cpu_to_le32(mdsc->mdsmap->m_epoch);
        head->op = cpu_to_le32(req->r_op);
        head->caller_uid = cpu_to_le32(from_kuid(&init_user_ns, req->r_uid));
        head->caller_gid = cpu_to_le32(from_kgid(&init_user_ns, req->r_gid));
        head->args = req->r_args;

        ceph_encode_filepath(&p, end, ino1, path1);
        ceph_encode_filepath(&p, end, ino2, path2);

        /* make note of release offset, in case we need to replay */
        req->r_request_release_offset = p - msg->front.iov_base;

        /* cap releases */
        releases = 0;
        if (req->r_inode_drop)
                releases += ceph_encode_inode_release(&p,
                      req->r_inode ? req->r_inode : req->r_dentry->d_inode,
                      mds, req->r_inode_drop, req->r_inode_unless, 0);
        if (req->r_dentry_drop)
                releases += ceph_encode_dentry_release(&p, req->r_dentry,
                       mds, req->r_dentry_drop, req->r_dentry_unless);
        if (req->r_old_dentry_drop)
                releases += ceph_encode_dentry_release(&p, req->r_old_dentry,
                       mds, req->r_old_dentry_drop, req->r_old_dentry_unless);
        if (req->r_old_inode_drop)
                releases += ceph_encode_inode_release(&p,
                      req->r_old_dentry->d_inode,
                      mds, req->r_old_inode_drop, req->r_old_inode_unless, 0);
        head->num_releases = cpu_to_le16(releases);

        BUG_ON(p > end);
        msg->front.iov_len = p - msg->front.iov_base;
        msg->hdr.front_len = cpu_to_le32(msg->front.iov_len);

        if (req->r_data_len) {
                /* outbound data set only by ceph_sync_setxattr() */
                BUG_ON(!req->r_pages);
                ceph_msg_data_add_pages(msg, req->r_pages, req->r_data_len, 0);
        }

        msg->hdr.data_len = cpu_to_le32(req->r_data_len);
        msg->hdr.data_off = cpu_to_le16(0);

out_free2:
        if (freepath2)
                kfree((char *)path2);
out_free1:
        if (freepath1)
                kfree((char *)path1);
out:
        return msg;
}

/*
 * called under mdsc->mutex if error, under no mutex if
 * success.
 */
static void complete_request(struct ceph_mds_client *mdsc,
                             struct ceph_mds_request *req)
{
        if (req->r_callback)
                req->r_callback(mdsc, req);
        else
                complete_all(&req->r_completion);
}

/*
 * called under mdsc->mutex
 */
static int __prepare_send_request(struct ceph_mds_client *mdsc,
                                  struct ceph_mds_request *req,
                                  int mds)
{
        struct ceph_mds_request_head *rhead;
        struct ceph_msg *msg;
        int flags = 0;

        req->r_attempts++;
        if (req->r_inode) {
                struct ceph_cap *cap =
                        ceph_get_cap_for_mds(ceph_inode(req->r_inode), mds);

                if (cap)
                        req->r_sent_on_mseq = cap->mseq;
                else
                        req->r_sent_on_mseq = -1;
        }
        dout("prepare_send_request %p tid %lld %s (attempt %d)\n", req,
             req->r_tid, ceph_mds_op_name(req->r_op), req->r_attempts);

        if (req->r_got_unsafe) {
                /*
                 * Replay.  Do not regenerate message (and rebuild
                 * paths, etc.); just use the original message.
                 * Rebuilding paths will break for renames because
                 * d_move mangles the src name.
                 */
                msg = req->r_request;
                rhead = msg->front.iov_base;

                flags = le32_to_cpu(rhead->flags);
                flags |= CEPH_MDS_FLAG_REPLAY;
                rhead->flags = cpu_to_le32(flags);

                if (req->r_target_inode)
                        rhead->ino = cpu_to_le64(ceph_ino(req->r_target_inode));

                rhead->num_retry = req->r_attempts - 1;

                /* remove cap/dentry releases from message */
                rhead->num_releases = 0;
                msg->hdr.front_len = cpu_to_le32(req->r_request_release_offset);
                msg->front.iov_len = req->r_request_release_offset;
                return 0;
        }

        if (req->r_request) {
                ceph_msg_put(req->r_request);
                req->r_request = NULL;
        }
        msg = create_request_message(mdsc, req, mds);
        if (IS_ERR(msg)) {
                req->r_err = PTR_ERR(msg);
                complete_request(mdsc, req);
                return PTR_ERR(msg);
        }
        req->r_request = msg;

        rhead = msg->front.iov_base;
        rhead->oldest_client_tid = cpu_to_le64(__get_oldest_tid(mdsc));
        if (req->r_got_unsafe)
                flags |= CEPH_MDS_FLAG_REPLAY;
        if (req->r_locked_dir)
                flags |= CEPH_MDS_FLAG_WANT_DENTRY;
        rhead->flags = cpu_to_le32(flags);
        rhead->num_fwd = req->r_num_fwd;
        rhead->num_retry = req->r_attempts - 1;
        rhead->ino = 0;

        dout(" r_locked_dir = %p\n", req->r_locked_dir);
        return 0;
}

/*
 * send request, or put it on the appropriate wait list.
 */
static int __do_request(struct ceph_mds_client *mdsc,
                        struct ceph_mds_request *req)
{
        struct ceph_mds_session *session = NULL;
        int mds = -1;
        int err = -EAGAIN;

        if (req->r_err || req->r_got_result)
                goto out;

        if (req->r_timeout &&
            time_after_eq(jiffies, req->r_started + req->r_timeout)) {
                dout("do_request timed out\n");
                err = -EIO;
                goto finish;
        }

        put_request_session(req);

        mds = __choose_mds(mdsc, req);
        if (mds < 0 ||
            ceph_mdsmap_get_state(mdsc->mdsmap, mds) < CEPH_MDS_STATE_ACTIVE) {
                dout("do_request no mds or not active, waiting for map\n");
                list_add(&req->r_wait, &mdsc->waiting_for_map);
                goto out;
        }

        /* get, open session */
        session = __ceph_lookup_mds_session(mdsc, mds);
        if (!session) {
                session = register_session(mdsc, mds);
                if (IS_ERR(session)) {
                        err = PTR_ERR(session);
                        goto finish;
                }
        }
        req->r_session = get_session(session);

        dout("do_request mds%d session %p state %s\n", mds, session,
             session_state_name(session->s_state));
        if (session->s_state != CEPH_MDS_SESSION_OPEN &&
            session->s_state != CEPH_MDS_SESSION_HUNG) {
                if (session->s_state == CEPH_MDS_SESSION_NEW ||
                    session->s_state == CEPH_MDS_SESSION_CLOSING)
                        __open_session(mdsc, session);
                list_add(&req->r_wait, &session->s_waiting);
                goto out_session;
        }

        /* send request */
        req->r_resend_mds = -1;   /* forget any previous mds hint */

        if (req->r_request_started == 0)   /* note request start time */
                req->r_request_started = jiffies;

        err = __prepare_send_request(mdsc, req, mds);
        if (!err) {
                ceph_msg_get(req->r_request);
                ceph_con_send(&session->s_con, req->r_request);
        }

out_session:
        ceph_put_mds_session(session);
out:
        return err;

finish:
        req->r_err = err;
        complete_request(mdsc, req);
        goto out;
}

/*
 * called under mdsc->mutex
 */
static void __wake_requests(struct ceph_mds_client *mdsc,
                            struct list_head *head)
{
        struct ceph_mds_request *req;
        LIST_HEAD(tmp_list);

        list_splice_init(head, &tmp_list);

        while (!list_empty(&tmp_list)) {
                req = list_entry(tmp_list.next,
                                 struct ceph_mds_request, r_wait);
                list_del_init(&req->r_wait);
                dout(" wake request %p tid %llu\n", req, req->r_tid);
                __do_request(mdsc, req);
        }
}

