dlmglue.c

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/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * dlmglue.c
 *
 * Code which implements an OCFS2 specific interface to our DLM.
 *
 * Copyright (C) 2003, 2004 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/mm.h>
#include <linux/kthread.h>
#include <linux/pagemap.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/time.h>
#include <linux/quotaops.h>

#define MLOG_MASK_PREFIX ML_DLM_GLUE
#include <cluster/masklog.h>

#include "ocfs2.h"
#include "ocfs2_lockingver.h"

#include "alloc.h"
#include "dcache.h"
#include "dlmglue.h"
#include "extent_map.h"
#include "file.h"
#include "heartbeat.h"
#include "inode.h"
#include "journal.h"
#include "stackglue.h"
#include "slot_map.h"
#include "super.h"
#include "uptodate.h"
#include "quota.h"
#include "refcounttree.h"

#include "buffer_head_io.h"

struct ocfs2_mask_waiter {
    struct list_head    mw_item;
    int         mw_status;
    struct completion   mw_complete;
    unsigned long       mw_mask;
    unsigned long       mw_goal;
#ifdef CONFIG_OCFS2_FS_STATS
    ktime_t         mw_lock_start;
#endif
};

static struct ocfs2_super *ocfs2_get_dentry_osb(struct ocfs2_lock_res *lockres);
static struct ocfs2_super *ocfs2_get_inode_osb(struct ocfs2_lock_res *lockres);
static struct ocfs2_super *ocfs2_get_file_osb(struct ocfs2_lock_res *lockres);
static struct ocfs2_super *ocfs2_get_qinfo_osb(struct ocfs2_lock_res *lockres);

/*
 * Return value from ->downconvert_worker functions.
 *
 * These control the precise actions of ocfs2_unblock_lock()
 * and ocfs2_process_blocked_lock()
 *
 */
enum ocfs2_unblock_action {
    UNBLOCK_CONTINUE    = 0, /* Continue downconvert */
    UNBLOCK_CONTINUE_POST   = 1, /* Continue downconvert, fire
                      * ->post_unlock callback */
    UNBLOCK_STOP_POST   = 2, /* Do not downconvert, fire
                      * ->post_unlock() callback. */
};

struct ocfs2_unblock_ctl {
    int requeue;
    enum ocfs2_unblock_action unblock_action;
};

/* Lockdep class keys */
struct lock_class_key lockdep_keys[OCFS2_NUM_LOCK_TYPES];

static int ocfs2_check_meta_downconvert(struct ocfs2_lock_res *lockres,
                    int new_level);
static void ocfs2_set_meta_lvb(struct ocfs2_lock_res *lockres);

static int ocfs2_data_convert_worker(struct ocfs2_lock_res *lockres,
                     int blocking);

static int ocfs2_dentry_convert_worker(struct ocfs2_lock_res *lockres,
                       int blocking);

static void ocfs2_dentry_post_unlock(struct ocfs2_super *osb,
                     struct ocfs2_lock_res *lockres);

static void ocfs2_set_qinfo_lvb(struct ocfs2_lock_res *lockres);

static int ocfs2_check_refcount_downconvert(struct ocfs2_lock_res *lockres,
                        int new_level);
static int ocfs2_refcount_convert_worker(struct ocfs2_lock_res *lockres,
                     int blocking);

#define mlog_meta_lvb(__level, __lockres) ocfs2_dump_meta_lvb_info(__level, __PRETTY_FUNCTION__, __LINE__, __lockres)

/* This aids in debugging situations where a bad LVB might be involved. */
static void ocfs2_dump_meta_lvb_info(u64 level,
                     const char *function,
                     unsigned int line,
                     struct ocfs2_lock_res *lockres)
{
    struct ocfs2_meta_lvb *lvb = ocfs2_dlm_lvb(&lockres->l_lksb);

    mlog(level, "LVB information for %s (called from %s:%u):\n",
         lockres->l_name, function, line);
    mlog(level, "version: %u, clusters: %u, generation: 0x%x\n",
         lvb->lvb_version, be32_to_cpu(lvb->lvb_iclusters),
         be32_to_cpu(lvb->lvb_igeneration));
    mlog(level, "size: %llu, uid %u, gid %u, mode 0x%x\n",
         (unsigned long long)be64_to_cpu(lvb->lvb_isize),
         be32_to_cpu(lvb->lvb_iuid), be32_to_cpu(lvb->lvb_igid),
         be16_to_cpu(lvb->lvb_imode));
    mlog(level, "nlink %u, atime_packed 0x%llx, ctime_packed 0x%llx, "
         "mtime_packed 0x%llx iattr 0x%x\n", be16_to_cpu(lvb->lvb_inlink),
         (long long)be64_to_cpu(lvb->lvb_iatime_packed),
         (long long)be64_to_cpu(lvb->lvb_ictime_packed),
         (long long)be64_to_cpu(lvb->lvb_imtime_packed),
         be32_to_cpu(lvb->lvb_iattr));
}


/*
 * OCFS2 Lock Resource Operations
 *
 * These fine tune the behavior of the generic dlmglue locking infrastructure.
 *
 * The most basic of lock types can point ->l_priv to their respective
 * struct ocfs2_super and allow the default actions to manage things.
 *
 * Right now, each lock type also needs to implement an init function,
 * and trivial lock/unlock wrappers. ocfs2_simple_drop_lockres()
 * should be called when the lock is no longer needed (i.e., object
 * destruction time).
 */
struct ocfs2_lock_res_ops {
    /*
     * Translate an ocfs2_lock_res * into an ocfs2_super *. Define
     * this callback if ->l_priv is not an ocfs2_super pointer
     */
    struct ocfs2_super * (*get_osb)(struct ocfs2_lock_res *);

    /*
     * Optionally called in the downconvert thread after a
     * successful downconvert. The lockres will not be referenced
     * after this callback is called, so it is safe to free
     * memory, etc.
     *
     * The exact semantics of when this is called are controlled
     * by ->downconvert_worker()
     */
    void (*post_unlock)(struct ocfs2_super *, struct ocfs2_lock_res *);

    /*
     * Allow a lock type to add checks to determine whether it is
     * safe to downconvert a lock. Return 0 to re-queue the
     * downconvert at a later time, nonzero to continue.
     *
     * For most locks, the default checks that there are no
     * incompatible holders are sufficient.
     *
     * Called with the lockres spinlock held.
     */
    int (*check_downconvert)(struct ocfs2_lock_res *, int);

    /*
     * Allows a lock type to populate the lock value block. This
     * is called on downconvert, and when we drop a lock.
     *
     * Locks that want to use this should set LOCK_TYPE_USES_LVB
     * in the flags field.
     *
     * Called with the lockres spinlock held.
     */
    void (*set_lvb)(struct ocfs2_lock_res *);

    /*
     * Called from the downconvert thread when it is determined
     * that a lock will be downconverted. This is called without
     * any locks held so the function can do work that might
     * schedule (syncing out data, etc).
     *
     * This should return any one of the ocfs2_unblock_action
     * values, depending on what it wants the thread to do.
     */
    int (*downconvert_worker)(struct ocfs2_lock_res *, int);

    /*
     * LOCK_TYPE_* flags which describe the specific requirements
     * of a lock type. Descriptions of each individual flag follow.
     */
    int flags;
};

/*
 * Some locks want to "refresh" potentially stale data when a
 * meaningful (PRMODE or EXMODE) lock level is first obtained. If this
 * flag is set, the OCFS2_LOCK_NEEDS_REFRESH flag will be set on the
 * individual lockres l_flags member from the ast function. It is
 * expected that the locking wrapper will clear the
 * OCFS2_LOCK_NEEDS_REFRESH flag when done.
 */
#define LOCK_TYPE_REQUIRES_REFRESH 0x1

/*
 * Indicate that a lock type makes use of the lock value block. The
 * ->set_lvb lock type callback must be defined.
 */
#define LOCK_TYPE_USES_LVB      0x2

static struct ocfs2_lock_res_ops ocfs2_inode_rw_lops = {
    .get_osb    = ocfs2_get_inode_osb,
    .flags      = 0,
};

static struct ocfs2_lock_res_ops ocfs2_inode_inode_lops = {
    .get_osb    = ocfs2_get_inode_osb,
    .check_downconvert = ocfs2_check_meta_downconvert,
    .set_lvb    = ocfs2_set_meta_lvb,
    .downconvert_worker = ocfs2_data_convert_worker,
    .flags      = LOCK_TYPE_REQUIRES_REFRESH|LOCK_TYPE_USES_LVB,
};

static struct ocfs2_lock_res_ops ocfs2_super_lops = {
    .flags      = LOCK_TYPE_REQUIRES_REFRESH,
};

static struct ocfs2_lock_res_ops ocfs2_rename_lops = {
    .flags      = 0,
};

static struct ocfs2_lock_res_ops ocfs2_nfs_sync_lops = {
    .flags      = 0,
};

static struct ocfs2_lock_res_ops ocfs2_orphan_scan_lops = {
    .flags      = LOCK_TYPE_REQUIRES_REFRESH|LOCK_TYPE_USES_LVB,
};

static struct ocfs2_lock_res_ops ocfs2_dentry_lops = {
    .get_osb    = ocfs2_get_dentry_osb,
    .post_unlock    = ocfs2_dentry_post_unlock,
    .downconvert_worker = ocfs2_dentry_convert_worker,
    .flags      = 0,
};

static struct ocfs2_lock_res_ops ocfs2_inode_open_lops = {
    .get_osb    = ocfs2_get_inode_osb,
    .flags      = 0,
};

static struct ocfs2_lock_res_ops ocfs2_flock_lops = {
    .get_osb    = ocfs2_get_file_osb,
    .flags      = 0,
};

static struct ocfs2_lock_res_ops ocfs2_qinfo_lops = {
    .set_lvb    = ocfs2_set_qinfo_lvb,
    .get_osb    = ocfs2_get_qinfo_osb,
    .flags      = LOCK_TYPE_REQUIRES_REFRESH | LOCK_TYPE_USES_LVB,
};

static struct ocfs2_lock_res_ops ocfs2_refcount_block_lops = {
    .check_downconvert = ocfs2_check_refcount_downconvert,
    .downconvert_worker = ocfs2_refcount_convert_worker,
    .flags      = 0,
};

static inline int ocfs2_is_inode_lock(struct ocfs2_lock_res *lockres)
{
    return lockres->l_type == OCFS2_LOCK_TYPE_META ||
        lockres->l_type == OCFS2_LOCK_TYPE_RW ||
        lockres->l_type == OCFS2_LOCK_TYPE_OPEN;
}

static inline struct ocfs2_lock_res *ocfs2_lksb_to_lock_res(struct ocfs2_dlm_lksb *lksb)
{
    return container_of(lksb, struct ocfs2_lock_res, l_lksb);
}

static inline struct inode *ocfs2_lock_res_inode(struct ocfs2_lock_res *lockres)
{
    BUG_ON(!ocfs2_is_inode_lock(lockres));

    return (struct inode *) lockres->l_priv;
}

static inline struct ocfs2_dentry_lock *ocfs2_lock_res_dl(struct ocfs2_lock_res *lockres)
{
    BUG_ON(lockres->l_type != OCFS2_LOCK_TYPE_DENTRY);

    return (struct ocfs2_dentry_lock *)lockres->l_priv;
}

static inline struct ocfs2_mem_dqinfo *ocfs2_lock_res_qinfo(struct ocfs2_lock_res *lockres)
{
    BUG_ON(lockres->l_type != OCFS2_LOCK_TYPE_QINFO);

    return (struct ocfs2_mem_dqinfo *)lockres->l_priv;
}

static inline struct ocfs2_refcount_tree *
ocfs2_lock_res_refcount_tree(struct ocfs2_lock_res *res)
{
    return container_of(res, struct ocfs2_refcount_tree, rf_lockres);
}

static inline struct ocfs2_super *ocfs2_get_lockres_osb(struct ocfs2_lock_res *lockres)
{
    if (lockres->l_ops->get_osb)
        return lockres->l_ops->get_osb(lockres);

    return (struct ocfs2_super *)lockres->l_priv;
}

static int ocfs2_lock_create(struct ocfs2_super *osb,
                 struct ocfs2_lock_res *lockres,
                 int level,
                 u32 dlm_flags);
static inline int ocfs2_may_continue_on_blocked_lock(struct ocfs2_lock_res *lockres,
                             int wanted);
static void __ocfs2_cluster_unlock(struct ocfs2_super *osb,
                   struct ocfs2_lock_res *lockres,
                   int level, unsigned long caller_ip);
static inline void ocfs2_cluster_unlock(struct ocfs2_super *osb,
                    struct ocfs2_lock_res *lockres,
                    int level)
{
    __ocfs2_cluster_unlock(osb, lockres, level, _RET_IP_);
}

static inline void ocfs2_generic_handle_downconvert_action(struct ocfs2_lock_res *lockres);
static inline void ocfs2_generic_handle_convert_action(struct ocfs2_lock_res *lockres);
static inline void ocfs2_generic_handle_attach_action(struct ocfs2_lock_res *lockres);
static int ocfs2_generic_handle_bast(struct ocfs2_lock_res *lockres, int level);
static void ocfs2_schedule_blocked_lock(struct ocfs2_super *osb,
                    struct ocfs2_lock_res *lockres);
static inline void ocfs2_recover_from_dlm_error(struct ocfs2_lock_res *lockres,
                        int convert);
#define ocfs2_log_dlm_error(_func, _err, _lockres) do {                 \
    if ((_lockres)->l_type != OCFS2_LOCK_TYPE_DENTRY)               \
        mlog(ML_ERROR, "DLM error %d while calling %s on resource %s\n",    \
             _err, _func, _lockres->l_name);                    \
    else                                        \
        mlog(ML_ERROR, "DLM error %d while calling %s on resource %.*s%08x\n",  \
             _err, _func, OCFS2_DENTRY_LOCK_INO_START - 1, (_lockres)->l_name,  \
             (unsigned int)ocfs2_get_dentry_lock_ino(_lockres));        \
} while (0)
static int ocfs2_downconvert_thread(void *arg);
static void ocfs2_downconvert_on_unlock(struct ocfs2_super *osb,
                    struct ocfs2_lock_res *lockres);
static int ocfs2_inode_lock_update(struct inode *inode,
                  struct buffer_head **bh);
static void ocfs2_drop_osb_locks(struct ocfs2_super *osb);
static inline int ocfs2_highest_compat_lock_level(int level);
static unsigned int ocfs2_prepare_downconvert(struct ocfs2_lock_res *lockres,
                          int new_level);
static int ocfs2_downconvert_lock(struct ocfs2_super *osb,
                  struct ocfs2_lock_res *lockres,
                  int new_level,
                  int lvb,
                  unsigned int generation);
static int ocfs2_prepare_cancel_convert(struct ocfs2_super *osb,
                        struct ocfs2_lock_res *lockres);
static int ocfs2_cancel_convert(struct ocfs2_super *osb,
                struct ocfs2_lock_res *lockres);


static void ocfs2_build_lock_name(enum ocfs2_lock_type type,
                  u64 blkno,
                  u32 generation,
                  char *name)
{
    int len;

    BUG_ON(type >= OCFS2_NUM_LOCK_TYPES);

    len = snprintf(name, OCFS2_LOCK_ID_MAX_LEN, "%c%s%016llx%08x",
               ocfs2_lock_type_char(type), OCFS2_LOCK_ID_PAD,
               (long long)blkno, generation);

    BUG_ON(len != (OCFS2_LOCK_ID_MAX_LEN - 1));

    mlog(0, "built lock resource with name: %s\n", name);
}

static DEFINE_SPINLOCK(ocfs2_dlm_tracking_lock);

static void ocfs2_add_lockres_tracking(struct ocfs2_lock_res *res,
                       struct ocfs2_dlm_debug *dlm_debug)
{
    mlog(0, "Add tracking for lockres %s\n", res->l_name);

    spin_lock(&ocfs2_dlm_tracking_lock);
    list_add(&res->l_debug_list, &dlm_debug->d_lockres_tracking);
    spin_unlock(&ocfs2_dlm_tracking_lock);
}

static void ocfs2_remove_lockres_tracking(struct ocfs2_lock_res *res)
{
    spin_lock(&ocfs2_dlm_tracking_lock);
    if (!list_empty(&res->l_debug_list))
        list_del_init(&res->l_debug_list);
    spin_unlock(&ocfs2_dlm_tracking_lock);
}

