Merge branch 'master' into gfs2

[deliverable/linux.git] / fs / gfs2 / glock.c

/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2006 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/completion.h>
#include <linux/buffer_head.h>
#include <linux/delay.h>
#include <linux/sort.h>
#include <linux/jhash.h>
#include <linux/kref.h>
#include <linux/kallsyms.h>
#include <linux/gfs2_ondisk.h>
#include <linux/list.h>
#include <asm/uaccess.h>

#include "gfs2.h"
#include "lm_interface.h"
#include "incore.h"
#include "glock.h"
#include "glops.h"
#include "inode.h"
#include "lm.h"
#include "lops.h"
#include "meta_io.h"
#include "quota.h"
#include "super.h"
#include "util.h"

struct greedy {
        struct gfs2_holder gr_gh;
        struct work_struct gr_work;
};

struct gfs2_gl_hash_bucket {
        struct hlist_head hb_list;
};

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

static int gfs2_dump_lockstate(struct gfs2_sbd *sdp);
static int dump_glock(struct gfs2_glock *gl);
static int dump_inode(struct gfs2_inode *ip);

#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 gfs2_gl_hash_bucket gl_hash_table[GFS2_GL_HASH_SIZE];

/*
 * Despite what you might think, the numbers below are not arbitrary :-)
 * They are taken from the ipv4 routing hash code, which is well tested
 * and thus should be nearly optimal. Later on we might tweek the numbers
 * but for now this should be fine.
 *
 * The reason for putting the locks in a separate array from the list heads
 * is that we can have fewer locks than list heads and save memory. We use
 * the same hash function for both, but with a different hash mask.
 */
#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK) || \
        defined(CONFIG_PROVE_LOCKING)

#ifdef CONFIG_LOCKDEP
# define GL_HASH_LOCK_SZ        256
#else
# if NR_CPUS >= 32
#  define GL_HASH_LOCK_SZ       4096
# elif NR_CPUS >= 16
#  define GL_HASH_LOCK_SZ       2048
# elif NR_CPUS >= 8
#  define GL_HASH_LOCK_SZ       1024
# elif NR_CPUS >= 4
#  define GL_HASH_LOCK_SZ       512
# else
#  define GL_HASH_LOCK_SZ       256
# endif
#endif

/* We never want more locks than chains */
#if GFS2_GL_HASH_SIZE < GL_HASH_LOCK_SZ
# undef GL_HASH_LOCK_SZ
# define GL_HASH_LOCK_SZ GFS2_GL_HASH_SIZE
#endif

static rwlock_t gl_hash_locks[GL_HASH_LOCK_SZ];

static inline rwlock_t *gl_lock_addr(unsigned int x)
{
        return &gl_hash_locks[x & (GL_HASH_LOCK_SZ-1)];
}
#else /* not SMP, so no spinlocks required */
static inline rwlock_t *gl_lock_addr(x)
{
        return NULL;
}
#endif

/**
 * relaxed_state_ok - is a requested lock compatible with the current lock mode?
 * @actual: the current state of the lock
 * @requested: the lock state that was requested by the caller
 * @flags: the modifier flags passed in by the caller
 *
 * Returns: 1 if the locks are compatible, 0 otherwise
 */

static inline int relaxed_state_ok(unsigned int actual, unsigned requested,
                                   int flags)
{
        if (actual == requested)
                return 1;

        if (flags & GL_EXACT)
                return 0;

        if (actual == LM_ST_EXCLUSIVE && requested == LM_ST_SHARED)
                return 1;

        if (actual != LM_ST_UNLOCKED && (flags & LM_FLAG_ANY))
                return 1;

        return 0;
}

/**
 * gl_hash() - Turn glock number into hash bucket number
 * @lock: The glock number
 *
 * Returns: The number of the corresponding hash bucket
 */

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;
}

/**
 * glock_free() - Perform a few checks and then release struct gfs2_glock
 * @gl: The glock to release
 *
 * Also calls lock module to release its internal structure for this glock.
 *
 */

static void glock_free(struct gfs2_glock *gl)
{
        struct gfs2_sbd *sdp = gl->gl_sbd;
        struct inode *aspace = gl->gl_aspace;

        gfs2_lm_put_lock(sdp, gl->gl_lock);

        if (aspace)
                gfs2_aspace_put(aspace);

        kmem_cache_free(gfs2_glock_cachep, gl);
}

/**
 * gfs2_glock_hold() - increment reference count on glock
 * @gl: The glock to hold
 *
 */

void gfs2_glock_hold(struct gfs2_glock *gl)
{
        kref_get(&gl->gl_ref);
}

/* All work is done after the return from kref_put() so we
   can release the write_lock before the free. */

static void kill_glock(struct kref *kref)
{
        struct gfs2_glock *gl = container_of(kref, struct gfs2_glock, gl_ref);
        struct gfs2_sbd *sdp = gl->gl_sbd;

        gfs2_assert(sdp, gl->gl_state == LM_ST_UNLOCKED);
        gfs2_assert(sdp, list_empty(&gl->gl_reclaim));
        gfs2_assert(sdp, list_empty(&gl->gl_holders));
        gfs2_assert(sdp, list_empty(&gl->gl_waiters1));
        gfs2_assert(sdp, list_empty(&gl->gl_waiters2));
        gfs2_assert(sdp, list_empty(&gl->gl_waiters3));
}

/**
 * gfs2_glock_put() - Decrement reference count on glock
 * @gl: The glock to put
 *
 */

int gfs2_glock_put(struct gfs2_glock *gl)
{
        int rv = 0;

        write_lock(gl_lock_addr(gl->gl_hash));
        if (kref_put(&gl->gl_ref, kill_glock)) {
                hlist_del(&gl->gl_list);
                write_unlock(gl_lock_addr(gl->gl_hash));
                BUG_ON(spin_is_locked(&gl->gl_spin));
                glock_free(gl);
                rv = 1;
                goto out;
        }
        write_unlock(gl_lock_addr(gl->gl_hash));
out:
        return rv;
}

/**
 * queue_empty - check to see if a glock's queue is empty
 * @gl: the glock
 * @head: the head of the queue to check
 *
 * This function protects the list in the event that a process already
 * has a holder on the list and is adding a second holder for itself.
 * The glmutex lock is what generally prevents processes from working
 * on the same glock at once, but the special case of adding a second
 * holder for yourself ("recursive" locking) doesn't involve locking
 * glmutex, making the spin lock necessary.
 *
 * Returns: 1 if the queue is empty
 */

static inline int queue_empty(struct gfs2_glock *gl, struct list_head *head)
{
        int empty;
        spin_lock(&gl->gl_spin);
        empty = list_empty(head);
        spin_unlock(&gl->gl_spin);
        return empty;
}

/**
 * search_bucket() - Find struct gfs2_glock by lock number
 * @bucket: the bucket to search
 * @name: The lock name
 *
 * Returns: NULL, or the struct gfs2_glock with the requested number
 */

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_node *h;

        hlist_for_each_entry(gl, h, &gl_hash_table[hash].hb_list, gl_list) {
                if (!lm_name_equal(&gl->gl_name, name))
                        continue;
                if (gl->gl_sbd != sdp)
                        continue;

                kref_get(&gl->gl_ref);

                return gl;
        }

        return NULL;
}

/**
 * gfs2_glock_find() - Find glock by lock number
 * @sdp: The GFS2 superblock
 * @name: The lock name
 *
 * Returns: NULL, or the struct gfs2_glock with the requested number
 */

static struct gfs2_glock *gfs2_glock_find(const struct gfs2_sbd *sdp,
                                          const struct lm_lockname *name)
{
        unsigned int hash = gl_hash(sdp, name);
        struct gfs2_glock *gl;

        read_lock(gl_lock_addr(hash));
        gl = search_bucket(hash, sdp, name);
        read_unlock(gl_lock_addr(hash));

        return gl;
}

/**
 * gfs2_glock_get() - Get a glock, or create one if one doesn't exist
 * @sdp: The GFS2 superblock
 * @number: the lock number
 * @glops: The glock_operations to use
 * @create: If 0, don't create the glock if it doesn't exist
 * @glp: the glock is returned here
 *
 * This does not lock a glock, just finds/creates structures for one.
 *
 * Returns: errno
 */

