text: // SPDX-License-Identifier: GPL-2.0-only
  /*
   * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
   * Copyright (C) 2004-2008 Red Hat, Inc.  All rights reserved.
   */
  
  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/spinlock.h>
  #include <linux/buffer_head.h>
  #include <linux/delay.h>
  #include <linux/sort.h>
  #include <linux/hash.h>
  #include <linux/jhash.h>
  #include <linux/kallsyms.h>
  #include <linux/gfs2_ondisk.h>
  #include <linux/list.h>
  #include <linux/wait.h>
  #include <linux/module.h>
  #include <linux/uaccess.h>
  #include <linux/seq_file.h>
  #include <linux/debugfs.h>
  #include <linux/kthread.h>
  #include <linux/freezer.h>
  #include <linux/workqueue.h>
  #include <linux/jiffies.h>
  #include <linux/rcupdate.h>
  #include <linux/rculist_bl.h>
  #include <linux/bit_spinlock.h>
  #include <linux/percpu.h>
  #include <linux/list_sort.h>
  #include <linux/lockref.h>
  #include <linux/rhashtable.h>
  
  #include "gfs2.h"
  #include "incore.h"
  #include "glock.h"
  #include "glops.h"
  #include "inode.h"
  #include "lops.h"
  #include "meta_io.h"
  #include "quota.h"
  #include "super.h"
  #include "util.h"
  #include "bmap.h"
  #define CREATE_TRACE_POINTS
  #include "trace_gfs2.h"
  
  struct gfs2_glock_iter {
  	struct gfs2_sbd *sdp;		/* incore superblock           */
  	struct rhashtable_iter hti;	/* rhashtable iterator         */
  	struct gfs2_glock *gl;		/* current glock struct        */
  	loff_t last_pos;		/* last position               */
  };
  
  typedef void (*glock_examiner) (struct gfs2_glock * gl);
  
  static void do_xmote(struct gfs2_glock *gl, struct gfs2_holder *gh, unsigned int target);
  
  static struct dentry *gfs2_root;
  static struct workqueue_struct *glock_workqueue;
  struct workqueue_struct *gfs2_delete_workqueue;
  static LIST_HEAD(lru_list);
  static atomic_t lru_count = ATOMIC_INIT(0);
  static DEFINE_SPINLOCK(lru_lock);
  
  #define GFS2_GL_HASH_SHIFT      15
  #define GFS2_GL_HASH_SIZE       BIT(GFS2_GL_HASH_SHIFT)
  
  static const struct rhashtable_params ht_parms = {
  	.nelem_hint = GFS2_GL_HASH_SIZE * 3 / 4,
  	.key_len = offsetofend(struct lm_lockname, ln_type),
  	.key_offset = offsetof(struct gfs2_glock, gl_name),
  	.head_offset = offsetof(struct gfs2_glock, gl_node),
  };
  
  static struct rhashtable gl_hash_table;
  
  #define GLOCK_WAIT_TABLE_BITS 12
  #define GLOCK_WAIT_TABLE_SIZE (1 << GLOCK_WAIT_TABLE_BITS)
  static wait_queue_head_t glock_wait_table[GLOCK_WAIT_TABLE_SIZE] __cacheline_aligned;
  
  struct wait_glock_queue {
  	struct lm_lockname *name;
  	wait_queue_entry_t wait;
  };
  
  static int glock_wake_function(wait_queue_entry_t *wait, unsigned int mode,
  			       int sync, void *key)
  {
  	struct wait_glock_queue *wait_glock =
  		container_of(wait, struct wait_glock_queue, wait);
  	struct lm_lockname *wait_name = wait_glock->name;
  	struct lm_lockname *wake_name = key;
  
  	if (wake_name->ln_sbd != wait_name->ln_sbd ||
  	    wake_name->ln_number != wait_name->ln_number ||
  	    wake_name->ln_type != wait_name->ln_type)
  		return 0;
  	return autoremove_wake_function(wait, mode, sync, key);
  }
  
  static wait_queue_head_t *glock_waitqueue(struct lm_lockname *name)
  {
  	u32 hash = jhash2((u32 *)name, ht_parms.key_len / 4, 0);
  
  	return glock_wait_table + hash_32(hash, GLOCK_WAIT_TABLE_BITS);
  }
  
  /**
   * wake_up_glock  -  Wake up waiters on a glock
   * @gl: the glock
   */
  static void wake_up_glock(struct gfs2_glock *gl)
  {
  	wait_queue_head_t *wq = glock_waitqueue(&gl->gl_name);
  
  	if (waitqueue_active(wq))
  		__wake_up(wq, TASK_NORMAL, 1, &gl->gl_name);
  }
  
  static void gfs2_glock_dealloc(struct rcu_head *rcu)
  {
  	struct gfs2_glock *gl = container_of(rcu, struct gfs2_glock, gl_rcu);
  
  	kfree(gl->gl_lksb.sb_lvbptr);
  	if (gl->gl_ops->go_flags & GLOF_ASPACE)
  		kmem_cache_free(gfs2_glock_aspace_cachep, gl);
  	else
  		kmem_cache_free(gfs2_glock_cachep, gl);
  }
  
  /**
   * glock_blocked_by_withdraw - determine if we can still use a glock
   * @gl: the glock
   *
   * We need to allow some glocks to be enqueued, dequeued, promoted, and demoted
   * when we're withdrawn. For example, to maintain metadata integrity, we should
   * disallow the use of inode and rgrp glocks when withdrawn. Other glocks, like
   * iopen or the transaction glocks may be safely used because none of their
   * metadata goes through the journal. So in general, we should disallow all
   * glocks that are journaled, and allow all the others. One exception is:
   * we need to allow our active journal to be promoted and demoted so others
   * may recover it and we can reacquire it when they're done.
   */
  static bool glock_blocked_by_withdraw(struct gfs2_glock *gl)
  {
  	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
  
  	if (likely(!gfs2_withdrawn(sdp)))
  		return false;
  	if (gl->gl_ops->go_flags & GLOF_NONDISK)
  		return false;
  	if (!sdp->sd_jdesc ||
  	    gl->gl_name.ln_number == sdp->sd_jdesc->jd_no_addr)
  		return false;
  	return true;
  }
  
  void gfs2_glock_free(struct gfs2_glock *gl)
  {
  	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
  
  	gfs2_glock_assert_withdraw(gl, atomic_read(&gl->gl_revokes) == 0);
  	rhashtable_remove_fast(&gl_hash_table, &gl->gl_node, ht_parms);
  	smp_mb();
  	wake_up_glock(gl);
  	call_rcu(&gl->gl_rcu, gfs2_glock_dealloc);
  	if (atomic_dec_and_test(&sdp->sd_glock_disposal))
  		wake_up(&sdp->sd_glock_wait);
  }
  
  /**
   * gfs2_glock_hold() - increment reference count on glock
   * @gl: The glock to hold
   *
   */
  
  void gfs2_glock_hold(struct gfs2_glock *gl)
  {
  	GLOCK_BUG_ON(gl, __lockref_is_dead(&gl->gl_lockref));
  	lockref_get(&gl->gl_lockref);
  }
  
  /**
   * demote_ok - Check to see if it's ok to unlock a glock
   * @gl: the glock
   *
   * Returns: 1 if it's ok
   */
  
  static int demote_ok(const struct gfs2_glock *gl)
  {
  	const struct gfs2_glock_operations *glops = gl->gl_ops;
  
  	if (gl->gl_state == LM_ST_UNLOCKED)
  		return 0;
  	if (!list_empty(&gl->gl_holders))
  		return 0;
  	if (glops->go_demote_ok)
  		return glops->go_demote_ok(gl);
  	return 1;
  }
  
  
  void gfs2_glock_add_to_lru(struct gfs2_glock *gl)
  {
  	if (!(gl->gl_ops->go_flags & GLOF_LRU))
  		return;
  
  	spin_lock(&lru_lock);
  
  	list_del(&gl->gl_lru);
  	list_add_tail(&gl->gl_lru, &lru_list);
  
  	if (!test_bit(GLF_LRU, &gl->gl_flags)) {
  		set_bit(GLF_LRU, &gl->gl_flags);
  		atomic_inc(&lru_count);
  	}
  
  	spin_unlock(&lru_lock);
  }
  
  static void gfs2_glock_remove_from_lru(struct gfs2_glock *gl)
  {
  	if (!(gl->gl_ops->go_flags & GLOF_LRU))
  		return;
  
  	spin_lock(&lru_lock);
  	if (test_bit(GLF_LRU, &gl->gl_flags)) {
  		list_del_init(&gl->gl_lru);
  		atomic_dec(&lru_count);
  		clear_bit(GLF_LRU, &gl->gl_flags);
  	}
  	spin_unlock(&lru_lock);
  }
  
  /*
   * Enqueue the glock on the work queue.  Passes one glock reference on to the
   * work queue.
   */
  static void __gfs2_glock_queue_work(struct gfs2_glock *gl, unsigned long delay) {
  	if (!queue_delayed_work(glock_workqueue, &gl->gl_work, delay)) {
  		/*
  		 * We are holding the lockref spinlock, and the work was still
  		 * queued above.  The queued work (glock_work_func) takes that
  		 * spinlock before dropping its glock reference(s), so it
  		 * cannot have dropped them in the meantime.
  		 */
  		GLOCK_BUG_ON(gl, gl->gl_lockref.count < 2);
  		gl->gl_lockref.count--;
  	}
  }
  
  static void gfs2_glock_queue_work(struct gfs2_glock *gl, unsigned long delay) {
  	spin_lock(&gl->gl_lockref.lock);
  	__gfs2_glock_queue_work(gl, delay);
  	spin_unlock(&gl->gl_lockref.lock);
  }
  
  static void __gfs2_glock_put(struct gfs2_glock *gl)
  {
  	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
  	struct address_space *mapping = gfs2_glock2aspace(gl);
  
  	lockref_mark_dead(&gl->gl_lockref);
  
  	gfs2_glock_remove_from_lru(gl);
  	spin_unlock(&gl->gl_lockref.lock);
  	GLOCK_BUG_ON(gl, !list_empty(&gl->gl_holders));
  	if (mapping) {
  		truncate_inode_pages_final(mapping);
  		if (!gfs2_withdrawn(sdp))
  			GLOCK_BUG_ON(gl, mapping->nrpages ||
  				     mapping->nrexceptional);
  	}
  	trace_gfs2_glock_put(gl);
  	sdp->sd_lockstruct.ls_ops->lm_put_lock(gl);
  }
  