#ifdef CONFIG_OCFS2_FS_STATS
static void ocfs2_init_lock_stats(struct ocfs2_lock_res *res)
{
    res->l_lock_refresh = 0;
    memset(&res->l_lock_prmode, 0, sizeof(struct ocfs2_lock_stats));
    memset(&res->l_lock_exmode, 0, sizeof(struct ocfs2_lock_stats));
}

static void ocfs2_update_lock_stats(struct ocfs2_lock_res *res, int level,
                    struct ocfs2_mask_waiter *mw, int ret)
{
    u32 usec;
    ktime_t kt;
    struct ocfs2_lock_stats *stats;

    if (level == LKM_PRMODE)
        stats = &res->l_lock_prmode;
    else if (level == LKM_EXMODE)
        stats = &res->l_lock_exmode;
    else
        return;

    kt = ktime_sub(ktime_get(), mw->mw_lock_start);
    usec = ktime_to_us(kt);

    stats->ls_gets++;
    stats->ls_total += ktime_to_ns(kt);
    /* overflow */
    if (unlikely(stats->ls_gets == 0)) {
        stats->ls_gets++;
        stats->ls_total = ktime_to_ns(kt);
    }

    if (stats->ls_max < usec)
        stats->ls_max = usec;

    if (ret)
        stats->ls_fail++;
}

static inline void ocfs2_track_lock_refresh(struct ocfs2_lock_res *lockres)
{
    lockres->l_lock_refresh++;
}

static inline void ocfs2_init_start_time(struct ocfs2_mask_waiter *mw)
{
    mw->mw_lock_start = ktime_get();
}
#else
static inline void ocfs2_init_lock_stats(struct ocfs2_lock_res *res)
{
}
static inline void ocfs2_update_lock_stats(struct ocfs2_lock_res *res,
               int level, struct ocfs2_mask_waiter *mw, int ret)
{
}
static inline void ocfs2_track_lock_refresh(struct ocfs2_lock_res *lockres)
{
}
static inline void ocfs2_init_start_time(struct ocfs2_mask_waiter *mw)
{
}
#endif

static void ocfs2_lock_res_init_common(struct ocfs2_super *osb,
                       struct ocfs2_lock_res *res,
                       enum ocfs2_lock_type type,
                       struct ocfs2_lock_res_ops *ops,
                       void *priv)
{
    res->l_type          = type;
    res->l_ops           = ops;
    res->l_priv          = priv;

    res->l_level         = DLM_LOCK_IV;
    res->l_requested     = DLM_LOCK_IV;
    res->l_blocking      = DLM_LOCK_IV;
    res->l_action        = OCFS2_AST_INVALID;
    res->l_unlock_action = OCFS2_UNLOCK_INVALID;

    res->l_flags         = OCFS2_LOCK_INITIALIZED;

    ocfs2_add_lockres_tracking(res, osb->osb_dlm_debug);

    ocfs2_init_lock_stats(res);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
    if (type != OCFS2_LOCK_TYPE_OPEN)
        lockdep_init_map(&res->l_lockdep_map, ocfs2_lock_type_strings[type],
                 &lockdep_keys[type], 0);
    else
        res->l_lockdep_map.key = NULL;
#endif
}

void ocfs2_lock_res_init_once(struct ocfs2_lock_res *res)
{
    /* This also clears out the lock status block */
    memset(res, 0, sizeof(struct ocfs2_lock_res));
    spin_lock_init(&res->l_lock);
    init_waitqueue_head(&res->l_event);
    INIT_LIST_HEAD(&res->l_blocked_list);
    INIT_LIST_HEAD(&res->l_mask_waiters);
}

void ocfs2_inode_lock_res_init(struct ocfs2_lock_res *res,
                   enum ocfs2_lock_type type,
                   unsigned int generation,
                   struct inode *inode)
{
    struct ocfs2_lock_res_ops *ops;

    switch(type) {
        case OCFS2_LOCK_TYPE_RW:
            ops = &ocfs2_inode_rw_lops;
            break;
        case OCFS2_LOCK_TYPE_META:
            ops = &ocfs2_inode_inode_lops;
            break;
        case OCFS2_LOCK_TYPE_OPEN:
            ops = &ocfs2_inode_open_lops;
            break;
        default:
            mlog_bug_on_msg(1, "type: %d\n", type);
            ops = NULL; /* thanks, gcc */
            break;
    };

    ocfs2_build_lock_name(type, OCFS2_I(inode)->ip_blkno,
                  generation, res->l_name);
    ocfs2_lock_res_init_common(OCFS2_SB(inode->i_sb), res, type, ops, inode);
}

static struct ocfs2_super *ocfs2_get_inode_osb(struct ocfs2_lock_res *lockres)
{
    struct inode *inode = ocfs2_lock_res_inode(lockres);

    return OCFS2_SB(inode->i_sb);
}

static struct ocfs2_super *ocfs2_get_qinfo_osb(struct ocfs2_lock_res *lockres)
{
    struct ocfs2_mem_dqinfo *info = lockres->l_priv;

    return OCFS2_SB(info->dqi_gi.dqi_sb);
}

static struct ocfs2_super *ocfs2_get_file_osb(struct ocfs2_lock_res *lockres)
{
    struct ocfs2_file_private *fp = lockres->l_priv;

    return OCFS2_SB(fp->fp_file->f_mapping->host->i_sb);
}

static __u64 ocfs2_get_dentry_lock_ino(struct ocfs2_lock_res *lockres)
{
    __be64 inode_blkno_be;

    memcpy(&inode_blkno_be, &lockres->l_name[OCFS2_DENTRY_LOCK_INO_START],
           sizeof(__be64));

    return be64_to_cpu(inode_blkno_be);
}

static struct ocfs2_super *ocfs2_get_dentry_osb(struct ocfs2_lock_res *lockres)
{
    struct ocfs2_dentry_lock *dl = lockres->l_priv;

    return OCFS2_SB(dl->dl_inode->i_sb);
}

void ocfs2_dentry_lock_res_init(struct ocfs2_dentry_lock *dl,
                u64 parent, struct inode *inode)
{
    int len;
    u64 inode_blkno = OCFS2_I(inode)->ip_blkno;
    __be64 inode_blkno_be = cpu_to_be64(inode_blkno);
    struct ocfs2_lock_res *lockres = &dl->dl_lockres;

    ocfs2_lock_res_init_once(lockres);

    /*
     * Unfortunately, the standard lock naming scheme won't work
     * here because we have two 16 byte values to use. Instead,
     * we'll stuff the inode number as a binary value. We still
     * want error prints to show something without garbling the
     * display, so drop a null byte in there before the inode
     * number. A future version of OCFS2 will likely use all
     * binary lock names. The stringified names have been a
     * tremendous aid in debugging, but now that the debugfs
     * interface exists, we can mangle things there if need be.
     *
     * NOTE: We also drop the standard "pad" value (the total lock
     * name size stays the same though - the last part is all
     * zeros due to the memset in ocfs2_lock_res_init_once()
     */
    len = snprintf(lockres->l_name, OCFS2_DENTRY_LOCK_INO_START,
               "%c%016llx",
               ocfs2_lock_type_char(OCFS2_LOCK_TYPE_DENTRY),
               (long long)parent);

    BUG_ON(len != (OCFS2_DENTRY_LOCK_INO_START - 1));

    memcpy(&lockres->l_name[OCFS2_DENTRY_LOCK_INO_START], &inode_blkno_be,
           sizeof(__be64));

    ocfs2_lock_res_init_common(OCFS2_SB(inode->i_sb), lockres,
                   OCFS2_LOCK_TYPE_DENTRY, &ocfs2_dentry_lops,
                   dl);
}

static void ocfs2_super_lock_res_init(struct ocfs2_lock_res *res,
                      struct ocfs2_super *osb)
{
    /* Superblock lockres doesn't come from a slab so we call init
     * once on it manually.  */
    ocfs2_lock_res_init_once(res);
    ocfs2_build_lock_name(OCFS2_LOCK_TYPE_SUPER, OCFS2_SUPER_BLOCK_BLKNO,
                  0, res->l_name);
    ocfs2_lock_res_init_common(osb, res, OCFS2_LOCK_TYPE_SUPER,
                   &ocfs2_super_lops, osb);
}

static void ocfs2_rename_lock_res_init(struct ocfs2_lock_res *res,
                       struct ocfs2_super *osb)
{
    /* Rename lockres doesn't come from a slab so we call init
     * once on it manually.  */
    ocfs2_lock_res_init_once(res);
    ocfs2_build_lock_name(OCFS2_LOCK_TYPE_RENAME, 0, 0, res->l_name);
    ocfs2_lock_res_init_common(osb, res, OCFS2_LOCK_TYPE_RENAME,
                   &ocfs2_rename_lops, osb);
}

static void ocfs2_nfs_sync_lock_res_init(struct ocfs2_lock_res *res,
                     struct ocfs2_super *osb)
{
    /* nfs_sync lockres doesn't come from a slab so we call init
     * once on it manually.  */
    ocfs2_lock_res_init_once(res);
    ocfs2_build_lock_name(OCFS2_LOCK_TYPE_NFS_SYNC, 0, 0, res->l_name);
    ocfs2_lock_res_init_common(osb, res, OCFS2_LOCK_TYPE_NFS_SYNC,
                   &ocfs2_nfs_sync_lops, osb);
}

static void ocfs2_orphan_scan_lock_res_init(struct ocfs2_lock_res *res,
                        struct ocfs2_super *osb)
{
    ocfs2_lock_res_init_once(res);
    ocfs2_build_lock_name(OCFS2_LOCK_TYPE_ORPHAN_SCAN, 0, 0, res->l_name);
    ocfs2_lock_res_init_common(osb, res, OCFS2_LOCK_TYPE_ORPHAN_SCAN,
                   &ocfs2_orphan_scan_lops, osb);
}

void ocfs2_file_lock_res_init(struct ocfs2_lock_res *lockres,
                  struct ocfs2_file_private *fp)
{
    struct inode *inode = fp->fp_file->f_mapping->host;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);

    ocfs2_lock_res_init_once(lockres);
    ocfs2_build_lock_name(OCFS2_LOCK_TYPE_FLOCK, oi->ip_blkno,
                  inode->i_generation, lockres->l_name);
    ocfs2_lock_res_init_common(OCFS2_SB(inode->i_sb), lockres,
                   OCFS2_LOCK_TYPE_FLOCK, &ocfs2_flock_lops,
                   fp);
    lockres->l_flags |= OCFS2_LOCK_NOCACHE;
}

void ocfs2_qinfo_lock_res_init(struct ocfs2_lock_res *lockres,
                   struct ocfs2_mem_dqinfo *info)
{
    ocfs2_lock_res_init_once(lockres);
    ocfs2_build_lock_name(OCFS2_LOCK_TYPE_QINFO, info->dqi_gi.dqi_type,
                  0, lockres->l_name);
    ocfs2_lock_res_init_common(OCFS2_SB(info->dqi_gi.dqi_sb), lockres,
                   OCFS2_LOCK_TYPE_QINFO, &ocfs2_qinfo_lops,
                   info);
}

void ocfs2_refcount_lock_res_init(struct ocfs2_lock_res *lockres,
                  struct ocfs2_super *osb, u64 ref_blkno,
                  unsigned int generation)
{
    ocfs2_lock_res_init_once(lockres);
    ocfs2_build_lock_name(OCFS2_LOCK_TYPE_REFCOUNT, ref_blkno,
                  generation, lockres->l_name);
    ocfs2_lock_res_init_common(osb, lockres, OCFS2_LOCK_TYPE_REFCOUNT,
                   &ocfs2_refcount_block_lops, osb);
}

void ocfs2_lock_res_free(struct ocfs2_lock_res *res)
{
    if (!(res->l_flags & OCFS2_LOCK_INITIALIZED))
        return;

    ocfs2_remove_lockres_tracking(res);

    mlog_bug_on_msg(!list_empty(&res->l_blocked_list),
            "Lockres %s is on the blocked list\n",
            res->l_name);
    mlog_bug_on_msg(!list_empty(&res->l_mask_waiters),
            "Lockres %s has mask waiters pending\n",
            res->l_name);
    mlog_bug_on_msg(spin_is_locked(&res->l_lock),
            "Lockres %s is locked\n",
            res->l_name);
    mlog_bug_on_msg(res->l_ro_holders,
            "Lockres %s has %u ro holders\n",
            res->l_name, res->l_ro_holders);
    mlog_bug_on_msg(res->l_ex_holders,
            "Lockres %s has %u ex holders\n",
            res->l_name, res->l_ex_holders);

    /* Need to clear out the lock status block for the dlm */
    memset(&res->l_lksb, 0, sizeof(res->l_lksb));

    res->l_flags = 0UL;
}

static inline void ocfs2_inc_holders(struct ocfs2_lock_res *lockres,
                     int level)
{
    BUG_ON(!lockres);

    switch(level) {
    case DLM_LOCK_EX:
        lockres->l_ex_holders++;
        break;
    case DLM_LOCK_PR:
        lockres->l_ro_holders++;
        break;
    default:
        BUG();
    }
}

static inline void ocfs2_dec_holders(struct ocfs2_lock_res *lockres,
                     int level)
{
    BUG_ON(!lockres);

    switch(level) {
    case DLM_LOCK_EX:
        BUG_ON(!lockres->l_ex_holders);
        lockres->l_ex_holders--;
        break;
    case DLM_LOCK_PR:
        BUG_ON(!lockres->l_ro_holders);
        lockres->l_ro_holders--;
        break;
    default:
        BUG();
    }
}

/* WARNING: This function lives in a world where the only three lock
 * levels are EX, PR, and NL. It *will* have to be adjusted when more
 * lock types are added. */
static inline int ocfs2_highest_compat_lock_level(int level)
{
    int new_level = DLM_LOCK_EX;

    if (level == DLM_LOCK_EX)
        new_level = DLM_LOCK_NL;
    else if (level == DLM_LOCK_PR)
        new_level = DLM_LOCK_PR;
    return new_level;
}

static void lockres_set_flags(struct ocfs2_lock_res *lockres,
                  unsigned long newflags)
{
    struct ocfs2_mask_waiter *mw, *tmp;

    assert_spin_locked(&lockres->l_lock);

    lockres->l_flags = newflags;

    list_for_each_entry_safe(mw, tmp, &lockres->l_mask_waiters, mw_item) {
        if ((lockres->l_flags & mw->mw_mask) != mw->mw_goal)
            continue;

        list_del_init(&mw->mw_item);
        mw->mw_status = 0;
        complete(&mw->mw_complete);
    }
}
static void lockres_or_flags(struct ocfs2_lock_res *lockres, unsigned long or)
{
    lockres_set_flags(lockres, lockres->l_flags | or);
}
static void lockres_clear_flags(struct ocfs2_lock_res *lockres,
                unsigned long clear)
{
    lockres_set_flags(lockres, lockres->l_flags & ~clear);
}

static inline void ocfs2_generic_handle_downconvert_action(struct ocfs2_lock_res *lockres)
{
    BUG_ON(!(lockres->l_flags & OCFS2_LOCK_BUSY));
    BUG_ON(!(lockres->l_flags & OCFS2_LOCK_ATTACHED));
    BUG_ON(!(lockres->l_flags & OCFS2_LOCK_BLOCKED));
    BUG_ON(lockres->l_blocking <= DLM_LOCK_NL);

    lockres->l_level = lockres->l_requested;
    if (lockres->l_level <=
        ocfs2_highest_compat_lock_level(lockres->l_blocking)) {
        lockres->l_blocking = DLM_LOCK_NL;
        lockres_clear_flags(lockres, OCFS2_LOCK_BLOCKED);
    }
    lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
}

static inline void ocfs2_generic_handle_convert_action(struct ocfs2_lock_res *lockres)
{
    BUG_ON(!(lockres->l_flags & OCFS2_LOCK_BUSY));
    BUG_ON(!(lockres->l_flags & OCFS2_LOCK_ATTACHED));

    /* Convert from RO to EX doesn't really need anything as our
     * information is already up to data. Convert from NL to
     * *anything* however should mark ourselves as needing an
     * update */
    if (lockres->l_level == DLM_LOCK_NL &&
        lockres->l_ops->flags & LOCK_TYPE_REQUIRES_REFRESH)
        lockres_or_flags(lockres, OCFS2_LOCK_NEEDS_REFRESH);

    lockres->l_level = lockres->l_requested;

    /*
     * We set the OCFS2_LOCK_UPCONVERT_FINISHING flag before clearing
     * the OCFS2_LOCK_BUSY flag to prevent the dc thread from
     * downconverting the lock before the upconvert has fully completed.
     */
    lockres_or_flags(lockres, OCFS2_LOCK_UPCONVERT_FINISHING);

    lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
}

static inline void ocfs2_generic_handle_attach_action(struct ocfs2_lock_res *lockres)
{
    BUG_ON((!(lockres->l_flags & OCFS2_LOCK_BUSY)));
    BUG_ON(lockres->l_flags & OCFS2_LOCK_ATTACHED);

    if (lockres->l_requested > DLM_LOCK_NL &&
        !(lockres->l_flags & OCFS2_LOCK_LOCAL) &&
        lockres->l_ops->flags & LOCK_TYPE_REQUIRES_REFRESH)
        lockres_or_flags(lockres, OCFS2_LOCK_NEEDS_REFRESH);

    lockres->l_level = lockres->l_requested;
    lockres_or_flags(lockres, OCFS2_LOCK_ATTACHED);
    lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
}

static int ocfs2_generic_handle_bast(struct ocfs2_lock_res *lockres,
                     int level)
{
    int needs_downconvert = 0;

    assert_spin_locked(&lockres->l_lock);

    if (level > lockres->l_blocking) {
        /* only schedule a downconvert if we haven't already scheduled
         * one that goes low enough to satisfy the level we're
         * blocking.  this also catches the case where we get
         * duplicate BASTs */
        if (ocfs2_highest_compat_lock_level(level) <
            ocfs2_highest_compat_lock_level(lockres->l_blocking))
            needs_downconvert = 1;

        lockres->l_blocking = level;
    }

    mlog(ML_BASTS, "lockres %s, block %d, level %d, l_block %d, dwn %d\n",
         lockres->l_name, level, lockres->l_level, lockres->l_blocking,
         needs_downconvert);

    if (needs_downconvert)
        lockres_or_flags(lockres, OCFS2_LOCK_BLOCKED);
    mlog(0, "needs_downconvert = %d\n", needs_downconvert);
    return needs_downconvert;
}

/*
 * OCFS2_LOCK_PENDING and l_pending_gen.
 *
 * Why does OCFS2_LOCK_PENDING exist?  To close a race between setting
 * OCFS2_LOCK_BUSY and calling ocfs2_dlm_lock().  See ocfs2_unblock_lock()
 * for more details on the race.
 *
 * OCFS2_LOCK_PENDING closes the race quite nicely.  However, it introduces
 * a race on itself.  In o2dlm, we can get the ast before ocfs2_dlm_lock()
 * returns.  The ast clears OCFS2_LOCK_BUSY, and must therefore clear
 * OCFS2_LOCK_PENDING at the same time.  When ocfs2_dlm_lock() returns,
 * the caller is going to try to clear PENDING again.  If nothing else is
 * happening, __lockres_clear_pending() sees PENDING is unset and does
 * nothing.
 *
 * But what if another path (eg downconvert thread) has just started a
 * new locking action?  The other path has re-set PENDING.  Our path
 * cannot clear PENDING, because that will re-open the original race
 * window.
 *
 * [Example]
 *
 * ocfs2_meta_lock()
 *  ocfs2_cluster_lock()
 *   set BUSY
 *   set PENDING
 *   drop l_lock
 *   ocfs2_dlm_lock()
 *    ocfs2_locking_ast()       ocfs2_downconvert_thread()
 *     clear PENDING             ocfs2_unblock_lock()
 *                    take_l_lock
 *                    !BUSY
 *                    ocfs2_prepare_downconvert()
 *                     set BUSY
 *                     set PENDING
 *                    drop l_lock
 *   take l_lock
 *   clear PENDING
 *   drop l_lock
 *          <window>
 *                    ocfs2_dlm_lock()
 *
 * So as you can see, we now have a window where l_lock is not held,
 * PENDING is not set, and ocfs2_dlm_lock() has not been called.
 *
 * The core problem is that ocfs2_cluster_lock() has cleared the PENDING
 * set by ocfs2_prepare_downconvert().  That wasn't nice.
 *
 * To solve this we introduce l_pending_gen.  A call to
 * lockres_clear_pending() will only do so when it is passed a generation
 * number that matches the lockres.  lockres_set_pending() will return the
 * current generation number.  When ocfs2_cluster_lock() goes to clear
 * PENDING, it passes the generation it got from set_pending().  In our
 * example above, the generation numbers will *not* match.  Thus,
 * ocfs2_cluster_lock() will not clear the PENDING set by
 * ocfs2_prepare_downconvert().
 */