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

        read_lock(gl_lock_addr(hash));
        gl = search_bucket(hash, sdp, &name);
        read_unlock(gl_lock_addr(hash));

        if (gl || !create) {
                *glp = gl;
                return 0;
        }

        gl = kmem_cache_alloc(gfs2_glock_cachep, GFP_KERNEL);
        if (!gl)
                return -ENOMEM;

        gl->gl_flags = 0;
        gl->gl_name = name;
        kref_init(&gl->gl_ref);
        gl->gl_state = LM_ST_UNLOCKED;
        gl->gl_hash = hash;
        gl->gl_owner = NULL;
        gl->gl_ip = 0;
        gl->gl_ops = glops;
        gl->gl_req_gh = NULL;
        gl->gl_req_bh = NULL;
        gl->gl_vn = 0;
        gl->gl_stamp = jiffies;
        gl->gl_object = NULL;
        gl->gl_sbd = sdp;
        gl->gl_aspace = NULL;
        lops_init_le(&gl->gl_le, &gfs2_glock_lops);

        /* If this glock protects actual on-disk data or metadata blocks,
           create a VFS inode to manage the pages/buffers holding them. */
        if (glops == &gfs2_inode_glops || glops == &gfs2_rgrp_glops) {
                gl->gl_aspace = gfs2_aspace_get(sdp);
                if (!gl->gl_aspace) {
                        error = -ENOMEM;
                        goto fail;
                }
        }

        error = gfs2_lm_get_lock(sdp, &name, &gl->gl_lock);
        if (error)
                goto fail_aspace;

        write_lock(gl_lock_addr(hash));
        tmp = search_bucket(hash, sdp, &name);
        if (tmp) {
                write_unlock(gl_lock_addr(hash));
                glock_free(gl);
                gl = tmp;
        } else {
                hlist_add_head(&gl->gl_list, &gl_hash_table[hash].hb_list);
                write_unlock(gl_lock_addr(hash));
        }

        *glp = gl;

        return 0;

fail_aspace:
        if (gl->gl_aspace)
                gfs2_aspace_put(gl->gl_aspace);
fail:
        kmem_cache_free(gfs2_glock_cachep, gl); 
        return error;
}

/**
 * gfs2_holder_init - initialize a struct gfs2_holder in the default way
 * @gl: the glock
 * @state: the state we're requesting
 * @flags: the modifier flags
 * @gh: the holder structure
 *
 */

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 = current;
        gh->gh_state = state;
        gh->gh_flags = flags;
        gh->gh_error = 0;
        gh->gh_iflags = 0;
        init_completion(&gh->gh_wait);

        if (gh->gh_state == LM_ST_EXCLUSIVE)
                gh->gh_flags |= GL_LOCAL_EXCL;

        gfs2_glock_hold(gl);
}

/**
 * gfs2_holder_reinit - reinitialize a struct gfs2_holder so we can requeue it
 * @state: the state we're requesting
 * @flags: the modifier flags
 * @gh: the holder structure
 *
 * Don't mess with the glock.
 *
 */

void gfs2_holder_reinit(unsigned int state, unsigned flags, struct gfs2_holder *gh)
{
        gh->gh_state = state;
        gh->gh_flags = flags;
        if (gh->gh_state == LM_ST_EXCLUSIVE)
                gh->gh_flags |= GL_LOCAL_EXCL;

        gh->gh_iflags &= 1 << HIF_ALLOCED;
        gh->gh_ip = (unsigned long)__builtin_return_address(0);
}

/**
 * gfs2_holder_uninit - uninitialize a holder structure (drop glock reference)
 * @gh: the holder structure
 *
 */

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

/**
 * gfs2_holder_get - get a struct gfs2_holder structure
 * @gl: the glock
 * @state: the state we're requesting
 * @flags: the modifier flags
 * @gfp_flags:
 *
 * Figure out how big an impact this function has.  Either:
 * 1) Replace it with a cache of structures hanging off the struct gfs2_sbd
 * 2) Leave it like it is
 *
 * Returns: the holder structure, NULL on ENOMEM
 */

static struct gfs2_holder *gfs2_holder_get(struct gfs2_glock *gl,
                                           unsigned int state,
                                           int flags, gfp_t gfp_flags)
{
        struct gfs2_holder *gh;

        gh = kmalloc(sizeof(struct gfs2_holder), gfp_flags);
        if (!gh)
                return NULL;

        gfs2_holder_init(gl, state, flags, gh);
        set_bit(HIF_ALLOCED, &gh->gh_iflags);
        gh->gh_ip = (unsigned long)__builtin_return_address(0);
        return gh;
}

/**
 * gfs2_holder_put - get rid of a struct gfs2_holder structure
 * @gh: the holder structure
 *
 */

static void gfs2_holder_put(struct gfs2_holder *gh)
{
        gfs2_holder_uninit(gh);
        kfree(gh);
}

/**
 * rq_mutex - process a mutex request in the queue
 * @gh: the glock holder
 *
 * Returns: 1 if the queue is blocked
 */

static int rq_mutex(struct gfs2_holder *gh)
{
        struct gfs2_glock *gl = gh->gh_gl;

        list_del_init(&gh->gh_list);
        /*  gh->gh_error never examined.  */
        set_bit(GLF_LOCK, &gl->gl_flags);
        complete(&gh->gh_wait);

        return 1;
}

/**
 * rq_promote - process a promote request in the queue
 * @gh: the glock holder
 *
 * Acquire a new inter-node lock, or change a lock state to more restrictive.
 *
 * Returns: 1 if the queue is blocked
 */

static int rq_promote(struct gfs2_holder *gh)
{
        struct gfs2_glock *gl = gh->gh_gl;
        struct gfs2_sbd *sdp = gl->gl_sbd;
        const struct gfs2_glock_operations *glops = gl->gl_ops;

        if (!relaxed_state_ok(gl->gl_state, gh->gh_state, gh->gh_flags)) {
                if (list_empty(&gl->gl_holders)) {
                        gl->gl_req_gh = gh;
                        set_bit(GLF_LOCK, &gl->gl_flags);
                        spin_unlock(&gl->gl_spin);

                        if (atomic_read(&sdp->sd_reclaim_count) >
                            gfs2_tune_get(sdp, gt_reclaim_limit) &&
                            !(gh->gh_flags & LM_FLAG_PRIORITY)) {
                                gfs2_reclaim_glock(sdp);
                                gfs2_reclaim_glock(sdp);
                        }

                        glops->go_xmote_th(gl, gh->gh_state, gh->gh_flags);
                        spin_lock(&gl->gl_spin);
                }
                return 1;
        }

        if (list_empty(&gl->gl_holders)) {
                set_bit(HIF_FIRST, &gh->gh_iflags);
                set_bit(GLF_LOCK, &gl->gl_flags);
        } else {
                struct gfs2_holder *next_gh;
                if (gh->gh_flags & GL_LOCAL_EXCL)
                        return 1;
                next_gh = list_entry(gl->gl_holders.next, struct gfs2_holder,
                                     gh_list);
                if (next_gh->gh_flags & GL_LOCAL_EXCL)
                         return 1;
        }

        list_move_tail(&gh->gh_list, &gl->gl_holders);
        gh->gh_error = 0;
        set_bit(HIF_HOLDER, &gh->gh_iflags);

        complete(&gh->gh_wait);

        return 0;
}

/**
 * rq_demote - process a demote request in the queue
 * @gh: the glock holder
 *
 * Returns: 1 if the queue is blocked
 */

static int rq_demote(struct gfs2_holder *gh)
{
        struct gfs2_glock *gl = gh->gh_gl;
        const struct gfs2_glock_operations *glops = gl->gl_ops;

        if (!list_empty(&gl->gl_holders))
                return 1;

        if (gl->gl_state == gh->gh_state || gl->gl_state == LM_ST_UNLOCKED) {
                list_del_init(&gh->gh_list);
                gh->gh_error = 0;
                spin_unlock(&gl->gl_spin);
                if (test_bit(HIF_DEALLOC, &gh->gh_iflags))
                        gfs2_holder_put(gh);
                else
                        complete(&gh->gh_wait);
                spin_lock(&gl->gl_spin);
        } else {
                gl->gl_req_gh = gh;
                set_bit(GLF_LOCK, &gl->gl_flags);
                spin_unlock(&gl->gl_spin);

