[linux-2.6-omap-h63xx.git] / fs / ocfs2 / dlmglue.c

/* -*- 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>

#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 "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
        unsigned long long      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);

/*
 * 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;
};

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);


#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 =
                (struct ocfs2_meta_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_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 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 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_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);
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 {                 \
        mlog(ML_ERROR, "DLM error %d while calling %s on resource %s\n", \
             _err, _func, _lockres->l_name);                            \
} 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;

        mlog_entry_void();

        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);

        mlog_exit_void();
}

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_num_prmode = 0;
        res->l_lock_num_prmode_failed = 0;
        res->l_lock_total_prmode = 0;
        res->l_lock_max_prmode = 0;
        res->l_lock_num_exmode = 0;
        res->l_lock_num_exmode_failed = 0;
        res->l_lock_total_exmode = 0;
        res->l_lock_max_exmode = 0;
        res->l_lock_refresh = 0;
}

static void ocfs2_update_lock_stats(struct ocfs2_lock_res *res, int level,
                                    struct ocfs2_mask_waiter *mw, int ret)
{
        unsigned long long *num, *sum;
        unsigned int *max, *failed;
        struct timespec ts = current_kernel_time();
        unsigned long long time = timespec_to_ns(&ts) - mw->mw_lock_start;

        if (level == LKM_PRMODE) {
                num = &res->l_lock_num_prmode;
                sum = &res->l_lock_total_prmode;
                max = &res->l_lock_max_prmode;
                failed = &res->l_lock_num_prmode_failed;
        } else if (level == LKM_EXMODE) {
                num = &res->l_lock_num_exmode;
                sum = &res->l_lock_total_exmode;
                max = &res->l_lock_max_exmode;
                failed = &res->l_lock_num_exmode_failed;
        } else
                return;

        (*num)++;
        (*sum) += time;
        if (time > *max)
                *max = time;
        if (ret)
                (*failed)++;
}

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)
{
        struct timespec ts = current_kernel_time();
        mw->mw_lock_start = timespec_to_ns(&ts);
}
#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);
}

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_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);
}

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_lock_res_free(struct ocfs2_lock_res *res)
{
        mlog_entry_void();

        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;
        mlog_exit_void();
}

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

        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();
        }

        mlog_exit_void();
}

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

        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();
        }
        mlog_exit_void();
}

/* 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)
{
        mlog_entry_void();

        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);

        mlog_exit_void();
}

static inline void ocfs2_generic_handle_convert_action(struct ocfs2_lock_res *lockres)
{
        mlog_entry_void();

        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;
        lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);

        mlog_exit_void();
}

static inline void ocfs2_generic_handle_attach_action(struct ocfs2_lock_res *lockres)
{
        mlog_entry_void();

        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);

        mlog_exit_void();
}

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

        assert_spin_locked(&lockres->l_lock);

        lockres_or_flags(lockres, OCFS2_LOCK_BLOCKED);

        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_exit(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(void *opaque, int level)
{
        struct ocfs2_lock_res *lockres = opaque;
        struct ocfs2_super *osb = ocfs2_get_lockres_osb(lockres);
        int needs_downconvert;
        unsigned long flags;

        BUG_ON(level <= DLM_LOCK_NL);

        mlog(0, "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(void *opaque)
{
        struct ocfs2_lock_res *lockres = opaque;
        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;
        }

        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 "
                     "lockres flags = 0x%lx, unlock action: %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 inline void ocfs2_recover_from_dlm_error(struct ocfs2_lock_res *lockres,
                                                int convert)
{
        unsigned long flags;

        mlog_entry_void();
        spin_lock_irqsave(&lockres->l_lock, flags);
        lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
        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);
        mlog_exit_void();
}

/* 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_entry_void();

        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);
        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:
        mlog_exit(ret);
        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)
{
        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;

        mlog_entry_void();

        ocfs2_init_mask_waiter(&mw);