/*
 * Wake up threads with requests pending for @mds, so that they can
 * resubmit their requests to a possibly different mds.
 */
static void kick_requests(struct ceph_mds_client *mdsc, int mds)
{
        struct ceph_mds_request *req;
        struct rb_node *p;

        dout("kick_requests mds%d\n", mds);
        for (p = rb_first(&mdsc->request_tree); p; p = rb_next(p)) {
                req = rb_entry(p, struct ceph_mds_request, r_node);
                if (req->r_got_unsafe)
                        continue;
                if (req->r_session &&
                    req->r_session->s_mds == mds) {
                        dout(" kicking tid %llu\n", req->r_tid);
                        __do_request(mdsc, req);
                }
        }
}

void ceph_mdsc_submit_request(struct ceph_mds_client *mdsc,
                              struct ceph_mds_request *req)
{
        dout("submit_request on %p\n", req);
        mutex_lock(&mdsc->mutex);
        __register_request(mdsc, req, NULL);
        __do_request(mdsc, req);
        mutex_unlock(&mdsc->mutex);
}

/*
 * Synchrously perform an mds request.  Take care of all of the
 * session setup, forwarding, retry details.
 */
int ceph_mdsc_do_request(struct ceph_mds_client *mdsc,
                         struct inode *dir,
                         struct ceph_mds_request *req)
{
        int err;

        dout("do_request on %p\n", req);

        /* take CAP_PIN refs for r_inode, r_locked_dir, r_old_dentry */
        if (req->r_inode)
                ceph_get_cap_refs(ceph_inode(req->r_inode), CEPH_CAP_PIN);
        if (req->r_locked_dir)
                ceph_get_cap_refs(ceph_inode(req->r_locked_dir), CEPH_CAP_PIN);
        if (req->r_old_dentry)
                ceph_get_cap_refs(ceph_inode(req->r_old_dentry_dir),
                                  CEPH_CAP_PIN);

        /* issue */
        mutex_lock(&mdsc->mutex);
        __register_request(mdsc, req, dir);
        __do_request(mdsc, req);

        if (req->r_err) {
                err = req->r_err;
                __unregister_request(mdsc, req);
                dout("do_request early error %d\n", err);
                goto out;
        }

        /* wait */
        mutex_unlock(&mdsc->mutex);
        dout("do_request waiting\n");
        if (req->r_timeout) {
                err = (long)wait_for_completion_killable_timeout(
                        &req->r_completion, req->r_timeout);
                if (err == 0)
                        err = -EIO;
        } else {
                err = wait_for_completion_killable(&req->r_completion);
        }
        dout("do_request waited, got %d\n", err);
        mutex_lock(&mdsc->mutex);

        /* only abort if we didn't race with a real reply */
        if (req->r_got_result) {
                err = le32_to_cpu(req->r_reply_info.head->result);
        } else if (err < 0) {
                dout("aborted request %lld with %d\n", req->r_tid, err);

                /*
                 * ensure we aren't running concurrently with
                 * ceph_fill_trace or ceph_readdir_prepopulate, which
                 * rely on locks (dir mutex) held by our caller.
                 */
                mutex_lock(&req->r_fill_mutex);
                req->r_err = err;
                req->r_aborted = true;
                mutex_unlock(&req->r_fill_mutex);

                if (req->r_locked_dir &&
                    (req->r_op & CEPH_MDS_OP_WRITE))
                        ceph_invalidate_dir_request(req);
        } else {
                err = req->r_err;
        }

out:
        mutex_unlock(&mdsc->mutex);
        dout("do_request %p done, result %d\n", req, err);
        return err;
}

/*
 * Invalidate dir's completeness, dentry lease state on an aborted MDS
 * namespace request.
 */
void ceph_invalidate_dir_request(struct ceph_mds_request *req)
{
        struct inode *inode = req->r_locked_dir;

        dout("invalidate_dir_request %p (complete, lease(s))\n", inode);

        ceph_dir_clear_complete(inode);
        if (req->r_dentry)
                ceph_invalidate_dentry_lease(req->r_dentry);
        if (req->r_old_dentry)
                ceph_invalidate_dentry_lease(req->r_old_dentry);
}

/*
 * Handle mds reply.
 *
 * We take the session mutex and parse and process the reply immediately.
 * This preserves the logical ordering of replies, capabilities, etc., sent
 * by the MDS as they are applied to our local cache.
 */
static void handle_reply(struct ceph_mds_session *session, struct ceph_msg *msg)
{
        struct ceph_mds_client *mdsc = session->s_mdsc;
        struct ceph_mds_request *req;
        struct ceph_mds_reply_head *head = msg->front.iov_base;
        struct ceph_mds_reply_info_parsed *rinfo;  /* parsed reply info */
        u64 tid;
        int err, result;
        int mds = session->s_mds;

        if (msg->front.iov_len < sizeof(*head)) {
                pr_err("mdsc_handle_reply got corrupt (short) reply\n");
                ceph_msg_dump(msg);
                return;
        }

        /* get request, session */
        tid = le64_to_cpu(msg->hdr.tid);
        mutex_lock(&mdsc->mutex);
        req = __lookup_request(mdsc, tid);
        if (!req) {
                dout("handle_reply on unknown tid %llu\n", tid);
                mutex_unlock(&mdsc->mutex);
                return;
        }
        dout("handle_reply %p\n", req);

        /* correct session? */
        if (req->r_session != session) {
                pr_err("mdsc_handle_reply got %llu on session mds%d"
                       " not mds%d\n", tid, session->s_mds,
                       req->r_session ? req->r_session->s_mds : -1);
                mutex_unlock(&mdsc->mutex);
                goto out;
        }

        /* dup? */
        if ((req->r_got_unsafe && !head->safe) ||
            (req->r_got_safe && head->safe)) {
                pr_warning("got a dup %s reply on %llu from mds%d\n",
                           head->safe ? "safe" : "unsafe", tid, mds);
                mutex_unlock(&mdsc->mutex);
                goto out;
        }
        if (req->r_got_safe && !head->safe) {
                pr_warning("got unsafe after safe on %llu from mds%d\n",
                           tid, mds);
                mutex_unlock(&mdsc->mutex);
                goto out;
        }

        result = le32_to_cpu(head->result);

        /*
         * Handle an ESTALE
         * if we're not talking to the authority, send to them
         * if the authority has changed while we weren't looking,
         * send to new authority
         * Otherwise we just have to return an ESTALE
         */
        if (result == -ESTALE) {
                dout("got ESTALE on request %llu", req->r_tid);
                if (!req->r_inode) {
                        /* do nothing; not an authority problem */
                } else if (req->r_direct_mode != USE_AUTH_MDS) {
                        dout("not using auth, setting for that now");
                        req->r_direct_mode = USE_AUTH_MDS;
                        __do_request(mdsc, req);
                        mutex_unlock(&mdsc->mutex);
                        goto out;
                } else  {
                        struct ceph_inode_info *ci = ceph_inode(req->r_inode);
                        struct ceph_cap *cap = NULL;

                        if (req->r_session)
                                cap = ceph_get_cap_for_mds(ci,
                                                   req->r_session->s_mds);

                        dout("already using auth");
                        if ((!cap || cap != ci->i_auth_cap) ||
                            (cap->mseq != req->r_sent_on_mseq)) {
                                dout("but cap changed, so resending");
                                __do_request(mdsc, req);
                                mutex_unlock(&mdsc->mutex);
                                goto out;
                        }
                }
                dout("have to return ESTALE on request %llu", req->r_tid);
        }


        if (head->safe) {
                req->r_got_safe = true;
                __unregister_request(mdsc, req);
                complete_all(&req->r_safe_completion);

                if (req->r_got_unsafe) {
                        /*
                         * We already handled the unsafe response, now do the
                         * cleanup.  No need to examine the response; the MDS
                         * doesn't include any result info in the safe
                         * response.  And even if it did, there is nothing
                         * useful we could do with a revised return value.
                         */
                        dout("got safe reply %llu, mds%d\n", tid, mds);
                        list_del_init(&req->r_unsafe_item);