  /*
   * Cause the glock to be put in work queue context.
   */
  void gfs2_glock_queue_put(struct gfs2_glock *gl)
  {
  	gfs2_glock_queue_work(gl, 0);
  }
  
  /**
   * gfs2_glock_put() - Decrement reference count on glock
   * @gl: The glock to put
   *
   */
  
  void gfs2_glock_put(struct gfs2_glock *gl)
  {
  	if (lockref_put_or_lock(&gl->gl_lockref))
  		return;
  
  	__gfs2_glock_put(gl);
  }
  
  /**
   * may_grant - check if its ok to grant a new lock
   * @gl: The glock
   * @gh: The lock request which we wish to grant
   *
   * Returns: true if its ok to grant the lock
   */
  
  static inline int may_grant(const struct gfs2_glock *gl, const struct gfs2_holder *gh)
  {
  	const struct gfs2_holder *gh_head = list_first_entry(&gl->gl_holders, const struct gfs2_holder, gh_list);
  	if ((gh->gh_state == LM_ST_EXCLUSIVE ||
  	     gh_head->gh_state == LM_ST_EXCLUSIVE) && gh != gh_head)
  		return 0;
  	if (gl->gl_state == gh->gh_state)
  		return 1;
  	if (gh->gh_flags & GL_EXACT)
  		return 0;
  	if (gl->gl_state == LM_ST_EXCLUSIVE) {
  		if (gh->gh_state == LM_ST_SHARED && gh_head->gh_state == LM_ST_SHARED)
  			return 1;
  		if (gh->gh_state == LM_ST_DEFERRED && gh_head->gh_state == LM_ST_DEFERRED)
  			return 1;
  	}
  	if (gl->gl_state != LM_ST_UNLOCKED && (gh->gh_flags & LM_FLAG_ANY))
  		return 1;
  	return 0;
  }
  
  static void gfs2_holder_wake(struct gfs2_holder *gh)
  {
  	clear_bit(HIF_WAIT, &gh->gh_iflags);
  	smp_mb__after_atomic();
  	wake_up_bit(&gh->gh_iflags, HIF_WAIT);
  	if (gh->gh_flags & GL_ASYNC) {
  		struct gfs2_sbd *sdp = gh->gh_gl->gl_name.ln_sbd;
  
  		wake_up(&sdp->sd_async_glock_wait);
  	}
  }
  
  /**
   * do_error - Something unexpected has happened during a lock request
   *
   */
  
  static void do_error(struct gfs2_glock *gl, const int ret)
  {
  	struct gfs2_holder *gh, *tmp;
  
  	list_for_each_entry_safe(gh, tmp, &gl->gl_holders, gh_list) {
  		if (test_bit(HIF_HOLDER, &gh->gh_iflags))
  			continue;
  		if (ret & LM_OUT_ERROR)
  			gh->gh_error = -EIO;
  		else if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))
  			gh->gh_error = GLR_TRYFAILED;
  		else
  			continue;
  		list_del_init(&gh->gh_list);
  		trace_gfs2_glock_queue(gh, 0);
  		gfs2_holder_wake(gh);
  	}
  }
  
  /**
   * do_promote - promote as many requests as possible on the current queue
   * @gl: The glock
   * 
   * Returns: 1 if there is a blocked holder at the head of the list, or 2
   *          if a type specific operation is underway.
   */
  
  static int do_promote(struct gfs2_glock *gl)
  __releases(&gl->gl_lockref.lock)
  __acquires(&gl->gl_lockref.lock)
  {
  	const struct gfs2_glock_operations *glops = gl->gl_ops;
  	struct gfs2_holder *gh, *tmp;
  	int ret;
  
  restart:
  	list_for_each_entry_safe(gh, tmp, &gl->gl_holders, gh_list) {
  		if (test_bit(HIF_HOLDER, &gh->gh_iflags))
  			continue;
  		if (may_grant(gl, gh)) {
  			if (gh->gh_list.prev == &gl->gl_holders &&
  			    glops->go_lock) {
  				spin_unlock(&gl->gl_lockref.lock);
  				/* FIXME: eliminate this eventually */
  				ret = glops->go_lock(gh);
  				spin_lock(&gl->gl_lockref.lock);
  				if (ret) {
  					if (ret == 1)
  						return 2;
  					gh->gh_error = ret;
  					list_del_init(&gh->gh_list);
  					trace_gfs2_glock_queue(gh, 0);
  					gfs2_holder_wake(gh);
  					goto restart;
  				}
  				set_bit(HIF_HOLDER, &gh->gh_iflags);
  				trace_gfs2_promote(gh, 1);
  				gfs2_holder_wake(gh);
  				goto restart;
  			}
  			set_bit(HIF_HOLDER, &gh->gh_iflags);
  			trace_gfs2_promote(gh, 0);
  			gfs2_holder_wake(gh);
  			continue;
  		}
  		if (gh->gh_list.prev == &gl->gl_holders)
  			return 1;
  		do_error(gl, 0);
  		break;
  	}
  	return 0;
  }
  
  /**
   * find_first_waiter - find the first gh that's waiting for the glock
   * @gl: the glock
   */
  
  static inline struct gfs2_holder *find_first_waiter(const struct gfs2_glock *gl)
  {
  	struct gfs2_holder *gh;
  
  	list_for_each_entry(gh, &gl->gl_holders, gh_list) {
  		if (!test_bit(HIF_HOLDER, &gh->gh_iflags))
  			return gh;
  	}
  	return NULL;
  }
  
  /**
   * state_change - record that the glock is now in a different state
   * @gl: the glock
   * @new_state the new state
   *
   */
  
  static void state_change(struct gfs2_glock *gl, unsigned int new_state)
  {
  	int held1, held2;
  
  	held1 = (gl->gl_state != LM_ST_UNLOCKED);
  	held2 = (new_state != LM_ST_UNLOCKED);
  
  	if (held1 != held2) {
  		GLOCK_BUG_ON(gl, __lockref_is_dead(&gl->gl_lockref));
  		if (held2)
  			gl->gl_lockref.count++;
  		else
  			gl->gl_lockref.count--;
  	}
  	if (new_state != gl->gl_target)
  		/* shorten our minimum hold time */
  		gl->gl_hold_time = max(gl->gl_hold_time - GL_GLOCK_HOLD_DECR,
  				       GL_GLOCK_MIN_HOLD);
  	gl->gl_state = new_state;
  	gl->gl_tchange = jiffies;
  }
  
  static void gfs2_set_demote(struct gfs2_glock *gl)
  {
  	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
  
  	set_bit(GLF_DEMOTE, &gl->gl_flags);
  	smp_mb();
  	wake_up(&sdp->sd_async_glock_wait);
  }
  
  static void gfs2_demote_wake(struct gfs2_glock *gl)
  {
  	gl->gl_demote_state = LM_ST_EXCLUSIVE;
  	clear_bit(GLF_DEMOTE, &gl->gl_flags);
  	smp_mb__after_atomic();
  	wake_up_bit(&gl->gl_flags, GLF_DEMOTE);
  }
  
  /**
   * finish_xmote - The DLM has replied to one of our lock requests
   * @gl: The glock
   * @ret: The status from the DLM
   *
   */
  
  static void finish_xmote(struct gfs2_glock *gl, unsigned int ret)
  {
  	const struct gfs2_glock_operations *glops = gl->gl_ops;
  	struct gfs2_holder *gh;
  	unsigned state = ret & LM_OUT_ST_MASK;
  	int rv;
  
  	spin_lock(&gl->gl_lockref.lock);
  	trace_gfs2_glock_state_change(gl, state);
  	state_change(gl, state);
  	gh = find_first_waiter(gl);
  
  	/* Demote to UN request arrived during demote to SH or DF */
  	if (test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags) &&
  	    state != LM_ST_UNLOCKED && gl->gl_demote_state == LM_ST_UNLOCKED)
  		gl->gl_target = LM_ST_UNLOCKED;
  
  	/* Check for state != intended state */
  	if (unlikely(state != gl->gl_target)) {
  		if (gh && !test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags)) {
  			/* move to back of queue and try next entry */
  			if (ret & LM_OUT_CANCELED) {
  				if ((gh->gh_flags & LM_FLAG_PRIORITY) == 0)
  					list_move_tail(&gh->gh_list, &gl->gl_holders);
  				gh = find_first_waiter(gl);
  				gl->gl_target = gh->gh_state;
  				goto retry;
  			}
  			/* Some error or failed "try lock" - report it */
  			if ((ret & LM_OUT_ERROR) ||
  			    (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))) {
  				gl->gl_target = gl->gl_state;
  				do_error(gl, ret);
  				goto out;
  			}
  		}
  		switch(state) {
  		/* Unlocked due to conversion deadlock, try again */
  		case LM_ST_UNLOCKED:
  retry:
  			do_xmote(gl, gh, gl->gl_target);
  			break;
  		/* Conversion fails, unlock and try again */
  		case LM_ST_SHARED:
  		case LM_ST_DEFERRED:
  			do_xmote(gl, gh, LM_ST_UNLOCKED);
  			break;
  		default: /* Everything else */
  			fs_err(gl->gl_name.ln_sbd, "wanted %u got %u\n",
  			       gl->gl_target, state);
  			GLOCK_BUG_ON(gl, 1);
  		}
  		spin_unlock(&gl->gl_lockref.lock);
  		return;
  	}
  
  	/* Fast path - we got what we asked for */
  	if (test_and_clear_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags))
  		gfs2_demote_wake(gl);
  	if (state != LM_ST_UNLOCKED) {
  		if (glops->go_xmote_bh) {
  			spin_unlock(&gl->gl_lockref.lock);
  			rv = glops->go_xmote_bh(gl, gh);
  			spin_lock(&gl->gl_lockref.lock);
  			if (rv) {
  				do_error(gl, rv);
  				goto out;
  			}
  		}
  		rv = do_promote(gl);
  		if (rv == 2)
  			goto out_locked;
  	}
  out:
  	clear_bit(GLF_LOCK, &gl->gl_flags);
  out_locked:
  	spin_unlock(&gl->gl_lockref.lock);
  }
  
