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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/crc32.h>
#include <linux/kthread.h>
#include <linux/pagemap.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>

#include <cluster/heartbeat.h>
#include <cluster/nodemanager.h>
#include <cluster/tcp.h>

#include <dlm/dlmapi.h>

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

#include "ocfs2.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 "slot_map.h"
#include "super.h"
#include "uptodate.h"
#include "vote.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;
};

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);

/*
 * 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 *) lockres->l_lksb.lvb;

      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 (or "vote") 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_meta_lops = {
      .get_osb    = ocfs2_get_inode_osb,
      .check_downconvert = ocfs2_check_meta_downconvert,
      .set_lvb    = ocfs2_set_meta_lvb,
      .flags            = LOCK_TYPE_REQUIRES_REFRESH|LOCK_TYPE_USES_LVB,
};

static struct ocfs2_lock_res_ops ocfs2_inode_data_lops = {
      .get_osb    = ocfs2_get_inode_osb,
      .downconvert_worker = ocfs2_data_convert_worker,
      .flags            = 0,
};

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 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_DATA ||
            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,
                       int 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, _stat, _lockres) do {    \
      mlog(ML_ERROR, "Dlm error \"%s\" while calling %s on "      \
            "resource %s: %s\n", dlm_errname(_stat), _func, \
            _lockres->l_name, dlm_errmsg(_stat));           \
} while (0)
static void ocfs2_vote_on_unlock(struct ocfs2_super *osb,
                         struct ocfs2_lock_res *lockres);
static int ocfs2_meta_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 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);
}

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         = LKM_IVMODE;
      res->l_requested     = LKM_IVMODE;
      res->l_blocking      = LKM_IVMODE;
      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);
}

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_meta_lops;
                  break;
            case OCFS2_LOCK_TYPE_DATA:
                  ops = &ocfs2_inode_data_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 __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_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 LKM_EXMODE:
            lockres->l_ex_holders++;
            break;
      case LKM_PRMODE:
            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 LKM_EXMODE:
            BUG_ON(!lockres->l_ex_holders);
            lockres->l_ex_holders--;
            break;
      case LKM_PRMODE:
            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 = LKM_EXMODE;

      if (level == LKM_EXMODE)
            new_level = LKM_NLMODE;
      else if (level == LKM_PRMODE)
            new_level = LKM_PRMODE;
      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 <= LKM_NLMODE);

      lockres->l_level = lockres->l_requested;
      if (lockres->l_level <=
          ocfs2_highest_compat_lock_level(lockres->l_blocking)) {
            lockres->l_blocking = LKM_NLMODE;
            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 == LKM_NLMODE &&
          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 > LKM_NLMODE &&
          !(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;
}

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 <= LKM_NLMODE);

      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));

      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_kick_vote_thread(osb);
}

static void ocfs2_locking_ast(void *opaque)
{
      struct ocfs2_lock_res *lockres = opaque;
      struct dlm_lockstatus *lksb = &lockres->l_lksb;
      unsigned long flags;

      spin_lock_irqsave(&lockres->l_lock, flags);

      if (lksb->status != DLM_NORMAL) {
            mlog(ML_ERROR, "lockres %s: lksb status value of %u!\n",
                 lockres->l_name, lksb->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();
      }

      /* set it to something invalid so if we get called again we
       * can catch it. */
      lockres->l_action = OCFS2_AST_INVALID;

      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,
                       int dlm_flags)
{
      int ret = 0;
      enum dlm_status status = DLM_NORMAL;
      unsigned long flags;

      mlog_entry_void();

      mlog(0, "lock %s, level = %d, flags = %d\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);
      spin_unlock_irqrestore(&lockres->l_lock, flags);

      status = dlmlock(osb->dlm,
                   level,
                   &lockres->l_lksb,
                   dlm_flags,
                   lockres->l_name,
                   OCFS2_LOCK_ID_MAX_LEN - 1,
                   ocfs2_locking_ast,
                   lockres,
                   ocfs2_blocking_ast);
      if (status != DLM_NORMAL) {
            ocfs2_log_dlm_error("dlmlock", status, lockres);
            ret = -EINVAL;
            ocfs2_recover_from_dlm_error(lockres, 1);
      }

      mlog(0, "lock %s, successfull return from dlmlock\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);
}

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_cluster_lock(struct ocfs2_super *osb,
                        struct ocfs2_lock_res *lockres,
                        int level,
                        int lkm_flags,
                        int arg_flags)
{
      struct ocfs2_mask_waiter mw;
      enum dlm_status status;
      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;

      mlog_entry_void();

      ocfs2_init_mask_waiter(&mw);

      if (lockres->l_ops->flags & LOCK_TYPE_USES_LVB)
            lkm_flags |= LKM_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 (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 &= ~LKM_CONVERT;
            } else {
                  lockres->l_action = OCFS2_AST_CONVERT;
                  lkm_flags |= LKM_CONVERT;
            }