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

again:
        wait = 0;

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

        spin_lock_irqsave(&lockres->l_lock, flags);

        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_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(0, "lock %s, convert from %d to level = %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);
                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, successfull 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;
        }

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

        ret = 0;
unlock:
        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);

        mlog_exit(ret);
        return ret;
}

static void ocfs2_cluster_unlock(struct ocfs2_super *osb,
                                 struct ocfs2_lock_res *lockres,
                                 int level)
{
        unsigned long flags;

        mlog_entry_void();
        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);
        mlog_exit_void();
}

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_entry_void();

        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:
        mlog_exit(ret);
        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_entry_void();

        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);

        mlog_exit(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_entry_void();

        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);

        mlog_exit_void();
}

/*
 * 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_entry_void();

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

        if (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:
        mlog_exit(status);
        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_entry_void();

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

        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:
        mlog_exit(status);
        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_entry_void();

        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:
        mlog_exit_void();
}

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
 * seperate 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,
                             lockres);
        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 sucess 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;

        mlog_entry_void();

        /* 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);

        mlog_exit_void();
}

#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;

        mlog_entry_void();

        lvb = (struct ocfs2_meta_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);

        mlog_exit_void();
}

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_entry_void();

        mlog_meta_lvb(0, lockres);

        lvb = (struct ocfs2_meta_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);
        inode->i_nlink   = 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);

        mlog_exit_void();
}

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

        if (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;

        mlog_entry_void();

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_exit(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;
        mlog_entry_void();

        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);

        mlog_exit_void();
}

/* 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);

        mlog_entry_void();

        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);

        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_block(OCFS2_SB(inode->i_sb), oi->ip_blkno,
                                          bh, OCFS2_BH_CACHED, inode);
                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.
                 *
                 * 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. */
                if (!OCFS2_IS_VALID_DINODE(fe)) {
                        OCFS2_RO_ON_INVALID_DINODE(inode->i_sb, fe);
                        status = -EIO;
                        goto bail_refresh;
                }
                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:
        mlog_exit(status);
        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_block(OCFS2_SB(inode->i_sb),
                                  OCFS2_I(inode)->ip_blkno,
                                  ret_bh,
                                  OCFS2_BH_CACHED,
                                  inode);
        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(struct inode *inode,
                         struct buffer_head **ret_bh,
                         int ex,
                         int arg_flags)
{
        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_entry_void();

        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 bail;
        }

        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);
        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;
        }

        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);

        mlog_exit(status);
        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;

        mlog_entry_void();
        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;

        mlog_exit(ret);
        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_entry_void();

        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);

        mlog_exit_void();
}

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;

        mlog_entry_void();

        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:
        mlog_exit(status);
        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_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))
                return -EROFS;

        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_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;
}

/* So that debugfs.ocfs2 can determine which format is being used */
#define OCFS2_DLM_DEBUG_STR_VERSION 2
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_num_prmode
# define lock_num_exmode(_l)            (_l)->l_lock_num_exmode
# define lock_num_prmode_failed(_l)     (_l)->l_lock_num_prmode_failed
# define lock_num_exmode_failed(_l)     (_l)->l_lock_num_exmode_failed
# define lock_total_prmode(_l)          (_l)->l_lock_total_prmode
# define lock_total_exmode(_l)          (_l)->l_lock_total_exmode
# define lock_max_prmode(_l)            (_l)->l_lock_max_prmode
# define lock_max_exmode(_l)            (_l)->l_lock_max_exmode
# 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)          (0)
# define lock_total_exmode(_l)          (0)
# 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, "%llu\t"
                   "%llu\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 = (struct seq_file *) 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 = (struct seq_file *) 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;

        mlog_entry_void();

        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),
                                       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);

        osb->cconn = conn;