                if (gh->gh_state == LM_ST_UNLOCKED ||
                    gl->gl_state != LM_ST_EXCLUSIVE)
                        glops->go_drop_th(gl);
                else
                        glops->go_xmote_th(gl, gh->gh_state, gh->gh_flags);

                spin_lock(&gl->gl_spin);
        }

        return 0;
}

/**
 * rq_greedy - process a queued request to drop greedy status
 * @gh: the glock holder
 *
 * Returns: 1 if the queue is blocked
 */

static int rq_greedy(struct gfs2_holder *gh)
{
        struct gfs2_glock *gl = gh->gh_gl;

        list_del_init(&gh->gh_list);
        /*  gh->gh_error never examined.  */
        clear_bit(GLF_GREEDY, &gl->gl_flags);
        spin_unlock(&gl->gl_spin);

        gfs2_holder_uninit(gh);
        kfree(container_of(gh, struct greedy, gr_gh));

        spin_lock(&gl->gl_spin);                

        return 0;
}

/**
 * run_queue - process holder structures on a glock
 * @gl: the glock
 *
 */
static void run_queue(struct gfs2_glock *gl)
{
        struct gfs2_holder *gh;
        int blocked = 1;

        for (;;) {
                if (test_bit(GLF_LOCK, &gl->gl_flags))
                        break;

                if (!list_empty(&gl->gl_waiters1)) {
                        gh = list_entry(gl->gl_waiters1.next,
                                        struct gfs2_holder, gh_list);

                        if (test_bit(HIF_MUTEX, &gh->gh_iflags))
                                blocked = rq_mutex(gh);
                        else
                                gfs2_assert_warn(gl->gl_sbd, 0);

                } else if (!list_empty(&gl->gl_waiters2) &&
                           !test_bit(GLF_SKIP_WAITERS2, &gl->gl_flags)) {
                        gh = list_entry(gl->gl_waiters2.next,
                                        struct gfs2_holder, gh_list);

                        if (test_bit(HIF_DEMOTE, &gh->gh_iflags))
                                blocked = rq_demote(gh);
                        else if (test_bit(HIF_GREEDY, &gh->gh_iflags))
                                blocked = rq_greedy(gh);
                        else
                                gfs2_assert_warn(gl->gl_sbd, 0);

                } else if (!list_empty(&gl->gl_waiters3)) {
                        gh = list_entry(gl->gl_waiters3.next,
                                        struct gfs2_holder, gh_list);

                        if (test_bit(HIF_PROMOTE, &gh->gh_iflags))
                                blocked = rq_promote(gh);
                        else
                                gfs2_assert_warn(gl->gl_sbd, 0);

                } else
                        break;

                if (blocked)
                        break;
        }
}

/**
 * gfs2_glmutex_lock - acquire a local lock on a glock
 * @gl: the glock
 *
 * Gives caller exclusive access to manipulate a glock structure.
 */

static void gfs2_glmutex_lock(struct gfs2_glock *gl)
{
        struct gfs2_holder gh;

        gfs2_holder_init(gl, 0, 0, &gh);
        set_bit(HIF_MUTEX, &gh.gh_iflags);

        spin_lock(&gl->gl_spin);
        if (test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
                list_add_tail(&gh.gh_list, &gl->gl_waiters1);
        } else {
                gl->gl_owner = current;
                gl->gl_ip = (unsigned long)__builtin_return_address(0);
                complete(&gh.gh_wait);
        }
        spin_unlock(&gl->gl_spin);

        wait_for_completion(&gh.gh_wait);
        gfs2_holder_uninit(&gh);
}

/**
 * gfs2_glmutex_trylock - try to acquire a local lock on a glock
 * @gl: the glock
 *
 * Returns: 1 if the glock is acquired
 */

static int gfs2_glmutex_trylock(struct gfs2_glock *gl)
{
        int acquired = 1;

        spin_lock(&gl->gl_spin);
        if (test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
                acquired = 0;
        } else {
                gl->gl_owner = current;
                gl->gl_ip = (unsigned long)__builtin_return_address(0);
        }
        spin_unlock(&gl->gl_spin);

        return acquired;
}

/**
 * gfs2_glmutex_unlock - release a local lock on a glock
 * @gl: the glock
 *
 */

static void gfs2_glmutex_unlock(struct gfs2_glock *gl)
{
        spin_lock(&gl->gl_spin);
        clear_bit(GLF_LOCK, &gl->gl_flags);
        gl->gl_owner = NULL;
        gl->gl_ip = 0;
        run_queue(gl);
        BUG_ON(!spin_is_locked(&gl->gl_spin));
        spin_unlock(&gl->gl_spin);
}

/**
 * handle_callback - add a demote request to a lock's queue
 * @gl: the glock
 * @state: the state the caller wants us to change to
 *
 * Note: This may fail sliently if we are out of memory.
 */

static void handle_callback(struct gfs2_glock *gl, unsigned int state)
{
        struct gfs2_holder *gh, *new_gh = NULL;

restart:
        spin_lock(&gl->gl_spin);

        list_for_each_entry(gh, &gl->gl_waiters2, gh_list) {
                if (test_bit(HIF_DEMOTE, &gh->gh_iflags) &&
                    gl->gl_req_gh != gh) {
                        if (gh->gh_state != state)
                                gh->gh_state = LM_ST_UNLOCKED;
                        goto out;
                }
        }

        if (new_gh) {
                list_add_tail(&new_gh->gh_list, &gl->gl_waiters2);
                new_gh = NULL;
        } else {
                spin_unlock(&gl->gl_spin);

                new_gh = gfs2_holder_get(gl, state, LM_FLAG_TRY, GFP_KERNEL);
                if (!new_gh)
                        return;
                set_bit(HIF_DEMOTE, &new_gh->gh_iflags);
                set_bit(HIF_DEALLOC, &new_gh->gh_iflags);

                goto restart;
        }

out:
        spin_unlock(&gl->gl_spin);

        if (new_gh)
                gfs2_holder_put(new_gh);
}

void gfs2_glock_inode_squish(struct inode *inode)
{
        struct gfs2_holder gh;
        struct gfs2_glock *gl = GFS2_I(inode)->i_gl;
        gfs2_holder_init(gl, LM_ST_UNLOCKED, 0, &gh);
        set_bit(HIF_DEMOTE, &gh.gh_iflags);
        spin_lock(&gl->gl_spin);
        gfs2_assert(inode->i_sb->s_fs_info, list_empty(&gl->gl_holders));
        list_add_tail(&gh.gh_list, &gl->gl_waiters2);
        run_queue(gl);
        spin_unlock(&gl->gl_spin);
        wait_for_completion(&gh.gh_wait);
        gfs2_holder_uninit(&gh);
}

/**
 * state_change - record that the glock is now in a different state
 * @gl: the glock
 * @new_state the new state
 *
 */

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(gl);
        }

        gl->gl_state = new_state;
}

/**
 * xmote_bh - Called after the lock module is done acquiring a lock
 * @gl: The glock in question
 * @ret: the int returned from the lock module
 *
 */

static void xmote_bh(struct gfs2_glock *gl, unsigned int ret)
{
        struct gfs2_sbd *sdp = gl->gl_sbd;
        const struct gfs2_glock_operations *glops = gl->gl_ops;
        struct gfs2_holder *gh = gl->gl_req_gh;
        int prev_state = gl->gl_state;
        int op_done = 1;

        gfs2_assert_warn(sdp, test_bit(GLF_LOCK, &gl->gl_flags));
        gfs2_assert_warn(sdp, queue_empty(gl, &gl->gl_holders));
        gfs2_assert_warn(sdp, !(ret & LM_OUT_ASYNC));

        state_change(gl, ret & LM_OUT_ST_MASK);

        if (prev_state != LM_ST_UNLOCKED && !(ret & LM_OUT_CACHEABLE)) {
                if (glops->go_inval)
                        glops->go_inval(gl, DIO_METADATA | DIO_DATA);
        } else if (gl->gl_state == LM_ST_DEFERRED) {
                /* We might not want to do this here.
                   Look at moving to the inode glops. */
                if (glops->go_inval)
                        glops->go_inval(gl, DIO_DATA);
        }