                        /* last unsafe request during umount? */
                        if (mdsc->stopping && !__get_oldest_req(mdsc))
                                complete_all(&mdsc->safe_umount_waiters);
                        mutex_unlock(&mdsc->mutex);
                        goto out;
                }
        } else {
                req->r_got_unsafe = true;
                list_add_tail(&req->r_unsafe_item, &req->r_session->s_unsafe);
        }

        dout("handle_reply tid %lld result %d\n", tid, result);
        rinfo = &req->r_reply_info;
        err = parse_reply_info(msg, rinfo, session->s_con.peer_features);
        mutex_unlock(&mdsc->mutex);

        mutex_lock(&session->s_mutex);
        if (err < 0) {
                pr_err("mdsc_handle_reply got corrupt reply mds%d(tid:%lld)\n", mds, tid);
                ceph_msg_dump(msg);
                goto out_err;
        }

        /* snap trace */
        if (rinfo->snapblob_len) {
                down_write(&mdsc->snap_rwsem);
                ceph_update_snap_trace(mdsc, rinfo->snapblob,
                               rinfo->snapblob + rinfo->snapblob_len,
                               le32_to_cpu(head->op) == CEPH_MDS_OP_RMSNAP);
                downgrade_write(&mdsc->snap_rwsem);
        } else {
                down_read(&mdsc->snap_rwsem);
        }

        /* insert trace into our cache */
        mutex_lock(&req->r_fill_mutex);
        err = ceph_fill_trace(mdsc->fsc->sb, req, req->r_session);
        if (err == 0) {
                if (result == 0 && (req->r_op == CEPH_MDS_OP_READDIR ||
                                    req->r_op == CEPH_MDS_OP_LSSNAP) &&
                    rinfo->dir_nr)
                        ceph_readdir_prepopulate(req, req->r_session);
                ceph_unreserve_caps(mdsc, &req->r_caps_reservation);
        }
        mutex_unlock(&req->r_fill_mutex);

        up_read(&mdsc->snap_rwsem);
out_err:
        mutex_lock(&mdsc->mutex);
        if (!req->r_aborted) {
                if (err) {
                        req->r_err = err;
                } else {
                        req->r_reply = msg;
                        ceph_msg_get(msg);
                        req->r_got_result = true;
                }
        } else {
                dout("reply arrived after request %lld was aborted\n", tid);
        }
        mutex_unlock(&mdsc->mutex);

        ceph_add_cap_releases(mdsc, req->r_session);
        mutex_unlock(&session->s_mutex);

        /* kick calling process */
        complete_request(mdsc, req);
out:
        ceph_mdsc_put_request(req);
        return;
}



/*
 * handle mds notification that our request has been forwarded.
 */
static void handle_forward(struct ceph_mds_client *mdsc,
                           struct ceph_mds_session *session,
                           struct ceph_msg *msg)
{
        struct ceph_mds_request *req;
        u64 tid = le64_to_cpu(msg->hdr.tid);
        u32 next_mds;
        u32 fwd_seq;
        int err = -EINVAL;
        void *p = msg->front.iov_base;
        void *end = p + msg->front.iov_len;

        ceph_decode_need(&p, end, 2*sizeof(u32), bad);
        next_mds = ceph_decode_32(&p);
        fwd_seq = ceph_decode_32(&p);

        mutex_lock(&mdsc->mutex);
        req = __lookup_request(mdsc, tid);
        if (!req) {
                dout("forward tid %llu to mds%d - req dne\n", tid, next_mds);
                goto out;  /* dup reply? */
        }

        if (req->r_aborted) {
                dout("forward tid %llu aborted, unregistering\n", tid);
                __unregister_request(mdsc, req);
        } else if (fwd_seq <= req->r_num_fwd) {
                dout("forward tid %llu to mds%d - old seq %d <= %d\n",
                     tid, next_mds, req->r_num_fwd, fwd_seq);
        } else {
                /* resend. forward race not possible; mds would drop */
                dout("forward tid %llu to mds%d (we resend)\n", tid, next_mds);
                BUG_ON(req->r_err);
                BUG_ON(req->r_got_result);
                req->r_num_fwd = fwd_seq;
                req->r_resend_mds = next_mds;
                put_request_session(req);
                __do_request(mdsc, req);
        }
        ceph_mdsc_put_request(req);
out:
        mutex_unlock(&mdsc->mutex);
        return;

bad:
        pr_err("mdsc_handle_forward decode error err=%d\n", err);
}

/*
 * handle a mds session control message
 */
static void handle_session(struct ceph_mds_session *session,
                           struct ceph_msg *msg)
{
        struct ceph_mds_client *mdsc = session->s_mdsc;
        u32 op;
        u64 seq;
        int mds = session->s_mds;
        struct ceph_mds_session_head *h = msg->front.iov_base;
        int wake = 0;

        /* decode */
        if (msg->front.iov_len != sizeof(*h))
                goto bad;
        op = le32_to_cpu(h->op);
        seq = le64_to_cpu(h->seq);

        mutex_lock(&mdsc->mutex);
        if (op == CEPH_SESSION_CLOSE)
                __unregister_session(mdsc, session);
        /* FIXME: this ttl calculation is generous */
        session->s_ttl = jiffies + HZ*mdsc->mdsmap->m_session_autoclose;
        mutex_unlock(&mdsc->mutex);

        mutex_lock(&session->s_mutex);

        dout("handle_session mds%d %s %p state %s seq %llu\n",
             mds, ceph_session_op_name(op), session,
             session_state_name(session->s_state), seq);

        if (session->s_state == CEPH_MDS_SESSION_HUNG) {
                session->s_state = CEPH_MDS_SESSION_OPEN;
                pr_info("mds%d came back\n", session->s_mds);
        }

        switch (op) {
        case CEPH_SESSION_OPEN:
                if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
                        pr_info("mds%d reconnect success\n", session->s_mds);
                session->s_state = CEPH_MDS_SESSION_OPEN;
                renewed_caps(mdsc, session, 0);
                wake = 1;
                if (mdsc->stopping)
                        __close_session(mdsc, session);
                break;

        case CEPH_SESSION_RENEWCAPS:
                if (session->s_renew_seq == seq)
                        renewed_caps(mdsc, session, 1);
                break;

        case CEPH_SESSION_CLOSE:
                if (session->s_state == CEPH_MDS_SESSION_RECONNECTING)
                        pr_info("mds%d reconnect denied\n", session->s_mds);
                remove_session_caps(session);
                wake = 1; /* for good measure */
                wake_up_all(&mdsc->session_close_wq);
                kick_requests(mdsc, mds);
                break;

        case CEPH_SESSION_STALE:
                pr_info("mds%d caps went stale, renewing\n",
                        session->s_mds);
                spin_lock(&session->s_gen_ttl_lock);
                session->s_cap_gen++;
                session->s_cap_ttl = jiffies - 1;
                spin_unlock(&session->s_gen_ttl_lock);
                send_renew_caps(mdsc, session);
                break;

        case CEPH_SESSION_RECALL_STATE:
                trim_caps(mdsc, session, le32_to_cpu(h->max_caps));
                break;

        default:
                pr_err("mdsc_handle_session bad op %d mds%d\n", op, mds);
                WARN_ON(1);
        }

        mutex_unlock(&session->s_mutex);
        if (wake) {
                mutex_lock(&mdsc->mutex);
                __wake_requests(mdsc, &session->s_waiting);
                mutex_unlock(&mdsc->mutex);
        }
        return;

bad:
        pr_err("mdsc_handle_session corrupt message mds%d len %d\n", mds,
               (int)msg->front.iov_len);
        ceph_msg_dump(msg);
        return;
}