  /**
   * do_xmote - Calls the DLM to change the state of a lock
   * @gl: The lock state
   * @gh: The holder (only for promotes)
   * @target: The target lock state
   *
   */
  
  static void do_xmote(struct gfs2_glock *gl, struct gfs2_holder *gh, unsigned int target)
  __releases(&gl->gl_lockref.lock)
  __acquires(&gl->gl_lockref.lock)
  {
  	const struct gfs2_glock_operations *glops = gl->gl_ops;
  	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
  	unsigned int lck_flags = (unsigned int)(gh ? gh->gh_flags : 0);
  	int ret;
  
  	if (target != LM_ST_UNLOCKED && glock_blocked_by_withdraw(gl) &&
  	    gh && !(gh->gh_flags & LM_FLAG_NOEXP))
  		return;
  	lck_flags &= (LM_FLAG_TRY | LM_FLAG_TRY_1CB | LM_FLAG_NOEXP |
  		      LM_FLAG_PRIORITY);
  	GLOCK_BUG_ON(gl, gl->gl_state == target);
  	GLOCK_BUG_ON(gl, gl->gl_state == gl->gl_target);
  	if ((target == LM_ST_UNLOCKED || target == LM_ST_DEFERRED) &&
  	    glops->go_inval) {
  		/*
  		 * If another process is already doing the invalidate, let that
  		 * finish first.  The glock state machine will get back to this
  		 * holder again later.
  		 */
  		if (test_and_set_bit(GLF_INVALIDATE_IN_PROGRESS,
  				     &gl->gl_flags))
  			return;
  		do_error(gl, 0); /* Fail queued try locks */
  	}
  	gl->gl_req = target;
  	set_bit(GLF_BLOCKING, &gl->gl_flags);
  	if ((gl->gl_req == LM_ST_UNLOCKED) ||
  	    (gl->gl_state == LM_ST_EXCLUSIVE) ||
  	    (lck_flags & (LM_FLAG_TRY|LM_FLAG_TRY_1CB)))
  		clear_bit(GLF_BLOCKING, &gl->gl_flags);
  	spin_unlock(&gl->gl_lockref.lock);
  	if (glops->go_sync) {
  		ret = glops->go_sync(gl);
  		/* If we had a problem syncing (due to io errors or whatever,
  		 * we should not invalidate the metadata or tell dlm to
  		 * release the glock to other nodes.
  		 */
  		if (ret) {
  			if (cmpxchg(&sdp->sd_log_error, 0, ret)) {
  				fs_err(sdp, "Error %d syncing glock \n", ret);
  				gfs2_dump_glock(NULL, gl, true);
  			}
  			goto skip_inval;
  		}
  	}
  	if (test_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags)) {
  		/*
  		 * The call to go_sync should have cleared out the ail list.
  		 * If there are still items, we have a problem. We ought to
  		 * withdraw, but we can't because the withdraw code also uses
  		 * glocks. Warn about the error, dump the glock, then fall
  		 * through and wait for logd to do the withdraw for us.
  		 */
  		if ((atomic_read(&gl->gl_ail_count) != 0) &&
  		    (!cmpxchg(&sdp->sd_log_error, 0, -EIO))) {
  			gfs2_glock_assert_warn(gl,
  					       !atomic_read(&gl->gl_ail_count));
  			gfs2_dump_glock(NULL, gl, true);
  		}
  		glops->go_inval(gl, target == LM_ST_DEFERRED ? 0 : DIO_METADATA);
  		clear_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags);
  	}
  
  skip_inval:
  	gfs2_glock_hold(gl);
  	/*
  	 * Check for an error encountered since we called go_sync and go_inval.
  	 * If so, we can't withdraw from the glock code because the withdraw
  	 * code itself uses glocks (see function signal_our_withdraw) to
  	 * change the mount to read-only. Most importantly, we must not call
  	 * dlm to unlock the glock until the journal is in a known good state
  	 * (after journal replay) otherwise other nodes may use the object
  	 * (rgrp or dinode) and then later, journal replay will corrupt the
  	 * file system. The best we can do here is wait for the logd daemon
  	 * to see sd_log_error and withdraw, and in the meantime, requeue the
  	 * work for later.
  	 *
  	 * However, if we're just unlocking the lock (say, for unmount, when
  	 * gfs2_gl_hash_clear calls clear_glock) and recovery is complete
  	 * then it's okay to tell dlm to unlock it.
  	 */
  	if (unlikely(sdp->sd_log_error && !gfs2_withdrawn(sdp)))
  		gfs2_withdraw_delayed(sdp);
  	if (glock_blocked_by_withdraw(gl)) {
  		if (target != LM_ST_UNLOCKED ||
  		    test_bit(SDF_WITHDRAW_RECOVERY, &sdp->sd_flags)) {
  			gfs2_glock_queue_work(gl, GL_GLOCK_DFT_HOLD);
  			goto out;
  		}
  	}
  
  	if (sdp->sd_lockstruct.ls_ops->lm_lock)	{
  		/* lock_dlm */
  		ret = sdp->sd_lockstruct.ls_ops->lm_lock(gl, target, lck_flags);
  		if (ret == -EINVAL && gl->gl_target == LM_ST_UNLOCKED &&
  		    target == LM_ST_UNLOCKED &&
  		    test_bit(SDF_SKIP_DLM_UNLOCK, &sdp->sd_flags)) {
  			finish_xmote(gl, target);
  			gfs2_glock_queue_work(gl, 0);
  		} else if (ret) {
  			fs_err(sdp, "lm_lock ret %d\n", ret);
  			GLOCK_BUG_ON(gl, !gfs2_withdrawn(sdp));
  		}
  	} else { /* lock_nolock */
  		finish_xmote(gl, target);
  		gfs2_glock_queue_work(gl, 0);
  	}
  out:
  	spin_lock(&gl->gl_lockref.lock);
  }
  
  /**
   * find_first_holder - find the first "holder" gh
   * @gl: the glock
   */
  
  static inline struct gfs2_holder *find_first_holder(const struct gfs2_glock *gl)
  {
  	struct gfs2_holder *gh;
  
  	if (!list_empty(&gl->gl_holders)) {
  		gh = list_first_entry(&gl->gl_holders, struct gfs2_holder, gh_list);
  		if (test_bit(HIF_HOLDER, &gh->gh_iflags))
  			return gh;
  	}
  	return NULL;
  }
  
  /**
   * run_queue - do all outstanding tasks related to a glock
   * @gl: The glock in question
   * @nonblock: True if we must not block in run_queue
   *
   */
  
  static void run_queue(struct gfs2_glock *gl, const int nonblock)
  __releases(&gl->gl_lockref.lock)
  __acquires(&gl->gl_lockref.lock)
  {
  	struct gfs2_holder *gh = NULL;
  	int ret;
  
  	if (test_and_set_bit(GLF_LOCK, &gl->gl_flags))
  		return;
  
  	GLOCK_BUG_ON(gl, test_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags));
  
  	if (test_bit(GLF_DEMOTE, &gl->gl_flags) &&
  	    gl->gl_demote_state != gl->gl_state) {
  		if (find_first_holder(gl))
  			goto out_unlock;
  		if (nonblock)
  			goto out_sched;
  		set_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);
  		GLOCK_BUG_ON(gl, gl->gl_demote_state == LM_ST_EXCLUSIVE);
  		gl->gl_target = gl->gl_demote_state;
  	} else {
  		if (test_bit(GLF_DEMOTE, &gl->gl_flags))
  			gfs2_demote_wake(gl);
  		ret = do_promote(gl);
  		if (ret == 0)
  			goto out_unlock;
  		if (ret == 2)
  			goto out;
  		gh = find_first_waiter(gl);
  		gl->gl_target = gh->gh_state;
  		if (!(gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)))
  			do_error(gl, 0); /* Fail queued try locks */
  	}
  	do_xmote(gl, gh, gl->gl_target);
  out:
  	return;
  
  out_sched:
  	clear_bit(GLF_LOCK, &gl->gl_flags);
  	smp_mb__after_atomic();
  	gl->gl_lockref.count++;
  	__gfs2_glock_queue_work(gl, 0);
  	return;
  
  out_unlock:
  	clear_bit(GLF_LOCK, &gl->gl_flags);
  	smp_mb__after_atomic();
  	return;
  }
  
  void gfs2_inode_remember_delete(struct gfs2_glock *gl, u64 generation)
  {
  	struct gfs2_inode_lvb *ri = (void *)gl->gl_lksb.sb_lvbptr;
  
  	if (ri->ri_magic == 0)
  		ri->ri_magic = cpu_to_be32(GFS2_MAGIC);
  	if (ri->ri_magic == cpu_to_be32(GFS2_MAGIC))
  		ri->ri_generation_deleted = cpu_to_be64(generation);
  }
  
  bool gfs2_inode_already_deleted(struct gfs2_glock *gl, u64 generation)
  {
  	struct gfs2_inode_lvb *ri = (void *)gl->gl_lksb.sb_lvbptr;
  
  	if (ri->ri_magic != cpu_to_be32(GFS2_MAGIC))
  		return false;
  	return generation <= be64_to_cpu(ri->ri_generation_deleted);
  }
  
  static void gfs2_glock_poke(struct gfs2_glock *gl)
  {
  	int flags = LM_FLAG_TRY_1CB | LM_FLAG_ANY | GL_SKIP;
  	struct gfs2_holder gh;
  	int error;
  
  	gfs2_holder_init(gl, LM_ST_SHARED, flags, &gh);
  	error = gfs2_glock_nq(&gh);
  	if (!error)
  		gfs2_glock_dq(&gh);
  	gfs2_holder_uninit(&gh);
  }
  
  static bool gfs2_try_evict(struct gfs2_glock *gl)
  {
  	struct gfs2_inode *ip;
  	bool evicted = false;
  
  	/*
  	 * If there is contention on the iopen glock and we have an inode, try
  	 * to grab and release the inode so that it can be evicted.  This will
  	 * allow the remote node to go ahead and delete the inode without us
  	 * having to do it, which will avoid rgrp glock thrashing.
  	 *
  	 * The remote node is likely still holding the corresponding inode
  	 * glock, so it will run before we get to verify that the delete has
  	 * happened below.
  	 */
  	spin_lock(&gl->gl_lockref.lock);
  	ip = gl->gl_object;
  	if (ip && !igrab(&ip->i_inode))
  		ip = NULL;
  	spin_unlock(&gl->gl_lockref.lock);
  	if (ip) {
  		struct gfs2_glock *inode_gl = NULL;
  
  		gl->gl_no_formal_ino = ip->i_no_formal_ino;
  		set_bit(GIF_DEFERRED_DELETE, &ip->i_flags);
  		d_prune_aliases(&ip->i_inode);
  		iput(&ip->i_inode);
  
