glock.c

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/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/buffer_head.h>
#include <linux/delay.h>
#include <linux/sort.h>
#include <linux/jhash.h>
#include <linux/kallsyms.h>
#include <linux/gfs2_ondisk.h>
#include <linux/list.h>
#include <linux/wait.h>
#include <linux/module.h>
#include <asm/uaccess.h>
#include <linux/seq_file.h>
#include <linux/debugfs.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/workqueue.h>
#include <linux/jiffies.h>
#include <linux/rcupdate.h>
#include <linux/rculist_bl.h>
#include <linux/bit_spinlock.h>
#include <linux/percpu.h>

#include "gfs2.h"
#include "incore.h"
#include "glock.h"
#include "glops.h"
#include "inode.h"
#include "lops.h"
#include "meta_io.h"
#include "quota.h"
#include "super.h"
#include "util.h"
#include "bmap.h"
#define CREATE_TRACE_POINTS
#include "trace_gfs2.h"

struct gfs2_glock_iter {
    int hash;           /* hash bucket index           */
    unsigned nhash;         /* Index within current bucket */
    struct gfs2_sbd *sdp;       /* incore superblock           */
    struct gfs2_glock *gl;      /* current glock struct        */
    loff_t last_pos;        /* last position               */
};

typedef void (*glock_examiner) (struct gfs2_glock * gl);

static int __dump_glock(struct seq_file *seq, const struct gfs2_glock *gl);
#define GLOCK_BUG_ON(gl,x) do { if (unlikely(x)) { __dump_glock(NULL, gl); BUG(); } } while(0)
static void do_xmote(struct gfs2_glock *gl, struct gfs2_holder *gh, unsigned int target);

static struct dentry *gfs2_root;
static struct workqueue_struct *glock_workqueue;
struct workqueue_struct *gfs2_delete_workqueue;
static LIST_HEAD(lru_list);
static atomic_t lru_count = ATOMIC_INIT(0);
static DEFINE_SPINLOCK(lru_lock);

#define GFS2_GL_HASH_SHIFT      15
#define GFS2_GL_HASH_SIZE       (1 << GFS2_GL_HASH_SHIFT)
#define GFS2_GL_HASH_MASK       (GFS2_GL_HASH_SIZE - 1)

static struct hlist_bl_head gl_hash_table[GFS2_GL_HASH_SIZE];
static struct dentry *gfs2_root;

static unsigned int gl_hash(const struct gfs2_sbd *sdp,
                const struct lm_lockname *name)
{
    unsigned int h;

    h = jhash(&name->ln_number, sizeof(u64), 0);
    h = jhash(&name->ln_type, sizeof(unsigned int), h);
    h = jhash(&sdp, sizeof(struct gfs2_sbd *), h);
    h &= GFS2_GL_HASH_MASK;

    return h;
}

static inline void spin_lock_bucket(unsigned int hash)
{
    hlist_bl_lock(&gl_hash_table[hash]);
}

static inline void spin_unlock_bucket(unsigned int hash)
{
    hlist_bl_unlock(&gl_hash_table[hash]);
}

static void gfs2_glock_dealloc(struct rcu_head *rcu)
{
    struct gfs2_glock *gl = container_of(rcu, struct gfs2_glock, gl_rcu);

    if (gl->gl_ops->go_flags & GLOF_ASPACE)
        kmem_cache_free(gfs2_glock_aspace_cachep, gl);
    else
        kmem_cache_free(gfs2_glock_cachep, gl);
}

void gfs2_glock_free(struct gfs2_glock *gl)
{
    struct gfs2_sbd *sdp = gl->gl_sbd;

    call_rcu(&gl->gl_rcu, gfs2_glock_dealloc);
    if (atomic_dec_and_test(&sdp->sd_glock_disposal))
        wake_up(&sdp->sd_glock_wait);
}

void gfs2_glock_hold(struct gfs2_glock *gl)
{
    GLOCK_BUG_ON(gl, atomic_read(&gl->gl_ref) == 0);
    atomic_inc(&gl->gl_ref);
}

static int demote_ok(const struct gfs2_glock *gl)
{
    const struct gfs2_glock_operations *glops = gl->gl_ops;

    if (gl->gl_state == LM_ST_UNLOCKED)
        return 0;
    if (!list_empty(&gl->gl_holders))
        return 0;
    if (glops->go_demote_ok)
        return glops->go_demote_ok(gl);
    return 1;
}


void gfs2_glock_add_to_lru(struct gfs2_glock *gl)
{
    spin_lock(&lru_lock);

    if (!list_empty(&gl->gl_lru))
        list_del_init(&gl->gl_lru);
    else
        atomic_inc(&lru_count);

    list_add_tail(&gl->gl_lru, &lru_list);
    set_bit(GLF_LRU, &gl->gl_flags);
    spin_unlock(&lru_lock);
}

static void __gfs2_glock_remove_from_lru(struct gfs2_glock *gl)
{
    if (!list_empty(&gl->gl_lru)) {
        list_del_init(&gl->gl_lru);
        atomic_dec(&lru_count);
        clear_bit(GLF_LRU, &gl->gl_flags);
    }
}

static void gfs2_glock_remove_from_lru(struct gfs2_glock *gl)
{
    spin_lock(&lru_lock);
    __gfs2_glock_remove_from_lru(gl);
    spin_unlock(&lru_lock);
}

void gfs2_glock_put_nolock(struct gfs2_glock *gl)
{
    if (atomic_dec_and_test(&gl->gl_ref))
        GLOCK_BUG_ON(gl, 1);
}

void gfs2_glock_put(struct gfs2_glock *gl)
{
    struct gfs2_sbd *sdp = gl->gl_sbd;
    struct address_space *mapping = gfs2_glock2aspace(gl);

    if (atomic_dec_and_lock(&gl->gl_ref, &lru_lock)) {
        __gfs2_glock_remove_from_lru(gl);
        spin_unlock(&lru_lock);
        spin_lock_bucket(gl->gl_hash);
        hlist_bl_del_rcu(&gl->gl_list);
        spin_unlock_bucket(gl->gl_hash);
        GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders));
        GLOCK_BUG_ON(gl, mapping && mapping->nrpages);
        trace_gfs2_glock_put(gl);
        sdp->sd_lockstruct.ls_ops->lm_put_lock(gl);
    }
}

static struct gfs2_glock *search_bucket(unsigned int hash,
                    const struct gfs2_sbd *sdp,
                    const struct lm_lockname *name)
{
    struct gfs2_glock *gl;
    struct hlist_bl_node *h;

    hlist_bl_for_each_entry_rcu(gl, h, &gl_hash_table[hash], gl_list) {
        if (!lm_name_equal(&gl->gl_name, name))
            continue;
        if (gl->gl_sbd != sdp)
            continue;
        if (atomic_inc_not_zero(&gl->gl_ref))
            return gl;
    }

    return NULL;
}

static inline int may_grant(const struct gfs2_glock *gl, const struct gfs2_holder *gh)
{
    const struct gfs2_holder *gh_head = list_entry(gl->gl_holders.next, const struct gfs2_holder, gh_list);
    if ((gh->gh_state == LM_ST_EXCLUSIVE ||
         gh_head->gh_state == LM_ST_EXCLUSIVE) && gh != gh_head)
        return 0;
    if (gl->gl_state == gh->gh_state)
        return 1;
    if (gh->gh_flags & GL_EXACT)
        return 0;
    if (gl->gl_state == LM_ST_EXCLUSIVE) {
        if (gh->gh_state == LM_ST_SHARED && gh_head->gh_state == LM_ST_SHARED)
            return 1;
        if (gh->gh_state == LM_ST_DEFERRED && gh_head->gh_state == LM_ST_DEFERRED)
            return 1;
    }
    if (gl->gl_state != LM_ST_UNLOCKED && (gh->gh_flags & LM_FLAG_ANY))
        return 1;
    return 0;
}

