Add hooks for disabling direct reclaim

[mirror_zfs.git] / module / spl / spl-kmem.c

/*
 *  Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
 *  Copyright (C) 2007 The Regents of the University of California.
 *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
 *  Written by Brian Behlendorf <behlendorf1@llnl.gov>.
 *  UCRL-CODE-235197
 *
 *  This file is part of the SPL, Solaris Porting Layer.
 *  For details, see <http://zfsonlinux.org/>.
 *
 *  The SPL is free software; you can redistribute it and/or modify it
 *  under the terms of the GNU General Public License as published by the
 *  Free Software Foundation; either version 2 of the License, or (at your
 *  option) any later version.
 *
 *  The SPL is distributed in the hope that it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with the SPL.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <sys/debug.h>
#include <sys/sysmacros.h>
#include <sys/kmem.h>
#include <sys/vmem.h>
#include <linux/mm.h>
#include <linux/ratelimit.h>

/*
 * As a general rule kmem_alloc() allocations should be small, preferably
 * just a few pages since they must by physically contiguous.  Therefore, a
 * rate limited warning will be printed to the console for any kmem_alloc()
 * which exceeds a reasonable threshold.
 *
 * The default warning threshold is set to eight pages but capped at 32K to
 * accommodate systems using large pages.  This value was selected to be small
 * enough to ensure the largest allocations are quickly noticed and fixed.
 * But large enough to avoid logging any warnings when a allocation size is
 * larger than optimal but not a serious concern.  Since this value is tunable,
 * developers are encouraged to set it lower when testing so any new largish
 * allocations are quickly caught.  These warnings may be disabled by setting
 * the threshold to zero.
 */
unsigned int spl_kmem_alloc_warn = MAX(8 * PAGE_SIZE, 32 * 1024);
module_param(spl_kmem_alloc_warn, uint, 0644);
MODULE_PARM_DESC(spl_kmem_alloc_warn,
        "Warning threshold in bytes for a kmem_alloc()");
EXPORT_SYMBOL(spl_kmem_alloc_warn);

/*
 * Large kmem_alloc() allocations will fail if they exceed KMALLOC_MAX_SIZE.
 * Allocations which are marginally smaller than this limit may succeed but
 * should still be avoided due to the expense of locating a contiguous range
 * of free pages.  Therefore, a maximum kmem size with reasonable safely
 * margin of 4x is set.  Kmem_alloc() allocations larger than this maximum
 * will quickly fail.  Vmem_alloc() allocations less than or equal to this
 * value will use kmalloc(), but shift to vmalloc() when exceeding this value.
 */
unsigned int spl_kmem_alloc_max = (KMALLOC_MAX_SIZE >> 2);
module_param(spl_kmem_alloc_max, uint, 0644);
MODULE_PARM_DESC(spl_kmem_alloc_max,
        "Maximum size in bytes for a kmem_alloc()");
EXPORT_SYMBOL(spl_kmem_alloc_max);

int
kmem_debugging(void)
{
        return (0);
}
EXPORT_SYMBOL(kmem_debugging);

char *
kmem_vasprintf(const char *fmt, va_list ap)
{
        va_list aq;
        char *ptr;

        do {
                va_copy(aq, ap);
                ptr = kvasprintf(GFP_KERNEL, fmt, aq);
                va_end(aq);
        } while (ptr == NULL);

        return (ptr);
}
EXPORT_SYMBOL(kmem_vasprintf);

char *
kmem_asprintf(const char *fmt, ...)
{
        va_list ap;
        char *ptr;

        do {
                va_start(ap, fmt);
                ptr = kvasprintf(GFP_KERNEL, fmt, ap);
                va_end(ap);
        } while (ptr == NULL);

        return (ptr);
}
EXPORT_SYMBOL(kmem_asprintf);

static char *
__strdup(const char *str, int flags)
{
        char *ptr;
        int n;

        n = strlen(str);
        ptr = kmalloc(n + 1, kmem_flags_convert(flags));
        if (ptr)
                memcpy(ptr, str, n + 1);

        return (ptr);
}

char *
strdup(const char *str)
{
        return (__strdup(str, KM_SLEEP));
}
EXPORT_SYMBOL(strdup);

void
strfree(char *str)
{
        kfree(str);
}
EXPORT_SYMBOL(strfree);

/*
 * Limit the number of large allocation stack traces dumped to not more than
 * 5 every 60 seconds to prevent denial-of-service attacks from debug code.
 */
DEFINE_RATELIMIT_STATE(kmem_alloc_ratelimit_state, 60 * HZ, 5);