        /*  Deal with each possible exit condition  */

        if (!gh)
                gl->gl_stamp = jiffies;
        else if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) {
                spin_lock(&gl->gl_spin);
                list_del_init(&gh->gh_list);
                gh->gh_error = -EIO;
                spin_unlock(&gl->gl_spin);
        } else if (test_bit(HIF_DEMOTE, &gh->gh_iflags)) {
                spin_lock(&gl->gl_spin);
                list_del_init(&gh->gh_list);
                if (gl->gl_state == gh->gh_state ||
                    gl->gl_state == LM_ST_UNLOCKED) {
                        gh->gh_error = 0;
                } else {
                        if (gfs2_assert_warn(sdp, gh->gh_flags &
                                        (LM_FLAG_TRY | LM_FLAG_TRY_1CB)) == -1)
                                fs_warn(sdp, "ret = 0x%.8X\n", ret);
                        gh->gh_error = GLR_TRYFAILED;
                }
                spin_unlock(&gl->gl_spin);

                if (ret & LM_OUT_CANCELED)
                        handle_callback(gl, LM_ST_UNLOCKED);

        } else if (ret & LM_OUT_CANCELED) {
                spin_lock(&gl->gl_spin);
                list_del_init(&gh->gh_list);
                gh->gh_error = GLR_CANCELED;
                spin_unlock(&gl->gl_spin);

        } else if (relaxed_state_ok(gl->gl_state, gh->gh_state, gh->gh_flags)) {
                spin_lock(&gl->gl_spin);
                list_move_tail(&gh->gh_list, &gl->gl_holders);
                gh->gh_error = 0;
                set_bit(HIF_HOLDER, &gh->gh_iflags);
                spin_unlock(&gl->gl_spin);

                set_bit(HIF_FIRST, &gh->gh_iflags);

                op_done = 0;

        } else if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)) {
                spin_lock(&gl->gl_spin);
                list_del_init(&gh->gh_list);
                gh->gh_error = GLR_TRYFAILED;
                spin_unlock(&gl->gl_spin);

        } else {
                if (gfs2_assert_withdraw(sdp, 0) == -1)
                        fs_err(sdp, "ret = 0x%.8X\n", ret);
        }

        if (glops->go_xmote_bh)
                glops->go_xmote_bh(gl);

        if (op_done) {
                spin_lock(&gl->gl_spin);
                gl->gl_req_gh = NULL;
                gl->gl_req_bh = NULL;
                clear_bit(GLF_LOCK, &gl->gl_flags);
                run_queue(gl);
                spin_unlock(&gl->gl_spin);
        }

        gfs2_glock_put(gl);

        if (gh) {
                if (test_bit(HIF_DEALLOC, &gh->gh_iflags))
                        gfs2_holder_put(gh);
                else
                        complete(&gh->gh_wait);
        }
}

/**
 * gfs2_glock_xmote_th - Call into the lock module to acquire or change a glock
 * @gl: The glock in question
 * @state: the requested state
 * @flags: modifier flags to the lock call
 *
 */

void gfs2_glock_xmote_th(struct gfs2_glock *gl, unsigned int state, int flags)
{
        struct gfs2_sbd *sdp = gl->gl_sbd;
        const struct gfs2_glock_operations *glops = gl->gl_ops;
        int lck_flags = flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB |
                                 LM_FLAG_NOEXP | LM_FLAG_ANY |
                                 LM_FLAG_PRIORITY);
        unsigned int lck_ret;

        gfs2_assert_warn(sdp, test_bit(GLF_LOCK, &gl->gl_flags));
        gfs2_assert_warn(sdp, queue_empty(gl, &gl->gl_holders));
        gfs2_assert_warn(sdp, state != LM_ST_UNLOCKED);
        gfs2_assert_warn(sdp, state != gl->gl_state);

        if (gl->gl_state == LM_ST_EXCLUSIVE && glops->go_sync)
                glops->go_sync(gl, DIO_METADATA | DIO_DATA | DIO_RELEASE);

        gfs2_glock_hold(gl);
        gl->gl_req_bh = xmote_bh;

        lck_ret = gfs2_lm_lock(sdp, gl->gl_lock, gl->gl_state, state, lck_flags);

        if (gfs2_assert_withdraw(sdp, !(lck_ret & LM_OUT_ERROR)))
                return;

        if (lck_ret & LM_OUT_ASYNC)
                gfs2_assert_warn(sdp, lck_ret == LM_OUT_ASYNC);
        else
                xmote_bh(gl, lck_ret);
}

/**
 * drop_bh - Called after a lock module unlock completes
 * @gl: the glock
 * @ret: the return status
 *
 * Doesn't wake up the process waiting on the struct gfs2_holder (if any)
 * Doesn't drop the reference on the glock the top half took out
 *
 */

static void drop_bh(struct gfs2_glock *gl, unsigned int ret)
{
        struct gfs2_sbd *sdp = gl->gl_sbd;
        const struct gfs2_glock_operations *glops = gl->gl_ops;
        struct gfs2_holder *gh = gl->gl_req_gh;

        clear_bit(GLF_PREFETCH, &gl->gl_flags);

        gfs2_assert_warn(sdp, test_bit(GLF_LOCK, &gl->gl_flags));
        gfs2_assert_warn(sdp, queue_empty(gl, &gl->gl_holders));
        gfs2_assert_warn(sdp, !ret);

        state_change(gl, LM_ST_UNLOCKED);

        if (glops->go_inval)
                glops->go_inval(gl, DIO_METADATA | DIO_DATA);

        if (gh) {
                spin_lock(&gl->gl_spin);
                list_del_init(&gh->gh_list);
                gh->gh_error = 0;
                spin_unlock(&gl->gl_spin);
        }

        if (glops->go_drop_bh)
                glops->go_drop_bh(gl);

        spin_lock(&gl->gl_spin);
        gl->gl_req_gh = NULL;
        gl->gl_req_bh = NULL;
        clear_bit(GLF_LOCK, &gl->gl_flags);
        run_queue(gl);
        spin_unlock(&gl->gl_spin);

        gfs2_glock_put(gl);

        if (gh) {
                if (test_bit(HIF_DEALLOC, &gh->gh_iflags))
                        gfs2_holder_put(gh);
                else
                        complete(&gh->gh_wait);
        }
}

/**
 * gfs2_glock_drop_th - call into the lock module to unlock a lock
 * @gl: the glock
 *
 */

void gfs2_glock_drop_th(struct gfs2_glock *gl)
{
        struct gfs2_sbd *sdp = gl->gl_sbd;
        const struct gfs2_glock_operations *glops = gl->gl_ops;
        unsigned int ret;

        gfs2_assert_warn(sdp, test_bit(GLF_LOCK, &gl->gl_flags));
        gfs2_assert_warn(sdp, queue_empty(gl, &gl->gl_holders));
        gfs2_assert_warn(sdp, gl->gl_state != LM_ST_UNLOCKED);

        if (gl->gl_state == LM_ST_EXCLUSIVE && glops->go_sync)
                glops->go_sync(gl, DIO_METADATA | DIO_DATA | DIO_RELEASE);

        gfs2_glock_hold(gl);
        gl->gl_req_bh = drop_bh;

        ret = gfs2_lm_unlock(sdp, gl->gl_lock, gl->gl_state);

        if (gfs2_assert_withdraw(sdp, !(ret & LM_OUT_ERROR)))
                return;

        if (!ret)
                drop_bh(gl, ret);
        else
                gfs2_assert_warn(sdp, ret == LM_OUT_ASYNC);
}