/*
 * called under session->mutex.
 */
static void replay_unsafe_requests(struct ceph_mds_client *mdsc,
                                   struct ceph_mds_session *session)
{
        struct ceph_mds_request *req, *nreq;
        int err;

        dout("replay_unsafe_requests mds%d\n", session->s_mds);

        mutex_lock(&mdsc->mutex);
        list_for_each_entry_safe(req, nreq, &session->s_unsafe, r_unsafe_item) {
                err = __prepare_send_request(mdsc, req, session->s_mds);
                if (!err) {
                        ceph_msg_get(req->r_request);
                        ceph_con_send(&session->s_con, req->r_request);
                }
        }
        mutex_unlock(&mdsc->mutex);
}

/*
 * Encode information about a cap for a reconnect with the MDS.
 */
static int encode_caps_cb(struct inode *inode, struct ceph_cap *cap,
                          void *arg)
{
        union {
                struct ceph_mds_cap_reconnect v2;
                struct ceph_mds_cap_reconnect_v1 v1;
        } rec;
        size_t reclen;
        struct ceph_inode_info *ci;
        struct ceph_reconnect_state *recon_state = arg;
        struct ceph_pagelist *pagelist = recon_state->pagelist;
        char *path;
        int pathlen, err;
        u64 pathbase;
        struct dentry *dentry;

        ci = cap->ci;

        dout(" adding %p ino %llx.%llx cap %p %lld %s\n",
             inode, ceph_vinop(inode), cap, cap->cap_id,
             ceph_cap_string(cap->issued));
        err = ceph_pagelist_encode_64(pagelist, ceph_ino(inode));
        if (err)
                return err;

        dentry = d_find_alias(inode);
        if (dentry) {
                path = ceph_mdsc_build_path(dentry, &pathlen, &pathbase, 0);
                if (IS_ERR(path)) {
                        err = PTR_ERR(path);
                        goto out_dput;
                }
        } else {
                path = NULL;
                pathlen = 0;
        }
        err = ceph_pagelist_encode_string(pagelist, path, pathlen);
        if (err)
                goto out_free;

        spin_lock(&ci->i_ceph_lock);
        cap->seq = 0;        /* reset cap seq */
        cap->issue_seq = 0;  /* and issue_seq */
        cap->mseq = 0;       /* and migrate_seq */

        if (recon_state->flock) {
                rec.v2.cap_id = cpu_to_le64(cap->cap_id);
                rec.v2.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
                rec.v2.issued = cpu_to_le32(cap->issued);
                rec.v2.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
                rec.v2.pathbase = cpu_to_le64(pathbase);
                rec.v2.flock_len = 0;
                reclen = sizeof(rec.v2);
        } else {
                rec.v1.cap_id = cpu_to_le64(cap->cap_id);
                rec.v1.wanted = cpu_to_le32(__ceph_caps_wanted(ci));
                rec.v1.issued = cpu_to_le32(cap->issued);
                rec.v1.size = cpu_to_le64(inode->i_size);
                ceph_encode_timespec(&rec.v1.mtime, &inode->i_mtime);
                ceph_encode_timespec(&rec.v1.atime, &inode->i_atime);
                rec.v1.snaprealm = cpu_to_le64(ci->i_snap_realm->ino);
                rec.v1.pathbase = cpu_to_le64(pathbase);
                reclen = sizeof(rec.v1);
        }
        spin_unlock(&ci->i_ceph_lock);

        if (recon_state->flock) {
                int num_fcntl_locks, num_flock_locks;
                struct ceph_filelock *flocks;

encode_again:
                spin_lock(&inode->i_lock);
                ceph_count_locks(inode, &num_fcntl_locks, &num_flock_locks);
                spin_unlock(&inode->i_lock);
                flocks = kmalloc((num_fcntl_locks+num_flock_locks) *
                                 sizeof(struct ceph_filelock), GFP_NOFS);
                if (!flocks) {
                        err = -ENOMEM;
                        goto out_free;
                }
                spin_lock(&inode->i_lock);
                err = ceph_encode_locks_to_buffer(inode, flocks,
                                                  num_fcntl_locks,
                                                  num_flock_locks);
                spin_unlock(&inode->i_lock);
                if (err) {
                        kfree(flocks);
                        if (err == -ENOSPC)
                                goto encode_again;
                        goto out_free;
                }
                /*
                 * number of encoded locks is stable, so copy to pagelist
                 */
                rec.v2.flock_len = cpu_to_le32(2*sizeof(u32) +
                                    (num_fcntl_locks+num_flock_locks) *
                                    sizeof(struct ceph_filelock));
                err = ceph_pagelist_append(pagelist, &rec, reclen);
                if (!err)
                        err = ceph_locks_to_pagelist(flocks, pagelist,
                                                     num_fcntl_locks,
                                                     num_flock_locks);
                kfree(flocks);
        } else {
                err = ceph_pagelist_append(pagelist, &rec, reclen);
        }
out_free:
        kfree(path);
out_dput:
        dput(dentry);
        return err;
}


/*
 * If an MDS fails and recovers, clients need to reconnect in order to
 * reestablish shared state.  This includes all caps issued through
 * this session _and_ the snap_realm hierarchy.  Because it's not
 * clear which snap realms the mds cares about, we send everything we
 * know about.. that ensures we'll then get any new info the
 * recovering MDS might have.
 *
 * This is a relatively heavyweight operation, but it's rare.
 *
 * called with mdsc->mutex held.
 */
static void send_mds_reconnect(struct ceph_mds_client *mdsc,
                               struct ceph_mds_session *session)
{
        struct ceph_msg *reply;
        struct rb_node *p;
        int mds = session->s_mds;
        int err = -ENOMEM;
        struct ceph_pagelist *pagelist;
        struct ceph_reconnect_state recon_state;

        pr_info("mds%d reconnect start\n", mds);

        pagelist = kmalloc(sizeof(*pagelist), GFP_NOFS);
        if (!pagelist)
                goto fail_nopagelist;
        ceph_pagelist_init(pagelist);

        reply = ceph_msg_new(CEPH_MSG_CLIENT_RECONNECT, 0, GFP_NOFS, false);
        if (!reply)
                goto fail_nomsg;

        mutex_lock(&session->s_mutex);
        session->s_state = CEPH_MDS_SESSION_RECONNECTING;
        session->s_seq = 0;

        ceph_con_close(&session->s_con);
        ceph_con_open(&session->s_con,
                      CEPH_ENTITY_TYPE_MDS, mds,
                      ceph_mdsmap_get_addr(mdsc->mdsmap, mds));

        /* replay unsafe requests */
        replay_unsafe_requests(mdsc, session);

        down_read(&mdsc->snap_rwsem);

        dout("session %p state %s\n", session,
             session_state_name(session->s_state));

        /* drop old cap expires; we're about to reestablish that state */
        discard_cap_releases(mdsc, session);

        /* traverse this session's caps */
        err = ceph_pagelist_encode_32(pagelist, session->s_nr_caps);
        if (err)
                goto fail;

        recon_state.pagelist = pagelist;
        recon_state.flock = session->s_con.peer_features & CEPH_FEATURE_FLOCK;
        err = iterate_session_caps(session, encode_caps_cb, &recon_state);
        if (err < 0)
                goto fail;