  		/* If the inode was evicted, gl->gl_object will now be NULL. */
  		spin_lock(&gl->gl_lockref.lock);
  		ip = gl->gl_object;
  		if (ip) {
  			inode_gl = ip->i_gl;
  			lockref_get(&inode_gl->gl_lockref);
  			clear_bit(GIF_DEFERRED_DELETE, &ip->i_flags);
  		}
  		spin_unlock(&gl->gl_lockref.lock);
  		if (inode_gl) {
  			gfs2_glock_poke(inode_gl);
  			gfs2_glock_put(inode_gl);
  		}
  		evicted = !ip;
  	}
  	return evicted;
  }
  
  static void delete_work_func(struct work_struct *work)
  {
  	struct delayed_work *dwork = to_delayed_work(work);
  	struct gfs2_glock *gl = container_of(dwork, struct gfs2_glock, gl_delete);
  	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
  	struct inode *inode;
  	u64 no_addr = gl->gl_name.ln_number;
  
  	spin_lock(&gl->gl_lockref.lock);
  	clear_bit(GLF_PENDING_DELETE, &gl->gl_flags);
  	spin_unlock(&gl->gl_lockref.lock);
  
  	/* If someone's using this glock to create a new dinode, the block must
  	   have been freed by another node, then re-used, in which case our
  	   iopen callback is too late after the fact. Ignore it. */
  	if (test_bit(GLF_INODE_CREATING, &gl->gl_flags))
  		goto out;
  
  	if (test_bit(GLF_DEMOTE, &gl->gl_flags)) {
  		/*
  		 * If we can evict the inode, give the remote node trying to
  		 * delete the inode some time before verifying that the delete
  		 * has happened.  Otherwise, if we cause contention on the inode glock
  		 * immediately, the remote node will think that we still have
  		 * the inode in use, and so it will give up waiting.
  		 *
  		 * If we can't evict the inode, signal to the remote node that
  		 * the inode is still in use.  We'll later try to delete the
  		 * inode locally in gfs2_evict_inode.
  		 *
  		 * FIXME: We only need to verify that the remote node has
  		 * deleted the inode because nodes before this remote delete
  		 * rework won't cooperate.  At a later time, when we no longer
  		 * care about compatibility with such nodes, we can skip this
  		 * step entirely.
  		 */
  		if (gfs2_try_evict(gl)) {
  			if (gfs2_queue_delete_work(gl, 5 * HZ))
  				return;
  		}
  		goto out;
  	}
  
  	inode = gfs2_lookup_by_inum(sdp, no_addr, gl->gl_no_formal_ino,
  				    GFS2_BLKST_UNLINKED);
  	if (!IS_ERR_OR_NULL(inode)) {
  		d_prune_aliases(inode);
  		iput(inode);
  	}
  out:
  	gfs2_glock_put(gl);
  }
  
  static void glock_work_func(struct work_struct *work)
  {
  	unsigned long delay = 0;
  	struct gfs2_glock *gl = container_of(work, struct gfs2_glock, gl_work.work);
  	unsigned int drop_refs = 1;
  
  	if (test_and_clear_bit(GLF_REPLY_PENDING, &gl->gl_flags)) {
  		finish_xmote(gl, gl->gl_reply);
  		drop_refs++;
  	}
  	spin_lock(&gl->gl_lockref.lock);
  	if (test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
  	    gl->gl_state != LM_ST_UNLOCKED &&
  	    gl->gl_demote_state != LM_ST_EXCLUSIVE) {
  		unsigned long holdtime, now = jiffies;
  
  		holdtime = gl->gl_tchange + gl->gl_hold_time;
  		if (time_before(now, holdtime))
  			delay = holdtime - now;
  
  		if (!delay) {
  			clear_bit(GLF_PENDING_DEMOTE, &gl->gl_flags);
  			gfs2_set_demote(gl);
  		}
  	}
  	run_queue(gl, 0);
  	if (delay) {
  		/* Keep one glock reference for the work we requeue. */
  		drop_refs--;
  		if (gl->gl_name.ln_type != LM_TYPE_INODE)
  			delay = 0;
  		__gfs2_glock_queue_work(gl, delay);
  	}
  
  	/*
  	 * Drop the remaining glock references manually here. (Mind that
  	 * __gfs2_glock_queue_work depends on the lockref spinlock begin held
  	 * here as well.)
  	 */
  	gl->gl_lockref.count -= drop_refs;
  	if (!gl->gl_lockref.count) {
  		__gfs2_glock_put(gl);
  		return;
  	}
  	spin_unlock(&gl->gl_lockref.lock);
  }
  
  static struct gfs2_glock *find_insert_glock(struct lm_lockname *name,
  					    struct gfs2_glock *new)
  {
  	struct wait_glock_queue wait;
  	wait_queue_head_t *wq = glock_waitqueue(name);
  	struct gfs2_glock *gl;
  
  	wait.name = name;
  	init_wait(&wait.wait);
  	wait.wait.func = glock_wake_function;
  
  again:
  	prepare_to_wait(wq, &wait.wait, TASK_UNINTERRUPTIBLE);
  	rcu_read_lock();
  	if (new) {
  		gl = rhashtable_lookup_get_insert_fast(&gl_hash_table,
  			&new->gl_node, ht_parms);
  		if (IS_ERR(gl))
  			goto out;
  	} else {
  		gl = rhashtable_lookup_fast(&gl_hash_table,
  			name, ht_parms);
  	}
  	if (gl && !lockref_get_not_dead(&gl->gl_lockref)) {
  		rcu_read_unlock();
  		schedule();
  		goto again;
  	}
  out:
  	rcu_read_unlock();
  	finish_wait(wq, &wait.wait);
  	return gl;
  }
  
  /**
   * gfs2_glock_get() - Get a glock, or create one if one doesn't exist
   * @sdp: The GFS2 superblock
   * @number: the lock number
   * @glops: The glock_operations to use
   * @create: If 0, don't create the glock if it doesn't exist
   * @glp: the glock is returned here
   *
   * This does not lock a glock, just finds/creates structures for one.
   *
   * Returns: errno
   */
  
  int gfs2_glock_get(struct gfs2_sbd *sdp, u64 number,
  		   const struct gfs2_glock_operations *glops, int create,
  		   struct gfs2_glock **glp)
  {
  	struct super_block *s = sdp->sd_vfs;
  	struct lm_lockname name = { .ln_number = number,
  				    .ln_type = glops->go_type,
  				    .ln_sbd = sdp };
  	struct gfs2_glock *gl, *tmp;
  	struct address_space *mapping;
  	struct kmem_cache *cachep;
  	int ret = 0;
  
  	gl = find_insert_glock(&name, NULL);
  	if (gl) {
  		*glp = gl;
  		return 0;
  	}
  	if (!create)
  		return -ENOENT;
  
  	if (glops->go_flags & GLOF_ASPACE)
  		cachep = gfs2_glock_aspace_cachep;
  	else
  		cachep = gfs2_glock_cachep;
  	gl = kmem_cache_alloc(cachep, GFP_NOFS);
  	if (!gl)
  		return -ENOMEM;
  
  	memset(&gl->gl_lksb, 0, sizeof(struct dlm_lksb));
  
  	if (glops->go_flags & GLOF_LVB) {
  		gl->gl_lksb.sb_lvbptr = kzalloc(GDLM_LVB_SIZE, GFP_NOFS);
  		if (!gl->gl_lksb.sb_lvbptr) {
  			kmem_cache_free(cachep, gl);
  			return -ENOMEM;
  		}
  	}
  
  	atomic_inc(&sdp->sd_glock_disposal);
  	gl->gl_node.next = NULL;
  	gl->gl_flags = 0;
  	gl->gl_name = name;
  	lockdep_set_subclass(&gl->gl_lockref.lock, glops->go_subclass);
  	gl->gl_lockref.count = 1;
  	gl->gl_state = LM_ST_UNLOCKED;
  	gl->gl_target = LM_ST_UNLOCKED;
  	gl->gl_demote_state = LM_ST_EXCLUSIVE;
  	gl->gl_ops = glops;
  	gl->gl_dstamp = 0;
  	preempt_disable();
  	/* We use the global stats to estimate the initial per-glock stats */
  	gl->gl_stats = this_cpu_ptr(sdp->sd_lkstats)->lkstats[glops->go_type];
  	preempt_enable();
  	gl->gl_stats.stats[GFS2_LKS_DCOUNT] = 0;
  	gl->gl_stats.stats[GFS2_LKS_QCOUNT] = 0;
  	gl->gl_tchange = jiffies;
  	gl->gl_object = NULL;
  	gl->gl_hold_time = GL_GLOCK_DFT_HOLD;
  	INIT_DELAYED_WORK(&gl->gl_work, glock_work_func);
  	if (gl->gl_name.ln_type == LM_TYPE_IOPEN)
  		INIT_DELAYED_WORK(&gl->gl_delete, delete_work_func);
  
  	mapping = gfs2_glock2aspace(gl);
  	if (mapping) {
                  mapping->a_ops = &gfs2_meta_aops;
  		mapping->host = s->s_bdev->bd_inode;
  		mapping->flags = 0;
  		mapping_set_gfp_mask(mapping, GFP_NOFS);
  		mapping->private_data = NULL;
  		mapping->writeback_index = 0;
  	}
  
  	tmp = find_insert_glock(&name, gl);
  	if (!tmp) {
  		*glp = gl;
  		goto out;
  	}
  	if (IS_ERR(tmp)) {
  		ret = PTR_ERR(tmp);
  		goto out_free;
  	}
  	*glp = tmp;
  
  out_free:
  	kfree(gl->gl_lksb.sb_lvbptr);
  	kmem_cache_free(cachep, gl);
  	if (atomic_dec_and_test(&sdp->sd_glock_disposal))
  		wake_up(&sdp->sd_glock_wait);
  
  out:
  	return ret;
  }
  
  /**
   * gfs2_holder_init - initialize a struct gfs2_holder in the default way
   * @gl: the glock
   * @state: the state we're requesting
   * @flags: the modifier flags
   * @gh: the holder structure
   *
   */
  
  void gfs2_holder_init(struct gfs2_glock *gl, unsigned int state, u16 flags,
  		      struct gfs2_holder *gh)
  {
  	INIT_LIST_HEAD(&gh->gh_list);
  	gh->gh_gl = gl;
  	gh->gh_ip = _RET_IP_;
  	gh->gh_owner_pid = get_pid(task_pid(current));
  	gh->gh_state = state;
  	gh->gh_flags = flags;
  	gh->gh_error = 0;
  	gh->gh_iflags = 0;
  	gfs2_glock_hold(gl);
  }
  