/**
 * do_cancels - cancel requests for locks stuck waiting on an expire flag
 * @gh: the LM_FLAG_PRIORITY holder waiting to acquire the lock
 *
 * Don't cancel GL_NOCANCEL requests.
 */

static void do_cancels(struct gfs2_holder *gh)
{
        struct gfs2_glock *gl = gh->gh_gl;

        spin_lock(&gl->gl_spin);

        while (gl->gl_req_gh != gh &&
               !test_bit(HIF_HOLDER, &gh->gh_iflags) &&
               !list_empty(&gh->gh_list)) {
                if (gl->gl_req_bh && !(gl->gl_req_gh &&
                                     (gl->gl_req_gh->gh_flags & GL_NOCANCEL))) {
                        spin_unlock(&gl->gl_spin);
                        gfs2_lm_cancel(gl->gl_sbd, gl->gl_lock);
                        msleep(100);
                        spin_lock(&gl->gl_spin);
                } else {
                        spin_unlock(&gl->gl_spin);
                        msleep(100);
                        spin_lock(&gl->gl_spin);
                }
        }

        spin_unlock(&gl->gl_spin);
}

/**
 * glock_wait_internal - wait on a glock acquisition
 * @gh: the glock holder
 *
 * Returns: 0 on success
 */

static int glock_wait_internal(struct gfs2_holder *gh)
{
        struct gfs2_glock *gl = gh->gh_gl;
        struct gfs2_sbd *sdp = gl->gl_sbd;
        const struct gfs2_glock_operations *glops = gl->gl_ops;

        if (test_bit(HIF_ABORTED, &gh->gh_iflags))
                return -EIO;

        if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)) {
                spin_lock(&gl->gl_spin);
                if (gl->gl_req_gh != gh &&
                    !test_bit(HIF_HOLDER, &gh->gh_iflags) &&
                    !list_empty(&gh->gh_list)) {
                        list_del_init(&gh->gh_list);
                        gh->gh_error = GLR_TRYFAILED;
                        run_queue(gl);
                        spin_unlock(&gl->gl_spin);
                        return gh->gh_error;
                }
                spin_unlock(&gl->gl_spin);
        }

        if (gh->gh_flags & LM_FLAG_PRIORITY)
                do_cancels(gh);

        wait_for_completion(&gh->gh_wait);

        if (gh->gh_error)
                return gh->gh_error;

        gfs2_assert_withdraw(sdp, test_bit(HIF_HOLDER, &gh->gh_iflags));
        gfs2_assert_withdraw(sdp, relaxed_state_ok(gl->gl_state, gh->gh_state,
                                                   gh->gh_flags));

        if (test_bit(HIF_FIRST, &gh->gh_iflags)) {
                gfs2_assert_warn(sdp, test_bit(GLF_LOCK, &gl->gl_flags));

                if (glops->go_lock) {
                        gh->gh_error = glops->go_lock(gh);
                        if (gh->gh_error) {
                                spin_lock(&gl->gl_spin);
                                list_del_init(&gh->gh_list);
                                spin_unlock(&gl->gl_spin);
                        }
                }

                spin_lock(&gl->gl_spin);
                gl->gl_req_gh = NULL;
                gl->gl_req_bh = NULL;
                clear_bit(GLF_LOCK, &gl->gl_flags);
                run_queue(gl);
                spin_unlock(&gl->gl_spin);
        }

        return gh->gh_error;
}

static inline struct gfs2_holder *
find_holder_by_owner(struct list_head *head, struct task_struct *owner)
{
        struct gfs2_holder *gh;

        list_for_each_entry(gh, head, gh_list) {
                if (gh->gh_owner == owner)
                        return gh;
        }

        return NULL;
}

/**
 * add_to_queue - Add a holder to the wait queue (but look for recursion)
 * @gh: the holder structure to add
 *
 */

static void add_to_queue(struct gfs2_holder *gh)
{
        struct gfs2_glock *gl = gh->gh_gl;
        struct gfs2_holder *existing;

        BUG_ON(!gh->gh_owner);

        existing = find_holder_by_owner(&gl->gl_holders, gh->gh_owner);
        if (existing) {
                print_symbol(KERN_WARNING "original: %s\n", existing->gh_ip);
                printk(KERN_INFO "pid : %d\n", existing->gh_owner->pid);
                printk(KERN_INFO "lock type : %d lock state : %d\n", 
                                existing->gh_gl->gl_name.ln_type, existing->gh_gl->gl_state);
                print_symbol(KERN_WARNING "new: %s\n", gh->gh_ip);
                printk(KERN_INFO "pid : %d\n", gh->gh_owner->pid);
                printk(KERN_INFO "lock type : %d lock state : %d\n", 
                                gl->gl_name.ln_type, gl->gl_state);
                BUG();
        }

        existing = find_holder_by_owner(&gl->gl_waiters3, gh->gh_owner);
        if (existing) {
                print_symbol(KERN_WARNING "original: %s\n", existing->gh_ip);
                print_symbol(KERN_WARNING "new: %s\n", gh->gh_ip);
                BUG();
        }

        if (gh->gh_flags & LM_FLAG_PRIORITY)
                list_add(&gh->gh_list, &gl->gl_waiters3);
        else
                list_add_tail(&gh->gh_list, &gl->gl_waiters3);  
}

/**
 * gfs2_glock_nq - enqueue a struct gfs2_holder onto a glock (acquire a glock)
 * @gh: the holder structure
 *
 * if (gh->gh_flags & GL_ASYNC), this never returns an error
 *
 * Returns: 0, GLR_TRYFAILED, or errno on failure
 */

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;

restart:
        if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) {
                set_bit(HIF_ABORTED, &gh->gh_iflags);
                return -EIO;
        }

        set_bit(HIF_PROMOTE, &gh->gh_iflags);

        spin_lock(&gl->gl_spin);
        add_to_queue(gh);
        run_queue(gl);
        spin_unlock(&gl->gl_spin);

        if (!(gh->gh_flags & GL_ASYNC)) {
                error = glock_wait_internal(gh);
                if (error == GLR_CANCELED) {
                        msleep(100);
                        goto restart;
                }
        }

        clear_bit(GLF_PREFETCH, &gl->gl_flags);

        if (error == GLR_TRYFAILED && (gh->gh_flags & GL_DUMP))
                dump_glock(gl);

        return error;
}

/**
 * gfs2_glock_poll - poll to see if an async request has been completed
 * @gh: the holder
 *
 * Returns: 1 if the request is ready to be gfs2_glock_wait()ed on
 */

int gfs2_glock_poll(struct gfs2_holder *gh)
{
        struct gfs2_glock *gl = gh->gh_gl;
        int ready = 0;

        spin_lock(&gl->gl_spin);

        if (test_bit(HIF_HOLDER, &gh->gh_iflags))
                ready = 1;
        else if (list_empty(&gh->gh_list)) {
                if (gh->gh_error == GLR_CANCELED) {
                        spin_unlock(&gl->gl_spin);
                        msleep(100);
                        if (gfs2_glock_nq(gh))
                                return 1;
                        return 0;
                } else
                        ready = 1;
        }

        spin_unlock(&gl->gl_spin);

        return ready;
}

/**
 * gfs2_glock_wait - wait for a lock acquisition that ended in a GLR_ASYNC
 * @gh: the holder structure
 *
 * Returns: 0, GLR_TRYFAILED, or errno on failure
 */

int gfs2_glock_wait(struct gfs2_holder *gh)
{
        int error;

        error = glock_wait_internal(gh);
        if (error == GLR_CANCELED) {
                msleep(100);
                gh->gh_flags &= ~GL_ASYNC;
                error = gfs2_glock_nq(gh);
        }

        return error;
}

/**
 * gfs2_glock_dq - dequeue a struct gfs2_holder from a glock (release a glock)
 * @gh: the glock holder
 *
 */

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

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

        gfs2_glmutex_lock(gl);

        spin_lock(&gl->gl_spin);
        list_del_init(&gh->gh_list);

        if (list_empty(&gl->gl_holders)) {
                spin_unlock(&gl->gl_spin);

                if (glops->go_unlock)
                        glops->go_unlock(gh);

                gl->gl_stamp = jiffies;

                spin_lock(&gl->gl_spin);
        }

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

/**
 * gfs2_glock_prefetch - Try to prefetch a glock
 * @gl: the glock
 * @state: the state to prefetch in
 * @flags: flags passed to go_xmote_th()
 *
 */

static void gfs2_glock_prefetch(struct gfs2_glock *gl, unsigned int state,
                                int flags)
{
        const struct gfs2_glock_operations *glops = gl->gl_ops;

        spin_lock(&gl->gl_spin);

        if (test_bit(GLF_LOCK, &gl->gl_flags) || !list_empty(&gl->gl_holders) ||
            !list_empty(&gl->gl_waiters1) || !list_empty(&gl->gl_waiters2) ||
            !list_empty(&gl->gl_waiters3) ||
            relaxed_state_ok(gl->gl_state, state, flags)) {
                spin_unlock(&gl->gl_spin);
                return;
        }

        set_bit(GLF_PREFETCH, &gl->gl_flags);
        set_bit(GLF_LOCK, &gl->gl_flags);
        spin_unlock(&gl->gl_spin);

        glops->go_xmote_th(gl, state, flags);
}

static void greedy_work(void *data)
{
        struct greedy *gr = data;
        struct gfs2_holder *gh = &gr->gr_gh;
        struct gfs2_glock *gl = gh->gh_gl;
        const struct gfs2_glock_operations *glops = gl->gl_ops;

        clear_bit(GLF_SKIP_WAITERS2, &gl->gl_flags);

        if (glops->go_greedy)
                glops->go_greedy(gl);

        spin_lock(&gl->gl_spin);

        if (list_empty(&gl->gl_waiters2)) {
                clear_bit(GLF_GREEDY, &gl->gl_flags);
                spin_unlock(&gl->gl_spin);
                gfs2_holder_uninit(gh);
                kfree(gr);
        } else {
                gfs2_glock_hold(gl);
                list_add_tail(&gh->gh_list, &gl->gl_waiters2);
                run_queue(gl);
                spin_unlock(&gl->gl_spin);
                gfs2_glock_put(gl);
        }
}