/* Unlocked version for ocfs2_locking_ast() */
static void __lockres_clear_pending(struct ocfs2_lock_res *lockres,
                    unsigned int generation,
                    struct ocfs2_super *osb)
{
    assert_spin_locked(&lockres->l_lock);

    /*
     * The ast and locking functions can race us here.  The winner
     * will clear pending, the loser will not.
     */
    if (!(lockres->l_flags & OCFS2_LOCK_PENDING) ||
        (lockres->l_pending_gen != generation))
        return;

    lockres_clear_flags(lockres, OCFS2_LOCK_PENDING);
    lockres->l_pending_gen++;

    /*
     * The downconvert thread may have skipped us because we
     * were PENDING.  Wake it up.
     */
    if (lockres->l_flags & OCFS2_LOCK_BLOCKED)
        ocfs2_wake_downconvert_thread(osb);
}

/* Locked version for callers of ocfs2_dlm_lock() */
static void lockres_clear_pending(struct ocfs2_lock_res *lockres,
                  unsigned int generation,
                  struct ocfs2_super *osb)
{
    unsigned long flags;

    spin_lock_irqsave(&lockres->l_lock, flags);
    __lockres_clear_pending(lockres, generation, osb);
    spin_unlock_irqrestore(&lockres->l_lock, flags);
}

static unsigned int lockres_set_pending(struct ocfs2_lock_res *lockres)
{
    assert_spin_locked(&lockres->l_lock);
    BUG_ON(!(lockres->l_flags & OCFS2_LOCK_BUSY));

    lockres_or_flags(lockres, OCFS2_LOCK_PENDING);

    return lockres->l_pending_gen;
}

static void ocfs2_blocking_ast(struct ocfs2_dlm_lksb *lksb, int level)
{
    struct ocfs2_lock_res *lockres = ocfs2_lksb_to_lock_res(lksb);
    struct ocfs2_super *osb = ocfs2_get_lockres_osb(lockres);
    int needs_downconvert;
    unsigned long flags;

    BUG_ON(level <= DLM_LOCK_NL);

    mlog(ML_BASTS, "BAST fired for lockres %s, blocking %d, level %d, "
         "type %s\n", lockres->l_name, level, lockres->l_level,
         ocfs2_lock_type_string(lockres->l_type));

    /*
     * We can skip the bast for locks which don't enable caching -
     * they'll be dropped at the earliest possible time anyway.
     */
    if (lockres->l_flags & OCFS2_LOCK_NOCACHE)
        return;

    spin_lock_irqsave(&lockres->l_lock, flags);
    needs_downconvert = ocfs2_generic_handle_bast(lockres, level);
    if (needs_downconvert)
        ocfs2_schedule_blocked_lock(osb, lockres);
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    wake_up(&lockres->l_event);

    ocfs2_wake_downconvert_thread(osb);
}

static void ocfs2_locking_ast(struct ocfs2_dlm_lksb *lksb)
{
    struct ocfs2_lock_res *lockres = ocfs2_lksb_to_lock_res(lksb);
    struct ocfs2_super *osb = ocfs2_get_lockres_osb(lockres);
    unsigned long flags;
    int status;

    spin_lock_irqsave(&lockres->l_lock, flags);

    status = ocfs2_dlm_lock_status(&lockres->l_lksb);

    if (status == -EAGAIN) {
        lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
        goto out;
    }

    if (status) {
        mlog(ML_ERROR, "lockres %s: lksb status value of %d!\n",
             lockres->l_name, status);
        spin_unlock_irqrestore(&lockres->l_lock, flags);
        return;
    }

    mlog(ML_BASTS, "AST fired for lockres %s, action %d, unlock %d, "
         "level %d => %d\n", lockres->l_name, lockres->l_action,
         lockres->l_unlock_action, lockres->l_level, lockres->l_requested);

    switch(lockres->l_action) {
    case OCFS2_AST_ATTACH:
        ocfs2_generic_handle_attach_action(lockres);
        lockres_clear_flags(lockres, OCFS2_LOCK_LOCAL);
        break;
    case OCFS2_AST_CONVERT:
        ocfs2_generic_handle_convert_action(lockres);
        break;
    case OCFS2_AST_DOWNCONVERT:
        ocfs2_generic_handle_downconvert_action(lockres);
        break;
    default:
        mlog(ML_ERROR, "lockres %s: AST fired with invalid action: %u, "
             "flags 0x%lx, unlock: %u\n",
             lockres->l_name, lockres->l_action, lockres->l_flags,
             lockres->l_unlock_action);
        BUG();
    }
out:
    /* set it to something invalid so if we get called again we
     * can catch it. */
    lockres->l_action = OCFS2_AST_INVALID;

    /* Did we try to cancel this lock?  Clear that state */
    if (lockres->l_unlock_action == OCFS2_UNLOCK_CANCEL_CONVERT)
        lockres->l_unlock_action = OCFS2_UNLOCK_INVALID;

    /*
     * We may have beaten the locking functions here.  We certainly
     * know that dlm_lock() has been called :-)
     * Because we can't have two lock calls in flight at once, we
     * can use lockres->l_pending_gen.
     */
    __lockres_clear_pending(lockres, lockres->l_pending_gen,  osb);

    wake_up(&lockres->l_event);
    spin_unlock_irqrestore(&lockres->l_lock, flags);
}

static void ocfs2_unlock_ast(struct ocfs2_dlm_lksb *lksb, int error)
{
    struct ocfs2_lock_res *lockres = ocfs2_lksb_to_lock_res(lksb);
    unsigned long flags;

    mlog(ML_BASTS, "UNLOCK AST fired for lockres %s, action = %d\n",
         lockres->l_name, lockres->l_unlock_action);

    spin_lock_irqsave(&lockres->l_lock, flags);
    if (error) {
        mlog(ML_ERROR, "Dlm passes error %d for lock %s, "
             "unlock_action %d\n", error, lockres->l_name,
             lockres->l_unlock_action);
        spin_unlock_irqrestore(&lockres->l_lock, flags);
        return;
    }

    switch(lockres->l_unlock_action) {
    case OCFS2_UNLOCK_CANCEL_CONVERT:
        mlog(0, "Cancel convert success for %s\n", lockres->l_name);
        lockres->l_action = OCFS2_AST_INVALID;
        /* Downconvert thread may have requeued this lock, we
         * need to wake it. */
        if (lockres->l_flags & OCFS2_LOCK_BLOCKED)
            ocfs2_wake_downconvert_thread(ocfs2_get_lockres_osb(lockres));
        break;
    case OCFS2_UNLOCK_DROP_LOCK:
        lockres->l_level = DLM_LOCK_IV;
        break;
    default:
        BUG();
    }

    lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
    lockres->l_unlock_action = OCFS2_UNLOCK_INVALID;
    wake_up(&lockres->l_event);
    spin_unlock_irqrestore(&lockres->l_lock, flags);
}

/*
 * This is the filesystem locking protocol.  It provides the lock handling
 * hooks for the underlying DLM.  It has a maximum version number.
 * The version number allows interoperability with systems running at
 * the same major number and an equal or smaller minor number.
 *
 * Whenever the filesystem does new things with locks (adds or removes a
 * lock, orders them differently, does different things underneath a lock),
 * the version must be changed.  The protocol is negotiated when joining
 * the dlm domain.  A node may join the domain if its major version is
 * identical to all other nodes and its minor version is greater than
 * or equal to all other nodes.  When its minor version is greater than
 * the other nodes, it will run at the minor version specified by the
 * other nodes.
 *
 * If a locking change is made that will not be compatible with older
 * versions, the major number must be increased and the minor version set
 * to zero.  If a change merely adds a behavior that can be disabled when
 * speaking to older versions, the minor version must be increased.  If a
 * change adds a fully backwards compatible change (eg, LVB changes that
 * are just ignored by older versions), the version does not need to be
 * updated.
 */
static struct ocfs2_locking_protocol lproto = {
    .lp_max_version = {
        .pv_major = OCFS2_LOCKING_PROTOCOL_MAJOR,
        .pv_minor = OCFS2_LOCKING_PROTOCOL_MINOR,
    },
    .lp_lock_ast        = ocfs2_locking_ast,
    .lp_blocking_ast    = ocfs2_blocking_ast,
    .lp_unlock_ast      = ocfs2_unlock_ast,
};

void ocfs2_set_locking_protocol(void)
{
    ocfs2_stack_glue_set_max_proto_version(&lproto.lp_max_version);
}

static inline void ocfs2_recover_from_dlm_error(struct ocfs2_lock_res *lockres,
                        int convert)
{
    unsigned long flags;

    spin_lock_irqsave(&lockres->l_lock, flags);
    lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
    lockres_clear_flags(lockres, OCFS2_LOCK_UPCONVERT_FINISHING);
    if (convert)
        lockres->l_action = OCFS2_AST_INVALID;
    else
        lockres->l_unlock_action = OCFS2_UNLOCK_INVALID;
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    wake_up(&lockres->l_event);
}

/* Note: If we detect another process working on the lock (i.e.,
 * OCFS2_LOCK_BUSY), we'll bail out returning 0. It's up to the caller
 * to do the right thing in that case.
 */
static int ocfs2_lock_create(struct ocfs2_super *osb,
                 struct ocfs2_lock_res *lockres,
                 int level,
                 u32 dlm_flags)
{
    int ret = 0;
    unsigned long flags;
    unsigned int gen;

    mlog(0, "lock %s, level = %d, flags = %u\n", lockres->l_name, level,
         dlm_flags);

    spin_lock_irqsave(&lockres->l_lock, flags);
    if ((lockres->l_flags & OCFS2_LOCK_ATTACHED) ||
        (lockres->l_flags & OCFS2_LOCK_BUSY)) {
        spin_unlock_irqrestore(&lockres->l_lock, flags);
        goto bail;
    }

    lockres->l_action = OCFS2_AST_ATTACH;
    lockres->l_requested = level;
    lockres_or_flags(lockres, OCFS2_LOCK_BUSY);
    gen = lockres_set_pending(lockres);
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    ret = ocfs2_dlm_lock(osb->cconn,
                 level,
                 &lockres->l_lksb,
                 dlm_flags,
                 lockres->l_name,
                 OCFS2_LOCK_ID_MAX_LEN - 1);
    lockres_clear_pending(lockres, gen, osb);
    if (ret) {
        ocfs2_log_dlm_error("ocfs2_dlm_lock", ret, lockres);
        ocfs2_recover_from_dlm_error(lockres, 1);
    }

    mlog(0, "lock %s, return from ocfs2_dlm_lock\n", lockres->l_name);

bail:
    return ret;
}

static inline int ocfs2_check_wait_flag(struct ocfs2_lock_res *lockres,
                    int flag)
{
    unsigned long flags;
    int ret;

    spin_lock_irqsave(&lockres->l_lock, flags);
    ret = lockres->l_flags & flag;
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    return ret;
}

static inline void ocfs2_wait_on_busy_lock(struct ocfs2_lock_res *lockres)

{
    wait_event(lockres->l_event,
           !ocfs2_check_wait_flag(lockres, OCFS2_LOCK_BUSY));
}

static inline void ocfs2_wait_on_refreshing_lock(struct ocfs2_lock_res *lockres)

{
    wait_event(lockres->l_event,
           !ocfs2_check_wait_flag(lockres, OCFS2_LOCK_REFRESHING));
}

/* predict what lock level we'll be dropping down to on behalf
 * of another node, and return true if the currently wanted
 * level will be compatible with it. */
static inline int ocfs2_may_continue_on_blocked_lock(struct ocfs2_lock_res *lockres,
                             int wanted)
{
    BUG_ON(!(lockres->l_flags & OCFS2_LOCK_BLOCKED));

    return wanted <= ocfs2_highest_compat_lock_level(lockres->l_blocking);
}

static void ocfs2_init_mask_waiter(struct ocfs2_mask_waiter *mw)
{
    INIT_LIST_HEAD(&mw->mw_item);
    init_completion(&mw->mw_complete);
    ocfs2_init_start_time(mw);
}

static int ocfs2_wait_for_mask(struct ocfs2_mask_waiter *mw)
{
    wait_for_completion(&mw->mw_complete);
    /* Re-arm the completion in case we want to wait on it again */
    INIT_COMPLETION(mw->mw_complete);
    return mw->mw_status;
}

static void lockres_add_mask_waiter(struct ocfs2_lock_res *lockres,
                    struct ocfs2_mask_waiter *mw,
                    unsigned long mask,
                    unsigned long goal)
{
    BUG_ON(!list_empty(&mw->mw_item));

    assert_spin_locked(&lockres->l_lock);

    list_add_tail(&mw->mw_item, &lockres->l_mask_waiters);
    mw->mw_mask = mask;
    mw->mw_goal = goal;
}

/* returns 0 if the mw that was removed was already satisfied, -EBUSY
 * if the mask still hadn't reached its goal */
static int lockres_remove_mask_waiter(struct ocfs2_lock_res *lockres,
                      struct ocfs2_mask_waiter *mw)
{
    unsigned long flags;
    int ret = 0;

    spin_lock_irqsave(&lockres->l_lock, flags);
    if (!list_empty(&mw->mw_item)) {
        if ((lockres->l_flags & mw->mw_mask) != mw->mw_goal)
            ret = -EBUSY;

        list_del_init(&mw->mw_item);
        init_completion(&mw->mw_complete);
    }
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    return ret;

}

static int ocfs2_wait_for_mask_interruptible(struct ocfs2_mask_waiter *mw,
                         struct ocfs2_lock_res *lockres)
{
    int ret;

    ret = wait_for_completion_interruptible(&mw->mw_complete);
    if (ret)
        lockres_remove_mask_waiter(lockres, mw);
    else
        ret = mw->mw_status;
    /* Re-arm the completion in case we want to wait on it again */
    INIT_COMPLETION(mw->mw_complete);
    return ret;
}

static int __ocfs2_cluster_lock(struct ocfs2_super *osb,
                struct ocfs2_lock_res *lockres,
                int level,
                u32 lkm_flags,
                int arg_flags,
                int l_subclass,
                unsigned long caller_ip)
{
    struct ocfs2_mask_waiter mw;
    int wait, catch_signals = !(osb->s_mount_opt & OCFS2_MOUNT_NOINTR);
    int ret = 0; /* gcc doesn't realize wait = 1 guarantees ret is set */
    unsigned long flags;
    unsigned int gen;
    int noqueue_attempted = 0;

    ocfs2_init_mask_waiter(&mw);

    if (lockres->l_ops->flags & LOCK_TYPE_USES_LVB)
        lkm_flags |= DLM_LKF_VALBLK;

again:
    wait = 0;

    spin_lock_irqsave(&lockres->l_lock, flags);

    if (catch_signals && signal_pending(current)) {
        ret = -ERESTARTSYS;
        goto unlock;
    }

    mlog_bug_on_msg(lockres->l_flags & OCFS2_LOCK_FREEING,
            "Cluster lock called on freeing lockres %s! flags "
            "0x%lx\n", lockres->l_name, lockres->l_flags);

    /* We only compare against the currently granted level
     * here. If the lock is blocked waiting on a downconvert,
     * we'll get caught below. */
    if (lockres->l_flags & OCFS2_LOCK_BUSY &&
        level > lockres->l_level) {
        /* is someone sitting in dlm_lock? If so, wait on
         * them. */
        lockres_add_mask_waiter(lockres, &mw, OCFS2_LOCK_BUSY, 0);
        wait = 1;
        goto unlock;
    }

    if (lockres->l_flags & OCFS2_LOCK_UPCONVERT_FINISHING) {
        /*
         * We've upconverted. If the lock now has a level we can
         * work with, we take it. If, however, the lock is not at the
         * required level, we go thru the full cycle. One way this could
         * happen is if a process requesting an upconvert to PR is
         * closely followed by another requesting upconvert to an EX.
         * If the process requesting EX lands here, we want it to
         * continue attempting to upconvert and let the process
         * requesting PR take the lock.
         * If multiple processes request upconvert to PR, the first one
         * here will take the lock. The others will have to go thru the
         * OCFS2_LOCK_BLOCKED check to ensure that there is no pending
         * downconvert request.
         */
        if (level <= lockres->l_level)
            goto update_holders;
    }

    if (lockres->l_flags & OCFS2_LOCK_BLOCKED &&
        !ocfs2_may_continue_on_blocked_lock(lockres, level)) {
        /* is the lock is currently blocked on behalf of
         * another node */
        lockres_add_mask_waiter(lockres, &mw, OCFS2_LOCK_BLOCKED, 0);
        wait = 1;
        goto unlock;
    }

    if (level > lockres->l_level) {
        if (noqueue_attempted > 0) {
            ret = -EAGAIN;
            goto unlock;
        }
        if (lkm_flags & DLM_LKF_NOQUEUE)
            noqueue_attempted = 1;

        if (lockres->l_action != OCFS2_AST_INVALID)
            mlog(ML_ERROR, "lockres %s has action %u pending\n",
                 lockres->l_name, lockres->l_action);

        if (!(lockres->l_flags & OCFS2_LOCK_ATTACHED)) {
            lockres->l_action = OCFS2_AST_ATTACH;
            lkm_flags &= ~DLM_LKF_CONVERT;
        } else {
            lockres->l_action = OCFS2_AST_CONVERT;
            lkm_flags |= DLM_LKF_CONVERT;
        }

        lockres->l_requested = level;
        lockres_or_flags(lockres, OCFS2_LOCK_BUSY);
        gen = lockres_set_pending(lockres);
        spin_unlock_irqrestore(&lockres->l_lock, flags);