/*
 * General purpose unified implementation of kmem_alloc(). It is an
 * amalgamation of Linux and Illumos allocator design. It should never be
 * exported to ensure that code using kmem_alloc()/kmem_zalloc() remains
 * relatively portable.  Consumers may only access this function through
 * wrappers that enforce the common flags to ensure portability.
 */
inline void *
spl_kmem_alloc_impl(size_t size, int flags, int node)
{
        gfp_t lflags = kmem_flags_convert(flags);
        void *ptr;

        /*
         * Log abnormally large allocations and rate limit the console output.
         * Allocations larger than spl_kmem_alloc_warn should be performed
         * through the vmem_alloc()/vmem_zalloc() interfaces.
         */
        if ((spl_kmem_alloc_warn > 0) && (size > spl_kmem_alloc_warn) &&
            !(flags & KM_VMEM) && __ratelimit(&kmem_alloc_ratelimit_state)) {
                printk(KERN_WARNING
                    "Large kmem_alloc(%lu, 0x%x), please file an issue at:\n"
                    "https://github.com/zfsonlinux/zfs/issues/new\n",
                    (unsigned long)size, flags);
                dump_stack();
        }

        /*
         * Use a loop because kmalloc_node() can fail when GFP_KERNEL is used
         * unlike kmem_alloc() with KM_SLEEP on Illumos.
         */
        do {
                /*
                 * Calling kmalloc_node() when the size >= spl_kmem_alloc_max
                 * is unsafe.  This must fail for all for kmem_alloc() and
                 * kmem_zalloc() callers.
                 *
                 * For vmem_alloc() and vmem_zalloc() callers it is permissible
                 * to use __vmalloc().  However, in general use of __vmalloc()
                 * is strongly discouraged because a global lock must be
                 * acquired.  Contention on this lock can significantly
                 * impact performance so frequently manipulating the virtual
                 * address space is strongly discouraged.
                 */
                if (unlikely(size > spl_kmem_alloc_max)) {
                        if (flags & KM_VMEM) {
                                ptr = spl_vmalloc(size, lflags, PAGE_KERNEL);
                        } else {
                                return (NULL);
                        }
                } else {
                        ptr = kmalloc_node(size, lflags, node);
                }

                if (likely(ptr) || (flags & KM_NOSLEEP))
                        return (ptr);

                if (unlikely(__ratelimit(&kmem_alloc_ratelimit_state))) {
                        printk(KERN_WARNING
                            "Possible memory allocation deadlock: "
                            "size=%lu lflags=0x%x",
                            (unsigned long)size, lflags);
                        dump_stack();
                }

                /*
                 * Use cond_resched() instead of congestion_wait() to avoid
                 * deadlocking systems where there are no block devices.
                 */
                cond_resched();
        } while (1);

        return (NULL);
}

inline void
spl_kmem_free_impl(const void *buf, size_t size)
{
        if (is_vmalloc_addr(buf))
                vfree(buf);
        else
                kfree(buf);
}

/*
 * Memory allocation and accounting for kmem_* * style allocations.  When
 * DEBUG_KMEM is enabled the total memory allocated will be tracked and
 * any memory leaked will be reported during module unload.
 *
 * ./configure --enable-debug-kmem
 */
#ifdef DEBUG_KMEM

/* Shim layer memory accounting */
#ifdef HAVE_ATOMIC64_T
atomic64_t kmem_alloc_used = ATOMIC64_INIT(0);
unsigned long long kmem_alloc_max = 0;
#else  /* HAVE_ATOMIC64_T */
atomic_t kmem_alloc_used = ATOMIC_INIT(0);
unsigned long long kmem_alloc_max = 0;
#endif /* HAVE_ATOMIC64_T */

EXPORT_SYMBOL(kmem_alloc_used);
EXPORT_SYMBOL(kmem_alloc_max);

inline void *
spl_kmem_alloc_debug(size_t size, int flags, int node)
{
        void *ptr;

        ptr = spl_kmem_alloc_impl(size, flags, node);
        if (ptr) {
                kmem_alloc_used_add(size);
                if (unlikely(kmem_alloc_used_read() > kmem_alloc_max))
                        kmem_alloc_max = kmem_alloc_used_read();
        }

        return (ptr);
}

inline void
spl_kmem_free_debug(const void *ptr, size_t size)
{
        kmem_alloc_used_sub(size);
        spl_kmem_free_impl(ptr, size);
}