static void gfs2_holder_wake(struct gfs2_holder *gh)
{
    clear_bit(HIF_WAIT, &gh->gh_iflags);
    smp_mb__after_clear_bit();
    wake_up_bit(&gh->gh_iflags, HIF_WAIT);
}

static inline void do_error(struct gfs2_glock *gl, const int ret)
{
    struct gfs2_holder *gh, *tmp;

    list_for_each_entry_safe(gh, tmp, &gl->gl_holders, gh_list) {
        if (test_bit(HIF_HOLDER, &gh->gh_iflags))
            continue;
        if (ret & LM_OUT_ERROR)
            gh->gh_error = -EIO;
        else if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))
            gh->gh_error = GLR_TRYFAILED;
        else
            continue;
        list_del_init(&gh->gh_list);
        trace_gfs2_glock_queue(gh, 0);
        gfs2_holder_wake(gh);
    }
}

static int do_promote(struct gfs2_glock *gl)
__releases(&gl->gl_spin)
__acquires(&gl->gl_spin)
{
    const struct gfs2_glock_operations *glops = gl->gl_ops;
    struct gfs2_holder *gh, *tmp;
    int ret;

restart:
    list_for_each_entry_safe(gh, tmp, &gl->gl_holders, gh_list) {
        if (test_bit(HIF_HOLDER, &gh->gh_iflags))
            continue;
        if (may_grant(gl, gh)) {
            if (gh->gh_list.prev == &gl->gl_holders &&
                glops->go_lock) {
                spin_unlock(&gl->gl_spin);
                /* FIXME: eliminate this eventually */
                ret = glops->go_lock(gh);
                spin_lock(&gl->gl_spin);
                if (ret) {
                    if (ret == 1)
                        return 2;
                    gh->gh_error = ret;
                    list_del_init(&gh->gh_list);
                    trace_gfs2_glock_queue(gh, 0);
                    gfs2_holder_wake(gh);
                    goto restart;
                }
                set_bit(HIF_HOLDER, &gh->gh_iflags);
                trace_gfs2_promote(gh, 1);
                gfs2_holder_wake(gh);
                goto restart;
            }
            set_bit(HIF_HOLDER, &gh->gh_iflags);
            trace_gfs2_promote(gh, 0);
            gfs2_holder_wake(gh);
            continue;
        }
        if (gh->gh_list.prev == &gl->gl_holders)
            return 1;
        do_error(gl, 0);
        break;
    }
    return 0;
}

static inline struct gfs2_holder *find_first_waiter(const struct gfs2_glock *gl)
{
    struct gfs2_holder *gh;

    list_for_each_entry(gh, &gl->gl_holders, gh_list) {
        if (!test_bit(HIF_HOLDER, &gh->gh_iflags))
            return gh;
    }
    return NULL;
}

static void state_change(struct gfs2_glock *gl, unsigned int new_state)
{
    int held1, held2;

    held1 = (gl->gl_state != LM_ST_UNLOCKED);
    held2 = (new_state != LM_ST_UNLOCKED);

    if (held1 != held2) {
        if (held2)
            gfs2_glock_hold(gl);
        else
            gfs2_glock_put_nolock(gl);
    }
    if (held1 && held2 && list_empty(&gl->gl_holders))
        clear_bit(GLF_QUEUED, &gl->gl_flags);

    if (new_state != gl->gl_target)
        /* shorten our minimum hold time */
        gl->gl_hold_time = max(gl->gl_hold_time - GL_GLOCK_HOLD_DECR,
                       GL_GLOCK_MIN_HOLD);
    gl->gl_state = new_state;
    gl->gl_tchange = jiffies;
}

static void gfs2_demote_wake(struct gfs2_glock *gl)
{
    gl->gl_demote_state = LM_ST_EXCLUSIVE;
    clear_bit(GLF_DEMOTE, &gl->gl_flags);
    smp_mb__after_clear_bit();
    wake_up_bit(&gl->gl_flags, GLF_DEMOTE);
}

static void finish_xmote(struct gfs2_glock *gl, unsigned int ret)
{
    const struct gfs2_glock_operations *glops = gl->gl_ops;
    struct gfs2_holder *gh;
    unsigned state = ret & LM_OUT_ST_MASK;
    int rv;

    spin_lock(&gl->gl_spin);
    trace_gfs2_glock_state_change(gl, state);
    state_change(gl, state);
    gh = find_first_waiter(gl);

    /* Demote to UN request arrived during demote to SH or DF */
    if (test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags) &&
        state != LM_ST_UNLOCKED && gl->gl_demote_state == LM_ST_UNLOCKED)
        gl->gl_target = LM_ST_UNLOCKED;

    /* Check for state != intended state */
    if (unlikely(state != gl->gl_target)) {
        if (gh && !test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags)) {
            /* move to back of queue and try next entry */
            if (ret & LM_OUT_CANCELED) {
                if ((gh->gh_flags & LM_FLAG_PRIORITY) == 0)
                    list_move_tail(&gh->gh_list, &gl->gl_holders);
                gh = find_first_waiter(gl);
                gl->gl_target = gh->gh_state;
                goto retry;
            }
            /* Some error or failed "try lock" - report it */
            if ((ret & LM_OUT_ERROR) ||
                (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))) {
                gl->gl_target = gl->gl_state;
                do_error(gl, ret);
                goto out;
            }
        }
        switch(state) {
        /* Unlocked due to conversion deadlock, try again */
        case LM_ST_UNLOCKED:
retry:
            do_xmote(gl, gh, gl->gl_target);
            break;
        /* Conversion fails, unlock and try again */
        case LM_ST_SHARED:
        case LM_ST_DEFERRED:
            do_xmote(gl, gh, LM_ST_UNLOCKED);
            break;
        default: /* Everything else */
            printk(KERN_ERR "GFS2: wanted %u got %u\n", gl->gl_target, state);
            GLOCK_BUG_ON(gl, 1);
        }
        spin_unlock(&gl->gl_spin);
        return;
    }

    /* Fast path - we got what we asked for */
    if (test_and_clear_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags))
        gfs2_demote_wake(gl);
    if (state != LM_ST_UNLOCKED) {
        if (glops->go_xmote_bh) {
            spin_unlock(&gl->gl_spin);
            rv = glops->go_xmote_bh(gl, gh);
            spin_lock(&gl->gl_spin);
            if (rv) {
                do_error(gl, rv);
                goto out;
            }
        }
        rv = do_promote(gl);
        if (rv == 2)
            goto out_locked;
    }
out:
    clear_bit(GLF_LOCK, &gl->gl_flags);
out_locked:
    spin_unlock(&gl->gl_spin);
}

static void do_xmote(struct gfs2_glock *gl, struct gfs2_holder *gh, unsigned int target)
__releases(&gl->gl_spin)
__acquires(&gl->gl_spin)
{
    const struct gfs2_glock_operations *glops = gl->gl_ops;
    struct gfs2_sbd *sdp = gl->gl_sbd;
    unsigned int lck_flags = gh ? gh->gh_flags : 0;
    int ret;