        BUG_ON(level == DLM_LOCK_IV);
        BUG_ON(level == DLM_LOCK_NL);

        mlog(ML_BASTS, "lockres %s, convert from %d to %d\n",
             lockres->l_name, lockres->l_level, level);

        /* call dlm_lock to upgrade lock now */
        ret = ocfs2_dlm_lock(osb->cconn,
                     level,
                     &lockres->l_lksb,
                     lkm_flags,
                     lockres->l_name,
                     OCFS2_LOCK_ID_MAX_LEN - 1);
        lockres_clear_pending(lockres, gen, osb);
        if (ret) {
            if (!(lkm_flags & DLM_LKF_NOQUEUE) ||
                (ret != -EAGAIN)) {
                ocfs2_log_dlm_error("ocfs2_dlm_lock",
                            ret, lockres);
            }
            ocfs2_recover_from_dlm_error(lockres, 1);
            goto out;
        }

        mlog(0, "lock %s, successful return from ocfs2_dlm_lock\n",
             lockres->l_name);

        /* At this point we've gone inside the dlm and need to
         * complete our work regardless. */
        catch_signals = 0;

        /* wait for busy to clear and carry on */
        goto again;
    }

update_holders:
    /* Ok, if we get here then we're good to go. */
    ocfs2_inc_holders(lockres, level);

    ret = 0;
unlock:
    lockres_clear_flags(lockres, OCFS2_LOCK_UPCONVERT_FINISHING);

    spin_unlock_irqrestore(&lockres->l_lock, flags);
out:
    /*
     * This is helping work around a lock inversion between the page lock
     * and dlm locks.  One path holds the page lock while calling aops
     * which block acquiring dlm locks.  The voting thread holds dlm
     * locks while acquiring page locks while down converting data locks.
     * This block is helping an aop path notice the inversion and back
     * off to unlock its page lock before trying the dlm lock again.
     */
    if (wait && arg_flags & OCFS2_LOCK_NONBLOCK &&
        mw.mw_mask & (OCFS2_LOCK_BUSY|OCFS2_LOCK_BLOCKED)) {
        wait = 0;
        if (lockres_remove_mask_waiter(lockres, &mw))
            ret = -EAGAIN;
        else
            goto again;
    }
    if (wait) {
        ret = ocfs2_wait_for_mask(&mw);
        if (ret == 0)
            goto again;
        mlog_errno(ret);
    }
    ocfs2_update_lock_stats(lockres, level, &mw, ret);

#ifdef CONFIG_DEBUG_LOCK_ALLOC
    if (!ret && lockres->l_lockdep_map.key != NULL) {
        if (level == DLM_LOCK_PR)
            rwsem_acquire_read(&lockres->l_lockdep_map, l_subclass,
                !!(arg_flags & OCFS2_META_LOCK_NOQUEUE),
                caller_ip);
        else
            rwsem_acquire(&lockres->l_lockdep_map, l_subclass,
                !!(arg_flags & OCFS2_META_LOCK_NOQUEUE),
                caller_ip);
    }
#endif
    return ret;
}

static inline int ocfs2_cluster_lock(struct ocfs2_super *osb,
                     struct ocfs2_lock_res *lockres,
                     int level,
                     u32 lkm_flags,
                     int arg_flags)
{
    return __ocfs2_cluster_lock(osb, lockres, level, lkm_flags, arg_flags,
                    0, _RET_IP_);
}


static void __ocfs2_cluster_unlock(struct ocfs2_super *osb,
                   struct ocfs2_lock_res *lockres,
                   int level,
                   unsigned long caller_ip)
{
    unsigned long flags;

    spin_lock_irqsave(&lockres->l_lock, flags);
    ocfs2_dec_holders(lockres, level);
    ocfs2_downconvert_on_unlock(osb, lockres);
    spin_unlock_irqrestore(&lockres->l_lock, flags);
#ifdef CONFIG_DEBUG_LOCK_ALLOC
    if (lockres->l_lockdep_map.key != NULL)
        rwsem_release(&lockres->l_lockdep_map, 1, caller_ip);
#endif
}

static int ocfs2_create_new_lock(struct ocfs2_super *osb,
                 struct ocfs2_lock_res *lockres,
                 int ex,
                 int local)
{
    int level =  ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    unsigned long flags;
    u32 lkm_flags = local ? DLM_LKF_LOCAL : 0;

    spin_lock_irqsave(&lockres->l_lock, flags);
    BUG_ON(lockres->l_flags & OCFS2_LOCK_ATTACHED);
    lockres_or_flags(lockres, OCFS2_LOCK_LOCAL);
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    return ocfs2_lock_create(osb, lockres, level, lkm_flags);
}

/* Grants us an EX lock on the data and metadata resources, skipping
 * the normal cluster directory lookup. Use this ONLY on newly created
 * inodes which other nodes can't possibly see, and which haven't been
 * hashed in the inode hash yet. This can give us a good performance
 * increase as it'll skip the network broadcast normally associated
 * with creating a new lock resource. */
int ocfs2_create_new_inode_locks(struct inode *inode)
{
    int ret;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    BUG_ON(!inode);
    BUG_ON(!ocfs2_inode_is_new(inode));

    mlog(0, "Inode %llu\n", (unsigned long long)OCFS2_I(inode)->ip_blkno);

    /* NOTE: That we don't increment any of the holder counts, nor
     * do we add anything to a journal handle. Since this is
     * supposed to be a new inode which the cluster doesn't know
     * about yet, there is no need to.  As far as the LVB handling
     * is concerned, this is basically like acquiring an EX lock
     * on a resource which has an invalid one -- we'll set it
     * valid when we release the EX. */

    ret = ocfs2_create_new_lock(osb, &OCFS2_I(inode)->ip_rw_lockres, 1, 1);
    if (ret) {
        mlog_errno(ret);
        goto bail;
    }

    /*
     * We don't want to use DLM_LKF_LOCAL on a meta data lock as they
     * don't use a generation in their lock names.
     */
    ret = ocfs2_create_new_lock(osb, &OCFS2_I(inode)->ip_inode_lockres, 1, 0);
    if (ret) {
        mlog_errno(ret);
        goto bail;
    }

    ret = ocfs2_create_new_lock(osb, &OCFS2_I(inode)->ip_open_lockres, 0, 0);
    if (ret) {
        mlog_errno(ret);
        goto bail;
    }

bail:
    return ret;
}

int ocfs2_rw_lock(struct inode *inode, int write)
{
    int status, level;
    struct ocfs2_lock_res *lockres;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    BUG_ON(!inode);

    mlog(0, "inode %llu take %s RW lock\n",
         (unsigned long long)OCFS2_I(inode)->ip_blkno,
         write ? "EXMODE" : "PRMODE");

    if (ocfs2_mount_local(osb))
        return 0;

    lockres = &OCFS2_I(inode)->ip_rw_lockres;

    level = write ? DLM_LOCK_EX : DLM_LOCK_PR;

    status = ocfs2_cluster_lock(OCFS2_SB(inode->i_sb), lockres, level, 0,
                    0);
    if (status < 0)
        mlog_errno(status);

    return status;
}

void ocfs2_rw_unlock(struct inode *inode, int write)
{
    int level = write ? DLM_LOCK_EX : DLM_LOCK_PR;
    struct ocfs2_lock_res *lockres = &OCFS2_I(inode)->ip_rw_lockres;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    mlog(0, "inode %llu drop %s RW lock\n",
         (unsigned long long)OCFS2_I(inode)->ip_blkno,
         write ? "EXMODE" : "PRMODE");

    if (!ocfs2_mount_local(osb))
        ocfs2_cluster_unlock(OCFS2_SB(inode->i_sb), lockres, level);
}

/*
 * ocfs2_open_lock always get PR mode lock.
 */
int ocfs2_open_lock(struct inode *inode)
{
    int status = 0;
    struct ocfs2_lock_res *lockres;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    BUG_ON(!inode);

    mlog(0, "inode %llu take PRMODE open lock\n",
         (unsigned long long)OCFS2_I(inode)->ip_blkno);

    if (ocfs2_is_hard_readonly(osb) || ocfs2_mount_local(osb))
        goto out;

    lockres = &OCFS2_I(inode)->ip_open_lockres;

    status = ocfs2_cluster_lock(OCFS2_SB(inode->i_sb), lockres,
                    DLM_LOCK_PR, 0, 0);
    if (status < 0)
        mlog_errno(status);

out:
    return status;
}

int ocfs2_try_open_lock(struct inode *inode, int write)
{
    int status = 0, level;
    struct ocfs2_lock_res *lockres;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    BUG_ON(!inode);

    mlog(0, "inode %llu try to take %s open lock\n",
         (unsigned long long)OCFS2_I(inode)->ip_blkno,
         write ? "EXMODE" : "PRMODE");

    if (ocfs2_is_hard_readonly(osb)) {
        if (write)
            status = -EROFS;
        goto out;
    }

    if (ocfs2_mount_local(osb))
        goto out;

    lockres = &OCFS2_I(inode)->ip_open_lockres;

    level = write ? DLM_LOCK_EX : DLM_LOCK_PR;

    /*
     * The file system may already holding a PRMODE/EXMODE open lock.
     * Since we pass DLM_LKF_NOQUEUE, the request won't block waiting on
     * other nodes and the -EAGAIN will indicate to the caller that
     * this inode is still in use.
     */
    status = ocfs2_cluster_lock(OCFS2_SB(inode->i_sb), lockres,
                    level, DLM_LKF_NOQUEUE, 0);

out:
    return status;
}

/*
 * ocfs2_open_unlock unlock PR and EX mode open locks.
 */
void ocfs2_open_unlock(struct inode *inode)
{
    struct ocfs2_lock_res *lockres = &OCFS2_I(inode)->ip_open_lockres;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    mlog(0, "inode %llu drop open lock\n",
         (unsigned long long)OCFS2_I(inode)->ip_blkno);

    if (ocfs2_mount_local(osb))
        goto out;

    if(lockres->l_ro_holders)
        ocfs2_cluster_unlock(OCFS2_SB(inode->i_sb), lockres,
                     DLM_LOCK_PR);
    if(lockres->l_ex_holders)
        ocfs2_cluster_unlock(OCFS2_SB(inode->i_sb), lockres,
                     DLM_LOCK_EX);

out:
    return;
}

static int ocfs2_flock_handle_signal(struct ocfs2_lock_res *lockres,
                     int level)
{
    int ret;
    struct ocfs2_super *osb = ocfs2_get_lockres_osb(lockres);
    unsigned long flags;
    struct ocfs2_mask_waiter mw;

    ocfs2_init_mask_waiter(&mw);

retry_cancel:
    spin_lock_irqsave(&lockres->l_lock, flags);
    if (lockres->l_flags & OCFS2_LOCK_BUSY) {
        ret = ocfs2_prepare_cancel_convert(osb, lockres);
        if (ret) {
            spin_unlock_irqrestore(&lockres->l_lock, flags);
            ret = ocfs2_cancel_convert(osb, lockres);
            if (ret < 0) {
                mlog_errno(ret);
                goto out;
            }
            goto retry_cancel;
        }
        lockres_add_mask_waiter(lockres, &mw, OCFS2_LOCK_BUSY, 0);
        spin_unlock_irqrestore(&lockres->l_lock, flags);

        ocfs2_wait_for_mask(&mw);
        goto retry_cancel;
    }

    ret = -ERESTARTSYS;
    /*
     * We may still have gotten the lock, in which case there's no
     * point to restarting the syscall.
     */
    if (lockres->l_level == level)
        ret = 0;

    mlog(0, "Cancel returning %d. flags: 0x%lx, level: %d, act: %d\n", ret,
         lockres->l_flags, lockres->l_level, lockres->l_action);

    spin_unlock_irqrestore(&lockres->l_lock, flags);

out:
    return ret;
}

/*
 * ocfs2_file_lock() and ocfs2_file_unlock() map to a single pair of
 * flock() calls. The locking approach this requires is sufficiently
 * different from all other cluster lock types that we implement a
 * separate path to the "low-level" dlm calls. In particular:
 *
 * - No optimization of lock levels is done - we take at exactly
 *   what's been requested.
 *
 * - No lock caching is employed. We immediately downconvert to
 *   no-lock at unlock time. This also means flock locks never go on
 *   the blocking list).
 *
 * - Since userspace can trivially deadlock itself with flock, we make
 *   sure to allow cancellation of a misbehaving applications flock()
 *   request.
 *
 * - Access to any flock lockres doesn't require concurrency, so we
 *   can simplify the code by requiring the caller to guarantee
 *   serialization of dlmglue flock calls.
 */
int ocfs2_file_lock(struct file *file, int ex, int trylock)
{
    int ret, level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    unsigned int lkm_flags = trylock ? DLM_LKF_NOQUEUE : 0;
    unsigned long flags;
    struct ocfs2_file_private *fp = file->private_data;
    struct ocfs2_lock_res *lockres = &fp->fp_flock;
    struct ocfs2_super *osb = OCFS2_SB(file->f_mapping->host->i_sb);
    struct ocfs2_mask_waiter mw;

    ocfs2_init_mask_waiter(&mw);

    if ((lockres->l_flags & OCFS2_LOCK_BUSY) ||
        (lockres->l_level > DLM_LOCK_NL)) {
        mlog(ML_ERROR,
             "File lock \"%s\" has busy or locked state: flags: 0x%lx, "
             "level: %u\n", lockres->l_name, lockres->l_flags,
             lockres->l_level);
        return -EINVAL;
    }

    spin_lock_irqsave(&lockres->l_lock, flags);
    if (!(lockres->l_flags & OCFS2_LOCK_ATTACHED)) {
        lockres_add_mask_waiter(lockres, &mw, OCFS2_LOCK_BUSY, 0);
        spin_unlock_irqrestore(&lockres->l_lock, flags);

        /*
         * Get the lock at NLMODE to start - that way we
         * can cancel the upconvert request if need be.
         */
        ret = ocfs2_lock_create(osb, lockres, DLM_LOCK_NL, 0);
        if (ret < 0) {
            mlog_errno(ret);
            goto out;
        }

        ret = ocfs2_wait_for_mask(&mw);
        if (ret) {
            mlog_errno(ret);
            goto out;
        }
        spin_lock_irqsave(&lockres->l_lock, flags);
    }

    lockres->l_action = OCFS2_AST_CONVERT;
    lkm_flags |= DLM_LKF_CONVERT;
    lockres->l_requested = level;
    lockres_or_flags(lockres, OCFS2_LOCK_BUSY);

    lockres_add_mask_waiter(lockres, &mw, OCFS2_LOCK_BUSY, 0);
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    ret = ocfs2_dlm_lock(osb->cconn, level, &lockres->l_lksb, lkm_flags,
                 lockres->l_name, OCFS2_LOCK_ID_MAX_LEN - 1);
    if (ret) {
        if (!trylock || (ret != -EAGAIN)) {
            ocfs2_log_dlm_error("ocfs2_dlm_lock", ret, lockres);
            ret = -EINVAL;
        }

        ocfs2_recover_from_dlm_error(lockres, 1);
        lockres_remove_mask_waiter(lockres, &mw);
        goto out;
    }

    ret = ocfs2_wait_for_mask_interruptible(&mw, lockres);
    if (ret == -ERESTARTSYS) {
        /*
         * Userspace can cause deadlock itself with
         * flock(). Current behavior locally is to allow the
         * deadlock, but abort the system call if a signal is
         * received. We follow this example, otherwise a
         * poorly written program could sit in kernel until
         * reboot.
         *
         * Handling this is a bit more complicated for Ocfs2
         * though. We can't exit this function with an
         * outstanding lock request, so a cancel convert is
         * required. We intentionally overwrite 'ret' - if the
         * cancel fails and the lock was granted, it's easier
         * to just bubble success back up to the user.
         */
        ret = ocfs2_flock_handle_signal(lockres, level);
    } else if (!ret && (level > lockres->l_level)) {
        /* Trylock failed asynchronously */
        BUG_ON(!trylock);
        ret = -EAGAIN;
    }

out:

    mlog(0, "Lock: \"%s\" ex: %d, trylock: %d, returns: %d\n",
         lockres->l_name, ex, trylock, ret);
    return ret;
}

void ocfs2_file_unlock(struct file *file)
{
    int ret;
    unsigned int gen;
    unsigned long flags;
    struct ocfs2_file_private *fp = file->private_data;
    struct ocfs2_lock_res *lockres = &fp->fp_flock;
    struct ocfs2_super *osb = OCFS2_SB(file->f_mapping->host->i_sb);
    struct ocfs2_mask_waiter mw;

    ocfs2_init_mask_waiter(&mw);

    if (!(lockres->l_flags & OCFS2_LOCK_ATTACHED))
        return;

    if (lockres->l_level == DLM_LOCK_NL)
        return;

    mlog(0, "Unlock: \"%s\" flags: 0x%lx, level: %d, act: %d\n",
         lockres->l_name, lockres->l_flags, lockres->l_level,
         lockres->l_action);

    spin_lock_irqsave(&lockres->l_lock, flags);
    /*
     * Fake a blocking ast for the downconvert code.
     */
    lockres_or_flags(lockres, OCFS2_LOCK_BLOCKED);
    lockres->l_blocking = DLM_LOCK_EX;

    gen = ocfs2_prepare_downconvert(lockres, DLM_LOCK_NL);
    lockres_add_mask_waiter(lockres, &mw, OCFS2_LOCK_BUSY, 0);
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    ret = ocfs2_downconvert_lock(osb, lockres, DLM_LOCK_NL, 0, gen);
    if (ret) {
        mlog_errno(ret);
        return;
    }

    ret = ocfs2_wait_for_mask(&mw);
    if (ret)
        mlog_errno(ret);
}

static void ocfs2_downconvert_on_unlock(struct ocfs2_super *osb,
                    struct ocfs2_lock_res *lockres)
{
    int kick = 0;