/**
 * gfs2_glock_be_greedy -
 * @gl:
 * @time:
 *
 * Returns: 0 if go_greedy will be called, 1 otherwise
 */

int gfs2_glock_be_greedy(struct gfs2_glock *gl, unsigned int time)
{
        struct greedy *gr;
        struct gfs2_holder *gh;

        if (!time || gl->gl_sbd->sd_args.ar_localcaching ||
            test_and_set_bit(GLF_GREEDY, &gl->gl_flags))
                return 1;

        gr = kmalloc(sizeof(struct greedy), GFP_KERNEL);
        if (!gr) {
                clear_bit(GLF_GREEDY, &gl->gl_flags);
                return 1;
        }
        gh = &gr->gr_gh;

        gfs2_holder_init(gl, 0, 0, gh);
        set_bit(HIF_GREEDY, &gh->gh_iflags);
        INIT_WORK(&gr->gr_work, greedy_work, gr);

        set_bit(GLF_SKIP_WAITERS2, &gl->gl_flags);
        schedule_delayed_work(&gr->gr_work, time);

        return 0;
}

/**
 * gfs2_glock_dq_uninit - dequeue a holder from a glock and initialize it
 * @gh: the holder structure
 *
 */

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

/**
 * gfs2_glock_nq_num - acquire a glock based on lock number
 * @sdp: the filesystem
 * @number: the lock number
 * @glops: the glock operations for the type of glock
 * @state: the state to acquire the glock in
 * @flags: modifier flags for the aquisition
 * @gh: the struct gfs2_holder
 *
 * Returns: errno
 */

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;
}

/**
 * glock_compare - Compare two struct gfs2_glock structures for sorting
 * @arg_a: the first structure
 * @arg_b: the second structure
 *
 */

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;
        if (gh_a->gh_state == LM_ST_SHARED && gh_b->gh_state == LM_ST_EXCLUSIVE)
                return 1;
        if (!(gh_a->gh_flags & GL_LOCAL_EXCL) && (gh_b->gh_flags & GL_LOCAL_EXCL))
                return 1;
        return 0;
}

/**
 * nq_m_sync - synchonously acquire more than one glock in deadlock free order
 * @num_gh: the number of structures
 * @ghs: an array of struct gfs2_holder structures
 *
 * Returns: 0 on success (all glocks acquired),
 *          errno on failure (no glocks acquired)
 */

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;
}

/**
 * gfs2_glock_nq_m - acquire multiple glocks
 * @num_gh: the number of structures
 * @ghs: an array of struct gfs2_holder structures
 *
 * Figure out how big an impact this function has.  Either:
 * 1) Replace this code with code that calls gfs2_glock_prefetch()
 * 2) Forget async stuff and just call nq_m_sync()
 * 3) Leave it like it is
 *
 * Returns: 0 on success (all glocks acquired),
 *          errno on failure (no glocks acquired)
 */

int gfs2_glock_nq_m(unsigned int num_gh, struct gfs2_holder *ghs)
{
        int *e;
        unsigned int x;
        int borked = 0, serious = 0;
        int error = 0;

        if (!num_gh)
                return 0;

        if (num_gh == 1) {
                ghs->gh_flags &= ~(LM_FLAG_TRY | GL_ASYNC);
                return gfs2_glock_nq(ghs);
        }

        e = kcalloc(num_gh, sizeof(struct gfs2_holder *), GFP_KERNEL);
        if (!e)
                return -ENOMEM;

        for (x = 0; x < num_gh; x++) {
                ghs[x].gh_flags |= LM_FLAG_TRY | GL_ASYNC;
                error = gfs2_glock_nq(&ghs[x]);
                if (error) {
                        borked = 1;
                        serious = error;
                        num_gh = x;
                        break;
                }
        }

        for (x = 0; x < num_gh; x++) {
                error = e[x] = glock_wait_internal(&ghs[x]);
                if (error) {
                        borked = 1;
                        if (error != GLR_TRYFAILED && error != GLR_CANCELED)
                                serious = error;
                }
        }

        if (!borked) {
                kfree(e);
                return 0;
        }

        for (x = 0; x < num_gh; x++)
                if (!e[x])
                        gfs2_glock_dq(&ghs[x]);

        if (serious)
                error = serious;
        else {
                for (x = 0; x < num_gh; x++)
                        gfs2_holder_reinit(ghs[x].gh_state, ghs[x].gh_flags,
                                          &ghs[x]);
                error = nq_m_sync(num_gh, ghs, (struct gfs2_holder **)e);
        }

        kfree(e);

        return error;
}

/**
 * gfs2_glock_dq_m - release multiple glocks
 * @num_gh: the number of structures
 * @ghs: an array of struct gfs2_holder structures
 *
 */

void gfs2_glock_dq_m(unsigned int num_gh, struct gfs2_holder *ghs)
{
        unsigned int x;

        for (x = 0; x < num_gh; x++)
                gfs2_glock_dq(&ghs[x]);
}

/**
 * gfs2_glock_dq_uninit_m - release multiple glocks
 * @num_gh: the number of structures
 * @ghs: an array of struct gfs2_holder structures
 *
 */

void gfs2_glock_dq_uninit_m(unsigned int num_gh, struct gfs2_holder *ghs)
{
        unsigned int x;

        for (x = 0; x < num_gh; x++)
                gfs2_glock_dq_uninit(&ghs[x]);
}

/**
 * gfs2_glock_prefetch_num - prefetch a glock based on lock number
 * @sdp: the filesystem
 * @number: the lock number
 * @glops: the glock operations for the type of glock
 * @state: the state to acquire the glock in
 * @flags: modifier flags for the aquisition
 *
 * Returns: errno
 */

void gfs2_glock_prefetch_num(struct gfs2_sbd *sdp, u64 number,
                             const struct gfs2_glock_operations *glops,
                             unsigned int state, int flags)
{
        struct gfs2_glock *gl;
        int error;

        if (atomic_read(&sdp->sd_reclaim_count) <
            gfs2_tune_get(sdp, gt_reclaim_limit)) {
                error = gfs2_glock_get(sdp, number, glops, CREATE, &gl);
                if (!error) {
                        gfs2_glock_prefetch(gl, state, flags);
                        gfs2_glock_put(gl);
                }
        }
}