  /**
   * gfs2_holder_reinit - reinitialize a struct gfs2_holder so we can requeue it
   * @state: the state we're requesting
   * @flags: the modifier flags
   * @gh: the holder structure
   *
   * Don't mess with the glock.
   *
   */
  
  void gfs2_holder_reinit(unsigned int state, u16 flags, struct gfs2_holder *gh)
  {
  	gh->gh_state = state;
  	gh->gh_flags = flags;
  	gh->gh_iflags = 0;
  	gh->gh_ip = _RET_IP_;
  	put_pid(gh->gh_owner_pid);
  	gh->gh_owner_pid = get_pid(task_pid(current));
  }
  
  /**
   * gfs2_holder_uninit - uninitialize a holder structure (drop glock reference)
   * @gh: the holder structure
   *
   */
  
  void gfs2_holder_uninit(struct gfs2_holder *gh)
  {
  	put_pid(gh->gh_owner_pid);
  	gfs2_glock_put(gh->gh_gl);
  	gfs2_holder_mark_uninitialized(gh);
  	gh->gh_ip = 0;
  }
  
  static void gfs2_glock_update_hold_time(struct gfs2_glock *gl,
  					unsigned long start_time)
  {
  	/* Have we waited longer that a second? */
  	if (time_after(jiffies, start_time + HZ)) {
  		/* Lengthen the minimum hold time. */
  		gl->gl_hold_time = min(gl->gl_hold_time + GL_GLOCK_HOLD_INCR,
  				       GL_GLOCK_MAX_HOLD);
  	}
  }
  
  /**
   * gfs2_glock_wait - wait on a glock acquisition
   * @gh: the glock holder
   *
   * Returns: 0 on success
   */
  
  int gfs2_glock_wait(struct gfs2_holder *gh)
  {
  	unsigned long start_time = jiffies;
  
  	might_sleep();
  	wait_on_bit(&gh->gh_iflags, HIF_WAIT, TASK_UNINTERRUPTIBLE);
  	gfs2_glock_update_hold_time(gh->gh_gl, start_time);
  	return gh->gh_error;
  }
  
  static int glocks_pending(unsigned int num_gh, struct gfs2_holder *ghs)
  {
  	int i;
  
  	for (i = 0; i < num_gh; i++)
  		if (test_bit(HIF_WAIT, &ghs[i].gh_iflags))
  			return 1;
  	return 0;
  }
  
  /**
   * gfs2_glock_async_wait - wait on multiple asynchronous glock acquisitions
   * @num_gh: the number of holders in the array
   * @ghs: the glock holder array
   *
   * Returns: 0 on success, meaning all glocks have been granted and are held.
   *          -ESTALE if the request timed out, meaning all glocks were released,
   *          and the caller should retry the operation.
   */
  
  int gfs2_glock_async_wait(unsigned int num_gh, struct gfs2_holder *ghs)
  {
  	struct gfs2_sbd *sdp = ghs[0].gh_gl->gl_name.ln_sbd;
  	int i, ret = 0, timeout = 0;
  	unsigned long start_time = jiffies;
  	bool keep_waiting;
  
  	might_sleep();
  	/*
  	 * Total up the (minimum hold time * 2) of all glocks and use that to
  	 * determine the max amount of time we should wait.
  	 */
  	for (i = 0; i < num_gh; i++)
  		timeout += ghs[i].gh_gl->gl_hold_time << 1;
  
  wait_for_dlm:
  	if (!wait_event_timeout(sdp->sd_async_glock_wait,
  				!glocks_pending(num_gh, ghs), timeout))
  		ret = -ESTALE; /* request timed out. */
  
  	/*
  	 * If dlm granted all our requests, we need to adjust the glock
  	 * minimum hold time values according to how long we waited.
  	 *
  	 * If our request timed out, we need to repeatedly release any held
  	 * glocks we acquired thus far to allow dlm to acquire the remaining
  	 * glocks without deadlocking.  We cannot currently cancel outstanding
  	 * glock acquisitions.
  	 *
  	 * The HIF_WAIT bit tells us which requests still need a response from
  	 * dlm.
  	 *
  	 * If dlm sent us any errors, we return the first error we find.
  	 */
  	keep_waiting = false;
  	for (i = 0; i < num_gh; i++) {
  		/* Skip holders we have already dequeued below. */
  		if (!gfs2_holder_queued(&ghs[i]))
  			continue;
  		/* Skip holders with a pending DLM response. */
  		if (test_bit(HIF_WAIT, &ghs[i].gh_iflags)) {
  			keep_waiting = true;
  			continue;
  		}
  
  		if (test_bit(HIF_HOLDER, &ghs[i].gh_iflags)) {
  			if (ret == -ESTALE)
  				gfs2_glock_dq(&ghs[i]);
  			else
  				gfs2_glock_update_hold_time(ghs[i].gh_gl,
  							    start_time);
  		}
  		if (!ret)
  			ret = ghs[i].gh_error;
  	}
  
  	if (keep_waiting)
  		goto wait_for_dlm;
  
  	/*
  	 * At this point, we've either acquired all locks or released them all.
  	 */
  	return ret;
  }
  
  /**
   * handle_callback - process a demote request
   * @gl: the glock
   * @state: the state the caller wants us to change to
   *
   * There are only two requests that we are going to see in actual
   * practise: LM_ST_SHARED and LM_ST_UNLOCKED
   */
  
  static void handle_callback(struct gfs2_glock *gl, unsigned int state,
  			    unsigned long delay, bool remote)
  {
  	if (delay)
  		set_bit(GLF_PENDING_DEMOTE, &gl->gl_flags);
  	else
  		gfs2_set_demote(gl);
  	if (gl->gl_demote_state == LM_ST_EXCLUSIVE) {
  		gl->gl_demote_state = state;
  		gl->gl_demote_time = jiffies;
  	} else if (gl->gl_demote_state != LM_ST_UNLOCKED &&
  			gl->gl_demote_state != state) {
  		gl->gl_demote_state = LM_ST_UNLOCKED;
  	}
  	if (gl->gl_ops->go_callback)
  		gl->gl_ops->go_callback(gl, remote);
  	trace_gfs2_demote_rq(gl, remote);
  }
  
  void gfs2_print_dbg(struct seq_file *seq, const char *fmt, ...)
  {
  	struct va_format vaf;
  	va_list args;
  
  	va_start(args, fmt);
  
  	if (seq) {
  		seq_vprintf(seq, fmt, args);
  	} else {
  		vaf.fmt = fmt;
  		vaf.va = &args;
  
  		pr_err("%pV", &vaf);
  	}
  
  	va_end(args);
  }
  
  /**
   * add_to_queue - Add a holder to the wait queue (but look for recursion)
   * @gh: the holder structure to add
   *
   * Eventually we should move the recursive locking trap to a
   * debugging option or something like that. This is the fast
   * path and needs to have the minimum number of distractions.
   * 
   */
  
  static inline void add_to_queue(struct gfs2_holder *gh)
  __releases(&gl->gl_lockref.lock)
  __acquires(&gl->gl_lockref.lock)
  {
  	struct gfs2_glock *gl = gh->gh_gl;
  	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
  	struct list_head *insert_pt = NULL;
  	struct gfs2_holder *gh2;
  	int try_futile = 0;
  
  	GLOCK_BUG_ON(gl, gh->gh_owner_pid == NULL);
  	if (test_and_set_bit(HIF_WAIT, &gh->gh_iflags))
  		GLOCK_BUG_ON(gl, true);
  
  	if (gh->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB)) {
  		if (test_bit(GLF_LOCK, &gl->gl_flags))
  			try_futile = !may_grant(gl, gh);
  		if (test_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags))
  			goto fail;
  	}
  
  	list_for_each_entry(gh2, &gl->gl_holders, gh_list) {
  		if (unlikely(gh2->gh_owner_pid == gh->gh_owner_pid &&
  		    (gh->gh_gl->gl_ops->go_type != LM_TYPE_FLOCK)))
  			goto trap_recursive;
  		if (try_futile &&
  		    !(gh2->gh_flags & (LM_FLAG_TRY | LM_FLAG_TRY_1CB))) {
  fail:
  			gh->gh_error = GLR_TRYFAILED;
  			gfs2_holder_wake(gh);
  			return;
  		}
  		if (test_bit(HIF_HOLDER, &gh2->gh_iflags))
  			continue;
  		if (unlikely((gh->gh_flags & LM_FLAG_PRIORITY) && !insert_pt))
  			insert_pt = &gh2->gh_list;
  	}
  	trace_gfs2_glock_queue(gh, 1);
  	gfs2_glstats_inc(gl, GFS2_LKS_QCOUNT);
  	gfs2_sbstats_inc(gl, GFS2_LKS_QCOUNT);
  	if (likely(insert_pt == NULL)) {
  		list_add_tail(&gh->gh_list, &gl->gl_holders);
  		if (unlikely(gh->gh_flags & LM_FLAG_PRIORITY))
  			goto do_cancel;
  		return;
  	}
  	list_add_tail(&gh->gh_list, insert_pt);
  do_cancel:
  	gh = list_first_entry(&gl->gl_holders, struct gfs2_holder, gh_list);
  	if (!(gh->gh_flags & LM_FLAG_PRIORITY)) {
  		spin_unlock(&gl->gl_lockref.lock);
  		if (sdp->sd_lockstruct.ls_ops->lm_cancel)
  			sdp->sd_lockstruct.ls_ops->lm_cancel(gl);
  		spin_lock(&gl->gl_lockref.lock);
  	}
  	return;
  
  trap_recursive:
  	fs_err(sdp, "original: %pSR\n", (void *)gh2->gh_ip);
  	fs_err(sdp, "pid: %d\n", pid_nr(gh2->gh_owner_pid));
  	fs_err(sdp, "lock type: %d req lock state : %d\n",
  	       gh2->gh_gl->gl_name.ln_type, gh2->gh_state);
  	fs_err(sdp, "new: %pSR\n", (void *)gh->gh_ip);
  	fs_err(sdp, "pid: %d\n", pid_nr(gh->gh_owner_pid));
  	fs_err(sdp, "lock type: %d req lock state : %d\n",
  	       gh->gh_gl->gl_name.ln_type, gh->gh_state);
  	gfs2_dump_glock(NULL, gl, true);
  	BUG();
  }
  