    lck_flags &= (LM_FLAG_TRY | LM_FLAG_TRY_1CB | LM_FLAG_NOEXP |
              LM_FLAG_PRIORITY);
    GLOCK_BUG_ON(gl, gl->gl_state == target);
    GLOCK_BUG_ON(gl, gl->gl_state == gl->gl_target);
    if ((target == LM_ST_UNLOCKED || target == LM_ST_DEFERRED) &&
        glops->go_inval) {
        set_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags);
        do_error(gl, 0); /* Fail queued try locks */
    }
    gl->gl_req = target;
    set_bit(GLF_BLOCKING, &gl->gl_flags);
    if ((gl->gl_req == LM_ST_UNLOCKED) ||
        (gl->gl_state == LM_ST_EXCLUSIVE) ||
        (lck_flags & (LM_FLAG_TRY|LM_FLAG_TRY_1CB)))
        clear_bit(GLF_BLOCKING, &gl->gl_flags);
    spin_unlock(&gl->gl_spin);
    if (glops->go_xmote_th)
        glops->go_xmote_th(gl);
    if (test_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags))
        glops->go_inval(gl, target == LM_ST_DEFERRED ? 0 : DIO_METADATA);
    clear_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags);

    gfs2_glock_hold(gl);
    if (sdp->sd_lockstruct.ls_ops->lm_lock) {
        /* lock_dlm */
        ret = sdp->sd_lockstruct.ls_ops->lm_lock(gl, target, lck_flags);
        GLOCK_BUG_ON(gl, ret);
    } else { /* lock_nolock */
        finish_xmote(gl, target);
        if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
            gfs2_glock_put(gl);
    }

    spin_lock(&gl->gl_spin);
}

static inline struct gfs2_holder *find_first_holder(const struct gfs2_glock *gl)
{
    struct gfs2_holder *gh;

    if (!list_empty(&gl->gl_holders)) {
        gh = list_entry(gl->gl_holders.next, struct gfs2_holder, gh_list);
        if (test_bit(HIF_HOLDER, &gh->gh_iflags))
            return gh;
    }
    return NULL;
}

static void run_queue(struct gfs2_glock *gl, const int nonblock)
__releases(&gl->gl_spin)
__acquires(&gl->gl_spin)
{
    struct gfs2_holder *gh = NULL;
    int ret;

    if (test_and_set_bit(GLF_LOCK, &gl->gl_flags))
        return;

    GLOCK_BUG_ON(gl, test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags));

    if (test_bit(GLF_DEMOTE, &gl->gl_flags) &&
        gl->gl_demote_state != gl->gl_state) {
        if (find_first_holder(gl))
            goto out_unlock;
        if (nonblock)
            goto out_sched;
        set_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);
        GLOCK_BUG_ON(gl, gl->gl_demote_state == LM_ST_EXCLUSIVE);
        gl->gl_target = gl->gl_demote_state;
    } else {
        if (test_bit(GLF_DEMOTE, &gl->gl_flags))
            gfs2_demote_wake(gl);
        ret = do_promote(gl);
        if (ret == 0)
            goto out_unlock;
        if (ret == 2)
            goto out;
        gh = find_first_waiter(gl);
        gl->gl_target = gh->gh_state;
        if (!(gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)))
            do_error(gl, 0); /* Fail queued try locks */
    }
    do_xmote(gl, gh, gl->gl_target);
out:
    return;

out_sched:
    clear_bit(GLF_LOCK, &gl->gl_flags);
    smp_mb__after_clear_bit();
    gfs2_glock_hold(gl);
    if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
        gfs2_glock_put_nolock(gl);
    return;

out_unlock:
    clear_bit(GLF_LOCK, &gl->gl_flags);
    smp_mb__after_clear_bit();
    return;
}

static void delete_work_func(struct work_struct *work)
{
    struct gfs2_glock *gl = container_of(work, struct gfs2_glock, gl_delete);
    struct gfs2_sbd *sdp = gl->gl_sbd;
    struct gfs2_inode *ip;
    struct inode *inode;
    u64 no_addr = gl->gl_name.ln_number;

    ip = gl->gl_object;
    /* Note: Unsafe to dereference ip as we don't hold right refs/locks */

    if (ip)
        inode = gfs2_ilookup(sdp->sd_vfs, no_addr, 1);
    else
        inode = gfs2_lookup_by_inum(sdp, no_addr, NULL, GFS2_BLKST_UNLINKED);
    if (inode && !IS_ERR(inode)) {
        d_prune_aliases(inode);
        iput(inode);
    }
    gfs2_glock_put(gl);
}

static void glock_work_func(struct work_struct *work)
{
    unsigned long delay = 0;
    struct gfs2_glock *gl = container_of(work, struct gfs2_glock, gl_work.work);
    int drop_ref = 0;

    if (test_and_clear_bit(GLF_REPLY_PENDING, &gl->gl_flags)) {
        finish_xmote(gl, gl->gl_reply);
        drop_ref = 1;
    }
    spin_lock(&gl->gl_spin);
    if (test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
        gl->gl_state != LM_ST_UNLOCKED &&
        gl->gl_demote_state != LM_ST_EXCLUSIVE) {
        unsigned long holdtime, now = jiffies;

        holdtime = gl->gl_tchange + gl->gl_hold_time;
        if (time_before(now, holdtime))
            delay = holdtime - now;

        if (!delay) {
            clear_bit(GLF_PENDING_DEMOTE, &gl->gl_flags);
            set_bit(GLF_DEMOTE, &gl->gl_flags);
        }
    }
    run_queue(gl, 0);
    spin_unlock(&gl->gl_spin);
    if (!delay)
        gfs2_glock_put(gl);
    else {
        if (gl->gl_name.ln_type != LM_TYPE_INODE)
            delay = 0;
        if (queue_delayed_work(glock_workqueue, &gl->gl_work, delay) == 0)
            gfs2_glock_put(gl);
    }
    if (drop_ref)
        gfs2_glock_put(gl);
}

int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
           const struct gfs2_glock_operations *glops, int create,
           struct gfs2_glock **glp)
{
    struct super_block *s = sdp->sd_vfs;
    struct lm_lockname name = { .ln_number = number, .ln_type = glops->go_type };
    struct gfs2_glock *gl, *tmp;
    unsigned int hash = gl_hash(sdp, &name);
    struct address_space *mapping;
    struct kmem_cache *cachep;

    rcu_read_lock();
    gl = search_bucket(hash, sdp, &name);
    rcu_read_unlock();

    *glp = gl;
    if (gl)
        return 0;
    if (!create)
        return -ENOENT;

    if (glops->go_flags & GLOF_ASPACE)
        cachep = gfs2_glock_aspace_cachep;
    else
        cachep = gfs2_glock_cachep;
    gl = kmem_cache_alloc(cachep, GFP_KERNEL);
    if (!gl)
        return -ENOMEM;

    atomic_inc(&sdp->sd_glock_disposal);
    gl->gl_sbd = sdp;
    gl->gl_flags = 0;
    gl->gl_name = name;
    atomic_set(&gl->gl_ref, 1);
    gl->gl_state = LM_ST_UNLOCKED;
    gl->gl_target = LM_ST_UNLOCKED;
    gl->gl_demote_state = LM_ST_EXCLUSIVE;
    gl->gl_hash = hash;
    gl->gl_ops = glops;
    gl->gl_dstamp = ktime_set(0, 0);
    preempt_disable();
    /* We use the global stats to estimate the initial per-glock stats */
    gl->gl_stats = this_cpu_ptr(sdp->sd_lkstats)->lkstats[glops->go_type];
    preempt_enable();
    gl->gl_stats.stats[GFS2_LKS_DCOUNT] = 0;
    gl->gl_stats.stats[GFS2_LKS_QCOUNT] = 0;
    memset(&gl->gl_lksb, 0, sizeof(struct dlm_lksb));
    memset(gl->gl_lvb, 0, 32 * sizeof(char));
    gl->gl_lksb.sb_lvbptr = gl->gl_lvb;
    gl->gl_tchange = jiffies;
    gl->gl_object = NULL;
    gl->gl_hold_time = GL_GLOCK_DFT_HOLD;
    INIT_DELAYED_WORK(&gl->gl_work, glock_work_func);
    INIT_WORK(&gl->gl_delete, delete_work_func);

    mapping = gfs2_glock2aspace(gl);
    if (mapping) {
                mapping->a_ops = &gfs2_meta_aops;
        mapping->host = s->s_bdev->bd_inode;
        mapping->flags = 0;
        mapping_set_gfp_mask(mapping, GFP_NOFS);
        mapping->assoc_mapping = NULL;
        mapping->backing_dev_info = s->s_bdi;
        mapping->writeback_index = 0;
    }

    spin_lock_bucket(hash);
    tmp = search_bucket(hash, sdp, &name);
    if (tmp) {
        spin_unlock_bucket(hash);
        kmem_cache_free(cachep, gl);
        atomic_dec(&sdp->sd_glock_disposal);
        gl = tmp;
    } else {
        hlist_bl_add_head_rcu(&gl->gl_list, &gl_hash_table[hash]);
        spin_unlock_bucket(hash);
    }