/**
 * gfs2_lvb_hold - attach a LVB from a glock
 * @gl: The glock in question
 *
 */

int gfs2_lvb_hold(struct gfs2_glock *gl)
{
        int error;

        gfs2_glmutex_lock(gl);

        if (!atomic_read(&gl->gl_lvb_count)) {
                error = gfs2_lm_hold_lvb(gl->gl_sbd, gl->gl_lock, &gl->gl_lvb);
                if (error) {
                        gfs2_glmutex_unlock(gl);
                        return error;
                }
                gfs2_glock_hold(gl);
        }
        atomic_inc(&gl->gl_lvb_count);

        gfs2_glmutex_unlock(gl);

        return 0;
}

/**
 * gfs2_lvb_unhold - detach a LVB from a glock
 * @gl: The glock in question
 *
 */

void gfs2_lvb_unhold(struct gfs2_glock *gl)
{
        gfs2_glock_hold(gl);
        gfs2_glmutex_lock(gl);

        gfs2_assert(gl->gl_sbd, atomic_read(&gl->gl_lvb_count) > 0);
        if (atomic_dec_and_test(&gl->gl_lvb_count)) {
                gfs2_lm_unhold_lvb(gl->gl_sbd, gl->gl_lock, gl->gl_lvb);
                gl->gl_lvb = NULL;
                gfs2_glock_put(gl);
        }

        gfs2_glmutex_unlock(gl);
        gfs2_glock_put(gl);
}

static void blocking_cb(struct gfs2_sbd *sdp, struct lm_lockname *name,
                        unsigned int state)
{
        struct gfs2_glock *gl;

        gl = gfs2_glock_find(sdp, name);
        if (!gl)
                return;

        if (gl->gl_ops->go_callback)
                gl->gl_ops->go_callback(gl, state);
        handle_callback(gl, state);

        spin_lock(&gl->gl_spin);
        run_queue(gl);
        spin_unlock(&gl->gl_spin);

        gfs2_glock_put(gl);
}

/**
 * gfs2_glock_cb - Callback used by locking module
 * @sdp: Pointer to the superblock
 * @type: Type of callback
 * @data: Type dependent data pointer
 *
 * Called by the locking module when it wants to tell us something.
 * Either we need to drop a lock, one of our ASYNC requests completed, or
 * a journal from another client needs to be recovered.
 */

void gfs2_glock_cb(void *cb_data, unsigned int type, void *data)
{
        struct gfs2_sbd *sdp = cb_data;

        switch (type) {
        case LM_CB_NEED_E:
                blocking_cb(sdp, data, LM_ST_UNLOCKED);
                return;

        case LM_CB_NEED_D:
                blocking_cb(sdp, data, LM_ST_DEFERRED);
                return;

        case LM_CB_NEED_S:
                blocking_cb(sdp, data, LM_ST_SHARED);
                return;

        case LM_CB_ASYNC: {
                struct lm_async_cb *async = data;
                struct gfs2_glock *gl;

                gl = gfs2_glock_find(sdp, &async->lc_name);
                if (gfs2_assert_warn(sdp, gl))
                        return;
                if (!gfs2_assert_warn(sdp, gl->gl_req_bh))
                        gl->gl_req_bh(gl, async->lc_ret);
                gfs2_glock_put(gl);
                return;
        }

        case LM_CB_NEED_RECOVERY:
                gfs2_jdesc_make_dirty(sdp, *(unsigned int *)data);
                if (sdp->sd_recoverd_process)
                        wake_up_process(sdp->sd_recoverd_process);
                return;

        case LM_CB_DROPLOCKS:
                gfs2_gl_hash_clear(sdp, NO_WAIT);
                gfs2_quota_scan(sdp);
                return;

        default:
                gfs2_assert_warn(sdp, 0);
                return;
        }
}

/**
 * demote_ok - Check to see if it's ok to unlock a glock
 * @gl: the glock
 *
 * Returns: 1 if it's ok
 */

static int demote_ok(struct gfs2_glock *gl)
{
        struct gfs2_sbd *sdp = gl->gl_sbd;
        const struct gfs2_glock_operations *glops = gl->gl_ops;
        int demote = 1;

        if (test_bit(GLF_STICKY, &gl->gl_flags))
                demote = 0;
        else if (test_bit(GLF_PREFETCH, &gl->gl_flags))
                demote = time_after_eq(jiffies, gl->gl_stamp +
                                    gfs2_tune_get(sdp, gt_prefetch_secs) * HZ);
        else if (glops->go_demote_ok)
                demote = glops->go_demote_ok(gl);

        return demote;
}

/**
 * gfs2_glock_schedule_for_reclaim - Add a glock to the reclaim list
 * @gl: the glock
 *
 */

void gfs2_glock_schedule_for_reclaim(struct gfs2_glock *gl)
{
        struct gfs2_sbd *sdp = gl->gl_sbd;

        spin_lock(&sdp->sd_reclaim_lock);
        if (list_empty(&gl->gl_reclaim)) {
                gfs2_glock_hold(gl);
                list_add(&gl->gl_reclaim, &sdp->sd_reclaim_list);
                atomic_inc(&sdp->sd_reclaim_count);
        }
        spin_unlock(&sdp->sd_reclaim_lock);

        wake_up(&sdp->sd_reclaim_wq);
}

/**
 * gfs2_reclaim_glock - process the next glock on the filesystem's reclaim list
 * @sdp: the filesystem
 *
 * Called from gfs2_glockd() glock reclaim daemon, or when promoting a
 * different glock and we notice that there are a lot of glocks in the
 * reclaim list.
 *
 */

void gfs2_reclaim_glock(struct gfs2_sbd *sdp)
{
        struct gfs2_glock *gl;

        spin_lock(&sdp->sd_reclaim_lock);
        if (list_empty(&sdp->sd_reclaim_list)) {
                spin_unlock(&sdp->sd_reclaim_lock);
                return;
        }
        gl = list_entry(sdp->sd_reclaim_list.next,
                        struct gfs2_glock, gl_reclaim);
        list_del_init(&gl->gl_reclaim);
        spin_unlock(&sdp->sd_reclaim_lock);

        atomic_dec(&sdp->sd_reclaim_count);
        atomic_inc(&sdp->sd_reclaimed);

        if (gfs2_glmutex_trylock(gl)) {
                if (queue_empty(gl, &gl->gl_holders) &&
                    gl->gl_state != LM_ST_UNLOCKED && demote_ok(gl))
                        handle_callback(gl, LM_ST_UNLOCKED);
                gfs2_glmutex_unlock(gl);
        }

        gfs2_glock_put(gl);
}

/**
 * examine_bucket - Call a function for glock in a hash bucket
 * @examiner: the function
 * @sdp: the filesystem
 * @bucket: the bucket
 *
 * Returns: 1 if the bucket has entries
 */

static int examine_bucket(glock_examiner examiner, struct gfs2_sbd *sdp,
                          unsigned int hash)
{
        struct gfs2_glock *gl, *prev = NULL;
        int has_entries = 0;
        struct hlist_head *head = &gl_hash_table[hash].hb_list;

        read_lock(gl_lock_addr(hash));
        /* Can't use hlist_for_each_entry - don't want prefetch here */
        if (hlist_empty(head))
                goto out;
        has_entries = 1;
        gl = list_entry(head->first, struct gfs2_glock, gl_list);
        while(1) {
                if (gl->gl_sbd == sdp) {
                        gfs2_glock_hold(gl);
                        read_unlock(gl_lock_addr(hash));
                        if (prev)
                                gfs2_glock_put(prev);
                        prev = gl;
                        examiner(gl);
                        read_lock(gl_lock_addr(hash));
                }
                if (gl->gl_list.next == NULL)
                        break;
                gl = list_entry(gl->gl_list.next, struct gfs2_glock, gl_list);
        }
out:
        read_unlock(gl_lock_addr(hash));
        if (prev)
                gfs2_glock_put(prev);
        return has_entries;
}

/**
 * scan_glock - look at a glock and see if we can reclaim it
 * @gl: the glock to look at
 *
 */

static void scan_glock(struct gfs2_glock *gl)
{
        if (gl->gl_ops == &gfs2_inode_glops)
                return;

        if (gfs2_glmutex_trylock(gl)) {
                if (queue_empty(gl, &gl->gl_holders) &&
                    gl->gl_state != LM_ST_UNLOCKED && demote_ok(gl))
                        goto out_schedule;
                gfs2_glmutex_unlock(gl);
        }
        return;

out_schedule:
        gfs2_glmutex_unlock(gl);
        gfs2_glock_schedule_for_reclaim(gl);
}

/**
 * gfs2_scand_internal - Look for glocks and inodes to toss from memory
 * @sdp: the filesystem
 *
 */

void gfs2_scand_internal(struct gfs2_sbd *sdp)
{
        unsigned int x;

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

/**
 * clear_glock - look at a glock and see if we can free it from glock cache
 * @gl: the glock to look at
 *
 */

static void clear_glock(struct gfs2_glock *gl)
{
        struct gfs2_sbd *sdp = gl->gl_sbd;
        int released;

        spin_lock(&sdp->sd_reclaim_lock);
        if (!list_empty(&gl->gl_reclaim)) {
                list_del_init(&gl->gl_reclaim);
                atomic_dec(&sdp->sd_reclaim_count);
                spin_unlock(&sdp->sd_reclaim_lock);
                released = gfs2_glock_put(gl);
                gfs2_assert(sdp, !released);
        } else {
                spin_unlock(&sdp->sd_reclaim_lock);
        }

        if (gfs2_glmutex_trylock(gl)) {
                if (queue_empty(gl, &gl->gl_holders) &&
                    gl->gl_state != LM_ST_UNLOCKED)
                        handle_callback(gl, LM_ST_UNLOCKED);
                gfs2_glmutex_unlock(gl);
        }
}