        /*
         * snaprealms.  we provide mds with the ino, seq (version), and
         * parent for all of our realms.  If the mds has any newer info,
         * it will tell us.
         */
        for (p = rb_first(&mdsc->snap_realms); p; p = rb_next(p)) {
                struct ceph_snap_realm *realm =
                        rb_entry(p, struct ceph_snap_realm, node);
                struct ceph_mds_snaprealm_reconnect sr_rec;

                dout(" adding snap realm %llx seq %lld parent %llx\n",
                     realm->ino, realm->seq, realm->parent_ino);
                sr_rec.ino = cpu_to_le64(realm->ino);
                sr_rec.seq = cpu_to_le64(realm->seq);
                sr_rec.parent = cpu_to_le64(realm->parent_ino);
                err = ceph_pagelist_append(pagelist, &sr_rec, sizeof(sr_rec));
                if (err)
                        goto fail;
        }

        if (recon_state.flock)
                reply->hdr.version = cpu_to_le16(2);
        if (pagelist->length) {
                /* set up outbound data if we have any */
                reply->hdr.data_len = cpu_to_le32(pagelist->length);
                ceph_msg_data_add_pagelist(reply, pagelist);
        }
        ceph_con_send(&session->s_con, reply);

        mutex_unlock(&session->s_mutex);

        mutex_lock(&mdsc->mutex);
        __wake_requests(mdsc, &session->s_waiting);
        mutex_unlock(&mdsc->mutex);

        up_read(&mdsc->snap_rwsem);
        return;

fail:
        ceph_msg_put(reply);
        up_read(&mdsc->snap_rwsem);
        mutex_unlock(&session->s_mutex);
fail_nomsg:
        ceph_pagelist_release(pagelist);
        kfree(pagelist);
fail_nopagelist:
        pr_err("error %d preparing reconnect for mds%d\n", err, mds);
        return;
}


/*
 * compare old and new mdsmaps, kicking requests
 * and closing out old connections as necessary
 *
 * called under mdsc->mutex.
 */
static void check_new_map(struct ceph_mds_client *mdsc,
                          struct ceph_mdsmap *newmap,
                          struct ceph_mdsmap *oldmap)
{
        int i;
        int oldstate, newstate;
        struct ceph_mds_session *s;

        dout("check_new_map new %u old %u\n",
             newmap->m_epoch, oldmap->m_epoch);

        for (i = 0; i < oldmap->m_max_mds && i < mdsc->max_sessions; i++) {
                if (mdsc->sessions[i] == NULL)
                        continue;
                s = mdsc->sessions[i];
                oldstate = ceph_mdsmap_get_state(oldmap, i);
                newstate = ceph_mdsmap_get_state(newmap, i);

                dout("check_new_map mds%d state %s%s -> %s%s (session %s)\n",
                     i, ceph_mds_state_name(oldstate),
                     ceph_mdsmap_is_laggy(oldmap, i) ? " (laggy)" : "",
                     ceph_mds_state_name(newstate),
                     ceph_mdsmap_is_laggy(newmap, i) ? " (laggy)" : "",
                     session_state_name(s->s_state));

                if (i >= newmap->m_max_mds ||
                    memcmp(ceph_mdsmap_get_addr(oldmap, i),
                           ceph_mdsmap_get_addr(newmap, i),
                           sizeof(struct ceph_entity_addr))) {
                        if (s->s_state == CEPH_MDS_SESSION_OPENING) {
                                /* the session never opened, just close it
                                 * out now */
                                __wake_requests(mdsc, &s->s_waiting);
                                __unregister_session(mdsc, s);
                        } else {
                                /* just close it */
                                mutex_unlock(&mdsc->mutex);
                                mutex_lock(&s->s_mutex);
                                mutex_lock(&mdsc->mutex);
                                ceph_con_close(&s->s_con);
                                mutex_unlock(&s->s_mutex);
                                s->s_state = CEPH_MDS_SESSION_RESTARTING;
                        }

                        /* kick any requests waiting on the recovering mds */
                        kick_requests(mdsc, i);
                } else if (oldstate == newstate) {
                        continue;  /* nothing new with this mds */
                }

                /*
                 * send reconnect?
                 */
                if (s->s_state == CEPH_MDS_SESSION_RESTARTING &&
                    newstate >= CEPH_MDS_STATE_RECONNECT) {
                        mutex_unlock(&mdsc->mutex);
                        send_mds_reconnect(mdsc, s);
                        mutex_lock(&mdsc->mutex);
                }

                /*
                 * kick request on any mds that has gone active.
                 */
                if (oldstate < CEPH_MDS_STATE_ACTIVE &&
                    newstate >= CEPH_MDS_STATE_ACTIVE) {
                        if (oldstate != CEPH_MDS_STATE_CREATING &&
                            oldstate != CEPH_MDS_STATE_STARTING)
                                pr_info("mds%d recovery completed\n", s->s_mds);
                        kick_requests(mdsc, i);
                        ceph_kick_flushing_caps(mdsc, s);
                        wake_up_session_caps(s, 1);
                }
        }

        for (i = 0; i < newmap->m_max_mds && i < mdsc->max_sessions; i++) {
                s = mdsc->sessions[i];
                if (!s)
                        continue;
                if (!ceph_mdsmap_is_laggy(newmap, i))
                        continue;
                if (s->s_state == CEPH_MDS_SESSION_OPEN ||
                    s->s_state == CEPH_MDS_SESSION_HUNG ||
                    s->s_state == CEPH_MDS_SESSION_CLOSING) {
                        dout(" connecting to export targets of laggy mds%d\n",
                             i);
                        __open_export_target_sessions(mdsc, s);
                }
        }
}



/*
 * leases
 */

/*
 * caller must hold session s_mutex, dentry->d_lock
 */
void __ceph_mdsc_drop_dentry_lease(struct dentry *dentry)
{
        struct ceph_dentry_info *di = ceph_dentry(dentry);

        ceph_put_mds_session(di->lease_session);
        di->lease_session = NULL;
}

static void handle_lease(struct ceph_mds_client *mdsc,
                         struct ceph_mds_session *session,
                         struct ceph_msg *msg)
{
        struct super_block *sb = mdsc->fsc->sb;
        struct inode *inode;
        struct dentry *parent, *dentry;
        struct ceph_dentry_info *di;
        int mds = session->s_mds;
        struct ceph_mds_lease *h = msg->front.iov_base;
        u32 seq;
        struct ceph_vino vino;
        struct qstr dname;
        int release = 0;

        dout("handle_lease from mds%d\n", mds);

        /* decode */
        if (msg->front.iov_len < sizeof(*h) + sizeof(u32))
                goto bad;
        vino.ino = le64_to_cpu(h->ino);
        vino.snap = CEPH_NOSNAP;
        seq = le32_to_cpu(h->seq);
        dname.name = (void *)h + sizeof(*h) + sizeof(u32);
        dname.len = msg->front.iov_len - sizeof(*h) - sizeof(u32);
        if (dname.len != get_unaligned_le32(h+1))
                goto bad;

        mutex_lock(&session->s_mutex);
        session->s_seq++;

        /* lookup inode */
        inode = ceph_find_inode(sb, vino);
        dout("handle_lease %s, ino %llx %p %.*s\n",
             ceph_lease_op_name(h->action), vino.ino, inode,
             dname.len, dname.name);
        if (inode == NULL) {
                dout("handle_lease no inode %llx\n", vino.ino);
                goto release;
        }

        /* dentry */
        parent = d_find_alias(inode);
        if (!parent) {
                dout("no parent dentry on inode %p\n", inode);
                WARN_ON(1);
                goto release;  /* hrm... */
        }
        dname.hash = full_name_hash(dname.name, dname.len);
        dentry = d_lookup(parent, &dname);
        dput(parent);
        if (!dentry)
                goto release;

        spin_lock(&dentry->d_lock);
        di = ceph_dentry(dentry);
        switch (h->action) {
        case CEPH_MDS_LEASE_REVOKE:
                if (di->lease_session == session) {
                        if (ceph_seq_cmp(di->lease_seq, seq) > 0)
                                h->seq = cpu_to_le32(di->lease_seq);
                        __ceph_mdsc_drop_dentry_lease(dentry);
                }
                release = 1;
                break;

        case CEPH_MDS_LEASE_RENEW:
                if (di->lease_session == session &&
                    di->lease_gen == session->s_cap_gen &&
                    di->lease_renew_from &&
                    di->lease_renew_after == 0) {
                        unsigned long duration =
                                le32_to_cpu(h->duration_ms) * HZ / 1000;