    /* If we know that another node is waiting on our lock, kick
     * the downconvert thread * pre-emptively when we reach a release
     * condition. */
    if (lockres->l_flags & OCFS2_LOCK_BLOCKED) {
        switch(lockres->l_blocking) {
        case DLM_LOCK_EX:
            if (!lockres->l_ex_holders && !lockres->l_ro_holders)
                kick = 1;
            break;
        case DLM_LOCK_PR:
            if (!lockres->l_ex_holders)
                kick = 1;
            break;
        default:
            BUG();
        }
    }

    if (kick)
        ocfs2_wake_downconvert_thread(osb);
}

#define OCFS2_SEC_BITS   34
#define OCFS2_SEC_SHIFT  (64 - 34)
#define OCFS2_NSEC_MASK  ((1ULL << OCFS2_SEC_SHIFT) - 1)

/* LVB only has room for 64 bits of time here so we pack it for
 * now. */
static u64 ocfs2_pack_timespec(struct timespec *spec)
{
    u64 res;
    u64 sec = spec->tv_sec;
    u32 nsec = spec->tv_nsec;

    res = (sec << OCFS2_SEC_SHIFT) | (nsec & OCFS2_NSEC_MASK);

    return res;
}

/* Call this with the lockres locked. I am reasonably sure we don't
 * need ip_lock in this function as anyone who would be changing those
 * values is supposed to be blocked in ocfs2_inode_lock right now. */
static void __ocfs2_stuff_meta_lvb(struct inode *inode)
{
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_lock_res *lockres = &oi->ip_inode_lockres;
    struct ocfs2_meta_lvb *lvb;

    lvb = ocfs2_dlm_lvb(&lockres->l_lksb);

    /*
     * Invalidate the LVB of a deleted inode - this way other
     * nodes are forced to go to disk and discover the new inode
     * status.
     */
    if (oi->ip_flags & OCFS2_INODE_DELETED) {
        lvb->lvb_version = 0;
        goto out;
    }

    lvb->lvb_version   = OCFS2_LVB_VERSION;
    lvb->lvb_isize     = cpu_to_be64(i_size_read(inode));
    lvb->lvb_iclusters = cpu_to_be32(oi->ip_clusters);
    lvb->lvb_iuid      = cpu_to_be32(inode->i_uid);
    lvb->lvb_igid      = cpu_to_be32(inode->i_gid);
    lvb->lvb_imode     = cpu_to_be16(inode->i_mode);
    lvb->lvb_inlink    = cpu_to_be16(inode->i_nlink);
    lvb->lvb_iatime_packed  =
        cpu_to_be64(ocfs2_pack_timespec(&inode->i_atime));
    lvb->lvb_ictime_packed =
        cpu_to_be64(ocfs2_pack_timespec(&inode->i_ctime));
    lvb->lvb_imtime_packed =
        cpu_to_be64(ocfs2_pack_timespec(&inode->i_mtime));
    lvb->lvb_iattr    = cpu_to_be32(oi->ip_attr);
    lvb->lvb_idynfeatures = cpu_to_be16(oi->ip_dyn_features);
    lvb->lvb_igeneration = cpu_to_be32(inode->i_generation);

out:
    mlog_meta_lvb(0, lockres);
}

static void ocfs2_unpack_timespec(struct timespec *spec,
                  u64 packed_time)
{
    spec->tv_sec = packed_time >> OCFS2_SEC_SHIFT;
    spec->tv_nsec = packed_time & OCFS2_NSEC_MASK;
}

static void ocfs2_refresh_inode_from_lvb(struct inode *inode)
{
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_lock_res *lockres = &oi->ip_inode_lockres;
    struct ocfs2_meta_lvb *lvb;

    mlog_meta_lvb(0, lockres);

    lvb = ocfs2_dlm_lvb(&lockres->l_lksb);

    /* We're safe here without the lockres lock... */
    spin_lock(&oi->ip_lock);
    oi->ip_clusters = be32_to_cpu(lvb->lvb_iclusters);
    i_size_write(inode, be64_to_cpu(lvb->lvb_isize));

    oi->ip_attr = be32_to_cpu(lvb->lvb_iattr);
    oi->ip_dyn_features = be16_to_cpu(lvb->lvb_idynfeatures);
    ocfs2_set_inode_flags(inode);

    /* fast-symlinks are a special case */
    if (S_ISLNK(inode->i_mode) && !oi->ip_clusters)
        inode->i_blocks = 0;
    else
        inode->i_blocks = ocfs2_inode_sector_count(inode);

    inode->i_uid     = be32_to_cpu(lvb->lvb_iuid);
    inode->i_gid     = be32_to_cpu(lvb->lvb_igid);
    inode->i_mode    = be16_to_cpu(lvb->lvb_imode);
    set_nlink(inode, be16_to_cpu(lvb->lvb_inlink));
    ocfs2_unpack_timespec(&inode->i_atime,
                  be64_to_cpu(lvb->lvb_iatime_packed));
    ocfs2_unpack_timespec(&inode->i_mtime,
                  be64_to_cpu(lvb->lvb_imtime_packed));
    ocfs2_unpack_timespec(&inode->i_ctime,
                  be64_to_cpu(lvb->lvb_ictime_packed));
    spin_unlock(&oi->ip_lock);
}

static inline int ocfs2_meta_lvb_is_trustable(struct inode *inode,
                          struct ocfs2_lock_res *lockres)
{
    struct ocfs2_meta_lvb *lvb = ocfs2_dlm_lvb(&lockres->l_lksb);

    if (ocfs2_dlm_lvb_valid(&lockres->l_lksb)
        && lvb->lvb_version == OCFS2_LVB_VERSION
        && be32_to_cpu(lvb->lvb_igeneration) == inode->i_generation)
        return 1;
    return 0;
}

/* Determine whether a lock resource needs to be refreshed, and
 * arbitrate who gets to refresh it.
 *
 *   0 means no refresh needed.
 *
 *   > 0 means you need to refresh this and you MUST call
 *   ocfs2_complete_lock_res_refresh afterwards. */
static int ocfs2_should_refresh_lock_res(struct ocfs2_lock_res *lockres)
{
    unsigned long flags;
    int status = 0;

refresh_check:
    spin_lock_irqsave(&lockres->l_lock, flags);
    if (!(lockres->l_flags & OCFS2_LOCK_NEEDS_REFRESH)) {
        spin_unlock_irqrestore(&lockres->l_lock, flags);
        goto bail;
    }

    if (lockres->l_flags & OCFS2_LOCK_REFRESHING) {
        spin_unlock_irqrestore(&lockres->l_lock, flags);

        ocfs2_wait_on_refreshing_lock(lockres);
        goto refresh_check;
    }

    /* Ok, I'll be the one to refresh this lock. */
    lockres_or_flags(lockres, OCFS2_LOCK_REFRESHING);
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    status = 1;
bail:
    mlog(0, "status %d\n", status);
    return status;
}

/* If status is non zero, I'll mark it as not being in refresh
 * anymroe, but i won't clear the needs refresh flag. */
static inline void ocfs2_complete_lock_res_refresh(struct ocfs2_lock_res *lockres,
                           int status)
{
    unsigned long flags;

    spin_lock_irqsave(&lockres->l_lock, flags);
    lockres_clear_flags(lockres, OCFS2_LOCK_REFRESHING);
    if (!status)
        lockres_clear_flags(lockres, OCFS2_LOCK_NEEDS_REFRESH);
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    wake_up(&lockres->l_event);
}

/* may or may not return a bh if it went to disk. */
static int ocfs2_inode_lock_update(struct inode *inode,
                  struct buffer_head **bh)
{
    int status = 0;
    struct ocfs2_inode_info *oi = OCFS2_I(inode);
    struct ocfs2_lock_res *lockres = &oi->ip_inode_lockres;
    struct ocfs2_dinode *fe;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    if (ocfs2_mount_local(osb))
        goto bail;

    spin_lock(&oi->ip_lock);
    if (oi->ip_flags & OCFS2_INODE_DELETED) {
        mlog(0, "Orphaned inode %llu was deleted while we "
             "were waiting on a lock. ip_flags = 0x%x\n",
             (unsigned long long)oi->ip_blkno, oi->ip_flags);
        spin_unlock(&oi->ip_lock);
        status = -ENOENT;
        goto bail;
    }
    spin_unlock(&oi->ip_lock);

    if (!ocfs2_should_refresh_lock_res(lockres))
        goto bail;

    /* This will discard any caching information we might have had
     * for the inode metadata. */
    ocfs2_metadata_cache_purge(INODE_CACHE(inode));

    ocfs2_extent_map_trunc(inode, 0);

    if (ocfs2_meta_lvb_is_trustable(inode, lockres)) {
        mlog(0, "Trusting LVB on inode %llu\n",
             (unsigned long long)oi->ip_blkno);
        ocfs2_refresh_inode_from_lvb(inode);
    } else {
        /* Boo, we have to go to disk. */
        /* read bh, cast, ocfs2_refresh_inode */
        status = ocfs2_read_inode_block(inode, bh);
        if (status < 0) {
            mlog_errno(status);
            goto bail_refresh;
        }
        fe = (struct ocfs2_dinode *) (*bh)->b_data;

        /* This is a good chance to make sure we're not
         * locking an invalid object.  ocfs2_read_inode_block()
         * already checked that the inode block is sane.
         *
         * We bug on a stale inode here because we checked
         * above whether it was wiped from disk. The wiping
         * node provides a guarantee that we receive that
         * message and can mark the inode before dropping any
         * locks associated with it. */
        mlog_bug_on_msg(inode->i_generation !=
                le32_to_cpu(fe->i_generation),
                "Invalid dinode %llu disk generation: %u "
                "inode->i_generation: %u\n",
                (unsigned long long)oi->ip_blkno,
                le32_to_cpu(fe->i_generation),
                inode->i_generation);
        mlog_bug_on_msg(le64_to_cpu(fe->i_dtime) ||
                !(fe->i_flags & cpu_to_le32(OCFS2_VALID_FL)),
                "Stale dinode %llu dtime: %llu flags: 0x%x\n",
                (unsigned long long)oi->ip_blkno,
                (unsigned long long)le64_to_cpu(fe->i_dtime),
                le32_to_cpu(fe->i_flags));

        ocfs2_refresh_inode(inode, fe);
        ocfs2_track_lock_refresh(lockres);
    }

    status = 0;
bail_refresh:
    ocfs2_complete_lock_res_refresh(lockres, status);
bail:
    return status;
}

static int ocfs2_assign_bh(struct inode *inode,
               struct buffer_head **ret_bh,
               struct buffer_head *passed_bh)
{
    int status;

    if (passed_bh) {
        /* Ok, the update went to disk for us, use the
         * returned bh. */
        *ret_bh = passed_bh;
        get_bh(*ret_bh);

        return 0;
    }

    status = ocfs2_read_inode_block(inode, ret_bh);
    if (status < 0)
        mlog_errno(status);

    return status;
}

/*
 * returns < 0 error if the callback will never be called, otherwise
 * the result of the lock will be communicated via the callback.
 */
int ocfs2_inode_lock_full_nested(struct inode *inode,
                 struct buffer_head **ret_bh,
                 int ex,
                 int arg_flags,
                 int subclass)
{
    int status, level, acquired;
    u32 dlm_flags;
    struct ocfs2_lock_res *lockres = NULL;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);
    struct buffer_head *local_bh = NULL;

    BUG_ON(!inode);

    mlog(0, "inode %llu, take %s META lock\n",
         (unsigned long long)OCFS2_I(inode)->ip_blkno,
         ex ? "EXMODE" : "PRMODE");

    status = 0;
    acquired = 0;
    /* We'll allow faking a readonly metadata lock for
     * rodevices. */
    if (ocfs2_is_hard_readonly(osb)) {
        if (ex)
            status = -EROFS;
        goto getbh;
    }

    if (ocfs2_mount_local(osb))
        goto local;

    if (!(arg_flags & OCFS2_META_LOCK_RECOVERY))
        ocfs2_wait_for_recovery(osb);

    lockres = &OCFS2_I(inode)->ip_inode_lockres;
    level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    dlm_flags = 0;
    if (arg_flags & OCFS2_META_LOCK_NOQUEUE)
        dlm_flags |= DLM_LKF_NOQUEUE;

    status = __ocfs2_cluster_lock(osb, lockres, level, dlm_flags,
                      arg_flags, subclass, _RET_IP_);
    if (status < 0) {
        if (status != -EAGAIN && status != -EIOCBRETRY)
            mlog_errno(status);
        goto bail;
    }

    /* Notify the error cleanup path to drop the cluster lock. */
    acquired = 1;

    /* We wait twice because a node may have died while we were in
     * the lower dlm layers. The second time though, we've
     * committed to owning this lock so we don't allow signals to
     * abort the operation. */
    if (!(arg_flags & OCFS2_META_LOCK_RECOVERY))
        ocfs2_wait_for_recovery(osb);

local:
    /*
     * We only see this flag if we're being called from
     * ocfs2_read_locked_inode(). It means we're locking an inode
     * which hasn't been populated yet, so clear the refresh flag
     * and let the caller handle it.
     */
    if (inode->i_state & I_NEW) {
        status = 0;
        if (lockres)
            ocfs2_complete_lock_res_refresh(lockres, 0);
        goto bail;
    }

    /* This is fun. The caller may want a bh back, or it may
     * not. ocfs2_inode_lock_update definitely wants one in, but
     * may or may not read one, depending on what's in the
     * LVB. The result of all of this is that we've *only* gone to
     * disk if we have to, so the complexity is worthwhile. */
    status = ocfs2_inode_lock_update(inode, &local_bh);
    if (status < 0) {
        if (status != -ENOENT)
            mlog_errno(status);
        goto bail;
    }
getbh:
    if (ret_bh) {
        status = ocfs2_assign_bh(inode, ret_bh, local_bh);
        if (status < 0) {
            mlog_errno(status);
            goto bail;
        }
    }

bail:
    if (status < 0) {
        if (ret_bh && (*ret_bh)) {
            brelse(*ret_bh);
            *ret_bh = NULL;
        }
        if (acquired)
            ocfs2_inode_unlock(inode, ex);
    }

    if (local_bh)
        brelse(local_bh);

    return status;
}

/*
 * This is working around a lock inversion between tasks acquiring DLM
 * locks while holding a page lock and the downconvert thread which
 * blocks dlm lock acquiry while acquiring page locks.
 *
 * ** These _with_page variantes are only intended to be called from aop
 * methods that hold page locks and return a very specific *positive* error
 * code that aop methods pass up to the VFS -- test for errors with != 0. **
 *
 * The DLM is called such that it returns -EAGAIN if it would have
 * blocked waiting for the downconvert thread.  In that case we unlock
 * our page so the downconvert thread can make progress.  Once we've
 * done this we have to return AOP_TRUNCATED_PAGE so the aop method
 * that called us can bubble that back up into the VFS who will then
 * immediately retry the aop call.
 *
 * We do a blocking lock and immediate unlock before returning, though, so that
 * the lock has a great chance of being cached on this node by the time the VFS
 * calls back to retry the aop.    This has a potential to livelock as nodes
 * ping locks back and forth, but that's a risk we're willing to take to avoid
 * the lock inversion simply.
 */
int ocfs2_inode_lock_with_page(struct inode *inode,
                  struct buffer_head **ret_bh,
                  int ex,
                  struct page *page)
{
    int ret;

    ret = ocfs2_inode_lock_full(inode, ret_bh, ex, OCFS2_LOCK_NONBLOCK);
    if (ret == -EAGAIN) {
        unlock_page(page);
        if (ocfs2_inode_lock(inode, ret_bh, ex) == 0)
            ocfs2_inode_unlock(inode, ex);
        ret = AOP_TRUNCATED_PAGE;
    }

    return ret;
}

int ocfs2_inode_lock_atime(struct inode *inode,
              struct vfsmount *vfsmnt,
              int *level)
{
    int ret;

    ret = ocfs2_inode_lock(inode, NULL, 0);
    if (ret < 0) {
        mlog_errno(ret);
        return ret;
    }