    *glp = gl;

    return 0;
}

void gfs2_holder_init(struct gfs2_glock *gl, unsigned int state, unsigned flags,
              struct gfs2_holder *gh)
{
    INIT_LIST_HEAD(&gh->gh_list);
    gh->gh_gl = gl;
    gh->gh_ip = (unsigned long)__builtin_return_address(0);
    gh->gh_owner_pid = get_pid(task_pid(current));
    gh->gh_state = state;
    gh->gh_flags = flags;
    gh->gh_error = 0;
    gh->gh_iflags = 0;
    gfs2_glock_hold(gl);
}

void gfs2_holder_reinit(unsigned int state, unsigned flags, struct gfs2_holder *gh)
{
    gh->gh_state = state;
    gh->gh_flags = flags;
    gh->gh_iflags = 0;
    gh->gh_ip = (unsigned long)__builtin_return_address(0);
    if (gh->gh_owner_pid)
        put_pid(gh->gh_owner_pid);
    gh->gh_owner_pid = get_pid(task_pid(current));
}

void gfs2_holder_uninit(struct gfs2_holder *gh)
{
    put_pid(gh->gh_owner_pid);
    gfs2_glock_put(gh->gh_gl);
    gh->gh_gl = NULL;
    gh->gh_ip = 0;
}

static int gfs2_glock_holder_wait(void *word)
{
        schedule();
        return 0;
}

static int gfs2_glock_demote_wait(void *word)
{
    schedule();
    return 0;
}

int gfs2_glock_wait(struct gfs2_holder *gh)
{
    unsigned long time1 = jiffies;

    might_sleep();
    wait_on_bit(&gh->gh_iflags, HIF_WAIT, gfs2_glock_holder_wait, TASK_UNINTERRUPTIBLE);
    if (time_after(jiffies, time1 + HZ)) /* have we waited > a second? */
        /* Lengthen the minimum hold time. */
        gh->gh_gl->gl_hold_time = min(gh->gh_gl->gl_hold_time +
                          GL_GLOCK_HOLD_INCR,
                          GL_GLOCK_MAX_HOLD);
    return gh->gh_error;
}

static void handle_callback(struct gfs2_glock *gl, unsigned int state,
                unsigned long delay)
{
    int bit = delay ? GLF_PENDING_DEMOTE : GLF_DEMOTE;

    set_bit(bit, &gl->gl_flags);
    if (gl->gl_demote_state == LM_ST_EXCLUSIVE) {
        gl->gl_demote_state = state;
        gl->gl_demote_time = jiffies;
    } else if (gl->gl_demote_state != LM_ST_UNLOCKED &&
            gl->gl_demote_state != state) {
        gl->gl_demote_state = LM_ST_UNLOCKED;
    }
    if (gl->gl_ops->go_callback)
        gl->gl_ops->go_callback(gl);
    trace_gfs2_demote_rq(gl);
}

void gfs2_print_dbg(struct seq_file *seq, const char *fmt, ...)
{
    struct va_format vaf;
    va_list args;

    va_start(args, fmt);

    if (seq) {
        seq_vprintf(seq, fmt, args);
    } else {
        vaf.fmt = fmt;
        vaf.va = &args;

        printk(KERN_ERR " %pV", &vaf);
    }

    va_end(args);
}

static inline void add_to_queue(struct gfs2_holder *gh)
__releases(&gl->gl_spin)
__acquires(&gl->gl_spin)
{
    struct gfs2_glock *gl = gh->gh_gl;
    struct gfs2_sbd *sdp = gl->gl_sbd;
    struct list_head *insert_pt = NULL;
    struct gfs2_holder *gh2;
    int try_futile = 0;

    BUG_ON(gh->gh_owner_pid == NULL);
    if (test_and_set_bit(HIF_WAIT, &gh->gh_iflags))
        BUG();

    if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)) {
        if (test_bit(GLF_LOCK, &gl->gl_flags))
            try_futile = !may_grant(gl, gh);
        if (test_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags))
            goto fail;
    }

    list_for_each_entry(gh2, &gl->gl_holders, gh_list) {
        if (unlikely(gh2->gh_owner_pid == gh->gh_owner_pid &&
            (gh->gh_gl->gl_ops->go_type != LM_TYPE_FLOCK)))
            goto trap_recursive;
        if (try_futile &&
            !(gh2->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))) {
fail:
            gh->gh_error = GLR_TRYFAILED;
            gfs2_holder_wake(gh);
            return;
        }
        if (test_bit(HIF_HOLDER, &gh2->gh_iflags))
            continue;
        if (unlikely((gh->gh_flags & LM_FLAG_PRIORITY) && !insert_pt))
            insert_pt = &gh2->gh_list;
    }
    set_bit(GLF_QUEUED, &gl->gl_flags);
    trace_gfs2_glock_queue(gh, 1);
    gfs2_glstats_inc(gl, GFS2_LKS_QCOUNT);
    gfs2_sbstats_inc(gl, GFS2_LKS_QCOUNT);
    if (likely(insert_pt == NULL)) {
        list_add_tail(&gh->gh_list, &gl->gl_holders);
        if (unlikely(gh->gh_flags & LM_FLAG_PRIORITY))
            goto do_cancel;
        return;
    }
    list_add_tail(&gh->gh_list, insert_pt);
do_cancel:
    gh = list_entry(gl->gl_holders.next, struct gfs2_holder, gh_list);
    if (!(gh->gh_flags & LM_FLAG_PRIORITY)) {
        spin_unlock(&gl->gl_spin);
        if (sdp->sd_lockstruct.ls_ops->lm_cancel)
            sdp->sd_lockstruct.ls_ops->lm_cancel(gl);
        spin_lock(&gl->gl_spin);
    }
    return;

trap_recursive:
    print_symbol(KERN_ERR "original: %s\n", gh2->gh_ip);
    printk(KERN_ERR "pid: %d\n", pid_nr(gh2->gh_owner_pid));
    printk(KERN_ERR "lock type: %d req lock state : %d\n",
           gh2->gh_gl->gl_name.ln_type, gh2->gh_state);
    print_symbol(KERN_ERR "new: %s\n", gh->gh_ip);
    printk(KERN_ERR "pid: %d\n", pid_nr(gh->gh_owner_pid));
    printk(KERN_ERR "lock type: %d req lock state : %d\n",
           gh->gh_gl->gl_name.ln_type, gh->gh_state);
    __dump_glock(NULL, gl);
    BUG();
}

int gfs2_glock_nq(struct gfs2_holder *gh)
{
    struct gfs2_glock *gl = gh->gh_gl;
    struct gfs2_sbd *sdp = gl->gl_sbd;
    int error = 0;

    if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags)))
        return -EIO;