  /**
   * gfs2_glock_nq - enqueue a struct gfs2_holder onto a glock (acquire a glock)
   * @gh: the holder structure
   *
   * if (gh->gh_flags & GL_ASYNC), this never returns an error
   *
   * Returns: 0, GLR_TRYFAILED, or errno on failure
   */
  
  int gfs2_glock_nq(struct gfs2_holder *gh)
  {
  	struct gfs2_glock *gl = gh->gh_gl;
  	int error = 0;
  
  	if (glock_blocked_by_withdraw(gl) && !(gh->gh_flags & LM_FLAG_NOEXP))
  		return -EIO;
  
  	if (test_bit(GLF_LRU, &gl->gl_flags))
  		gfs2_glock_remove_from_lru(gl);
  
  	spin_lock(&gl->gl_lockref.lock);
  	add_to_queue(gh);
  	if (unlikely((LM_FLAG_NOEXP & gh->gh_flags) &&
  		     test_and_clear_bit(GLF_FROZEN, &gl->gl_flags))) {
  		set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
  		gl->gl_lockref.count++;
  		__gfs2_glock_queue_work(gl, 0);
  	}
  	run_queue(gl, 1);
  	spin_unlock(&gl->gl_lockref.lock);
  
  	if (!(gh->gh_flags & GL_ASYNC))
  		error = gfs2_glock_wait(gh);
  
  	return error;
  }
  
  /**
   * gfs2_glock_poll - poll to see if an async request has been completed
   * @gh: the holder
   *
   * Returns: 1 if the request is ready to be gfs2_glock_wait()ed on
   */
  
  int gfs2_glock_poll(struct gfs2_holder *gh)
  {
  	return test_bit(HIF_WAIT, &gh->gh_iflags) ? 0 : 1;
  }
  
  /**
   * gfs2_glock_dq - dequeue a struct gfs2_holder from a glock (release a glock)
   * @gh: the glock holder
   *
   */
  
  void gfs2_glock_dq(struct gfs2_holder *gh)
  {
  	struct gfs2_glock *gl = gh->gh_gl;
  	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
  	unsigned delay = 0;
  	int fast_path = 0;
  
  	spin_lock(&gl->gl_lockref.lock);
  	/*
  	 * If we're in the process of file system withdraw, we cannot just
  	 * dequeue any glocks until our journal is recovered, lest we
  	 * introduce file system corruption. We need two exceptions to this
  	 * rule: We need to allow unlocking of nondisk glocks and the glock
  	 * for our own journal that needs recovery.
  	 */
  	if (test_bit(SDF_WITHDRAW_RECOVERY, &sdp->sd_flags) &&
  	    glock_blocked_by_withdraw(gl) &&
  	    gh->gh_gl != sdp->sd_jinode_gl) {
  		sdp->sd_glock_dqs_held++;
  		might_sleep();
  		wait_on_bit(&sdp->sd_flags, SDF_WITHDRAW_RECOVERY,
  			    TASK_UNINTERRUPTIBLE);
  	}
  	if (gh->gh_flags & GL_NOCACHE)
  		handle_callback(gl, LM_ST_UNLOCKED, 0, false);
  
  	list_del_init(&gh->gh_list);
  	clear_bit(HIF_HOLDER, &gh->gh_iflags);
  	if (find_first_holder(gl) == NULL) {
  		if (list_empty(&gl->gl_holders) &&
  		    !test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
  		    !test_bit(GLF_DEMOTE, &gl->gl_flags))
  			fast_path = 1;
  	}
  	if (!test_bit(GLF_LFLUSH, &gl->gl_flags) && demote_ok(gl))
  		gfs2_glock_add_to_lru(gl);
  
  	trace_gfs2_glock_queue(gh, 0);
  	if (unlikely(!fast_path)) {
  		gl->gl_lockref.count++;
  		if (test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags) &&
  		    !test_bit(GLF_DEMOTE, &gl->gl_flags) &&
  		    gl->gl_name.ln_type == LM_TYPE_INODE)
  			delay = gl->gl_hold_time;
  		__gfs2_glock_queue_work(gl, delay);
  	}
  	spin_unlock(&gl->gl_lockref.lock);
  }
  
  void gfs2_glock_dq_wait(struct gfs2_holder *gh)
  {
  	struct gfs2_glock *gl = gh->gh_gl;
  	gfs2_glock_dq(gh);
  	might_sleep();
  	wait_on_bit(&gl->gl_flags, GLF_DEMOTE, TASK_UNINTERRUPTIBLE);
  }
  
  /**
   * gfs2_glock_dq_uninit - dequeue a holder from a glock and initialize it
   * @gh: the holder structure
   *
   */
  
  void gfs2_glock_dq_uninit(struct gfs2_holder *gh)
  {
  	gfs2_glock_dq(gh);
  	gfs2_holder_uninit(gh);
  }
  
  /**
   * gfs2_glock_nq_num - acquire a glock based on lock number
   * @sdp: the filesystem
   * @number: the lock number
   * @glops: the glock operations for the type of glock
   * @state: the state to acquire the glock in
   * @flags: modifier flags for the acquisition
   * @gh: the struct gfs2_holder
   *
   * Returns: errno
   */
  
  int gfs2_glock_nq_num(struct gfs2_sbd *sdp, u64 number,
  		      const struct gfs2_glock_operations *glops,
  		      unsigned int state, u16 flags, struct gfs2_holder *gh)
  {
  	struct gfs2_glock *gl;
  	int error;
  
  	error = gfs2_glock_get(sdp, number, glops, CREATE, &gl);
  	if (!error) {
  		error = gfs2_glock_nq_init(gl, state, flags, gh);
  		gfs2_glock_put(gl);
  	}
  
  	return error;
  }
  
  /**
   * glock_compare - Compare two struct gfs2_glock structures for sorting
   * @arg_a: the first structure
   * @arg_b: the second structure
   *
   */
  
  static int glock_compare(const void *arg_a, const void *arg_b)
  {
  	const struct gfs2_holder *gh_a = *(const struct gfs2_holder **)arg_a;
  	const struct gfs2_holder *gh_b = *(const struct gfs2_holder **)arg_b;
  	const struct lm_lockname *a = &gh_a->gh_gl->gl_name;
  	const struct lm_lockname *b = &gh_b->gh_gl->gl_name;
  
  	if (a->ln_number > b->ln_number)
  		return 1;
  	if (a->ln_number < b->ln_number)
  		return -1;
  	BUG_ON(gh_a->gh_gl->gl_ops->go_type == gh_b->gh_gl->gl_ops->go_type);
  	return 0;
  }
  
  /**
   * nq_m_sync - synchonously acquire more than one glock in deadlock free order
   * @num_gh: the number of structures
   * @ghs: an array of struct gfs2_holder structures
   *
   * Returns: 0 on success (all glocks acquired),
   *          errno on failure (no glocks acquired)
   */
  
  static int nq_m_sync(unsigned int num_gh, struct gfs2_holder *ghs,
  		     struct gfs2_holder **p)
  {
  	unsigned int x;
  	int error = 0;
  
  	for (x = 0; x < num_gh; x++)
  		p[x] = &ghs[x];
  
  	sort(p, num_gh, sizeof(struct gfs2_holder *), glock_compare, NULL);
  
  	for (x = 0; x < num_gh; x++) {
  		p[x]->gh_flags &= ~(LM_FLAG_TRY | GL_ASYNC);
  
  		error = gfs2_glock_nq(p[x]);
  		if (error) {
  			while (x--)
  				gfs2_glock_dq(p[x]);
  			break;
  		}
  	}
  
  	return error;
  }
  
  /**
   * gfs2_glock_nq_m - acquire multiple glocks
   * @num_gh: the number of structures
   * @ghs: an array of struct gfs2_holder structures
   *
   *
   * Returns: 0 on success (all glocks acquired),
   *          errno on failure (no glocks acquired)
   */
  
  int gfs2_glock_nq_m(unsigned int num_gh, struct gfs2_holder *ghs)
  {
  	struct gfs2_holder *tmp[4];
  	struct gfs2_holder **pph = tmp;
  	int error = 0;
  
  	switch(num_gh) {
  	case 0:
  		return 0;
  	case 1:
  		ghs->gh_flags &= ~(LM_FLAG_TRY | GL_ASYNC);
  		return gfs2_glock_nq(ghs);
  	default:
  		if (num_gh <= 4)
  			break;
  		pph = kmalloc_array(num_gh, sizeof(struct gfs2_holder *),
  				    GFP_NOFS);
  		if (!pph)
  			return -ENOMEM;
  	}
  
  	error = nq_m_sync(num_gh, ghs, pph);
  
  	if (pph != tmp)
  		kfree(pph);
  
  	return error;
  }
  
  /**
   * gfs2_glock_dq_m - release multiple glocks
   * @num_gh: the number of structures
   * @ghs: an array of struct gfs2_holder structures
   *
   */
  
  void gfs2_glock_dq_m(unsigned int num_gh, struct gfs2_holder *ghs)
  {
  	while (num_gh--)
  		gfs2_glock_dq(&ghs[num_gh]);
  }
  
  void gfs2_glock_cb(struct gfs2_glock *gl, unsigned int state)
  {
  	unsigned long delay = 0;
  	unsigned long holdtime;
  	unsigned long now = jiffies;
  
  	gfs2_glock_hold(gl);
  	spin_lock(&gl->gl_lockref.lock);
  	holdtime = gl->gl_tchange + gl->gl_hold_time;
  	if (!list_empty(&gl->gl_holders) &&
  	    gl->gl_name.ln_type == LM_TYPE_INODE) {
  		if (time_before(now, holdtime))
  			delay = holdtime - now;
  		if (test_bit(GLF_REPLY_PENDING, &gl->gl_flags))
  			delay = gl->gl_hold_time;
  	}
  	handle_callback(gl, state, delay, true);
  	__gfs2_glock_queue_work(gl, delay);
  	spin_unlock(&gl->gl_lockref.lock);
  }
  