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

            BUG_ON(level == LKM_IVMODE);
            BUG_ON(level == LKM_NLMODE);

            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 */
            status = dlmlock(osb->dlm,
                         level,
                         &lockres->l_lksb,
                         lkm_flags,
                         lockres->l_name,
                         OCFS2_LOCK_ID_MAX_LEN - 1,
                         ocfs2_locking_ast,
                         lockres,
                         ocfs2_blocking_ast);
            if (status != DLM_NORMAL) {
                  if ((lkm_flags & LKM_NOQUEUE) &&
                      (status == DLM_NOTQUEUED))
                        ret = -EAGAIN;
                  else {
                        ocfs2_log_dlm_error("dlmlock", status,
                                        lockres);
                        ret = -EINVAL;
                  }
                  ocfs2_recover_from_dlm_error(lockres, 1);
                  goto out;
            }

            mlog(0, "lock %s, successfull return from dlmlock\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);
      }

      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_vote_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 ? LKM_EXMODE : LKM_PRMODE;
      unsigned long flags;
      int lkm_flags = local ? LKM_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 LKM_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_meta_lockres, 1, 0);
      if (ret) {
            mlog_errno(ret);
            goto bail;
      }

      ret = ocfs2_create_new_lock(osb, &OCFS2_I(inode)->ip_data_lockres, 1, 1);
      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 ? LKM_EXMODE : LKM_PRMODE;

      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 ? LKM_EXMODE : LKM_PRMODE;
      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,
                            LKM_PRMODE, 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 ? LKM_EXMODE : LKM_PRMODE;

      /*
       * The file system may already holding a PRMODE/EXMODE open lock.
       * Since we pass LKM_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, LKM_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,
                             LKM_PRMODE);
      if(lockres->l_ex_holders)
            ocfs2_cluster_unlock(OCFS2_SB(inode->i_sb), lockres,
                             LKM_EXMODE);

out:
      mlog_exit_void();
}

int ocfs2_data_lock_full(struct inode *inode,
                   int write,
                   int arg_flags)
{
      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 take %s DATA lock\n",
           (unsigned long long)OCFS2_I(inode)->ip_blkno,
           write ? "EXMODE" : "PRMODE");

      /* We'll allow faking a readonly data lock for
       * rodevices. */
      if (ocfs2_is_hard_readonly(OCFS2_SB(inode->i_sb))) {
            if (write) {
                  status = -EROFS;
                  mlog_errno(status);
            }
            goto out;
      }

      if (ocfs2_mount_local(osb))
            goto out;

      lockres = &OCFS2_I(inode)->ip_data_lockres;

      level = write ? LKM_EXMODE : LKM_PRMODE;

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

out:
      mlog_exit(status);
      return status;
}

/* see ocfs2_meta_lock_with_page() */
int ocfs2_data_lock_with_page(struct inode *inode,
                        int write,
                        struct page *page)
{
      int ret;

      ret = ocfs2_data_lock_full(inode, write, OCFS2_LOCK_NONBLOCK);
      if (ret == -EAGAIN) {
            unlock_page(page);
            if (ocfs2_data_lock(inode, write) == 0)
                  ocfs2_data_unlock(inode, write);
            ret = AOP_TRUNCATED_PAGE;
      }

      return ret;
}

static void ocfs2_vote_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 vote thread * pre-emptively when we reach a release
       * condition. */
      if (lockres->l_flags & OCFS2_LOCK_BLOCKED) {
            switch(lockres->l_blocking) {
            case LKM_EXMODE:
                  if (!lockres->l_ex_holders && !lockres->l_ro_holders)
                        kick = 1;
                  break;
            case LKM_PRMODE:
                  if (!lockres->l_ex_holders)
                        kick = 1;
                  break;
            default:
                  BUG();
            }
      }

      if (kick)
            ocfs2_kick_vote_thread(osb);

      mlog_exit_void();
}

void ocfs2_data_unlock(struct inode *inode,
                   int write)
{
      int level = write ? LKM_EXMODE : LKM_PRMODE;
      struct ocfs2_lock_res *lockres = &OCFS2_I(inode)->ip_data_lockres;
      struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

      mlog_entry_void();

      mlog(0, "inode %llu drop %s DATA lock\n",
           (unsigned long long)OCFS2_I(inode)->ip_blkno,
           write ? "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();
}

#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_meta_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_meta_lockres;
      struct ocfs2_meta_lvb *lvb;

      mlog_entry_void();

      lvb = (struct ocfs2_meta_lvb *) lockres->l_lksb.lvb;