/*
 * When DEBUG_KMEM_TRACKING is enabled not only will total bytes be tracked
 * but also the location of every alloc and free.  When the SPL module is
 * unloaded a list of all leaked addresses and where they were allocated
 * will be dumped to the console.  Enabling this feature has a significant
 * impact on performance but it makes finding memory leaks straight forward.
 *
 * Not surprisingly with debugging enabled the xmem_locks are very highly
 * contended particularly on xfree().  If we want to run with this detailed
 * debugging enabled for anything other than debugging  we need to minimize
 * the contention by moving to a lock per xmem_table entry model.
 *
 * ./configure --enable-debug-kmem-tracking
 */
#ifdef DEBUG_KMEM_TRACKING

#include <linux/hash.h>
#include <linux/ctype.h>

#define KMEM_HASH_BITS          10
#define KMEM_TABLE_SIZE         (1 << KMEM_HASH_BITS)

typedef struct kmem_debug {
        struct hlist_node kd_hlist;     /* Hash node linkage */
        struct list_head kd_list;       /* List of all allocations */
        void *kd_addr;                  /* Allocation pointer */
        size_t kd_size;                 /* Allocation size */
        const char *kd_func;            /* Allocation function */
        int kd_line;                    /* Allocation line */
} kmem_debug_t;

static spinlock_t kmem_lock;
static struct hlist_head kmem_table[KMEM_TABLE_SIZE];
static struct list_head kmem_list;

static kmem_debug_t *
kmem_del_init(spinlock_t *lock, struct hlist_head *table,
    int bits, const void *addr)
{
        struct hlist_head *head;
        struct hlist_node *node;
        struct kmem_debug *p;
        unsigned long flags;

        spin_lock_irqsave(lock, flags);

        head = &table[hash_ptr((void *)addr, bits)];
        hlist_for_each(node, head) {
                p = list_entry(node, struct kmem_debug, kd_hlist);
                if (p->kd_addr == addr) {
                        hlist_del_init(&p->kd_hlist);
                        list_del_init(&p->kd_list);
                        spin_unlock_irqrestore(lock, flags);
                        return (p);
                }
        }

        spin_unlock_irqrestore(lock, flags);

        return (NULL);
}

inline void *
spl_kmem_alloc_track(size_t size, int flags,
    const char *func, int line, int node)
{
        void *ptr = NULL;
        kmem_debug_t *dptr;
        unsigned long irq_flags;

        dptr = kmalloc(sizeof (kmem_debug_t), kmem_flags_convert(flags));
        if (dptr == NULL)
                return (NULL);

        dptr->kd_func = __strdup(func, flags);
        if (dptr->kd_func == NULL) {
                kfree(dptr);
                return (NULL);
        }

        ptr = spl_kmem_alloc_debug(size, flags, node);
        if (ptr == NULL) {
                kfree(dptr->kd_func);
                kfree(dptr);
                return (NULL);
        }

        INIT_HLIST_NODE(&dptr->kd_hlist);
        INIT_LIST_HEAD(&dptr->kd_list);

        dptr->kd_addr = ptr;
        dptr->kd_size = size;
        dptr->kd_line = line;

        spin_lock_irqsave(&kmem_lock, irq_flags);
        hlist_add_head(&dptr->kd_hlist,
            &kmem_table[hash_ptr(ptr, KMEM_HASH_BITS)]);
        list_add_tail(&dptr->kd_list, &kmem_list);
        spin_unlock_irqrestore(&kmem_lock, irq_flags);

        return (ptr);
}

inline void
spl_kmem_free_track(const void *ptr, size_t size)
{
        kmem_debug_t *dptr;

        /* Must exist in hash due to kmem_alloc() */
        dptr = kmem_del_init(&kmem_lock, kmem_table, KMEM_HASH_BITS, ptr);
        ASSERT3P(dptr, !=, NULL);
        ASSERT3S(dptr->kd_size, ==, size);

        kfree(dptr->kd_func);
        kfree(dptr);

        spl_kmem_free_debug(ptr, size);
}
#endif /* DEBUG_KMEM_TRACKING */
#endif /* DEBUG_KMEM */

/*
 * Public kmem_alloc(), kmem_zalloc() and kmem_free() interfaces.
 */
void *
spl_kmem_alloc(size_t size, int flags, const char *func, int line)
{
        ASSERT0(flags & ~KM_PUBLIC_MASK);

#if !defined(DEBUG_KMEM)
        return (spl_kmem_alloc_impl(size, flags, NUMA_NO_NODE));
#elif !defined(DEBUG_KMEM_TRACKING)
        return (spl_kmem_alloc_debug(size, flags, NUMA_NO_NODE));
#else
        return (spl_kmem_alloc_track(size, flags, func, line, NUMA_NO_NODE));
#endif
}
EXPORT_SYMBOL(spl_kmem_alloc);

void *
spl_kmem_zalloc(size_t size, int flags, const char *func, int line)
{
        ASSERT0(flags & ~KM_PUBLIC_MASK);

        flags |= KM_ZERO;