    if (test_bit(GLF_LRU, &gl->gl_flags))
        gfs2_glock_remove_from_lru(gl);

    spin_lock(&gl->gl_spin);
    add_to_queue(gh);
    if ((LM_FLAG_NOEXP & gh->gh_flags) &&
        test_and_clear_bit(GLF_FROZEN, &gl->gl_flags))
        set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
    run_queue(gl, 1);
    spin_unlock(&gl->gl_spin);

    if (!(gh->gh_flags & GL_ASYNC))
        error = gfs2_glock_wait(gh);

    return error;
}

int gfs2_glock_poll(struct gfs2_holder *gh)
{
    return test_bit(HIF_WAIT, &gh->gh_iflags) ? 0 : 1;
}

void gfs2_glock_dq(struct gfs2_holder *gh)
{
    struct gfs2_glock *gl = gh->gh_gl;
    const struct gfs2_glock_operations *glops = gl->gl_ops;
    unsigned delay = 0;
    int fast_path = 0;

    spin_lock(&gl->gl_spin);
    if (gh->gh_flags & GL_NOCACHE)
        handle_callback(gl, LM_ST_UNLOCKED, 0);

    list_del_init(&gh->gh_list);
    if (find_first_holder(gl) == NULL) {
        if (glops->go_unlock) {
            GLOCK_BUG_ON(gl, test_and_set_bit(GLF_LOCK, &gl->gl_flags));
            spin_unlock(&gl->gl_spin);
            glops->go_unlock(gh);
            spin_lock(&gl->gl_spin);
            clear_bit(GLF_LOCK, &gl->gl_flags);
        }
        if (list_empty(&gl->gl_holders) &&
            !test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
            !test_bit(GLF_DEMOTE, &gl->gl_flags))
            fast_path = 1;
    }
    if (!test_bit(GLF_LFLUSH, &gl->gl_flags) && demote_ok(gl))
        gfs2_glock_add_to_lru(gl);

    trace_gfs2_glock_queue(gh, 0);
    spin_unlock(&gl->gl_spin);
    if (likely(fast_path))
        return;

    gfs2_glock_hold(gl);
    if (test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
        !test_bit(GLF_DEMOTE, &gl->gl_flags) &&
        gl->gl_name.ln_type == LM_TYPE_INODE)
        delay = gl->gl_hold_time;
    if (queue_delayed_work(glock_workqueue, &gl->gl_work, delay) == 0)
        gfs2_glock_put(gl);
}

void gfs2_glock_dq_wait(struct gfs2_holder *gh)
{
    struct gfs2_glock *gl = gh->gh_gl;
    gfs2_glock_dq(gh);
    might_sleep();
    wait_on_bit(&gl->gl_flags, GLF_DEMOTE, gfs2_glock_demote_wait, TASK_UNINTERRUPTIBLE);
}

void gfs2_glock_dq_uninit(struct gfs2_holder *gh)
{
    gfs2_glock_dq(gh);
    gfs2_holder_uninit(gh);
}

int gfs2_glock_nq_num(struct gfs2_sbd *sdp, u64 number,
              const struct gfs2_glock_operations *glops,
              unsigned int state, int flags, struct gfs2_holder *gh)
{
    struct gfs2_glock *gl;
    int error;

    error = gfs2_glock_get(sdp, number, glops, CREATE, &gl);
    if (!error) {
        error = gfs2_glock_nq_init(gl, state, flags, gh);
        gfs2_glock_put(gl);
    }

    return error;
}

static int glock_compare(const void *arg_a, const void *arg_b)
{
    const struct gfs2_holder *gh_a = *(const struct gfs2_holder **)arg_a;
    const struct gfs2_holder *gh_b = *(const struct gfs2_holder **)arg_b;
    const struct lm_lockname *a = &gh_a->gh_gl->gl_name;
    const struct lm_lockname *b = &gh_b->gh_gl->gl_name;

    if (a->ln_number > b->ln_number)
        return 1;
    if (a->ln_number < b->ln_number)
        return -1;
    BUG_ON(gh_a->gh_gl->gl_ops->go_type == gh_b->gh_gl->gl_ops->go_type);
    return 0;
}

static int nq_m_sync(unsigned int num_gh, struct gfs2_holder *ghs,
             struct gfs2_holder **p)
{
    unsigned int x;
    int error = 0;

    for (x = 0; x < num_gh; x++)
        p[x] = &ghs[x];

    sort(p, num_gh, sizeof(struct gfs2_holder *), glock_compare, NULL);

    for (x = 0; x < num_gh; x++) {
        p[x]->gh_flags &= ~(LM_FLAG_TRY | GL_ASYNC);

        error = gfs2_glock_nq(p[x]);
        if (error) {
            while (x--)
                gfs2_glock_dq(p[x]);
            break;
        }
    }

    return error;
}

int gfs2_glock_nq_m(unsigned int num_gh, struct gfs2_holder *ghs)
{
    struct gfs2_holder *tmp[4];
    struct gfs2_holder **pph = tmp;
    int error = 0;

    switch(num_gh) {
    case 0:
        return 0;
    case 1:
        ghs->gh_flags &= ~(LM_FLAG_TRY | GL_ASYNC);
        return gfs2_glock_nq(ghs);
    default:
        if (num_gh <= 4)
            break;
        pph = kmalloc(num_gh * sizeof(struct gfs2_holder *), GFP_NOFS);
        if (!pph)
            return -ENOMEM;
    }

    error = nq_m_sync(num_gh, ghs, pph);

    if (pph != tmp)
        kfree(pph);

    return error;
}

void gfs2_glock_dq_m(unsigned int num_gh, struct gfs2_holder *ghs)
{
    while (num_gh--)
        gfs2_glock_dq(&ghs[num_gh]);
}

void gfs2_glock_dq_uninit_m(unsigned int num_gh, struct gfs2_holder *ghs)
{
    while (num_gh--)
        gfs2_glock_dq_uninit(&ghs[num_gh]);
}

void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state)
{
    unsigned long delay = 0;
    unsigned long holdtime;
    unsigned long now = jiffies;

    gfs2_glock_hold(gl);
    holdtime = gl->gl_tchange + gl->gl_hold_time;
    if (test_bit(GLF_QUEUED, &gl->gl_flags) &&
        gl->gl_name.ln_type == LM_TYPE_INODE) {
        if (time_before(now, holdtime))
            delay = holdtime - now;
        if (test_bit(GLF_REPLY_PENDING, &gl->gl_flags))
            delay = gl->gl_hold_time;
    }

    spin_lock(&gl->gl_spin);
    handle_callback(gl, state, delay);
    spin_unlock(&gl->gl_spin);
    if (queue_delayed_work(glock_workqueue, &gl->gl_work, delay) == 0)
        gfs2_glock_put(gl);
}

static int gfs2_should_freeze(const struct gfs2_glock *gl)
{
    const struct gfs2_holder *gh;

    if (gl->gl_reply & ~LM_OUT_ST_MASK)
        return 0;
    if (gl->gl_target == LM_ST_UNLOCKED)
        return 0;

    list_for_each_entry(gh, &gl->gl_holders, gh_list) {
        if (test_bit(HIF_HOLDER, &gh->gh_iflags))
            continue;
        if (LM_FLAG_NOEXP & gh->gh_flags)
            return 0;
    }

    return 1;
}

void gfs2_glock_complete(struct gfs2_glock *gl, int ret)
{
    struct lm_lockstruct *ls = &gl->gl_sbd->sd_lockstruct;

    spin_lock(&gl->gl_spin);
    gl->gl_reply = ret;

    if (unlikely(test_bit(DFL_BLOCK_LOCKS, &ls->ls_recover_flags))) {
        if (gfs2_should_freeze(gl)) {
            set_bit(GLF_FROZEN, &gl->gl_flags);
            spin_unlock(&gl->gl_spin);
            return;
        }
    }

    spin_unlock(&gl->gl_spin);
    set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
    smp_wmb();
    gfs2_glock_hold(gl);
    if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
        gfs2_glock_put(gl);
}


static int gfs2_shrink_glock_memory(struct shrinker *shrink,
                    struct shrink_control *sc)
{
    struct gfs2_glock *gl;
    int may_demote;
    int nr_skipped = 0;
    int nr = sc->nr_to_scan;
    gfp_t gfp_mask = sc->gfp_mask;
    LIST_HEAD(skipped);

    if (nr == 0)
        goto out;

    if (!(gfp_mask & __GFP_FS))
        return -1;

    spin_lock(&lru_lock);
    while(nr && !list_empty(&lru_list)) {
        gl = list_entry(lru_list.next, struct gfs2_glock, gl_lru);
        list_del_init(&gl->gl_lru);
        clear_bit(GLF_LRU, &gl->gl_flags);
        atomic_dec(&lru_count);