    /*
     * If we should update atime, we will get EX lock,
     * otherwise we just get PR lock.
     */
    if (ocfs2_should_update_atime(inode, vfsmnt)) {
        struct buffer_head *bh = NULL;

        ocfs2_inode_unlock(inode, 0);
        ret = ocfs2_inode_lock(inode, &bh, 1);
        if (ret < 0) {
            mlog_errno(ret);
            return ret;
        }
        *level = 1;
        if (ocfs2_should_update_atime(inode, vfsmnt))
            ocfs2_update_inode_atime(inode, bh);
        if (bh)
            brelse(bh);
    } else
        *level = 0;

    return ret;
}

void ocfs2_inode_unlock(struct inode *inode,
               int ex)
{
    int level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    struct ocfs2_lock_res *lockres = &OCFS2_I(inode)->ip_inode_lockres;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    mlog(0, "inode %llu drop %s META lock\n",
         (unsigned long long)OCFS2_I(inode)->ip_blkno,
         ex ? "EXMODE" : "PRMODE");

    if (!ocfs2_is_hard_readonly(OCFS2_SB(inode->i_sb)) &&
        !ocfs2_mount_local(osb))
        ocfs2_cluster_unlock(OCFS2_SB(inode->i_sb), lockres, level);
}

int ocfs2_orphan_scan_lock(struct ocfs2_super *osb, u32 *seqno)
{
    struct ocfs2_lock_res *lockres;
    struct ocfs2_orphan_scan_lvb *lvb;
    int status = 0;

    if (ocfs2_is_hard_readonly(osb))
        return -EROFS;

    if (ocfs2_mount_local(osb))
        return 0;

    lockres = &osb->osb_orphan_scan.os_lockres;
    status = ocfs2_cluster_lock(osb, lockres, DLM_LOCK_EX, 0, 0);
    if (status < 0)
        return status;

    lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
    if (ocfs2_dlm_lvb_valid(&lockres->l_lksb) &&
        lvb->lvb_version == OCFS2_ORPHAN_LVB_VERSION)
        *seqno = be32_to_cpu(lvb->lvb_os_seqno);
    else
        *seqno = osb->osb_orphan_scan.os_seqno + 1;

    return status;
}

void ocfs2_orphan_scan_unlock(struct ocfs2_super *osb, u32 seqno)
{
    struct ocfs2_lock_res *lockres;
    struct ocfs2_orphan_scan_lvb *lvb;

    if (!ocfs2_is_hard_readonly(osb) && !ocfs2_mount_local(osb)) {
        lockres = &osb->osb_orphan_scan.os_lockres;
        lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
        lvb->lvb_version = OCFS2_ORPHAN_LVB_VERSION;
        lvb->lvb_os_seqno = cpu_to_be32(seqno);
        ocfs2_cluster_unlock(osb, lockres, DLM_LOCK_EX);
    }
}

int ocfs2_super_lock(struct ocfs2_super *osb,
             int ex)
{
    int status = 0;
    int level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    struct ocfs2_lock_res *lockres = &osb->osb_super_lockres;

    if (ocfs2_is_hard_readonly(osb))
        return -EROFS;

    if (ocfs2_mount_local(osb))
        goto bail;

    status = ocfs2_cluster_lock(osb, lockres, level, 0, 0);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    /* The super block lock path is really in the best position to
     * know when resources covered by the lock need to be
     * refreshed, so we do it here. Of course, making sense of
     * everything is up to the caller :) */
    status = ocfs2_should_refresh_lock_res(lockres);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }
    if (status) {
        status = ocfs2_refresh_slot_info(osb);

        ocfs2_complete_lock_res_refresh(lockres, status);

        if (status < 0)
            mlog_errno(status);
        ocfs2_track_lock_refresh(lockres);
    }
bail:
    return status;
}

void ocfs2_super_unlock(struct ocfs2_super *osb,
            int ex)
{
    int level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    struct ocfs2_lock_res *lockres = &osb->osb_super_lockres;

    if (!ocfs2_mount_local(osb))
        ocfs2_cluster_unlock(osb, lockres, level);
}

int ocfs2_rename_lock(struct ocfs2_super *osb)
{
    int status;
    struct ocfs2_lock_res *lockres = &osb->osb_rename_lockres;

    if (ocfs2_is_hard_readonly(osb))
        return -EROFS;

    if (ocfs2_mount_local(osb))
        return 0;

    status = ocfs2_cluster_lock(osb, lockres, DLM_LOCK_EX, 0, 0);
    if (status < 0)
        mlog_errno(status);

    return status;
}

void ocfs2_rename_unlock(struct ocfs2_super *osb)
{
    struct ocfs2_lock_res *lockres = &osb->osb_rename_lockres;

    if (!ocfs2_mount_local(osb))
        ocfs2_cluster_unlock(osb, lockres, DLM_LOCK_EX);
}

int ocfs2_nfs_sync_lock(struct ocfs2_super *osb, int ex)
{
    int status;
    struct ocfs2_lock_res *lockres = &osb->osb_nfs_sync_lockres;

    if (ocfs2_is_hard_readonly(osb))
        return -EROFS;

    if (ocfs2_mount_local(osb))
        return 0;

    status = ocfs2_cluster_lock(osb, lockres, ex ? LKM_EXMODE : LKM_PRMODE,
                    0, 0);
    if (status < 0)
        mlog(ML_ERROR, "lock on nfs sync lock failed %d\n", status);

    return status;
}

void ocfs2_nfs_sync_unlock(struct ocfs2_super *osb, int ex)
{
    struct ocfs2_lock_res *lockres = &osb->osb_nfs_sync_lockres;

    if (!ocfs2_mount_local(osb))
        ocfs2_cluster_unlock(osb, lockres,
                     ex ? LKM_EXMODE : LKM_PRMODE);
}

int ocfs2_dentry_lock(struct dentry *dentry, int ex)
{
    int ret;
    int level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
    struct ocfs2_super *osb = OCFS2_SB(dentry->d_sb);

    BUG_ON(!dl);

    if (ocfs2_is_hard_readonly(osb)) {
        if (ex)
            return -EROFS;
        return 0;
    }

    if (ocfs2_mount_local(osb))
        return 0;

    ret = ocfs2_cluster_lock(osb, &dl->dl_lockres, level, 0, 0);
    if (ret < 0)
        mlog_errno(ret);

    return ret;
}

void ocfs2_dentry_unlock(struct dentry *dentry, int ex)
{
    int level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    struct ocfs2_dentry_lock *dl = dentry->d_fsdata;
    struct ocfs2_super *osb = OCFS2_SB(dentry->d_sb);

    if (!ocfs2_is_hard_readonly(osb) && !ocfs2_mount_local(osb))
        ocfs2_cluster_unlock(osb, &dl->dl_lockres, level);
}

/* Reference counting of the dlm debug structure. We want this because
 * open references on the debug inodes can live on after a mount, so
 * we can't rely on the ocfs2_super to always exist. */
static void ocfs2_dlm_debug_free(struct kref *kref)
{
    struct ocfs2_dlm_debug *dlm_debug;

    dlm_debug = container_of(kref, struct ocfs2_dlm_debug, d_refcnt);

    kfree(dlm_debug);
}

void ocfs2_put_dlm_debug(struct ocfs2_dlm_debug *dlm_debug)
{
    if (dlm_debug)
        kref_put(&dlm_debug->d_refcnt, ocfs2_dlm_debug_free);
}

static void ocfs2_get_dlm_debug(struct ocfs2_dlm_debug *debug)
{
    kref_get(&debug->d_refcnt);
}

struct ocfs2_dlm_debug *ocfs2_new_dlm_debug(void)
{
    struct ocfs2_dlm_debug *dlm_debug;

    dlm_debug = kmalloc(sizeof(struct ocfs2_dlm_debug), GFP_KERNEL);
    if (!dlm_debug) {
        mlog_errno(-ENOMEM);
        goto out;
    }

    kref_init(&dlm_debug->d_refcnt);
    INIT_LIST_HEAD(&dlm_debug->d_lockres_tracking);
    dlm_debug->d_locking_state = NULL;
out:
    return dlm_debug;
}

/* Access to this is arbitrated for us via seq_file->sem. */
struct ocfs2_dlm_seq_priv {
    struct ocfs2_dlm_debug *p_dlm_debug;
    struct ocfs2_lock_res p_iter_res;
    struct ocfs2_lock_res p_tmp_res;
};

static struct ocfs2_lock_res *ocfs2_dlm_next_res(struct ocfs2_lock_res *start,
                         struct ocfs2_dlm_seq_priv *priv)
{
    struct ocfs2_lock_res *iter, *ret = NULL;
    struct ocfs2_dlm_debug *dlm_debug = priv->p_dlm_debug;

    assert_spin_locked(&ocfs2_dlm_tracking_lock);

    list_for_each_entry(iter, &start->l_debug_list, l_debug_list) {
        /* discover the head of the list */
        if (&iter->l_debug_list == &dlm_debug->d_lockres_tracking) {
            mlog(0, "End of list found, %p\n", ret);
            break;
        }

        /* We track our "dummy" iteration lockres' by a NULL
         * l_ops field. */
        if (iter->l_ops != NULL) {
            ret = iter;
            break;
        }
    }

    return ret;
}

static void *ocfs2_dlm_seq_start(struct seq_file *m, loff_t *pos)
{
    struct ocfs2_dlm_seq_priv *priv = m->private;
    struct ocfs2_lock_res *iter;

    spin_lock(&ocfs2_dlm_tracking_lock);
    iter = ocfs2_dlm_next_res(&priv->p_iter_res, priv);
    if (iter) {
        /* Since lockres' have the lifetime of their container
         * (which can be inodes, ocfs2_supers, etc) we want to
         * copy this out to a temporary lockres while still
         * under the spinlock. Obviously after this we can't
         * trust any pointers on the copy returned, but that's
         * ok as the information we want isn't typically held
         * in them. */
        priv->p_tmp_res = *iter;
        iter = &priv->p_tmp_res;
    }
    spin_unlock(&ocfs2_dlm_tracking_lock);

    return iter;
}

static void ocfs2_dlm_seq_stop(struct seq_file *m, void *v)
{
}

static void *ocfs2_dlm_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
    struct ocfs2_dlm_seq_priv *priv = m->private;
    struct ocfs2_lock_res *iter = v;
    struct ocfs2_lock_res *dummy = &priv->p_iter_res;

    spin_lock(&ocfs2_dlm_tracking_lock);
    iter = ocfs2_dlm_next_res(iter, priv);
    list_del_init(&dummy->l_debug_list);
    if (iter) {
        list_add(&dummy->l_debug_list, &iter->l_debug_list);
        priv->p_tmp_res = *iter;
        iter = &priv->p_tmp_res;
    }
    spin_unlock(&ocfs2_dlm_tracking_lock);

    return iter;
}

/*
 * Version is used by debugfs.ocfs2 to determine the format being used
 *
 * New in version 2
 *  - Lock stats printed
 * New in version 3
 *  - Max time in lock stats is in usecs (instead of nsecs)
 */
#define OCFS2_DLM_DEBUG_STR_VERSION 3
static int ocfs2_dlm_seq_show(struct seq_file *m, void *v)
{
    int i;
    char *lvb;
    struct ocfs2_lock_res *lockres = v;

    if (!lockres)
        return -EINVAL;

    seq_printf(m, "0x%x\t", OCFS2_DLM_DEBUG_STR_VERSION);

    if (lockres->l_type == OCFS2_LOCK_TYPE_DENTRY)
        seq_printf(m, "%.*s%08x\t", OCFS2_DENTRY_LOCK_INO_START - 1,
               lockres->l_name,
               (unsigned int)ocfs2_get_dentry_lock_ino(lockres));
    else
        seq_printf(m, "%.*s\t", OCFS2_LOCK_ID_MAX_LEN, lockres->l_name);

    seq_printf(m, "%d\t"
           "0x%lx\t"
           "0x%x\t"
           "0x%x\t"
           "%u\t"
           "%u\t"
           "%d\t"
           "%d\t",
           lockres->l_level,
           lockres->l_flags,
           lockres->l_action,
           lockres->l_unlock_action,
           lockres->l_ro_holders,
           lockres->l_ex_holders,
           lockres->l_requested,
           lockres->l_blocking);

    /* Dump the raw LVB */
    lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
    for(i = 0; i < DLM_LVB_LEN; i++)
        seq_printf(m, "0x%x\t", lvb[i]);

#ifdef CONFIG_OCFS2_FS_STATS
# define lock_num_prmode(_l)        ((_l)->l_lock_prmode.ls_gets)
# define lock_num_exmode(_l)        ((_l)->l_lock_exmode.ls_gets)
# define lock_num_prmode_failed(_l) ((_l)->l_lock_prmode.ls_fail)
# define lock_num_exmode_failed(_l) ((_l)->l_lock_exmode.ls_fail)
# define lock_total_prmode(_l)      ((_l)->l_lock_prmode.ls_total)
# define lock_total_exmode(_l)      ((_l)->l_lock_exmode.ls_total)
# define lock_max_prmode(_l)        ((_l)->l_lock_prmode.ls_max)
# define lock_max_exmode(_l)        ((_l)->l_lock_exmode.ls_max)
# define lock_refresh(_l)       ((_l)->l_lock_refresh)
#else
# define lock_num_prmode(_l)        (0)
# define lock_num_exmode(_l)        (0)
# define lock_num_prmode_failed(_l) (0)
# define lock_num_exmode_failed(_l) (0)
# define lock_total_prmode(_l)      (0ULL)
# define lock_total_exmode(_l)      (0ULL)
# define lock_max_prmode(_l)        (0)
# define lock_max_exmode(_l)        (0)
# define lock_refresh(_l)       (0)
#endif
    /* The following seq_print was added in version 2 of this output */
    seq_printf(m, "%u\t"
           "%u\t"
           "%u\t"
           "%u\t"
           "%llu\t"
           "%llu\t"
           "%u\t"
           "%u\t"
           "%u\t",
           lock_num_prmode(lockres),
           lock_num_exmode(lockres),
           lock_num_prmode_failed(lockres),
           lock_num_exmode_failed(lockres),
           lock_total_prmode(lockres),
           lock_total_exmode(lockres),
           lock_max_prmode(lockres),
           lock_max_exmode(lockres),
           lock_refresh(lockres));

    /* End the line */
    seq_printf(m, "\n");
    return 0;
}

static const struct seq_operations ocfs2_dlm_seq_ops = {
    .start =    ocfs2_dlm_seq_start,
    .stop =     ocfs2_dlm_seq_stop,
    .next =     ocfs2_dlm_seq_next,
    .show =     ocfs2_dlm_seq_show,
};

static int ocfs2_dlm_debug_release(struct inode *inode, struct file *file)
{
    struct seq_file *seq = file->private_data;
    struct ocfs2_dlm_seq_priv *priv = seq->private;
    struct ocfs2_lock_res *res = &priv->p_iter_res;

    ocfs2_remove_lockres_tracking(res);
    ocfs2_put_dlm_debug(priv->p_dlm_debug);
    return seq_release_private(inode, file);
}

static int ocfs2_dlm_debug_open(struct inode *inode, struct file *file)
{
    int ret;
    struct ocfs2_dlm_seq_priv *priv;
    struct seq_file *seq;
    struct ocfs2_super *osb;

    priv = kzalloc(sizeof(struct ocfs2_dlm_seq_priv), GFP_KERNEL);
    if (!priv) {
        ret = -ENOMEM;
        mlog_errno(ret);
        goto out;
    }
    osb = inode->i_private;
    ocfs2_get_dlm_debug(osb->osb_dlm_debug);
    priv->p_dlm_debug = osb->osb_dlm_debug;
    INIT_LIST_HEAD(&priv->p_iter_res.l_debug_list);

    ret = seq_open(file, &ocfs2_dlm_seq_ops);
    if (ret) {
        kfree(priv);
        mlog_errno(ret);
        goto out;
    }

    seq = file->private_data;
    seq->private = priv;

    ocfs2_add_lockres_tracking(&priv->p_iter_res,
                   priv->p_dlm_debug);

out:
    return ret;
}

static const struct file_operations ocfs2_dlm_debug_fops = {
    .open =     ocfs2_dlm_debug_open,
    .release =  ocfs2_dlm_debug_release,
    .read =     seq_read,
    .llseek =   seq_lseek,
};

static int ocfs2_dlm_init_debug(struct ocfs2_super *osb)
{
    int ret = 0;
    struct ocfs2_dlm_debug *dlm_debug = osb->osb_dlm_debug;

    dlm_debug->d_locking_state = debugfs_create_file("locking_state",
                             S_IFREG|S_IRUSR,
                             osb->osb_debug_root,
                             osb,
                             &ocfs2_dlm_debug_fops);
    if (!dlm_debug->d_locking_state) {
        ret = -EINVAL;
        mlog(ML_ERROR,
             "Unable to create locking state debugfs file.\n");
        goto out;
    }

    ocfs2_get_dlm_debug(dlm_debug);
out:
    return ret;
}

static void ocfs2_dlm_shutdown_debug(struct ocfs2_super *osb)
{
    struct ocfs2_dlm_debug *dlm_debug = osb->osb_dlm_debug;

    if (dlm_debug) {
        debugfs_remove(dlm_debug->d_locking_state);
        ocfs2_put_dlm_debug(dlm_debug);
    }
}

int ocfs2_dlm_init(struct ocfs2_super *osb)
{
    int status = 0;
    struct ocfs2_cluster_connection *conn = NULL;

    if (ocfs2_mount_local(osb)) {
        osb->node_num = 0;
        goto local;
    }

    status = ocfs2_dlm_init_debug(osb);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }

    /* launch downconvert thread */
    osb->dc_task = kthread_run(ocfs2_downconvert_thread, osb, "ocfs2dc");
    if (IS_ERR(osb->dc_task)) {
        status = PTR_ERR(osb->dc_task);
        osb->dc_task = NULL;
        mlog_errno(status);
        goto bail;
    }

    /* for now, uuid == domain */
    status = ocfs2_cluster_connect(osb->osb_cluster_stack,
                       osb->uuid_str,
                       strlen(osb->uuid_str),
                       &lproto, ocfs2_do_node_down, osb,
                       &conn);
    if (status) {
        mlog_errno(status);
        goto bail;
    }

    status = ocfs2_cluster_this_node(&osb->node_num);
    if (status < 0) {
        mlog_errno(status);
        mlog(ML_ERROR,
             "could not find this host's node number\n");
        ocfs2_cluster_disconnect(conn, 0);
        goto bail;
    }

local:
    ocfs2_super_lock_res_init(&osb->osb_super_lockres, osb);
    ocfs2_rename_lock_res_init(&osb->osb_rename_lockres, osb);
    ocfs2_nfs_sync_lock_res_init(&osb->osb_nfs_sync_lockres, osb);
    ocfs2_orphan_scan_lock_res_init(&osb->osb_orphan_scan.os_lockres, osb);

    osb->cconn = conn;

    status = 0;
bail:
    if (status < 0) {
        ocfs2_dlm_shutdown_debug(osb);
        if (osb->dc_task)
            kthread_stop(osb->dc_task);
    }

    return status;
}

void ocfs2_dlm_shutdown(struct ocfs2_super *osb,
            int hangup_pending)
{
    ocfs2_drop_osb_locks(osb);

    /*
     * Now that we have dropped all locks and ocfs2_dismount_volume()
     * has disabled recovery, the DLM won't be talking to us.  It's
     * safe to tear things down before disconnecting the cluster.
     */

    if (osb->dc_task) {
        kthread_stop(osb->dc_task);
        osb->dc_task = NULL;
    }

    ocfs2_lock_res_free(&osb->osb_super_lockres);
    ocfs2_lock_res_free(&osb->osb_rename_lockres);
    ocfs2_lock_res_free(&osb->osb_nfs_sync_lockres);
    ocfs2_lock_res_free(&osb->osb_orphan_scan.os_lockres);

    ocfs2_cluster_disconnect(osb->cconn, hangup_pending);
    osb->cconn = NULL;

    ocfs2_dlm_shutdown_debug(osb);
}

static int ocfs2_drop_lock(struct ocfs2_super *osb,
               struct ocfs2_lock_res *lockres)
{
    int ret;
    unsigned long flags;
    u32 lkm_flags = 0;