                        di->lease_seq = seq;
                        dentry->d_time = di->lease_renew_from + duration;
                        di->lease_renew_after = di->lease_renew_from +
                                (duration >> 1);
                        di->lease_renew_from = 0;
                }
                break;
        }
        spin_unlock(&dentry->d_lock);
        dput(dentry);

        if (!release)
                goto out;

release:
        /* let's just reuse the same message */
        h->action = CEPH_MDS_LEASE_REVOKE_ACK;
        ceph_msg_get(msg);
        ceph_con_send(&session->s_con, msg);

out:
        iput(inode);
        mutex_unlock(&session->s_mutex);
        return;

bad:
        pr_err("corrupt lease message\n");
        ceph_msg_dump(msg);
}

void ceph_mdsc_lease_send_msg(struct ceph_mds_session *session,
                              struct inode *inode,
                              struct dentry *dentry, char action,
                              u32 seq)
{
        struct ceph_msg *msg;
        struct ceph_mds_lease *lease;
        int len = sizeof(*lease) + sizeof(u32);
        int dnamelen = 0;

        dout("lease_send_msg inode %p dentry %p %s to mds%d\n",
             inode, dentry, ceph_lease_op_name(action), session->s_mds);
        dnamelen = dentry->d_name.len;
        len += dnamelen;

        msg = ceph_msg_new(CEPH_MSG_CLIENT_LEASE, len, GFP_NOFS, false);
        if (!msg)
                return;
        lease = msg->front.iov_base;
        lease->action = action;
        lease->ino = cpu_to_le64(ceph_vino(inode).ino);
        lease->first = lease->last = cpu_to_le64(ceph_vino(inode).snap);
        lease->seq = cpu_to_le32(seq);
        put_unaligned_le32(dnamelen, lease + 1);
        memcpy((void *)(lease + 1) + 4, dentry->d_name.name, dnamelen);

        /*
         * if this is a preemptive lease RELEASE, no need to
         * flush request stream, since the actual request will
         * soon follow.
         */
        msg->more_to_follow = (action == CEPH_MDS_LEASE_RELEASE);

        ceph_con_send(&session->s_con, msg);
}

/*
 * Preemptively release a lease we expect to invalidate anyway.
 * Pass @inode always, @dentry is optional.
 */
void ceph_mdsc_lease_release(struct ceph_mds_client *mdsc, struct inode *inode,
                             struct dentry *dentry)
{
        struct ceph_dentry_info *di;
        struct ceph_mds_session *session;
        u32 seq;

        BUG_ON(inode == NULL);
        BUG_ON(dentry == NULL);

        /* is dentry lease valid? */
        spin_lock(&dentry->d_lock);
        di = ceph_dentry(dentry);
        if (!di || !di->lease_session ||
            di->lease_session->s_mds < 0 ||
            di->lease_gen != di->lease_session->s_cap_gen ||
            !time_before(jiffies, dentry->d_time)) {
                dout("lease_release inode %p dentry %p -- "
                     "no lease\n",
                     inode, dentry);
                spin_unlock(&dentry->d_lock);
                return;
        }

        /* we do have a lease on this dentry; note mds and seq */
        session = ceph_get_mds_session(di->lease_session);
        seq = di->lease_seq;
        __ceph_mdsc_drop_dentry_lease(dentry);
        spin_unlock(&dentry->d_lock);

        dout("lease_release inode %p dentry %p to mds%d\n",
             inode, dentry, session->s_mds);
        ceph_mdsc_lease_send_msg(session, inode, dentry,
                                 CEPH_MDS_LEASE_RELEASE, seq);
        ceph_put_mds_session(session);
}

/*
 * drop all leases (and dentry refs) in preparation for umount
 */
static void drop_leases(struct ceph_mds_client *mdsc)
{
        int i;

        dout("drop_leases\n");
        mutex_lock(&mdsc->mutex);
        for (i = 0; i < mdsc->max_sessions; i++) {
                struct ceph_mds_session *s = __ceph_lookup_mds_session(mdsc, i);
                if (!s)
                        continue;
                mutex_unlock(&mdsc->mutex);
                mutex_lock(&s->s_mutex);
                mutex_unlock(&s->s_mutex);
                ceph_put_mds_session(s);
                mutex_lock(&mdsc->mutex);
        }
        mutex_unlock(&mdsc->mutex);
}



/*
 * delayed work -- periodically trim expired leases, renew caps with mds
 */
static void schedule_delayed(struct ceph_mds_client *mdsc)
{
        int delay = 5;
        unsigned hz = round_jiffies_relative(HZ * delay);
        schedule_delayed_work(&mdsc->delayed_work, hz);
}

static void delayed_work(struct work_struct *work)
{
        int i;
        struct ceph_mds_client *mdsc =
                container_of(work, struct ceph_mds_client, delayed_work.work);
        int renew_interval;
        int renew_caps;

        dout("mdsc delayed_work\n");
        ceph_check_delayed_caps(mdsc);

        mutex_lock(&mdsc->mutex);
        renew_interval = mdsc->mdsmap->m_session_timeout >> 2;
        renew_caps = time_after_eq(jiffies, HZ*renew_interval +
                                   mdsc->last_renew_caps);
        if (renew_caps)
                mdsc->last_renew_caps = jiffies;

        for (i = 0; i < mdsc->max_sessions; i++) {
                struct ceph_mds_session *s = __ceph_lookup_mds_session(mdsc, i);
                if (s == NULL)
                        continue;
                if (s->s_state == CEPH_MDS_SESSION_CLOSING) {
                        dout("resending session close request for mds%d\n",
                             s->s_mds);
                        request_close_session(mdsc, s);
                        ceph_put_mds_session(s);
                        continue;
                }
                if (s->s_ttl && time_after(jiffies, s->s_ttl)) {
                        if (s->s_state == CEPH_MDS_SESSION_OPEN) {
                                s->s_state = CEPH_MDS_SESSION_HUNG;
                                pr_info("mds%d hung\n", s->s_mds);
                        }
                }
                if (s->s_state < CEPH_MDS_SESSION_OPEN) {
                        /* this mds is failed or recovering, just wait */
                        ceph_put_mds_session(s);
                        continue;
                }
                mutex_unlock(&mdsc->mutex);

                mutex_lock(&s->s_mutex);
                if (renew_caps)
                        send_renew_caps(mdsc, s);
                else
                        ceph_con_keepalive(&s->s_con);
                ceph_add_cap_releases(mdsc, s);
                if (s->s_state == CEPH_MDS_SESSION_OPEN ||
                    s->s_state == CEPH_MDS_SESSION_HUNG)
                        ceph_send_cap_releases(mdsc, s);
                mutex_unlock(&s->s_mutex);
                ceph_put_mds_session(s);

                mutex_lock(&mdsc->mutex);
        }
        mutex_unlock(&mdsc->mutex);

        schedule_delayed(mdsc);
}

int ceph_mdsc_init(struct ceph_fs_client *fsc)