        /* Test for being demotable */
        if (!test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
            gfs2_glock_hold(gl);
            spin_unlock(&lru_lock);
            spin_lock(&gl->gl_spin);
            may_demote = demote_ok(gl);
            if (may_demote) {
                handle_callback(gl, LM_ST_UNLOCKED, 0);
                nr--;
            }
            clear_bit(GLF_LOCK, &gl->gl_flags);
            smp_mb__after_clear_bit();
            if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
                gfs2_glock_put_nolock(gl);
            spin_unlock(&gl->gl_spin);
            spin_lock(&lru_lock);
            continue;
        }
        nr_skipped++;
        list_add(&gl->gl_lru, &skipped);
        set_bit(GLF_LRU, &gl->gl_flags);
    }
    list_splice(&skipped, &lru_list);
    atomic_add(nr_skipped, &lru_count);
    spin_unlock(&lru_lock);
out:
    return (atomic_read(&lru_count) / 100) * sysctl_vfs_cache_pressure;
}

static struct shrinker glock_shrinker = {
    .shrink = gfs2_shrink_glock_memory,
    .seeks = DEFAULT_SEEKS,
};

static void examine_bucket(glock_examiner examiner, const struct gfs2_sbd *sdp,
              unsigned int hash)
{
    struct gfs2_glock *gl;
    struct hlist_bl_head *head = &gl_hash_table[hash];
    struct hlist_bl_node *pos;

    rcu_read_lock();
    hlist_bl_for_each_entry_rcu(gl, pos, head, gl_list) {
        if ((gl->gl_sbd == sdp) && atomic_read(&gl->gl_ref))
            examiner(gl);
    }
    rcu_read_unlock();
    cond_resched();
}

static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd *sdp)
{
    unsigned x;

    for (x = 0; x < GFS2_GL_HASH_SIZE; x++)
        examine_bucket(examiner, sdp, x);
}


static void thaw_glock(struct gfs2_glock *gl)
{
    if (!test_and_clear_bit(GLF_FROZEN, &gl->gl_flags))
        return;
    set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
    gfs2_glock_hold(gl);
    if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
        gfs2_glock_put(gl);
}

static void clear_glock(struct gfs2_glock *gl)
{
    gfs2_glock_remove_from_lru(gl);

    spin_lock(&gl->gl_spin);
    if (gl->gl_state != LM_ST_UNLOCKED)
        handle_callback(gl, LM_ST_UNLOCKED, 0);
    spin_unlock(&gl->gl_spin);
    gfs2_glock_hold(gl);
    if (queue_delayed_work(glock_workqueue, &gl->gl_work, 0) == 0)
        gfs2_glock_put(gl);
}

void gfs2_glock_thaw(struct gfs2_sbd *sdp)
{
    glock_hash_walk(thaw_glock, sdp);
}

static int dump_glock(struct seq_file *seq, struct gfs2_glock *gl)
{
    int ret;
    spin_lock(&gl->gl_spin);
    ret = __dump_glock(seq, gl);
    spin_unlock(&gl->gl_spin);
    return ret;
}

static void dump_glock_func(struct gfs2_glock *gl)
{
    dump_glock(NULL, gl);
}

void gfs2_gl_hash_clear(struct gfs2_sbd *sdp)
{
    glock_hash_walk(clear_glock, sdp);
    flush_workqueue(glock_workqueue);
    wait_event(sdp->sd_glock_wait, atomic_read(&sdp->sd_glock_disposal) == 0);
    glock_hash_walk(dump_glock_func, sdp);
}

void gfs2_glock_finish_truncate(struct gfs2_inode *ip)
{
    struct gfs2_glock *gl = ip->i_gl;
    int ret;

    ret = gfs2_truncatei_resume(ip);
    gfs2_assert_withdraw(gl->gl_sbd, ret == 0);

    spin_lock(&gl->gl_spin);
    clear_bit(GLF_LOCK, &gl->gl_flags);
    run_queue(gl, 1);
    spin_unlock(&gl->gl_spin);
}

static const char *state2str(unsigned state)
{
    switch(state) {
    case LM_ST_UNLOCKED:
        return "UN";
    case LM_ST_SHARED:
        return "SH";
    case LM_ST_DEFERRED:
        return "DF";
    case LM_ST_EXCLUSIVE:
        return "EX";
    }
    return "??";
}

static const char *hflags2str(char *buf, unsigned flags, unsigned long iflags)
{
    char *p = buf;
    if (flags & LM_FLAG_TRY)
        *p++ = 't';
    if (flags & LM_FLAG_TRY_1CB)
        *p++ = 'T';
    if (flags & LM_FLAG_NOEXP)
        *p++ = 'e';
    if (flags & LM_FLAG_ANY)
        *p++ = 'A';
    if (flags & LM_FLAG_PRIORITY)
        *p++ = 'p';
    if (flags & GL_ASYNC)
        *p++ = 'a';
    if (flags & GL_EXACT)
        *p++ = 'E';
    if (flags & GL_NOCACHE)
        *p++ = 'c';
    if (test_bit(HIF_HOLDER, &iflags))
        *p++ = 'H';
    if (test_bit(HIF_WAIT, &iflags))
        *p++ = 'W';
    if (test_bit(HIF_FIRST, &iflags))
        *p++ = 'F';
    *p = 0;
    return buf;
}

static int dump_holder(struct seq_file *seq, const struct gfs2_holder *gh)
{
    struct task_struct *gh_owner = NULL;
    char flags_buf[32];

    if (gh->gh_owner_pid)
        gh_owner = pid_task(gh->gh_owner_pid, PIDTYPE_PID);
    gfs2_print_dbg(seq, " H: s:%s f:%s e:%d p:%ld [%s] %pS\n",
               state2str(gh->gh_state),
               hflags2str(flags_buf, gh->gh_flags, gh->gh_iflags),
               gh->gh_error,
               gh->gh_owner_pid ? (long)pid_nr(gh->gh_owner_pid) : -1,
               gh_owner ? gh_owner->comm : "(ended)",
               (void *)gh->gh_ip);
    return 0;
}

static const char *gflags2str(char *buf, const struct gfs2_glock *gl)
{
    const unsigned long *gflags = &gl->gl_flags;
    char *p = buf;