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

        mlog_exit(status);
        return status;
}

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

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

        ocfs2_dlm_shutdown_debug(osb);

        mlog_exit_void();
}

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

        mlog_entry_void();

        mlog(0, "UNLOCK AST called on lock %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;
                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;
        spin_unlock_irqrestore(&lockres->l_lock, flags);

        wake_up(&lockres->l_event);

        mlog_exit_void();
}

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,
                               lockres);
        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, successfull return from ocfs2_dlm_unlock\n",
             lockres->l_name);

        ocfs2_wait_on_busy_lock(lockres);
out:
        mlog_exit(0);
        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);
}

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

        mlog_entry_void();

        /* 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;

        mlog_exit(status);
        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->l_level (%d) <= new_level (%d)\n",
                     lockres->l_level, new_level);
                BUG();
        }

        mlog(0, "lock %s, new_level = %d, l_blocking = %d\n",
             lockres->l_name, 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_entry_void();

        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);
        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:
        mlog_exit(ret);
        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);

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

        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(0, "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);

        return 1;
}

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

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

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

        mlog(0, "lock %s return from ocfs2_dlm_unlock\n", lockres->l_name);

        mlog_exit(ret);
        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 ret = 0;
        int set_lvb = 0;
        unsigned int gen;

        mlog_entry_void();

        spin_lock_irqsave(&lockres->l_lock, flags);

        BUG_ON(!(lockres->l_flags & OCFS2_LOCK_BLOCKED));

recheck:
        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)
                        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;
        }

        /* 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))
                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)
                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))
                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))
                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;
        spin_unlock_irqrestore(&lockres->l_lock, flags);

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

        if (ctl->unblock_action == UNBLOCK_STOP_POST)
                goto leave;

        spin_lock_irqsave(&lockres->l_lock, flags);
        if (blocking != lockres->l_blocking) {
                /* If this changed underneath us, then we can't drop
                 * it just yet. */
                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:
        mlog_exit(ret);
        return ret;

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

        mlog_exit(0);
        return 0;
}

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

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

        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_check_meta_downconvert(struct ocfs2_lock_res *lockres,
                                        int new_level)
{
        struct inode *inode = ocfs2_lock_res_inode(lockres);
        int checkpointed = ocfs2_inode_fully_checkpointed(inode);

        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(inode->i_sb));
        return 0;
}

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;
}

/*
 * 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_locking_protocol(&lproto);
}


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. */

        mlog_entry_void();

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

        mlog(0, "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(0, "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);

        mlog_exit_void();
}

static void ocfs2_schedule_blocked_lock(struct ocfs2_super *osb,
                                        struct ocfs2_lock_res *lockres)
{
        mlog_entry_void();

        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(0, "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(&osb->dc_task_lock);
        if (list_empty(&lockres->l_blocked_list)) {
                list_add_tail(&lockres->l_blocked_list,
                              &osb->blocked_lock_list);
                osb->blocked_lock_count++;
        }
        spin_unlock(&osb->dc_task_lock);

        mlog_exit_void();
}

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

        mlog_entry_void();

        spin_lock(&osb->dc_task_lock);
        /* 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(&osb->dc_task_lock);

                BUG_ON(!processed);
                processed--;

                ocfs2_process_blocked_lock(osb, lockres);

                spin_lock(&osb->dc_task_lock);
        }
        spin_unlock(&osb->dc_task_lock);

        mlog_exit_void();
}

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

        spin_lock(&osb->dc_task_lock);
        if (list_empty(&osb->blocked_lock_list))
                empty = 1;

        spin_unlock(&osb->dc_task_lock);
        return empty;
}

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

        spin_lock(&osb->dc_task_lock);
        if (osb->dc_work_sequence != osb->dc_wake_sequence)
                should_wake = 1;
        spin_unlock(&osb->dc_task_lock);

        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)
{
        spin_lock(&osb->dc_task_lock);
        /* 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(&osb->dc_task_lock);
        wake_up(&osb->dc_event);
}