{
        struct ceph_mds_client *mdsc;

        mdsc = kzalloc(sizeof(struct ceph_mds_client), GFP_NOFS);
        if (!mdsc)
                return -ENOMEM;
        mdsc->fsc = fsc;
        fsc->mdsc = mdsc;
        mutex_init(&mdsc->mutex);
        mdsc->mdsmap = kzalloc(sizeof(*mdsc->mdsmap), GFP_NOFS);
        if (mdsc->mdsmap == NULL) {
                kfree(mdsc);
                return -ENOMEM;
        }

        init_completion(&mdsc->safe_umount_waiters);
        init_waitqueue_head(&mdsc->session_close_wq);
        INIT_LIST_HEAD(&mdsc->waiting_for_map);
        mdsc->sessions = NULL;
        mdsc->max_sessions = 0;
        mdsc->stopping = 0;
        init_rwsem(&mdsc->snap_rwsem);
        mdsc->snap_realms = RB_ROOT;
        INIT_LIST_HEAD(&mdsc->snap_empty);
        spin_lock_init(&mdsc->snap_empty_lock);
        mdsc->last_tid = 0;
        mdsc->request_tree = RB_ROOT;
        INIT_DELAYED_WORK(&mdsc->delayed_work, delayed_work);
        mdsc->last_renew_caps = jiffies;
        INIT_LIST_HEAD(&mdsc->cap_delay_list);
        spin_lock_init(&mdsc->cap_delay_lock);
        INIT_LIST_HEAD(&mdsc->snap_flush_list);
        spin_lock_init(&mdsc->snap_flush_lock);
        mdsc->cap_flush_seq = 0;
        INIT_LIST_HEAD(&mdsc->cap_dirty);
        INIT_LIST_HEAD(&mdsc->cap_dirty_migrating);
        mdsc->num_cap_flushing = 0;
        spin_lock_init(&mdsc->cap_dirty_lock);
        init_waitqueue_head(&mdsc->cap_flushing_wq);
        spin_lock_init(&mdsc->dentry_lru_lock);
        INIT_LIST_HEAD(&mdsc->dentry_lru);

        ceph_caps_init(mdsc);
        ceph_adjust_min_caps(mdsc, fsc->min_caps);

        return 0;
}

/*
 * Wait for safe replies on open mds requests.  If we time out, drop
 * all requests from the tree to avoid dangling dentry refs.
 */
static void wait_requests(struct ceph_mds_client *mdsc)
{
        struct ceph_mds_request *req;
        struct ceph_fs_client *fsc = mdsc->fsc;

        mutex_lock(&mdsc->mutex);
        if (__get_oldest_req(mdsc)) {
                mutex_unlock(&mdsc->mutex);

                dout("wait_requests waiting for requests\n");
                wait_for_completion_timeout(&mdsc->safe_umount_waiters,
                                    fsc->client->options->mount_timeout * HZ);

                /* tear down remaining requests */
                mutex_lock(&mdsc->mutex);
                while ((req = __get_oldest_req(mdsc))) {
                        dout("wait_requests timed out on tid %llu\n",
                             req->r_tid);
                        __unregister_request(mdsc, req);
                }
        }
        mutex_unlock(&mdsc->mutex);
        dout("wait_requests done\n");
}

/*
 * called before mount is ro, and before dentries are torn down.
 * (hmm, does this still race with new lookups?)
 */
void ceph_mdsc_pre_umount(struct ceph_mds_client *mdsc)
{
        dout("pre_umount\n");
        mdsc->stopping = 1;

        drop_leases(mdsc);
        ceph_flush_dirty_caps(mdsc);
        wait_requests(mdsc);

        /*
         * wait for reply handlers to drop their request refs and
         * their inode/dcache refs
         */
        ceph_msgr_flush();
}

/*
 * wait for all write mds requests to flush.
 */
static void wait_unsafe_requests(struct ceph_mds_client *mdsc, u64 want_tid)
{
        struct ceph_mds_request *req = NULL, *nextreq;
        struct rb_node *n;

        mutex_lock(&mdsc->mutex);
        dout("wait_unsafe_requests want %lld\n", want_tid);
restart:
        req = __get_oldest_req(mdsc);
        while (req && req->r_tid <= want_tid) {
                /* find next request */
                n = rb_next(&req->r_node);
                if (n)
                        nextreq = rb_entry(n, struct ceph_mds_request, r_node);
                else
                        nextreq = NULL;
                if ((req->r_op & CEPH_MDS_OP_WRITE)) {
                        /* write op */
                        ceph_mdsc_get_request(req);
                        if (nextreq)
                                ceph_mdsc_get_request(nextreq);
                        mutex_unlock(&mdsc->mutex);
                        dout("wait_unsafe_requests  wait on %llu (want %llu)\n",
                             req->r_tid, want_tid);
                        wait_for_completion(&req->r_safe_completion);
                        mutex_lock(&mdsc->mutex);
                        ceph_mdsc_put_request(req);
                        if (!nextreq)
                                break;  /* next dne before, so we're done! */
                        if (RB_EMPTY_NODE(&nextreq->r_node)) {
                                /* next request was removed from tree */
                                ceph_mdsc_put_request(nextreq);
                                goto restart;
                        }
                        ceph_mdsc_put_request(nextreq);  /* won't go away */
                }
                req = nextreq;
        }
        mutex_unlock(&mdsc->mutex);
        dout("wait_unsafe_requests done\n");
}

void ceph_mdsc_sync(struct ceph_mds_client *mdsc)
{
        u64 want_tid, want_flush;

        if (mdsc->fsc->mount_state == CEPH_MOUNT_SHUTDOWN)
                return;

        dout("sync\n");
        mutex_lock(&mdsc->mutex);
        want_tid = mdsc->last_tid;
        want_flush = mdsc->cap_flush_seq;
        mutex_unlock(&mdsc->mutex);
        dout("sync want tid %lld flush_seq %lld\n", want_tid, want_flush);

        ceph_flush_dirty_caps(mdsc);

        wait_unsafe_requests(mdsc, want_tid);
        wait_event(mdsc->cap_flushing_wq, check_cap_flush(mdsc, want_flush));
}

/*
 * true if all sessions are closed, or we force unmount
 */
static bool done_closing_sessions(struct ceph_mds_client *mdsc)
{
        int i, n = 0;

        if (mdsc->fsc->mount_state == CEPH_MOUNT_SHUTDOWN)
                return true;

        mutex_lock(&mdsc->mutex);
        for (i = 0; i < mdsc->max_sessions; i++)
                if (mdsc->sessions[i])
                        n++;
        mutex_unlock(&mdsc->mutex);
        return n == 0;
}

/*
 * called after sb is ro.
 */
void ceph_mdsc_close_sessions(struct ceph_mds_client *mdsc)
{
        struct ceph_mds_session *session;
        int i;
        struct ceph_fs_client *fsc = mdsc->fsc;
        unsigned long timeout = fsc->client->options->mount_timeout * HZ;

        dout("close_sessions\n");

        /* close sessions */
        mutex_lock(&mdsc->mutex);
        for (i = 0; i < mdsc->max_sessions; i++) {
                session = __ceph_lookup_mds_session(mdsc, i);
                if (!session)
                        continue;
                mutex_unlock(&mdsc->mutex);
                mutex_lock(&session->s_mutex);
                __close_session(mdsc, session);
                mutex_unlock(&session->s_mutex);
                ceph_put_mds_session(session);
                mutex_lock(&mdsc->mutex);
        }
        mutex_unlock(&mdsc->mutex);

        dout("waiting for sessions to close\n");
        wait_event_timeout(mdsc->session_close_wq, done_closing_sessions(mdsc),
                           timeout);

        /* tear down remaining sessions */
        mutex_lock(&mdsc->mutex);
        for (i = 0; i < mdsc->max_sessions; i++) {
                if (mdsc->sessions[i]) {
                        session = get_session(mdsc->sessions[i]);
                        __unregister_session(mdsc, session);
                        mutex_unlock(&mdsc->mutex);
                        mutex_lock(&session->s_mutex);
                        remove_session_caps(session);
                        mutex_unlock(&session->s_mutex);
                        ceph_put_mds_session(session);
                        mutex_lock(&mdsc->mutex);
                }
        }
        WARN_ON(!list_empty(&mdsc->cap_delay_list));
        mutex_unlock(&mdsc->mutex);

        ceph_cleanup_empty_realms(mdsc);

        cancel_delayed_work_sync(&mdsc->delayed_work); /* cancel timer */

        dout("stopped\n");
}

static void ceph_mdsc_stop(struct ceph_mds_client *mdsc)
{
        dout("stop\n");
        cancel_delayed_work_sync(&mdsc->delayed_work); /* cancel timer */
        if (mdsc->mdsmap)
                ceph_mdsmap_destroy(mdsc->mdsmap);
        kfree(mdsc->sessions);
        ceph_caps_finalize(mdsc);
}

void ceph_mdsc_destroy(struct ceph_fs_client *fsc)
{
        struct ceph_mds_client *mdsc = fsc->mdsc;

        dout("mdsc_destroy %p\n", mdsc);
        ceph_mdsc_stop(mdsc);