    if (test_bit(GLF_LOCK, gflags))
        *p++ = 'l';
    if (test_bit(GLF_DEMOTE, gflags))
        *p++ = 'D';
    if (test_bit(GLF_PENDING_DEMOTE, gflags))
        *p++ = 'd';
    if (test_bit(GLF_DEMOTE_IN_PROGRESS, gflags))
        *p++ = 'p';
    if (test_bit(GLF_DIRTY, gflags))
        *p++ = 'y';
    if (test_bit(GLF_LFLUSH, gflags))
        *p++ = 'f';
    if (test_bit(GLF_INVALIDATE_IN_PROGRESS, gflags))
        *p++ = 'i';
    if (test_bit(GLF_REPLY_PENDING, gflags))
        *p++ = 'r';
    if (test_bit(GLF_INITIAL, gflags))
        *p++ = 'I';
    if (test_bit(GLF_FROZEN, gflags))
        *p++ = 'F';
    if (test_bit(GLF_QUEUED, gflags))
        *p++ = 'q';
    if (test_bit(GLF_LRU, gflags))
        *p++ = 'L';
    if (gl->gl_object)
        *p++ = 'o';
    if (test_bit(GLF_BLOCKING, gflags))
        *p++ = 'b';
    *p = 0;
    return buf;
}

static int __dump_glock(struct seq_file *seq, const struct gfs2_glock *gl)
{
    const struct gfs2_glock_operations *glops = gl->gl_ops;
    unsigned long long dtime;
    const struct gfs2_holder *gh;
    char gflags_buf[32];
    int error = 0;

    dtime = jiffies - gl->gl_demote_time;
    dtime *= 1000000/HZ; /* demote time in uSec */
    if (!test_bit(GLF_DEMOTE, &gl->gl_flags))
        dtime = 0;
    gfs2_print_dbg(seq, "G:  s:%s n:%u/%llx f:%s t:%s d:%s/%llu a:%d v:%d r:%d m:%ld\n",
          state2str(gl->gl_state),
          gl->gl_name.ln_type,
          (unsigned long long)gl->gl_name.ln_number,
          gflags2str(gflags_buf, gl),
          state2str(gl->gl_target),
          state2str(gl->gl_demote_state), dtime,
          atomic_read(&gl->gl_ail_count),
          atomic_read(&gl->gl_revokes),
          atomic_read(&gl->gl_ref), gl->gl_hold_time);

    list_for_each_entry(gh, &gl->gl_holders, gh_list) {
        error = dump_holder(seq, gh);
        if (error)
            goto out;
    }
    if (gl->gl_state != LM_ST_UNLOCKED && glops->go_dump)
        error = glops->go_dump(seq, gl);
out:
    return error;
}

static int gfs2_glstats_seq_show(struct seq_file *seq, void *iter_ptr)
{
    struct gfs2_glock *gl = iter_ptr;

    seq_printf(seq, "G: n:%u/%llx rtt:%lld/%lld rttb:%lld/%lld irt:%lld/%lld dcnt: %lld qcnt: %lld\n",
           gl->gl_name.ln_type,
           (unsigned long long)gl->gl_name.ln_number,
           (long long)gl->gl_stats.stats[GFS2_LKS_SRTT],
           (long long)gl->gl_stats.stats[GFS2_LKS_SRTTVAR],
           (long long)gl->gl_stats.stats[GFS2_LKS_SRTTB],
           (long long)gl->gl_stats.stats[GFS2_LKS_SRTTVARB],
           (long long)gl->gl_stats.stats[GFS2_LKS_SIRT],
           (long long)gl->gl_stats.stats[GFS2_LKS_SIRTVAR],
           (long long)gl->gl_stats.stats[GFS2_LKS_DCOUNT],
           (long long)gl->gl_stats.stats[GFS2_LKS_QCOUNT]);
    return 0;
}

static const char *gfs2_gltype[] = {
    "type",
    "reserved",
    "nondisk",
    "inode",
    "rgrp",
    "meta",
    "iopen",
    "flock",
    "plock",
    "quota",
    "journal",
};

static const char *gfs2_stype[] = {
    [GFS2_LKS_SRTT]     = "srtt",
    [GFS2_LKS_SRTTVAR]  = "srttvar",
    [GFS2_LKS_SRTTB]    = "srttb",
    [GFS2_LKS_SRTTVARB] = "srttvarb",
    [GFS2_LKS_SIRT]     = "sirt",
    [GFS2_LKS_SIRTVAR]  = "sirtvar",
    [GFS2_LKS_DCOUNT]   = "dlm",
    [GFS2_LKS_QCOUNT]   = "queue",
};

#define GFS2_NR_SBSTATS (ARRAY_SIZE(gfs2_gltype) * ARRAY_SIZE(gfs2_stype))

static int gfs2_sbstats_seq_show(struct seq_file *seq, void *iter_ptr)
{
    struct gfs2_glock_iter *gi = seq->private;
    struct gfs2_sbd *sdp = gi->sdp;
    unsigned index = gi->hash >> 3;
    unsigned subindex = gi->hash & 0x07;
    s64 value;
    int i;

    if (index == 0 && subindex != 0)
        return 0;

    seq_printf(seq, "%-10s %8s:", gfs2_gltype[index],
           (index == 0) ? "cpu": gfs2_stype[subindex]);

    for_each_possible_cpu(i) {
                const struct gfs2_pcpu_lkstats *lkstats = per_cpu_ptr(sdp->sd_lkstats, i);
        if (index == 0) {
            value = i;
        } else {
            value = lkstats->lkstats[index - 1].stats[subindex];
        }
        seq_printf(seq, " %15lld", (long long)value);
    }
    seq_putc(seq, '\n');
    return 0;
}

int __init gfs2_glock_init(void)
{
    unsigned i;
    for(i = 0; i < GFS2_GL_HASH_SIZE; i++) {
        INIT_HLIST_BL_HEAD(&gl_hash_table[i]);
    }

    glock_workqueue = alloc_workqueue("glock_workqueue", WQ_MEM_RECLAIM |
                      WQ_HIGHPRI | WQ_FREEZABLE, 0);
    if (IS_ERR(glock_workqueue))
        return PTR_ERR(glock_workqueue);
    gfs2_delete_workqueue = alloc_workqueue("delete_workqueue",
                        WQ_MEM_RECLAIM | WQ_FREEZABLE,
                        0);
    if (IS_ERR(gfs2_delete_workqueue)) {
        destroy_workqueue(glock_workqueue);
        return PTR_ERR(gfs2_delete_workqueue);
    }

    register_shrinker(&glock_shrinker);

    return 0;
}

void gfs2_glock_exit(void)
{
    unregister_shrinker(&glock_shrinker);
    destroy_workqueue(glock_workqueue);
    destroy_workqueue(gfs2_delete_workqueue);
}

static inline struct gfs2_glock *glock_hash_chain(unsigned hash)
{
    return hlist_bl_entry(hlist_bl_first_rcu(&gl_hash_table[hash]),
                  struct gfs2_glock, gl_list);
}

static inline struct gfs2_glock *glock_hash_next(struct gfs2_glock *gl)
{
    return hlist_bl_entry(rcu_dereference(gl->gl_list.next),
                  struct gfs2_glock, gl_list);
}

static int gfs2_glock_iter_next(struct gfs2_glock_iter *gi)
{
    struct gfs2_glock *gl;

    do {
        gl = gi->gl;
        if (gl) {
            gi->gl = glock_hash_next(gl);
            gi->nhash++;
        } else {
            if (gi->hash >= GFS2_GL_HASH_SIZE) {
                rcu_read_unlock();
                return 1;
            }
            gi->gl = glock_hash_chain(gi->hash);
            gi->nhash = 0;
        }
        while (gi->gl == NULL) {
            gi->hash++;
            if (gi->hash >= GFS2_GL_HASH_SIZE) {
                rcu_read_unlock();
                return 1;
            }
            gi->gl = glock_hash_chain(gi->hash);
            gi->nhash = 0;
        }
    /* Skip entries for other sb and dead entries */
    } while (gi->sdp != gi->gl->gl_sbd || atomic_read(&gi->gl->gl_ref) == 0);

    return 0;
}

static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos)
{
    struct gfs2_glock_iter *gi = seq->private;
    loff_t n = *pos;

    if (gi->last_pos <= *pos)
        n = gi->nhash + (*pos - gi->last_pos);
    else
        gi->hash = 0;

    gi->nhash = 0;
    rcu_read_lock();

    do {
        if (gfs2_glock_iter_next(gi))
            return NULL;
    } while (n--);

    gi->last_pos = *pos;
    return gi->gl;
}

static void *gfs2_glock_seq_next(struct seq_file *seq, void *iter_ptr,
                 loff_t *pos)
{
    struct gfs2_glock_iter *gi = seq->private;