    /* We didn't get anywhere near actually using this lockres. */
    if (!(lockres->l_flags & OCFS2_LOCK_INITIALIZED))
        goto out;

    if (lockres->l_ops->flags & LOCK_TYPE_USES_LVB)
        lkm_flags |= DLM_LKF_VALBLK;

    spin_lock_irqsave(&lockres->l_lock, flags);

    mlog_bug_on_msg(!(lockres->l_flags & OCFS2_LOCK_FREEING),
            "lockres %s, flags 0x%lx\n",
            lockres->l_name, lockres->l_flags);

    while (lockres->l_flags & OCFS2_LOCK_BUSY) {
        mlog(0, "waiting on busy lock \"%s\": flags = %lx, action = "
             "%u, unlock_action = %u\n",
             lockres->l_name, lockres->l_flags, lockres->l_action,
             lockres->l_unlock_action);

        spin_unlock_irqrestore(&lockres->l_lock, flags);

        /* XXX: Today we just wait on any busy
         * locks... Perhaps we need to cancel converts in the
         * future? */
        ocfs2_wait_on_busy_lock(lockres);

        spin_lock_irqsave(&lockres->l_lock, flags);
    }

    if (lockres->l_ops->flags & LOCK_TYPE_USES_LVB) {
        if (lockres->l_flags & OCFS2_LOCK_ATTACHED &&
            lockres->l_level == DLM_LOCK_EX &&
            !(lockres->l_flags & OCFS2_LOCK_NEEDS_REFRESH))
            lockres->l_ops->set_lvb(lockres);
    }

    if (lockres->l_flags & OCFS2_LOCK_BUSY)
        mlog(ML_ERROR, "destroying busy lock: \"%s\"\n",
             lockres->l_name);
    if (lockres->l_flags & OCFS2_LOCK_BLOCKED)
        mlog(0, "destroying blocked lock: \"%s\"\n", lockres->l_name);

    if (!(lockres->l_flags & OCFS2_LOCK_ATTACHED)) {
        spin_unlock_irqrestore(&lockres->l_lock, flags);
        goto out;
    }

    lockres_clear_flags(lockres, OCFS2_LOCK_ATTACHED);

    /* make sure we never get here while waiting for an ast to
     * fire. */
    BUG_ON(lockres->l_action != OCFS2_AST_INVALID);

    /* is this necessary? */
    lockres_or_flags(lockres, OCFS2_LOCK_BUSY);
    lockres->l_unlock_action = OCFS2_UNLOCK_DROP_LOCK;
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    mlog(0, "lock %s\n", lockres->l_name);

    ret = ocfs2_dlm_unlock(osb->cconn, &lockres->l_lksb, lkm_flags);
    if (ret) {
        ocfs2_log_dlm_error("ocfs2_dlm_unlock", ret, lockres);
        mlog(ML_ERROR, "lockres flags: %lu\n", lockres->l_flags);
        ocfs2_dlm_dump_lksb(&lockres->l_lksb);
        BUG();
    }
    mlog(0, "lock %s, successful return from ocfs2_dlm_unlock\n",
         lockres->l_name);

    ocfs2_wait_on_busy_lock(lockres);
out:
    return 0;
}

/* Mark the lockres as being dropped. It will no longer be
 * queued if blocking, but we still may have to wait on it
 * being dequeued from the downconvert thread before we can consider
 * it safe to drop.
 *
 * You can *not* attempt to call cluster_lock on this lockres anymore. */
void ocfs2_mark_lockres_freeing(struct ocfs2_lock_res *lockres)
{
    int status;
    struct ocfs2_mask_waiter mw;
    unsigned long flags;

    ocfs2_init_mask_waiter(&mw);

    spin_lock_irqsave(&lockres->l_lock, flags);
    lockres->l_flags |= OCFS2_LOCK_FREEING;
    while (lockres->l_flags & OCFS2_LOCK_QUEUED) {
        lockres_add_mask_waiter(lockres, &mw, OCFS2_LOCK_QUEUED, 0);
        spin_unlock_irqrestore(&lockres->l_lock, flags);

        mlog(0, "Waiting on lockres %s\n", lockres->l_name);

        status = ocfs2_wait_for_mask(&mw);
        if (status)
            mlog_errno(status);

        spin_lock_irqsave(&lockres->l_lock, flags);
    }
    spin_unlock_irqrestore(&lockres->l_lock, flags);
}

void ocfs2_simple_drop_lockres(struct ocfs2_super *osb,
                   struct ocfs2_lock_res *lockres)
{
    int ret;

    ocfs2_mark_lockres_freeing(lockres);
    ret = ocfs2_drop_lock(osb, lockres);
    if (ret)
        mlog_errno(ret);
}

static void ocfs2_drop_osb_locks(struct ocfs2_super *osb)
{
    ocfs2_simple_drop_lockres(osb, &osb->osb_super_lockres);
    ocfs2_simple_drop_lockres(osb, &osb->osb_rename_lockres);
    ocfs2_simple_drop_lockres(osb, &osb->osb_nfs_sync_lockres);
    ocfs2_simple_drop_lockres(osb, &osb->osb_orphan_scan.os_lockres);
}

int ocfs2_drop_inode_locks(struct inode *inode)
{
    int status, err;

    /* No need to call ocfs2_mark_lockres_freeing here -
     * ocfs2_clear_inode has done it for us. */

    err = ocfs2_drop_lock(OCFS2_SB(inode->i_sb),
                  &OCFS2_I(inode)->ip_open_lockres);
    if (err < 0)
        mlog_errno(err);

    status = err;

    err = ocfs2_drop_lock(OCFS2_SB(inode->i_sb),
                  &OCFS2_I(inode)->ip_inode_lockres);
    if (err < 0)
        mlog_errno(err);
    if (err < 0 && !status)
        status = err;

    err = ocfs2_drop_lock(OCFS2_SB(inode->i_sb),
                  &OCFS2_I(inode)->ip_rw_lockres);
    if (err < 0)
        mlog_errno(err);
    if (err < 0 && !status)
        status = err;

    return status;
}

static unsigned int ocfs2_prepare_downconvert(struct ocfs2_lock_res *lockres,
                          int new_level)
{
    assert_spin_locked(&lockres->l_lock);

    BUG_ON(lockres->l_blocking <= DLM_LOCK_NL);

    if (lockres->l_level <= new_level) {
        mlog(ML_ERROR, "lockres %s, lvl %d <= %d, blcklst %d, mask %d, "
             "type %d, flags 0x%lx, hold %d %d, act %d %d, req %d, "
             "block %d, pgen %d\n", lockres->l_name, lockres->l_level,
             new_level, list_empty(&lockres->l_blocked_list),
             list_empty(&lockres->l_mask_waiters), lockres->l_type,
             lockres->l_flags, lockres->l_ro_holders,
             lockres->l_ex_holders, lockres->l_action,
             lockres->l_unlock_action, lockres->l_requested,
             lockres->l_blocking, lockres->l_pending_gen);
        BUG();
    }

    mlog(ML_BASTS, "lockres %s, level %d => %d, blocking %d\n",
         lockres->l_name, lockres->l_level, new_level, lockres->l_blocking);

    lockres->l_action = OCFS2_AST_DOWNCONVERT;
    lockres->l_requested = new_level;
    lockres_or_flags(lockres, OCFS2_LOCK_BUSY);
    return lockres_set_pending(lockres);
}

static int ocfs2_downconvert_lock(struct ocfs2_super *osb,
                  struct ocfs2_lock_res *lockres,
                  int new_level,
                  int lvb,
                  unsigned int generation)
{
    int ret;
    u32 dlm_flags = DLM_LKF_CONVERT;

    mlog(ML_BASTS, "lockres %s, level %d => %d\n", lockres->l_name,
         lockres->l_level, new_level);

    if (lvb)
        dlm_flags |= DLM_LKF_VALBLK;

    ret = ocfs2_dlm_lock(osb->cconn,
                 new_level,
                 &lockres->l_lksb,
                 dlm_flags,
                 lockres->l_name,
                 OCFS2_LOCK_ID_MAX_LEN - 1);
    lockres_clear_pending(lockres, generation, osb);
    if (ret) {
        ocfs2_log_dlm_error("ocfs2_dlm_lock", ret, lockres);
        ocfs2_recover_from_dlm_error(lockres, 1);
        goto bail;
    }

    ret = 0;
bail:
    return ret;
}

/* returns 1 when the caller should unlock and call ocfs2_dlm_unlock */
static int ocfs2_prepare_cancel_convert(struct ocfs2_super *osb,
                        struct ocfs2_lock_res *lockres)
{
    assert_spin_locked(&lockres->l_lock);

    if (lockres->l_unlock_action == OCFS2_UNLOCK_CANCEL_CONVERT) {
        /* If we're already trying to cancel a lock conversion
         * then just drop the spinlock and allow the caller to
         * requeue this lock. */
        mlog(ML_BASTS, "lockres %s, skip convert\n", lockres->l_name);
        return 0;
    }

    /* were we in a convert when we got the bast fire? */
    BUG_ON(lockres->l_action != OCFS2_AST_CONVERT &&
           lockres->l_action != OCFS2_AST_DOWNCONVERT);
    /* set things up for the unlockast to know to just
     * clear out the ast_action and unset busy, etc. */
    lockres->l_unlock_action = OCFS2_UNLOCK_CANCEL_CONVERT;

    mlog_bug_on_msg(!(lockres->l_flags & OCFS2_LOCK_BUSY),
            "lock %s, invalid flags: 0x%lx\n",
            lockres->l_name, lockres->l_flags);

    mlog(ML_BASTS, "lockres %s\n", lockres->l_name);

    return 1;
}

static int ocfs2_cancel_convert(struct ocfs2_super *osb,
                struct ocfs2_lock_res *lockres)
{
    int ret;

    ret = ocfs2_dlm_unlock(osb->cconn, &lockres->l_lksb,
                   DLM_LKF_CANCEL);
    if (ret) {
        ocfs2_log_dlm_error("ocfs2_dlm_unlock", ret, lockres);
        ocfs2_recover_from_dlm_error(lockres, 0);
    }

    mlog(ML_BASTS, "lockres %s\n", lockres->l_name);

    return ret;
}

static int ocfs2_unblock_lock(struct ocfs2_super *osb,
                  struct ocfs2_lock_res *lockres,
                  struct ocfs2_unblock_ctl *ctl)
{
    unsigned long flags;
    int blocking;
    int new_level;
    int level;
    int ret = 0;
    int set_lvb = 0;
    unsigned int gen;

    spin_lock_irqsave(&lockres->l_lock, flags);

recheck:
    /*
     * Is it still blocking? If not, we have no more work to do.
     */
    if (!(lockres->l_flags & OCFS2_LOCK_BLOCKED)) {
        BUG_ON(lockres->l_blocking != DLM_LOCK_NL);
        spin_unlock_irqrestore(&lockres->l_lock, flags);
        ret = 0;
        goto leave;
    }

    if (lockres->l_flags & OCFS2_LOCK_BUSY) {
        /* XXX
         * This is a *big* race.  The OCFS2_LOCK_PENDING flag
         * exists entirely for one reason - another thread has set
         * OCFS2_LOCK_BUSY, but has *NOT* yet called dlm_lock().
         *
         * If we do ocfs2_cancel_convert() before the other thread
         * calls dlm_lock(), our cancel will do nothing.  We will
         * get no ast, and we will have no way of knowing the
         * cancel failed.  Meanwhile, the other thread will call
         * into dlm_lock() and wait...forever.
         *
         * Why forever?  Because another node has asked for the
         * lock first; that's why we're here in unblock_lock().
         *
         * The solution is OCFS2_LOCK_PENDING.  When PENDING is
         * set, we just requeue the unblock.  Only when the other
         * thread has called dlm_lock() and cleared PENDING will
         * we then cancel their request.
         *
         * All callers of dlm_lock() must set OCFS2_DLM_PENDING
         * at the same time they set OCFS2_DLM_BUSY.  They must
         * clear OCFS2_DLM_PENDING after dlm_lock() returns.
         */
        if (lockres->l_flags & OCFS2_LOCK_PENDING) {
            mlog(ML_BASTS, "lockres %s, ReQ: Pending\n",
                 lockres->l_name);
            goto leave_requeue;
        }

        ctl->requeue = 1;
        ret = ocfs2_prepare_cancel_convert(osb, lockres);
        spin_unlock_irqrestore(&lockres->l_lock, flags);
        if (ret) {
            ret = ocfs2_cancel_convert(osb, lockres);
            if (ret < 0)
                mlog_errno(ret);
        }
        goto leave;
    }

    /*
     * This prevents livelocks. OCFS2_LOCK_UPCONVERT_FINISHING flag is
     * set when the ast is received for an upconvert just before the
     * OCFS2_LOCK_BUSY flag is cleared. Now if the fs received a bast
     * on the heels of the ast, we want to delay the downconvert just
     * enough to allow the up requestor to do its task. Because this
     * lock is in the blocked queue, the lock will be downconverted
     * as soon as the requestor is done with the lock.
     */
    if (lockres->l_flags & OCFS2_LOCK_UPCONVERT_FINISHING)
        goto leave_requeue;

    /*
     * How can we block and yet be at NL?  We were trying to upconvert
     * from NL and got canceled.  The code comes back here, and now
     * we notice and clear BLOCKING.
     */
    if (lockres->l_level == DLM_LOCK_NL) {
        BUG_ON(lockres->l_ex_holders || lockres->l_ro_holders);
        mlog(ML_BASTS, "lockres %s, Aborting dc\n", lockres->l_name);
        lockres->l_blocking = DLM_LOCK_NL;
        lockres_clear_flags(lockres, OCFS2_LOCK_BLOCKED);
        spin_unlock_irqrestore(&lockres->l_lock, flags);
        goto leave;
    }

    /* if we're blocking an exclusive and we have *any* holders,
     * then requeue. */
    if ((lockres->l_blocking == DLM_LOCK_EX)
        && (lockres->l_ex_holders || lockres->l_ro_holders)) {
        mlog(ML_BASTS, "lockres %s, ReQ: EX/PR Holders %u,%u\n",
             lockres->l_name, lockres->l_ex_holders,
             lockres->l_ro_holders);
        goto leave_requeue;
    }

    /* If it's a PR we're blocking, then only
     * requeue if we've got any EX holders */
    if (lockres->l_blocking == DLM_LOCK_PR &&
        lockres->l_ex_holders) {
        mlog(ML_BASTS, "lockres %s, ReQ: EX Holders %u\n",
             lockres->l_name, lockres->l_ex_holders);
        goto leave_requeue;
    }

    /*
     * Can we get a lock in this state if the holder counts are
     * zero? The meta data unblock code used to check this.
     */
    if ((lockres->l_ops->flags & LOCK_TYPE_REQUIRES_REFRESH)
        && (lockres->l_flags & OCFS2_LOCK_REFRESHING)) {
        mlog(ML_BASTS, "lockres %s, ReQ: Lock Refreshing\n",
             lockres->l_name);
        goto leave_requeue;
    }

    new_level = ocfs2_highest_compat_lock_level(lockres->l_blocking);

    if (lockres->l_ops->check_downconvert
        && !lockres->l_ops->check_downconvert(lockres, new_level)) {
        mlog(ML_BASTS, "lockres %s, ReQ: Checkpointing\n",
             lockres->l_name);
        goto leave_requeue;
    }

    /* If we get here, then we know that there are no more
     * incompatible holders (and anyone asking for an incompatible
     * lock is blocked). We can now downconvert the lock */
    if (!lockres->l_ops->downconvert_worker)
        goto downconvert;

    /* Some lockres types want to do a bit of work before
     * downconverting a lock. Allow that here. The worker function
     * may sleep, so we save off a copy of what we're blocking as
     * it may change while we're not holding the spin lock. */
    blocking = lockres->l_blocking;
    level = lockres->l_level;
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    ctl->unblock_action = lockres->l_ops->downconvert_worker(lockres, blocking);

    if (ctl->unblock_action == UNBLOCK_STOP_POST) {
        mlog(ML_BASTS, "lockres %s, UNBLOCK_STOP_POST\n",
             lockres->l_name);
        goto leave;
    }

    spin_lock_irqsave(&lockres->l_lock, flags);
    if ((blocking != lockres->l_blocking) || (level != lockres->l_level)) {
        /* If this changed underneath us, then we can't drop
         * it just yet. */
        mlog(ML_BASTS, "lockres %s, block=%d:%d, level=%d:%d, "
             "Recheck\n", lockres->l_name, blocking,
             lockres->l_blocking, level, lockres->l_level);
        goto recheck;
    }

downconvert:
    ctl->requeue = 0;

    if (lockres->l_ops->flags & LOCK_TYPE_USES_LVB) {
        if (lockres->l_level == DLM_LOCK_EX)
            set_lvb = 1;

        /*
         * We only set the lvb if the lock has been fully
         * refreshed - otherwise we risk setting stale
         * data. Otherwise, there's no need to actually clear
         * out the lvb here as it's value is still valid.
         */
        if (set_lvb && !(lockres->l_flags & OCFS2_LOCK_NEEDS_REFRESH))
            lockres->l_ops->set_lvb(lockres);
    }

    gen = ocfs2_prepare_downconvert(lockres, new_level);
    spin_unlock_irqrestore(&lockres->l_lock, flags);
    ret = ocfs2_downconvert_lock(osb, lockres, new_level, set_lvb,
                     gen);

leave:
    if (ret)
        mlog_errno(ret);
    return ret;

leave_requeue:
    spin_unlock_irqrestore(&lockres->l_lock, flags);
    ctl->requeue = 1;

    return 0;
}

static int ocfs2_data_convert_worker(struct ocfs2_lock_res *lockres,
                     int blocking)
{
    struct inode *inode;
    struct address_space *mapping;
    struct ocfs2_inode_info *oi;

        inode = ocfs2_lock_res_inode(lockres);
    mapping = inode->i_mapping;

    if (S_ISDIR(inode->i_mode)) {
        oi = OCFS2_I(inode);
        oi->ip_dir_lock_gen++;
        mlog(0, "generation: %u\n", oi->ip_dir_lock_gen);
        goto out;
    }

    if (!S_ISREG(inode->i_mode))
        goto out;