      /*
       * 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_meta_lockres;
      struct ocfs2_meta_lvb *lvb;

      mlog_entry_void();

      mlog_meta_lvb(0, lockres);

      lvb = (struct ocfs2_meta_lvb *) lockres->l_lksb.lvb;

      /* 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 *) lockres->l_lksb.lvb;

      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_meta_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_meta_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);
      }

      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_meta_lock_full(struct inode *inode,
                   struct buffer_head **ret_bh,
                   int ex,
                   int arg_flags)
{
      int status, level, dlm_flags, acquired;
      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))
            wait_event(osb->recovery_event,
                     ocfs2_node_map_is_empty(osb, &osb->recovery_map));

      lockres = &OCFS2_I(inode)->ip_meta_lockres;
      level = ex ? LKM_EXMODE : LKM_PRMODE;
      dlm_flags = 0;
      if (arg_flags & OCFS2_META_LOCK_NOQUEUE)
            dlm_flags |= LKM_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))
            wait_event(osb->recovery_event,
                     ocfs2_node_map_is_empty(osb, &osb->recovery_map));

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_meta_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_meta_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_meta_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 vote 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 vote thread.  In that case we unlock our page so the vote
 * 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_meta_lock_with_page(struct inode *inode,
                        struct buffer_head **ret_bh,
                        int ex,
                        struct page *page)
{
      int ret;

      ret = ocfs2_meta_lock_full(inode, ret_bh, ex, OCFS2_LOCK_NONBLOCK);
      if (ret == -EAGAIN) {
            unlock_page(page);
            if (ocfs2_meta_lock(inode, ret_bh, ex) == 0)
                  ocfs2_meta_unlock(inode, ex);
            ret = AOP_TRUNCATED_PAGE;
      }

      return ret;
}

int ocfs2_meta_lock_atime(struct inode *inode,
                    struct vfsmount *vfsmnt,
                    int *level)
{
      int ret;

      mlog_entry_void();
      ret = ocfs2_meta_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_meta_unlock(inode, 0);
            ret = ocfs2_meta_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_meta_unlock(struct inode *inode,
                   int ex)
{
      int level = ex ? LKM_EXMODE : LKM_PRMODE;
      struct ocfs2_lock_res *lockres = &OCFS2_I(inode)->ip_meta_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 ? LKM_EXMODE : LKM_PRMODE;
      struct ocfs2_lock_res *lockres = &osb->osb_super_lockres;
      struct buffer_head *bh;
      struct ocfs2_slot_info *si = osb->slot_info;

      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) {
            bh = si->si_bh;
            status = ocfs2_read_block(osb, bh->b_blocknr, &bh, 0,
                                si->si_inode);
            if (status == 0)
                  ocfs2_update_slot_info(si);

            ocfs2_complete_lock_res_refresh(lockres, status);

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

void ocfs2_super_unlock(struct ocfs2_super *osb,
                  int ex)
{
      int level = ex ? LKM_EXMODE : LKM_PRMODE;
      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, LKM_EXMODE, 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, LKM_EXMODE);
}

int ocfs2_dentry_lock(struct dentry *dentry, int ex)
{
      int ret;
      int level = ex ? LKM_EXMODE : LKM_PRMODE;
      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 ? LKM_EXMODE : LKM_PRMODE;
      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 1
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 = lockres->l_lksb.lvb;
      for(i = 0; i < DLM_LVB_LEN; i++)
            seq_printf(m, "0x%x\t", lvb[i]);

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

static 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;
      u32 dlm_key;
      struct dlm_ctxt *dlm = NULL;

      mlog_entry_void();

      if (ocfs2_mount_local(osb))
            goto local;

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

      /* launch vote thread */
      osb->vote_task = kthread_run(ocfs2_vote_thread, osb, "ocfs2vote");
      if (IS_ERR(osb->vote_task)) {
            status = PTR_ERR(osb->vote_task);
            osb->vote_task = NULL;
            mlog_errno(status);
            goto bail;
      }

      /* used by the dlm code to make message headers unique, each
       * node in this domain must agree on this. */
      dlm_key = crc32_le(0, osb->uuid_str, strlen(osb->uuid_str));

      /* for now, uuid == domain */
      dlm = dlm_register_domain(osb->uuid_str, dlm_key);
      if (IS_ERR(dlm)) {
            status = PTR_ERR(dlm);
            mlog_errno(status);
            goto bail;
      }

      dlm_register_eviction_cb(dlm, &osb->osb_eviction_cb);

local:
      ocfs2_super_lock_res_init(&osb->osb_super_lockres, osb);
      ocfs2_rename_lock_res_init(&osb->osb_rename_lockres, osb);

      osb->dlm = dlm;