    (*pos)++;
    gi->last_pos = *pos;
    if (gfs2_glock_iter_next(gi))
        return NULL;

    return gi->gl;
}

static void gfs2_glock_seq_stop(struct seq_file *seq, void *iter_ptr)
{
    struct gfs2_glock_iter *gi = seq->private;

    if (gi->gl)
        rcu_read_unlock();
    gi->gl = NULL;
}

static int gfs2_glock_seq_show(struct seq_file *seq, void *iter_ptr)
{
    return dump_glock(seq, iter_ptr);
}

static void *gfs2_sbstats_seq_start(struct seq_file *seq, loff_t *pos)
{
    struct gfs2_glock_iter *gi = seq->private;

    gi->hash = *pos;
    if (*pos >= GFS2_NR_SBSTATS)
        return NULL;
    preempt_disable();
    return SEQ_START_TOKEN;
}

static void *gfs2_sbstats_seq_next(struct seq_file *seq, void *iter_ptr,
                   loff_t *pos)
{
    struct gfs2_glock_iter *gi = seq->private;
    (*pos)++;
    gi->hash++;
    if (gi->hash >= GFS2_NR_SBSTATS) {
        preempt_enable();
        return NULL;
    }
    return SEQ_START_TOKEN;
}

static void gfs2_sbstats_seq_stop(struct seq_file *seq, void *iter_ptr)
{
    preempt_enable();
}

static const struct seq_operations gfs2_glock_seq_ops = {
    .start = gfs2_glock_seq_start,
    .next  = gfs2_glock_seq_next,
    .stop  = gfs2_glock_seq_stop,
    .show  = gfs2_glock_seq_show,
};

static const struct seq_operations gfs2_glstats_seq_ops = {
    .start = gfs2_glock_seq_start,
    .next  = gfs2_glock_seq_next,
    .stop  = gfs2_glock_seq_stop,
    .show  = gfs2_glstats_seq_show,
};

static const struct seq_operations gfs2_sbstats_seq_ops = {
    .start = gfs2_sbstats_seq_start,
    .next  = gfs2_sbstats_seq_next,
    .stop  = gfs2_sbstats_seq_stop,
    .show  = gfs2_sbstats_seq_show,
};

#define GFS2_SEQ_GOODSIZE min(PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER, 65536UL)

static int gfs2_glocks_open(struct inode *inode, struct file *file)
{
    int ret = seq_open_private(file, &gfs2_glock_seq_ops,
                   sizeof(struct gfs2_glock_iter));
    if (ret == 0) {
        struct seq_file *seq = file->private_data;
        struct gfs2_glock_iter *gi = seq->private;
        gi->sdp = inode->i_private;
        seq->buf = kmalloc(GFS2_SEQ_GOODSIZE, GFP_KERNEL | __GFP_NOWARN);
        if (seq->buf)
            seq->size = GFS2_SEQ_GOODSIZE;
    }
    return ret;
}

static int gfs2_glstats_open(struct inode *inode, struct file *file)
{
    int ret = seq_open_private(file, &gfs2_glstats_seq_ops,
                   sizeof(struct gfs2_glock_iter));
    if (ret == 0) {
        struct seq_file *seq = file->private_data;
        struct gfs2_glock_iter *gi = seq->private;
        gi->sdp = inode->i_private;
        seq->buf = kmalloc(GFS2_SEQ_GOODSIZE, GFP_KERNEL | __GFP_NOWARN);
        if (seq->buf)
            seq->size = GFS2_SEQ_GOODSIZE;
    }
    return ret;
}

static int gfs2_sbstats_open(struct inode *inode, struct file *file)
{
    int ret = seq_open_private(file, &gfs2_sbstats_seq_ops,
                   sizeof(struct gfs2_glock_iter));
    if (ret == 0) {
        struct seq_file *seq = file->private_data;
        struct gfs2_glock_iter *gi = seq->private;
        gi->sdp = inode->i_private;
    }
    return ret;
}

static const struct file_operations gfs2_glocks_fops = {
    .owner   = THIS_MODULE,
    .open    = gfs2_glocks_open,
    .read    = seq_read,
    .llseek  = seq_lseek,
    .release = seq_release_private,
};

static const struct file_operations gfs2_glstats_fops = {
    .owner   = THIS_MODULE,
    .open    = gfs2_glstats_open,
    .read    = seq_read,
    .llseek  = seq_lseek,
    .release = seq_release_private,
};

static const struct file_operations gfs2_sbstats_fops = {
    .owner   = THIS_MODULE,
    .open    = gfs2_sbstats_open,
    .read    = seq_read,
    .llseek  = seq_lseek,
    .release = seq_release_private,
};

int gfs2_create_debugfs_file(struct gfs2_sbd *sdp)
{
    sdp->debugfs_dir = debugfs_create_dir(sdp->sd_table_name, gfs2_root);
    if (!sdp->debugfs_dir)
        return -ENOMEM;
    sdp->debugfs_dentry_glocks = debugfs_create_file("glocks",
                             S_IFREG | S_IRUGO,
                             sdp->debugfs_dir, sdp,
                             &gfs2_glocks_fops);
    if (!sdp->debugfs_dentry_glocks)
        goto fail;

    sdp->debugfs_dentry_glstats = debugfs_create_file("glstats",
                            S_IFREG | S_IRUGO,
                            sdp->debugfs_dir, sdp,
                            &gfs2_glstats_fops);
    if (!sdp->debugfs_dentry_glstats)
        goto fail;

    sdp->debugfs_dentry_sbstats = debugfs_create_file("sbstats",
                            S_IFREG | S_IRUGO,
                            sdp->debugfs_dir, sdp,
                            &gfs2_sbstats_fops);
    if (!sdp->debugfs_dentry_sbstats)
        goto fail;

    return 0;
fail:
    gfs2_delete_debugfs_file(sdp);
    return -ENOMEM;
}

void gfs2_delete_debugfs_file(struct gfs2_sbd *sdp)
{
    if (sdp->debugfs_dir) {
        if (sdp->debugfs_dentry_glocks) {
            debugfs_remove(sdp->debugfs_dentry_glocks);
            sdp->debugfs_dentry_glocks = NULL;
        }
        if (sdp->debugfs_dentry_glstats) {
            debugfs_remove(sdp->debugfs_dentry_glstats);
            sdp->debugfs_dentry_glstats = NULL;
        }
        if (sdp->debugfs_dentry_sbstats) {
            debugfs_remove(sdp->debugfs_dentry_sbstats);
            sdp->debugfs_dentry_sbstats = NULL;
        }
        debugfs_remove(sdp->debugfs_dir);
        sdp->debugfs_dir = NULL;
    }
}

int gfs2_register_debugfs(void)
{
    gfs2_root = debugfs_create_dir("gfs2", NULL);
    return gfs2_root ? 0 : -ENOMEM;
}

void gfs2_unregister_debugfs(void)
{
    debugfs_remove(gfs2_root);
    gfs2_root = NULL;
}