        /* flush out any connection work with references to us */
        ceph_msgr_flush();

        fsc->mdsc = NULL;
        kfree(mdsc);
        dout("mdsc_destroy %p done\n", mdsc);
}


/*
 * handle mds map update.
 */
void ceph_mdsc_handle_map(struct ceph_mds_client *mdsc, struct ceph_msg *msg)
{
        u32 epoch;
        u32 maplen;
        void *p = msg->front.iov_base;
        void *end = p + msg->front.iov_len;
        struct ceph_mdsmap *newmap, *oldmap;
        struct ceph_fsid fsid;
        int err = -EINVAL;

        ceph_decode_need(&p, end, sizeof(fsid)+2*sizeof(u32), bad);
        ceph_decode_copy(&p, &fsid, sizeof(fsid));
        if (ceph_check_fsid(mdsc->fsc->client, &fsid) < 0)
                return;
        epoch = ceph_decode_32(&p);
        maplen = ceph_decode_32(&p);
        dout("handle_map epoch %u len %d\n", epoch, (int)maplen);

        /* do we need it? */
        ceph_monc_got_mdsmap(&mdsc->fsc->client->monc, epoch);
        mutex_lock(&mdsc->mutex);
        if (mdsc->mdsmap && epoch <= mdsc->mdsmap->m_epoch) {
                dout("handle_map epoch %u <= our %u\n",
                     epoch, mdsc->mdsmap->m_epoch);
                mutex_unlock(&mdsc->mutex);
                return;
        }

        newmap = ceph_mdsmap_decode(&p, end);
        if (IS_ERR(newmap)) {
                err = PTR_ERR(newmap);
                goto bad_unlock;
        }

        /* swap into place */
        if (mdsc->mdsmap) {
                oldmap = mdsc->mdsmap;
                mdsc->mdsmap = newmap;
                check_new_map(mdsc, newmap, oldmap);
                ceph_mdsmap_destroy(oldmap);
        } else {
                mdsc->mdsmap = newmap;  /* first mds map */
        }
        mdsc->fsc->sb->s_maxbytes = mdsc->mdsmap->m_max_file_size;

        __wake_requests(mdsc, &mdsc->waiting_for_map);

        mutex_unlock(&mdsc->mutex);
        schedule_delayed(mdsc);
        return;

bad_unlock:
        mutex_unlock(&mdsc->mutex);
bad:
        pr_err("error decoding mdsmap %d\n", err);
        return;
}

static struct ceph_connection *con_get(struct ceph_connection *con)
{
        struct ceph_mds_session *s = con->private;

        if (get_session(s)) {
                dout("mdsc con_get %p ok (%d)\n", s, atomic_read(&s->s_ref));
                return con;
        }
        dout("mdsc con_get %p FAIL\n", s);
        return NULL;
}

static void con_put(struct ceph_connection *con)
{
        struct ceph_mds_session *s = con->private;

        dout("mdsc con_put %p (%d)\n", s, atomic_read(&s->s_ref) - 1);
        ceph_put_mds_session(s);
}

/*
 * if the client is unresponsive for long enough, the mds will kill
 * the session entirely.
 */
static void peer_reset(struct ceph_connection *con)
{
        struct ceph_mds_session *s = con->private;
        struct ceph_mds_client *mdsc = s->s_mdsc;

        pr_warning("mds%d closed our session\n", s->s_mds);
        send_mds_reconnect(mdsc, s);
}

static void dispatch(struct ceph_connection *con, struct ceph_msg *msg)
{
        struct ceph_mds_session *s = con->private;
        struct ceph_mds_client *mdsc = s->s_mdsc;
        int type = le16_to_cpu(msg->hdr.type);

        mutex_lock(&mdsc->mutex);
        if (__verify_registered_session(mdsc, s) < 0) {
                mutex_unlock(&mdsc->mutex);
                goto out;
        }
        mutex_unlock(&mdsc->mutex);

        switch (type) {
        case CEPH_MSG_MDS_MAP:
                ceph_mdsc_handle_map(mdsc, msg);
                break;
        case CEPH_MSG_CLIENT_SESSION:
                handle_session(s, msg);
                break;
        case CEPH_MSG_CLIENT_REPLY:
                handle_reply(s, msg);
                break;
        case CEPH_MSG_CLIENT_REQUEST_FORWARD:
                handle_forward(mdsc, s, msg);
                break;
        case CEPH_MSG_CLIENT_CAPS:
                ceph_handle_caps(s, msg);
                break;
        case CEPH_MSG_CLIENT_SNAP:
                ceph_handle_snap(mdsc, s, msg);
                break;
        case CEPH_MSG_CLIENT_LEASE:
                handle_lease(mdsc, s, msg);
                break;

        default:
                pr_err("received unknown message type %d %s\n", type,
                       ceph_msg_type_name(type));
        }
out:
        ceph_msg_put(msg);
}

/*
 * authentication
 */

/*
 * Note: returned pointer is the address of a structure that's
 * managed separately.  Caller must *not* attempt to free it.
 */
static struct ceph_auth_handshake *get_authorizer(struct ceph_connection *con,
                                        int *proto, int force_new)
{
        struct ceph_mds_session *s = con->private;
        struct ceph_mds_client *mdsc = s->s_mdsc;
        struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;
        struct ceph_auth_handshake *auth = &s->s_auth;

        if (force_new && auth->authorizer) {
                ceph_auth_destroy_authorizer(ac, auth->authorizer);
                auth->authorizer = NULL;
        }
        if (!auth->authorizer) {
                int ret = ceph_auth_create_authorizer(ac, CEPH_ENTITY_TYPE_MDS,
                                                      auth);
                if (ret)
                        return ERR_PTR(ret);
        } else {
                int ret = ceph_auth_update_authorizer(ac, CEPH_ENTITY_TYPE_MDS,
                                                      auth);
                if (ret)
                        return ERR_PTR(ret);
        }
        *proto = ac->protocol;

        return auth;
}


static int verify_authorizer_reply(struct ceph_connection *con, int len)
{
        struct ceph_mds_session *s = con->private;
        struct ceph_mds_client *mdsc = s->s_mdsc;
        struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;

        return ceph_auth_verify_authorizer_reply(ac, s->s_auth.authorizer, len);
}

static int invalidate_authorizer(struct ceph_connection *con)
{
        struct ceph_mds_session *s = con->private;
        struct ceph_mds_client *mdsc = s->s_mdsc;
        struct ceph_auth_client *ac = mdsc->fsc->client->monc.auth;

        ceph_auth_invalidate_authorizer(ac, CEPH_ENTITY_TYPE_MDS);

        return ceph_monc_validate_auth(&mdsc->fsc->client->monc);
}

static struct ceph_msg *mds_alloc_msg(struct ceph_connection *con,
                                struct ceph_msg_header *hdr, int *skip)
{
        struct ceph_msg *msg;
        int type = (int) le16_to_cpu(hdr->type);
        int front_len = (int) le32_to_cpu(hdr->front_len);

        if (con->in_msg)
                return con->in_msg;

        *skip = 0;
        msg = ceph_msg_new(type, front_len, GFP_NOFS, false);
        if (!msg) {
                pr_err("unable to allocate msg type %d len %d\n",
                       type, front_len);
                return NULL;
        }

        return msg;
}

static const struct ceph_connection_operations mds_con_ops = {
        .get = con_get,
        .put = con_put,
        .dispatch = dispatch,
        .get_authorizer = get_authorizer,
        .verify_authorizer_reply = verify_authorizer_reply,
        .invalidate_authorizer = invalidate_authorizer,
        .peer_reset = peer_reset,
        .alloc_msg = mds_alloc_msg,
};

/* eof */