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

      mlog_exit(status);
      return status;
}

void ocfs2_dlm_shutdown(struct ocfs2_super *osb)
{
      mlog_entry_void();

      dlm_unregister_eviction_cb(&osb->osb_eviction_cb);

      ocfs2_drop_osb_locks(osb);

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

      ocfs2_lock_res_free(&osb->osb_super_lockres);
      ocfs2_lock_res_free(&osb->osb_rename_lockres);

      dlm_unregister_domain(osb->dlm);
      osb->dlm = NULL;

      ocfs2_dlm_shutdown_debug(osb);

      mlog_exit_void();
}

static void ocfs2_unlock_ast(void *opaque, enum dlm_status status)
{
      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);
      /* We tried to cancel a convert request, but it was already
       * granted. All we want to do here is clear our unlock
       * state. The wake_up call done at the bottom is redundant
       * (ocfs2_prepare_cancel_convert doesn't sleep on this) but doesn't
       * hurt anything anyway */
      if (status == DLM_CANCELGRANT &&
          lockres->l_unlock_action == OCFS2_UNLOCK_CANCEL_CONVERT) {
            mlog(0, "Got cancelgrant for %s\n", lockres->l_name);

            /* We don't clear the busy flag in this case as it
             * should have been cleared by the ast which the dlm
             * has called. */
            goto complete_unlock;
      }

      if (status != DLM_NORMAL) {
            mlog(ML_ERROR, "Dlm passes status %d for lock %s, "
                 "unlock_action %d\n", status, 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 = LKM_IVMODE;
            break;
      default:
            BUG();
      }

      lockres_clear_flags(lockres, OCFS2_LOCK_BUSY);
complete_unlock:
      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)
{
      enum dlm_status status;
      unsigned long flags;
      int 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 |= LKM_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 == LKM_EXMODE &&
                !(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);

      status = dlmunlock(osb->dlm, &lockres->l_lksb, lkm_flags,
                     ocfs2_unlock_ast, lockres);
      if (status != DLM_NORMAL) {
            ocfs2_log_dlm_error("dlmunlock", status, lockres);
            mlog(ML_ERROR, "lockres flags: %lu\n", lockres->l_flags);
            dlm_print_one_lock(lockres->l_lksb.lockid);
            BUG();
      }
      mlog(0, "lock %s, successfull return from dlmunlock\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 vote 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_data_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_meta_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 void ocfs2_prepare_downconvert(struct ocfs2_lock_res *lockres,
                              int new_level)
{
      assert_spin_locked(&lockres->l_lock);

      BUG_ON(lockres->l_blocking <= LKM_NLMODE);

      if (lockres->l_level <= new_level) {
            mlog(ML_ERROR, "lockres->l_level (%u) <= new_level (%u)\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);
}

static int ocfs2_downconvert_lock(struct ocfs2_super *osb,
                          struct ocfs2_lock_res *lockres,
                          int new_level,
                          int lvb)
{
      int ret, dlm_flags = LKM_CONVERT;
      enum dlm_status status;

      mlog_entry_void();

      if (lvb)
            dlm_flags |= LKM_VALBLK;

      status = dlmlock(osb->dlm,
                   new_level,
                   &lockres->l_lksb,
                   dlm_flags,
                   lockres->l_name,
                   OCFS2_LOCK_ID_MAX_LEN - 1,
                   ocfs2_locking_ast,
                   lockres,
                   ocfs2_blocking_ast);
      if (status != DLM_NORMAL) {
            ocfs2_log_dlm_error("dlmlock", status, lockres);
            ret = -EINVAL;
            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 dlmunlock */
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;
      enum dlm_status status;

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

      ret = 0;
      status = dlmunlock(osb->dlm,
                     &lockres->l_lksb,
                     LKM_CANCEL,
                     ocfs2_unlock_ast,
                     lockres);
      if (status != DLM_NORMAL) {
            ocfs2_log_dlm_error("dlmunlock", status, lockres);
            ret = -EINVAL;
            ocfs2_recover_from_dlm_error(lockres, 0);
      }

      mlog(0, "lock %s return from dlmunlock\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;

      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) {
            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 == LKM_EXMODE)
          && (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 == LKM_PRMODE &&
          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 == LKM_EXMODE)
                  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);
      }

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

      /*
       * 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 == LKM_EXMODE) {
            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);
      }

      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 != LKM_NLMODE && new_level != LKM_PRMODE);
      BUG_ON(lockres->l_level != LKM_EXMODE && !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 vote 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 == LKM_PRMODE)
            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;
}

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 vote 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->vote_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->vote_task_lock);

      mlog_exit_void();
}

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