    /*
     * We need this before the filemap_fdatawrite() so that it can
     * transfer the dirty bit from the PTE to the
     * page. Unfortunately this means that even for EX->PR
     * downconverts, we'll lose our mappings and have to build
     * them up again.
     */
    unmap_mapping_range(mapping, 0, 0, 0);

    if (filemap_fdatawrite(mapping)) {
        mlog(ML_ERROR, "Could not sync inode %llu for downconvert!",
             (unsigned long long)OCFS2_I(inode)->ip_blkno);
    }
    sync_mapping_buffers(mapping);
    if (blocking == DLM_LOCK_EX) {
        truncate_inode_pages(mapping, 0);
    } else {
        /* We only need to wait on the I/O if we're not also
         * truncating pages because truncate_inode_pages waits
         * for us above. We don't truncate pages if we're
         * blocking anything < EXMODE because we want to keep
         * them around in that case. */
        filemap_fdatawait(mapping);
    }

out:
    return UNBLOCK_CONTINUE;
}

static int ocfs2_ci_checkpointed(struct ocfs2_caching_info *ci,
                 struct ocfs2_lock_res *lockres,
                 int new_level)
{
    int checkpointed = ocfs2_ci_fully_checkpointed(ci);

    BUG_ON(new_level != DLM_LOCK_NL && new_level != DLM_LOCK_PR);
    BUG_ON(lockres->l_level != DLM_LOCK_EX && !checkpointed);

    if (checkpointed)
        return 1;

    ocfs2_start_checkpoint(OCFS2_SB(ocfs2_metadata_cache_get_super(ci)));
    return 0;
}

static int ocfs2_check_meta_downconvert(struct ocfs2_lock_res *lockres,
                    int new_level)
{
    struct inode *inode = ocfs2_lock_res_inode(lockres);

    return ocfs2_ci_checkpointed(INODE_CACHE(inode), lockres, new_level);
}

static void ocfs2_set_meta_lvb(struct ocfs2_lock_res *lockres)
{
    struct inode *inode = ocfs2_lock_res_inode(lockres);

    __ocfs2_stuff_meta_lvb(inode);
}

/*
 * Does the final reference drop on our dentry lock. Right now this
 * happens in the downconvert thread, but we could choose to simplify the
 * dlmglue API and push these off to the ocfs2_wq in the future.
 */
static void ocfs2_dentry_post_unlock(struct ocfs2_super *osb,
                     struct ocfs2_lock_res *lockres)
{
    struct ocfs2_dentry_lock *dl = ocfs2_lock_res_dl(lockres);
    ocfs2_dentry_lock_put(osb, dl);
}

/*
 * d_delete() matching dentries before the lock downconvert.
 *
 * At this point, any process waiting to destroy the
 * dentry_lock due to last ref count is stopped by the
 * OCFS2_LOCK_QUEUED flag.
 *
 * We have two potential problems
 *
 * 1) If we do the last reference drop on our dentry_lock (via dput)
 *    we'll wind up in ocfs2_release_dentry_lock(), waiting on
 *    the downconvert to finish. Instead we take an elevated
 *    reference and push the drop until after we've completed our
 *    unblock processing.
 *
 * 2) There might be another process with a final reference,
 *    waiting on us to finish processing. If this is the case, we
 *    detect it and exit out - there's no more dentries anyway.
 */
static int ocfs2_dentry_convert_worker(struct ocfs2_lock_res *lockres,
                       int blocking)
{
    struct ocfs2_dentry_lock *dl = ocfs2_lock_res_dl(lockres);
    struct ocfs2_inode_info *oi = OCFS2_I(dl->dl_inode);
    struct dentry *dentry;
    unsigned long flags;
    int extra_ref = 0;

    /*
     * This node is blocking another node from getting a read
     * lock. This happens when we've renamed within a
     * directory. We've forced the other nodes to d_delete(), but
     * we never actually dropped our lock because it's still
     * valid. The downconvert code will retain a PR for this node,
     * so there's no further work to do.
     */
    if (blocking == DLM_LOCK_PR)
        return UNBLOCK_CONTINUE;

    /*
     * Mark this inode as potentially orphaned. The code in
     * ocfs2_delete_inode() will figure out whether it actually
     * needs to be freed or not.
     */
    spin_lock(&oi->ip_lock);
    oi->ip_flags |= OCFS2_INODE_MAYBE_ORPHANED;
    spin_unlock(&oi->ip_lock);

    /*
     * Yuck. We need to make sure however that the check of
     * OCFS2_LOCK_FREEING and the extra reference are atomic with
     * respect to a reference decrement or the setting of that
     * flag.
     */
    spin_lock_irqsave(&lockres->l_lock, flags);
    spin_lock(&dentry_attach_lock);
    if (!(lockres->l_flags & OCFS2_LOCK_FREEING)
        && dl->dl_count) {
        dl->dl_count++;
        extra_ref = 1;
    }
    spin_unlock(&dentry_attach_lock);
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    mlog(0, "extra_ref = %d\n", extra_ref);

    /*
     * We have a process waiting on us in ocfs2_dentry_iput(),
     * which means we can't have any more outstanding
     * aliases. There's no need to do any more work.
     */
    if (!extra_ref)
        return UNBLOCK_CONTINUE;

    spin_lock(&dentry_attach_lock);
    while (1) {
        dentry = ocfs2_find_local_alias(dl->dl_inode,
                        dl->dl_parent_blkno, 1);
        if (!dentry)
            break;
        spin_unlock(&dentry_attach_lock);

        mlog(0, "d_delete(%.*s);\n", dentry->d_name.len,
             dentry->d_name.name);

        /*
         * The following dcache calls may do an
         * iput(). Normally we don't want that from the
         * downconverting thread, but in this case it's ok
         * because the requesting node already has an
         * exclusive lock on the inode, so it can't be queued
         * for a downconvert.
         */
        d_delete(dentry);
        dput(dentry);

        spin_lock(&dentry_attach_lock);
    }
    spin_unlock(&dentry_attach_lock);

    /*
     * If we are the last holder of this dentry lock, there is no
     * reason to downconvert so skip straight to the unlock.
     */
    if (dl->dl_count == 1)
        return UNBLOCK_STOP_POST;

    return UNBLOCK_CONTINUE_POST;
}

static int ocfs2_check_refcount_downconvert(struct ocfs2_lock_res *lockres,
                        int new_level)
{
    struct ocfs2_refcount_tree *tree =
                ocfs2_lock_res_refcount_tree(lockres);

    return ocfs2_ci_checkpointed(&tree->rf_ci, lockres, new_level);
}

static int ocfs2_refcount_convert_worker(struct ocfs2_lock_res *lockres,
                     int blocking)
{
    struct ocfs2_refcount_tree *tree =
                ocfs2_lock_res_refcount_tree(lockres);

    ocfs2_metadata_cache_purge(&tree->rf_ci);

    return UNBLOCK_CONTINUE;
}

static void ocfs2_set_qinfo_lvb(struct ocfs2_lock_res *lockres)
{
    struct ocfs2_qinfo_lvb *lvb;
    struct ocfs2_mem_dqinfo *oinfo = ocfs2_lock_res_qinfo(lockres);
    struct mem_dqinfo *info = sb_dqinfo(oinfo->dqi_gi.dqi_sb,
                        oinfo->dqi_gi.dqi_type);

    lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
    lvb->lvb_version = OCFS2_QINFO_LVB_VERSION;
    lvb->lvb_bgrace = cpu_to_be32(info->dqi_bgrace);
    lvb->lvb_igrace = cpu_to_be32(info->dqi_igrace);
    lvb->lvb_syncms = cpu_to_be32(oinfo->dqi_syncms);
    lvb->lvb_blocks = cpu_to_be32(oinfo->dqi_gi.dqi_blocks);
    lvb->lvb_free_blk = cpu_to_be32(oinfo->dqi_gi.dqi_free_blk);
    lvb->lvb_free_entry = cpu_to_be32(oinfo->dqi_gi.dqi_free_entry);
}

void ocfs2_qinfo_unlock(struct ocfs2_mem_dqinfo *oinfo, int ex)
{
    struct ocfs2_lock_res *lockres = &oinfo->dqi_gqlock;
    struct ocfs2_super *osb = OCFS2_SB(oinfo->dqi_gi.dqi_sb);
    int level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;

    if (!ocfs2_is_hard_readonly(osb) && !ocfs2_mount_local(osb))
        ocfs2_cluster_unlock(osb, lockres, level);
}

static int ocfs2_refresh_qinfo(struct ocfs2_mem_dqinfo *oinfo)
{
    struct mem_dqinfo *info = sb_dqinfo(oinfo->dqi_gi.dqi_sb,
                        oinfo->dqi_gi.dqi_type);
    struct ocfs2_lock_res *lockres = &oinfo->dqi_gqlock;
    struct ocfs2_qinfo_lvb *lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
    struct buffer_head *bh = NULL;
    struct ocfs2_global_disk_dqinfo *gdinfo;
    int status = 0;

    if (ocfs2_dlm_lvb_valid(&lockres->l_lksb) &&
        lvb->lvb_version == OCFS2_QINFO_LVB_VERSION) {
        info->dqi_bgrace = be32_to_cpu(lvb->lvb_bgrace);
        info->dqi_igrace = be32_to_cpu(lvb->lvb_igrace);
        oinfo->dqi_syncms = be32_to_cpu(lvb->lvb_syncms);
        oinfo->dqi_gi.dqi_blocks = be32_to_cpu(lvb->lvb_blocks);
        oinfo->dqi_gi.dqi_free_blk = be32_to_cpu(lvb->lvb_free_blk);
        oinfo->dqi_gi.dqi_free_entry =
                    be32_to_cpu(lvb->lvb_free_entry);
    } else {
        status = ocfs2_read_quota_phys_block(oinfo->dqi_gqinode,
                             oinfo->dqi_giblk, &bh);
        if (status) {
            mlog_errno(status);
            goto bail;
        }
        gdinfo = (struct ocfs2_global_disk_dqinfo *)
                    (bh->b_data + OCFS2_GLOBAL_INFO_OFF);
        info->dqi_bgrace = le32_to_cpu(gdinfo->dqi_bgrace);
        info->dqi_igrace = le32_to_cpu(gdinfo->dqi_igrace);
        oinfo->dqi_syncms = le32_to_cpu(gdinfo->dqi_syncms);
        oinfo->dqi_gi.dqi_blocks = le32_to_cpu(gdinfo->dqi_blocks);
        oinfo->dqi_gi.dqi_free_blk = le32_to_cpu(gdinfo->dqi_free_blk);
        oinfo->dqi_gi.dqi_free_entry =
                    le32_to_cpu(gdinfo->dqi_free_entry);
        brelse(bh);
        ocfs2_track_lock_refresh(lockres);
    }

bail:
    return status;
}

/* Lock quota info, this function expects at least shared lock on the quota file
 * so that we can safely refresh quota info from disk. */
int ocfs2_qinfo_lock(struct ocfs2_mem_dqinfo *oinfo, int ex)
{
    struct ocfs2_lock_res *lockres = &oinfo->dqi_gqlock;
    struct ocfs2_super *osb = OCFS2_SB(oinfo->dqi_gi.dqi_sb);
    int level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    int status = 0;

    /* On RO devices, locking really isn't needed... */
    if (ocfs2_is_hard_readonly(osb)) {
        if (ex)
            status = -EROFS;
        goto bail;
    }
    if (ocfs2_mount_local(osb))
        goto bail;

    status = ocfs2_cluster_lock(osb, lockres, level, 0, 0);
    if (status < 0) {
        mlog_errno(status);
        goto bail;
    }
    if (!ocfs2_should_refresh_lock_res(lockres))
        goto bail;
    /* OK, we have the lock but we need to refresh the quota info */
    status = ocfs2_refresh_qinfo(oinfo);
    if (status)
        ocfs2_qinfo_unlock(oinfo, ex);
    ocfs2_complete_lock_res_refresh(lockres, status);
bail:
    return status;
}

int ocfs2_refcount_lock(struct ocfs2_refcount_tree *ref_tree, int ex)
{
    int status;
    int level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    struct ocfs2_lock_res *lockres = &ref_tree->rf_lockres;
    struct ocfs2_super *osb = lockres->l_priv;


    if (ocfs2_is_hard_readonly(osb))
        return -EROFS;

    if (ocfs2_mount_local(osb))
        return 0;

    status = ocfs2_cluster_lock(osb, lockres, level, 0, 0);
    if (status < 0)
        mlog_errno(status);

    return status;
}

void ocfs2_refcount_unlock(struct ocfs2_refcount_tree *ref_tree, int ex)
{
    int level = ex ? DLM_LOCK_EX : DLM_LOCK_PR;
    struct ocfs2_lock_res *lockres = &ref_tree->rf_lockres;
    struct ocfs2_super *osb = lockres->l_priv;

    if (!ocfs2_mount_local(osb))
        ocfs2_cluster_unlock(osb, lockres, level);
}

static void ocfs2_process_blocked_lock(struct ocfs2_super *osb,
                       struct ocfs2_lock_res *lockres)
{
    int status;
    struct ocfs2_unblock_ctl ctl = {0, 0,};
    unsigned long flags;

    /* Our reference to the lockres in this function can be
     * considered valid until we remove the OCFS2_LOCK_QUEUED
     * flag. */

    BUG_ON(!lockres);
    BUG_ON(!lockres->l_ops);

    mlog(ML_BASTS, "lockres %s blocked\n", lockres->l_name);

    /* Detect whether a lock has been marked as going away while
     * the downconvert thread was processing other things. A lock can
     * still be marked with OCFS2_LOCK_FREEING after this check,
     * but short circuiting here will still save us some
     * performance. */
    spin_lock_irqsave(&lockres->l_lock, flags);
    if (lockres->l_flags & OCFS2_LOCK_FREEING)
        goto unqueue;
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    status = ocfs2_unblock_lock(osb, lockres, &ctl);
    if (status < 0)
        mlog_errno(status);

    spin_lock_irqsave(&lockres->l_lock, flags);
unqueue:
    if (lockres->l_flags & OCFS2_LOCK_FREEING || !ctl.requeue) {
        lockres_clear_flags(lockres, OCFS2_LOCK_QUEUED);
    } else
        ocfs2_schedule_blocked_lock(osb, lockres);

    mlog(ML_BASTS, "lockres %s, requeue = %s.\n", lockres->l_name,
         ctl.requeue ? "yes" : "no");
    spin_unlock_irqrestore(&lockres->l_lock, flags);

    if (ctl.unblock_action != UNBLOCK_CONTINUE
        && lockres->l_ops->post_unlock)
        lockres->l_ops->post_unlock(osb, lockres);
}

static void ocfs2_schedule_blocked_lock(struct ocfs2_super *osb,
                    struct ocfs2_lock_res *lockres)
{
    unsigned long flags;

    assert_spin_locked(&lockres->l_lock);

    if (lockres->l_flags & OCFS2_LOCK_FREEING) {
        /* Do not schedule a lock for downconvert when it's on
         * the way to destruction - any nodes wanting access
         * to the resource will get it soon. */
        mlog(ML_BASTS, "lockres %s won't be scheduled: flags 0x%lx\n",
             lockres->l_name, lockres->l_flags);
        return;
    }

    lockres_or_flags(lockres, OCFS2_LOCK_QUEUED);

    spin_lock_irqsave(&osb->dc_task_lock, flags);
    if (list_empty(&lockres->l_blocked_list)) {
        list_add_tail(&lockres->l_blocked_list,
                  &osb->blocked_lock_list);
        osb->blocked_lock_count++;
    }
    spin_unlock_irqrestore(&osb->dc_task_lock, flags);
}

static void ocfs2_downconvert_thread_do_work(struct ocfs2_super *osb)
{
    unsigned long processed;
    unsigned long flags;
    struct ocfs2_lock_res *lockres;

    spin_lock_irqsave(&osb->dc_task_lock, flags);
    /* grab this early so we know to try again if a state change and
     * wake happens part-way through our work  */
    osb->dc_work_sequence = osb->dc_wake_sequence;

    processed = osb->blocked_lock_count;
    while (processed) {
        BUG_ON(list_empty(&osb->blocked_lock_list));

        lockres = list_entry(osb->blocked_lock_list.next,
                     struct ocfs2_lock_res, l_blocked_list);
        list_del_init(&lockres->l_blocked_list);
        osb->blocked_lock_count--;
        spin_unlock_irqrestore(&osb->dc_task_lock, flags);

        BUG_ON(!processed);
        processed--;

        ocfs2_process_blocked_lock(osb, lockres);

        spin_lock_irqsave(&osb->dc_task_lock, flags);
    }
    spin_unlock_irqrestore(&osb->dc_task_lock, flags);
}

static int ocfs2_downconvert_thread_lists_empty(struct ocfs2_super *osb)
{
    int empty = 0;
    unsigned long flags;

    spin_lock_irqsave(&osb->dc_task_lock, flags);
    if (list_empty(&osb->blocked_lock_list))
        empty = 1;

    spin_unlock_irqrestore(&osb->dc_task_lock, flags);
    return empty;
}

static int ocfs2_downconvert_thread_should_wake(struct ocfs2_super *osb)
{
    int should_wake = 0;
    unsigned long flags;

    spin_lock_irqsave(&osb->dc_task_lock, flags);
    if (osb->dc_work_sequence != osb->dc_wake_sequence)
        should_wake = 1;
    spin_unlock_irqrestore(&osb->dc_task_lock, flags);

    return should_wake;
}

static int ocfs2_downconvert_thread(void *arg)
{
    int status = 0;
    struct ocfs2_super *osb = arg;

    /* only quit once we've been asked to stop and there is no more
     * work available */
    while (!(kthread_should_stop() &&
        ocfs2_downconvert_thread_lists_empty(osb))) {

        wait_event_interruptible(osb->dc_event,
                     ocfs2_downconvert_thread_should_wake(osb) ||
                     kthread_should_stop());

        mlog(0, "downconvert_thread: awoken\n");

        ocfs2_downconvert_thread_do_work(osb);
    }

    osb->dc_task = NULL;
    return status;
}

void ocfs2_wake_downconvert_thread(struct ocfs2_super *osb)
{
    unsigned long flags;

    spin_lock_irqsave(&osb->dc_task_lock, flags);
    /* make sure the voting thread gets a swipe at whatever changes
     * the caller may have made to the voting state */
    osb->dc_wake_sequence++;
    spin_unlock_irqrestore(&osb->dc_task_lock, flags);
    wake_up(&osb->dc_event);
}