/**
 * gfs2_gl_hash_clear - Empty out the glock hash table
 * @sdp: the filesystem
 * @wait: wait until it's all gone
 *
 * Called when unmounting the filesystem, or when inter-node lock manager
 * requests DROPLOCKS because it is running out of capacity.
 */

void gfs2_gl_hash_clear(struct gfs2_sbd *sdp, int wait)
{
        unsigned long t;
        unsigned int x;
        int cont;

        t = jiffies;

        for (;;) {
                cont = 0;
                for (x = 0; x < GFS2_GL_HASH_SIZE; x++) {
                        if (examine_bucket(clear_glock, sdp, x)) 
                                cont = 1;
                }

                if (!wait || !cont)
                        break;

                if (time_after_eq(jiffies,
                                  t + gfs2_tune_get(sdp, gt_stall_secs) * HZ)) {
                        fs_warn(sdp, "Unmount seems to be stalled. "
                                     "Dumping lock state...\n");
                        gfs2_dump_lockstate(sdp);
                        t = jiffies;
                }

                invalidate_inodes(sdp->sd_vfs);
                msleep(10);
        }
}

/*
 *  Diagnostic routines to help debug distributed deadlock
 */

/**
 * dump_holder - print information about a glock holder
 * @str: a string naming the type of holder
 * @gh: the glock holder
 *
 * Returns: 0 on success, -ENOBUFS when we run out of space
 */

static int dump_holder(char *str, struct gfs2_holder *gh)
{
        unsigned int x;
        int error = -ENOBUFS;

        printk(KERN_INFO "  %s\n", str);
        printk(KERN_INFO "    owner = %ld\n",
                   (gh->gh_owner) ? (long)gh->gh_owner->pid : -1);
        printk(KERN_INFO "    gh_state = %u\n", gh->gh_state);
        printk(KERN_INFO "    gh_flags =");
        for (x = 0; x < 32; x++)
                if (gh->gh_flags & (1 << x))
                        printk(" %u", x);
        printk(" \n");
        printk(KERN_INFO "    error = %d\n", gh->gh_error);
        printk(KERN_INFO "    gh_iflags =");
        for (x = 0; x < 32; x++)
                if (test_bit(x, &gh->gh_iflags))
                        printk(" %u", x);
        printk(" \n");
        print_symbol(KERN_INFO "    initialized at: %s\n", gh->gh_ip);

        error = 0;

        return error;
}

/**
 * dump_inode - print information about an inode
 * @ip: the inode
 *
 * Returns: 0 on success, -ENOBUFS when we run out of space
 */

static int dump_inode(struct gfs2_inode *ip)
{
        unsigned int x;
        int error = -ENOBUFS;

        printk(KERN_INFO "  Inode:\n");
        printk(KERN_INFO "    num = %llu %llu\n",
                    (unsigned long long)ip->i_num.no_formal_ino,
                    (unsigned long long)ip->i_num.no_addr);
        printk(KERN_INFO "    type = %u\n", IF2DT(ip->i_di.di_mode));
        printk(KERN_INFO "    i_flags =");
        for (x = 0; x < 32; x++)
                if (test_bit(x, &ip->i_flags))
                        printk(" %u", x);
        printk(" \n");

        error = 0;

        return error;
}

/**
 * dump_glock - print information about a glock
 * @gl: the glock
 * @count: where we are in the buffer
 *
 * Returns: 0 on success, -ENOBUFS when we run out of space
 */

static int dump_glock(struct gfs2_glock *gl)
{
        struct gfs2_holder *gh;
        unsigned int x;
        int error = -ENOBUFS;

        spin_lock(&gl->gl_spin);

        printk(KERN_INFO "Glock 0x%p (%u, %llu)\n", gl, gl->gl_name.ln_type,
               (unsigned long long)gl->gl_name.ln_number);
        printk(KERN_INFO "  gl_flags =");
        for (x = 0; x < 32; x++) {
                if (test_bit(x, &gl->gl_flags))
                        printk(" %u", x);
        }
        printk(" \n");
        printk(KERN_INFO "  gl_ref = %d\n", atomic_read(&gl->gl_ref.refcount));
        printk(KERN_INFO "  gl_state = %u\n", gl->gl_state);
        printk(KERN_INFO "  gl_owner = %s\n", gl->gl_owner->comm);
        print_symbol(KERN_INFO "  gl_ip = %s\n", gl->gl_ip);
        printk(KERN_INFO "  req_gh = %s\n", (gl->gl_req_gh) ? "yes" : "no");
        printk(KERN_INFO "  req_bh = %s\n", (gl->gl_req_bh) ? "yes" : "no");
        printk(KERN_INFO "  lvb_count = %d\n", atomic_read(&gl->gl_lvb_count));
        printk(KERN_INFO "  object = %s\n", (gl->gl_object) ? "yes" : "no");
        printk(KERN_INFO "  le = %s\n",
                   (list_empty(&gl->gl_le.le_list)) ? "no" : "yes");
        printk(KERN_INFO "  reclaim = %s\n",
                    (list_empty(&gl->gl_reclaim)) ? "no" : "yes");
        if (gl->gl_aspace)
                printk(KERN_INFO "  aspace = 0x%p nrpages = %lu\n", gl->gl_aspace,
                       gl->gl_aspace->i_mapping->nrpages);
        else
                printk(KERN_INFO "  aspace = no\n");
        printk(KERN_INFO "  ail = %d\n", atomic_read(&gl->gl_ail_count));
        if (gl->gl_req_gh) {
                error = dump_holder("Request", gl->gl_req_gh);
                if (error)
                        goto out;
        }
        list_for_each_entry(gh, &gl->gl_holders, gh_list) {
                error = dump_holder("Holder", gh);
                if (error)
                        goto out;
        }
        list_for_each_entry(gh, &gl->gl_waiters1, gh_list) {
                error = dump_holder("Waiter1", gh);
                if (error)
                        goto out;
        }
        list_for_each_entry(gh, &gl->gl_waiters2, gh_list) {
                error = dump_holder("Waiter2", gh);
                if (error)
                        goto out;
        }
        list_for_each_entry(gh, &gl->gl_waiters3, gh_list) {
                error = dump_holder("Waiter3", gh);
                if (error)
                        goto out;
        }
        if (gl->gl_ops == &gfs2_inode_glops && gl->gl_object) {
                if (!test_bit(GLF_LOCK, &gl->gl_flags) &&
                    list_empty(&gl->gl_holders)) {
                        error = dump_inode(gl->gl_object);
                        if (error)
                                goto out;
                } else {
                        error = -ENOBUFS;
                        printk(KERN_INFO "  Inode: busy\n");
                }
        }

        error = 0;

out:
        spin_unlock(&gl->gl_spin);
        return error;
}

/**
 * gfs2_dump_lockstate - print out the current lockstate
 * @sdp: the filesystem
 * @ub: the buffer to copy the information into
 *
 * If @ub is NULL, dump the lockstate to the console.
 *
 */

static int gfs2_dump_lockstate(struct gfs2_sbd *sdp)
{
        struct gfs2_glock *gl;
        struct hlist_node *h;
        unsigned int x;
        int error = 0;

        for (x = 0; x < GFS2_GL_HASH_SIZE; x++) {

                read_lock(gl_lock_addr(x));

                hlist_for_each_entry(gl, h, &gl_hash_table[x].hb_list, gl_list) {
                        if (gl->gl_sbd != sdp)
                                continue;

                        error = dump_glock(gl);
                        if (error)
                                break;
                }

                read_unlock(gl_lock_addr(x));

                if (error)
                        break;
        }


        return error;
}

int __init gfs2_glock_init(void)
{
        unsigned i;
        for(i = 0; i < GFS2_GL_HASH_SIZE; i++) {
                INIT_HLIST_HEAD(&gl_hash_table[i].hb_list);
        }
#ifdef GL_HASH_LOCK_SZ
        for(i = 0; i < GL_HASH_LOCK_SZ; i++) {
                rwlock_init(&gl_hash_locks[i]);
        }
#endif
        return 0;
}