  /**
   * gfs2_should_freeze - Figure out if glock should be frozen
   * @gl: The glock in question
   *
   * Glocks are not frozen if (a) the result of the dlm operation is
   * an error, (b) the locking operation was an unlock operation or
   * (c) if there is a "noexp" flagged request anywhere in the queue
   *
   * Returns: 1 if freezing should occur, 0 otherwise
   */
  
  static int gfs2_should_freeze(const struct gfs2_glock *gl)
  {
  	const struct gfs2_holder *gh;
  
  	if (gl->gl_reply & ~LM_OUT_ST_MASK)
  		return 0;
  	if (gl->gl_target == LM_ST_UNLOCKED)
  		return 0;
  
  	list_for_each_entry(gh, &gl->gl_holders, gh_list) {
  		if (test_bit(HIF_HOLDER, &gh->gh_iflags))
  			continue;
  		if (LM_FLAG_NOEXP & gh->gh_flags)
  			return 0;
  	}
  
  	return 1;
  }
  
  /**
   * gfs2_glock_complete - Callback used by locking
   * @gl: Pointer to the glock
   * @ret: The return value from the dlm
   *
   * The gl_reply field is under the gl_lockref.lock lock so that it is ok
   * to use a bitfield shared with other glock state fields.
   */
  
  void gfs2_glock_complete(struct gfs2_glock *gl, int ret)
  {
  	struct lm_lockstruct *ls = &gl->gl_name.ln_sbd->sd_lockstruct;
  
  	spin_lock(&gl->gl_lockref.lock);
  	gl->gl_reply = ret;
  
  	if (unlikely(test_bit(DFL_BLOCK_LOCKS, &ls->ls_recover_flags))) {
  		if (gfs2_should_freeze(gl)) {
  			set_bit(GLF_FROZEN, &gl->gl_flags);
  			spin_unlock(&gl->gl_lockref.lock);
  			return;
  		}
  	}
  
  	gl->gl_lockref.count++;
  	set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
  	__gfs2_glock_queue_work(gl, 0);
  	spin_unlock(&gl->gl_lockref.lock);
  }
  
  static int glock_cmp(void *priv, struct list_head *a, struct list_head *b)
  {
  	struct gfs2_glock *gla, *glb;
  
  	gla = list_entry(a, struct gfs2_glock, gl_lru);
  	glb = list_entry(b, struct gfs2_glock, gl_lru);
  
  	if (gla->gl_name.ln_number > glb->gl_name.ln_number)
  		return 1;
  	if (gla->gl_name.ln_number < glb->gl_name.ln_number)
  		return -1;
  
  	return 0;
  }
  
  /**
   * gfs2_dispose_glock_lru - Demote a list of glocks
   * @list: The list to dispose of
   *
   * Disposing of glocks may involve disk accesses, so that here we sort
   * the glocks by number (i.e. disk location of the inodes) so that if
   * there are any such accesses, they'll be sent in order (mostly).
   *
   * Must be called under the lru_lock, but may drop and retake this
   * lock. While the lru_lock is dropped, entries may vanish from the
   * list, but no new entries will appear on the list (since it is
   * private)
   */
  
  static void gfs2_dispose_glock_lru(struct list_head *list)
  __releases(&lru_lock)
  __acquires(&lru_lock)
  {
  	struct gfs2_glock *gl;
  
  	list_sort(NULL, list, glock_cmp);
  
  	while(!list_empty(list)) {
  		gl = list_first_entry(list, struct gfs2_glock, gl_lru);
  		list_del_init(&gl->gl_lru);
  		if (!spin_trylock(&gl->gl_lockref.lock)) {
  add_back_to_lru:
  			list_add(&gl->gl_lru, &lru_list);
  			set_bit(GLF_LRU, &gl->gl_flags);
  			atomic_inc(&lru_count);
  			continue;
  		}
  		if (test_and_set_bit(GLF_LOCK, &gl->gl_flags)) {
  			spin_unlock(&gl->gl_lockref.lock);
  			goto add_back_to_lru;
  		}
  		gl->gl_lockref.count++;
  		if (demote_ok(gl))
  			handle_callback(gl, LM_ST_UNLOCKED, 0, false);
  		WARN_ON(!test_and_clear_bit(GLF_LOCK, &gl->gl_flags));
  		__gfs2_glock_queue_work(gl, 0);
  		spin_unlock(&gl->gl_lockref.lock);
  		cond_resched_lock(&lru_lock);
  	}
  }
  
  /**
   * gfs2_scan_glock_lru - Scan the LRU looking for locks to demote
   * @nr: The number of entries to scan
   *
   * This function selects the entries on the LRU which are able to
   * be demoted, and then kicks off the process by calling
   * gfs2_dispose_glock_lru() above.
   */
  
  static long gfs2_scan_glock_lru(int nr)
  {
  	struct gfs2_glock *gl;
  	LIST_HEAD(skipped);
  	LIST_HEAD(dispose);
  	long freed = 0;
  
  	spin_lock(&lru_lock);
  	while ((nr-- >= 0) && !list_empty(&lru_list)) {
  		gl = list_first_entry(&lru_list, struct gfs2_glock, gl_lru);
  
  		/* Test for being demotable */
  		if (!test_bit(GLF_LOCK, &gl->gl_flags)) {
  			list_move(&gl->gl_lru, &dispose);
  			atomic_dec(&lru_count);
  			clear_bit(GLF_LRU, &gl->gl_flags);
  			freed++;
  			continue;
  		}
  
  		list_move(&gl->gl_lru, &skipped);
  	}
  	list_splice(&skipped, &lru_list);
  	if (!list_empty(&dispose))
  		gfs2_dispose_glock_lru(&dispose);
  	spin_unlock(&lru_lock);
  
  	return freed;
  }
  
  static unsigned long gfs2_glock_shrink_scan(struct shrinker *shrink,
  					    struct shrink_control *sc)
  {
  	if (!(sc->gfp_mask & __GFP_FS))
  		return SHRINK_STOP;
  	return gfs2_scan_glock_lru(sc->nr_to_scan);
  }
  
  static unsigned long gfs2_glock_shrink_count(struct shrinker *shrink,
  					     struct shrink_control *sc)
  {
  	return vfs_pressure_ratio(atomic_read(&lru_count));
  }
  
  static struct shrinker glock_shrinker = {
  	.seeks = DEFAULT_SEEKS,
  	.count_objects = gfs2_glock_shrink_count,
  	.scan_objects = gfs2_glock_shrink_scan,
  };
  
  /**
   * glock_hash_walk - Call a function for glock in a hash bucket
   * @examiner: the function
   * @sdp: the filesystem
   *
   * Note that the function can be called multiple times on the same
   * object.  So the user must ensure that the function can cope with
   * that.
   */
  
  static void glock_hash_walk(glock_examiner examiner, const struct gfs2_sbd *sdp)
  {
  	struct gfs2_glock *gl;
  	struct rhashtable_iter iter;
  
  	rhashtable_walk_enter(&gl_hash_table, &iter);
  
  	do {
  		rhashtable_walk_start(&iter);
  
  		while ((gl = rhashtable_walk_next(&iter)) && !IS_ERR(gl))
  			if (gl->gl_name.ln_sbd == sdp &&
  			    lockref_get_not_dead(&gl->gl_lockref))
  				examiner(gl);
  
  		rhashtable_walk_stop(&iter);
  	} while (cond_resched(), gl == ERR_PTR(-EAGAIN));
  
  	rhashtable_walk_exit(&iter);
  }
  
  bool gfs2_queue_delete_work(struct gfs2_glock *gl, unsigned long delay)
  {
  	bool queued;
  
  	spin_lock(&gl->gl_lockref.lock);
  	queued = queue_delayed_work(gfs2_delete_workqueue,
  				    &gl->gl_delete, delay);
  	if (queued)
  		set_bit(GLF_PENDING_DELETE, &gl->gl_flags);
  	spin_unlock(&gl->gl_lockref.lock);
  	return queued;
  }
  
  void gfs2_cancel_delete_work(struct gfs2_glock *gl)
  {
  	if (cancel_delayed_work_sync(&gl->gl_delete)) {
  		clear_bit(GLF_PENDING_DELETE, &gl->gl_flags);
  		gfs2_glock_put(gl);
  	}
  }
  
  bool gfs2_delete_work_queued(const struct gfs2_glock *gl)
  {
  	return test_bit(GLF_PENDING_DELETE, &gl->gl_flags);
  }
  
  static void flush_delete_work(struct gfs2_glock *gl)
  {
  	if (gl->gl_name.ln_type == LM_TYPE_IOPEN) {
  		if (cancel_delayed_work(&gl->gl_delete)) {
  			queue_delayed_work(gfs2_delete_workqueue,
  					   &gl->gl_delete, 0);
  		}
  	}
  	gfs2_glock_queue_work(gl, 0);
  }
  
  void gfs2_flush_delete_work(struct gfs2_sbd *sdp)
  {
  	glock_hash_walk(flush_delete_work, sdp);
  	flush_workqueue(gfs2_delete_workqueue);
  }
  
  /**
   * thaw_glock - thaw out a glock which has an unprocessed reply waiting
   * @gl: The glock to thaw
   *
   */
  
  static void thaw_glock(struct gfs2_glock *gl)
  {
  	if (!test_and_clear_bit(GLF_FROZEN, &gl->gl_flags)) {
  		gfs2_glock_put(gl);
  		return;
  	}
  	set_bit(GLF_REPLY_PENDING, &gl->gl_flags);
  	gfs2_glock_queue_work(gl, 0);
  }
  
  /**
   * clear_glock - look at a glock and see if we can free it from glock cache
   * @gl: the glock to look at
   *
   */
  
  static void clear_glock(struct gfs2_glock *gl)
  {
  	gfs2_glock_remove_from_lru(gl);
  
  	spin_lock(&gl->gl_lockref.lock);
  	if (gl->gl_state != LM_ST_UNLOCKED)
  		handle_callback(gl, LM_ST_UNLOCKED, 0, false);
  	__gfs2_glock_queue_work(gl, 0);
  	spin_unlock(&gl->gl_lockref.lock);
  }
  
  /**
   * gfs2_glock_thaw - Thaw any frozen glocks
   * @sdp: The super block
   *
   */
  
  void gfs2_glock_thaw(struct gfs2_sbd *sdp)
  {
  	glock_hash_walk(thaw_glock, sdp);
  }
  
  static void dump_glock(struct seq_file *seq, struct gfs2_glock *gl, bool fsid)
  {
  	spin_lock(&gl->gl_lockref.lock);
  	gfs2_dump_glock(seq, gl, fsid);
  	spin_unlock(&gl->gl_lockref.lock);
  }
  
  static void dump_glock_func(struct gfs2_glock *gl)
  {
  	dump_glock(NULL, gl, true);
  }
  