#if !defined(DEBUG_KMEM)
        return (spl_kmem_alloc_impl(size, flags, NUMA_NO_NODE));
#elif !defined(DEBUG_KMEM_TRACKING)
        return (spl_kmem_alloc_debug(size, flags, NUMA_NO_NODE));
#else
        return (spl_kmem_alloc_track(size, flags, func, line, NUMA_NO_NODE));
#endif
}
EXPORT_SYMBOL(spl_kmem_zalloc);

void
spl_kmem_free(const void *buf, size_t size)
{
#if !defined(DEBUG_KMEM)
        return (spl_kmem_free_impl(buf, size));
#elif !defined(DEBUG_KMEM_TRACKING)
        return (spl_kmem_free_debug(buf, size));
#else
        return (spl_kmem_free_track(buf, size));
#endif
}
EXPORT_SYMBOL(spl_kmem_free);

#if defined(DEBUG_KMEM) && defined(DEBUG_KMEM_TRACKING)
static char *
spl_sprintf_addr(kmem_debug_t *kd, char *str, int len, int min)
{
        int size = ((len - 1) < kd->kd_size) ? (len - 1) : kd->kd_size;
        int i, flag = 1;

        ASSERT(str != NULL && len >= 17);
        memset(str, 0, len);

        /*
         * Check for a fully printable string, and while we are at
         * it place the printable characters in the passed buffer.
         */
        for (i = 0; i < size; i++) {
                str[i] = ((char *)(kd->kd_addr))[i];
                if (isprint(str[i])) {
                        continue;
                } else {
                        /*
                         * Minimum number of printable characters found
                         * to make it worthwhile to print this as ascii.
                         */
                        if (i > min)
                                break;

                        flag = 0;
                        break;
                }
        }

        if (!flag) {
                sprintf(str, "%02x%02x%02x%02x%02x%02x%02x%02x",
                    *((uint8_t *)kd->kd_addr),
                    *((uint8_t *)kd->kd_addr + 2),
                    *((uint8_t *)kd->kd_addr + 4),
                    *((uint8_t *)kd->kd_addr + 6),
                    *((uint8_t *)kd->kd_addr + 8),
                    *((uint8_t *)kd->kd_addr + 10),
                    *((uint8_t *)kd->kd_addr + 12),
                    *((uint8_t *)kd->kd_addr + 14));
        }

        return (str);
}

static int
spl_kmem_init_tracking(struct list_head *list, spinlock_t *lock, int size)
{
        int i;

        spin_lock_init(lock);
        INIT_LIST_HEAD(list);

        for (i = 0; i < size; i++)
                INIT_HLIST_HEAD(&kmem_table[i]);

        return (0);
}

static void
spl_kmem_fini_tracking(struct list_head *list, spinlock_t *lock)
{
        unsigned long flags;
        kmem_debug_t *kd;
        char str[17];

        spin_lock_irqsave(lock, flags);
        if (!list_empty(list))
                printk(KERN_WARNING "%-16s %-5s %-16s %s:%s\n", "address",
                    "size", "data", "func", "line");

        list_for_each_entry(kd, list, kd_list)
                printk(KERN_WARNING "%p %-5d %-16s %s:%d\n", kd->kd_addr,
                    (int)kd->kd_size, spl_sprintf_addr(kd, str, 17, 8),
                    kd->kd_func, kd->kd_line);

        spin_unlock_irqrestore(lock, flags);
}
#endif /* DEBUG_KMEM && DEBUG_KMEM_TRACKING */

int
spl_kmem_init(void)
{
#ifdef DEBUG_KMEM
        kmem_alloc_used_set(0);

#ifdef DEBUG_KMEM_TRACKING
        spl_kmem_init_tracking(&kmem_list, &kmem_lock, KMEM_TABLE_SIZE);
#endif /* DEBUG_KMEM_TRACKING */
#endif /* DEBUG_KMEM */

        return (0);
}

void
spl_kmem_fini(void)
{
#ifdef DEBUG_KMEM
        /*
         * Display all unreclaimed memory addresses, including the
         * allocation size and the first few bytes of what's located
         * at that address to aid in debugging.  Performance is not
         * a serious concern here since it is module unload time.
         */
        if (kmem_alloc_used_read() != 0)
                printk(KERN_WARNING "kmem leaked %ld/%llu bytes\n",
                    (unsigned long)kmem_alloc_used_read(), kmem_alloc_max);

#ifdef DEBUG_KMEM_TRACKING
        spl_kmem_fini_tracking(&kmem_list, &kmem_lock);
#endif /* DEBUG_KMEM_TRACKING */
#endif /* DEBUG_KMEM */
}