  /**
   * gfs2_gl_hash_clear - Empty out the glock hash table
   * @sdp: the filesystem
   * @wait: wait until it's all gone
   *
   * Called when unmounting the filesystem.
   */
  
  void gfs2_gl_hash_clear(struct gfs2_sbd *sdp)
  {
  	set_bit(SDF_SKIP_DLM_UNLOCK, &sdp->sd_flags);
  	flush_workqueue(glock_workqueue);
  	glock_hash_walk(clear_glock, sdp);
  	flush_workqueue(glock_workqueue);
  	wait_event_timeout(sdp->sd_glock_wait,
  			   atomic_read(&sdp->sd_glock_disposal) == 0,
  			   HZ * 600);
  	glock_hash_walk(dump_glock_func, sdp);
  }
  
  void gfs2_glock_finish_truncate(struct gfs2_inode *ip)
  {
  	struct gfs2_glock *gl = ip->i_gl;
  	int ret;
  
  	ret = gfs2_truncatei_resume(ip);
  	gfs2_glock_assert_withdraw(gl, ret == 0);
  
  	spin_lock(&gl->gl_lockref.lock);
  	clear_bit(GLF_LOCK, &gl->gl_flags);
  	run_queue(gl, 1);
  	spin_unlock(&gl->gl_lockref.lock);
  }
  
  static const char *state2str(unsigned state)
  {
  	switch(state) {
  	case LM_ST_UNLOCKED:
  		return "UN";
  	case LM_ST_SHARED:
  		return "SH";
  	case LM_ST_DEFERRED:
  		return "DF";
  	case LM_ST_EXCLUSIVE:
  		return "EX";
  	}
  	return "??";
  }
  
  static const char *hflags2str(char *buf, u16 flags, unsigned long iflags)
  {
  	char *p = buf;
  	if (flags & LM_FLAG_TRY)
  		*p++ = 't';
  	if (flags & LM_FLAG_TRY_1CB)
  		*p++ = 'T';
  	if (flags & LM_FLAG_NOEXP)
  		*p++ = 'e';
  	if (flags & LM_FLAG_ANY)
  		*p++ = 'A';
  	if (flags & LM_FLAG_PRIORITY)
  		*p++ = 'p';
  	if (flags & GL_ASYNC)
  		*p++ = 'a';
  	if (flags & GL_EXACT)
  		*p++ = 'E';
  	if (flags & GL_NOCACHE)
  		*p++ = 'c';
  	if (test_bit(HIF_HOLDER, &iflags))
  		*p++ = 'H';
  	if (test_bit(HIF_WAIT, &iflags))
  		*p++ = 'W';
  	if (test_bit(HIF_FIRST, &iflags))
  		*p++ = 'F';
  	*p = 0;
  	return buf;
  }
  
  /**
   * dump_holder - print information about a glock holder
   * @seq: the seq_file struct
   * @gh: the glock holder
   * @fs_id_buf: pointer to file system id (if requested)
   *
   */
  
  static void dump_holder(struct seq_file *seq, const struct gfs2_holder *gh,
  			const char *fs_id_buf)
  {
  	struct task_struct *gh_owner = NULL;
  	char flags_buf[32];
  
  	rcu_read_lock();
  	if (gh->gh_owner_pid)
  		gh_owner = pid_task(gh->gh_owner_pid, PIDTYPE_PID);
  	gfs2_print_dbg(seq, "%s H: s:%s f:%s e:%d p:%ld [%s] %pS\n",
  		       fs_id_buf, state2str(gh->gh_state),
  		       hflags2str(flags_buf, gh->gh_flags, gh->gh_iflags),
  		       gh->gh_error,
  		       gh->gh_owner_pid ? (long)pid_nr(gh->gh_owner_pid) : -1,
  		       gh_owner ? gh_owner->comm : "(ended)",
  		       (void *)gh->gh_ip);
  	rcu_read_unlock();
  }
  
  static const char *gflags2str(char *buf, const struct gfs2_glock *gl)
  {
  	const unsigned long *gflags = &gl->gl_flags;
  	char *p = buf;
  
  	if (test_bit(GLF_LOCK, gflags))
  		*p++ = 'l';
  	if (test_bit(GLF_DEMOTE, gflags))
  		*p++ = 'D';
  	if (test_bit(GLF_PENDING_DEMOTE, gflags))
  		*p++ = 'd';
  	if (test_bit(GLF_DEMOTE_IN_PROGRESS, gflags))
  		*p++ = 'p';
  	if (test_bit(GLF_DIRTY, gflags))
  		*p++ = 'y';
  	if (test_bit(GLF_LFLUSH, gflags))
  		*p++ = 'f';
  	if (test_bit(GLF_INVALIDATE_IN_PROGRESS, gflags))
  		*p++ = 'i';
  	if (test_bit(GLF_REPLY_PENDING, gflags))
  		*p++ = 'r';
  	if (test_bit(GLF_INITIAL, gflags))
  		*p++ = 'I';
  	if (test_bit(GLF_FROZEN, gflags))
  		*p++ = 'F';
  	if (!list_empty(&gl->gl_holders))
  		*p++ = 'q';
  	if (test_bit(GLF_LRU, gflags))
  		*p++ = 'L';
  	if (gl->gl_object)
  		*p++ = 'o';
  	if (test_bit(GLF_BLOCKING, gflags))
  		*p++ = 'b';
  	if (test_bit(GLF_INODE_CREATING, gflags))
  		*p++ = 'c';
  	if (test_bit(GLF_PENDING_DELETE, gflags))
  		*p++ = 'P';
  	if (test_bit(GLF_FREEING, gflags))
  		*p++ = 'x';
  	*p = 0;
  	return buf;
  }
  
  /**
   * gfs2_dump_glock - print information about a glock
   * @seq: The seq_file struct
   * @gl: the glock
   * @fsid: If true, also dump the file system id
   *
   * The file format is as follows:
   * One line per object, capital letters are used to indicate objects
   * G = glock, I = Inode, R = rgrp, H = holder. Glocks are not indented,
   * other objects are indented by a single space and follow the glock to
   * which they are related. Fields are indicated by lower case letters
   * followed by a colon and the field value, except for strings which are in
   * [] so that its possible to see if they are composed of spaces for
   * example. The field's are n = number (id of the object), f = flags,
   * t = type, s = state, r = refcount, e = error, p = pid.
   *
   */
  
  void gfs2_dump_glock(struct seq_file *seq, struct gfs2_glock *gl, bool fsid)
  {
  	const struct gfs2_glock_operations *glops = gl->gl_ops;
  	unsigned long long dtime;
  	const struct gfs2_holder *gh;
  	char gflags_buf[32];
  	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
  	char fs_id_buf[sizeof(sdp->sd_fsname) + 7];
  	unsigned long nrpages = 0;
  
  	if (gl->gl_ops->go_flags & GLOF_ASPACE) {
  		struct address_space *mapping = gfs2_glock2aspace(gl);
  
  		nrpages = mapping->nrpages;
  	}
  	memset(fs_id_buf, 0, sizeof(fs_id_buf));
  	if (fsid && sdp) /* safety precaution */
  		sprintf(fs_id_buf, "fsid=%s: ", sdp->sd_fsname);
  	dtime = jiffies - gl->gl_demote_time;
  	dtime *= 1000000/HZ; /* demote time in uSec */
  	if (!test_bit(GLF_DEMOTE, &gl->gl_flags))
  		dtime = 0;
  	gfs2_print_dbg(seq, "%sG:  s:%s n:%u/%llx f:%s t:%s d:%s/%llu a:%d "
  		       "v:%d r:%d m:%ld p:%lu\n",
  		       fs_id_buf, state2str(gl->gl_state),
  		       gl->gl_name.ln_type,
  		       (unsigned long long)gl->gl_name.ln_number,
  		       gflags2str(gflags_buf, gl),
  		       state2str(gl->gl_target),
  		       state2str(gl->gl_demote_state), dtime,
  		       atomic_read(&gl->gl_ail_count),
  		       atomic_read(&gl->gl_revokes),
  		       (int)gl->gl_lockref.count, gl->gl_hold_time, nrpages);
  
  	list_for_each_entry(gh, &gl->gl_holders, gh_list)
  		dump_holder(seq, gh, fs_id_buf);
  
  	if (gl->gl_state != LM_ST_UNLOCKED && glops->go_dump)
  		glops->go_dump(seq, gl, fs_id_buf);
  }
  
  static int gfs2_glstats_seq_show(struct seq_file *seq, void *iter_ptr)
  {
  	struct gfs2_glock *gl = iter_ptr;
  
  	seq_printf(seq, "G: n:%u/%llx rtt:%llu/%llu rttb:%llu/%llu irt:%llu/%llu dcnt: %llu qcnt: %llu\n",
  		   gl->gl_name.ln_type,
  		   (unsigned long long)gl->gl_name.ln_number,
  		   (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SRTT],
  		   (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SRTTVAR],
  		   (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SRTTB],
  		   (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SRTTVARB],
  		   (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SIRT],
  		   (unsigned long long)gl->gl_stats.stats[GFS2_LKS_SIRTVAR],
  		   (unsigned long long)gl->gl_stats.stats[GFS2_LKS_DCOUNT],
  		   (unsigned long long)gl->gl_stats.stats[GFS2_LKS_QCOUNT]);
  	return 0;
  }
  
  static const char *gfs2_gltype[] = {
  	"type",
  	"reserved",
  	"nondisk",
  	"inode",
  	"rgrp",
  	"meta",
  	"iopen",
  	"flock",
  	"plock",
  	"quota",
  	"journal",
  };
  
  static const char *gfs2_stype[] = {
  	[GFS2_LKS_SRTT]		= "srtt",
  	[GFS2_LKS_SRTTVAR]	= "srttvar",
  	[GFS2_LKS_SRTTB]	= "srttb",
  	[GFS2_LKS_SRTTVARB]	= "srttvarb",
  	[GFS2_LKS_SIRT]		= "sirt",
  	[GFS2_LKS_SIRTVAR]	= "sirtvar",
  	[GFS2_LKS_DCOUNT]	= "dlm",
  	[GFS2_LKS_QCOUNT]	= "queue",
  };
  
  #define GFS2_NR_SBSTATS (ARRAY_SIZE(gfs2_gltype) * ARRAY_SIZE(gfs2_stype))
  
  static int gfs2_sbstats_seq_show(struct seq_file *seq, void *iter_ptr)
  {
  	struct gfs2_sbd *sdp = seq->private;
  	loff_t pos = *(loff_t *)iter_ptr;
  	unsigned index = pos >> 3;
  	unsigned subindex = pos & 0x07;
  	int i;
  
  	if (index == 0 && subindex != 0)
  		return 0;
  
  	seq_printf(seq, "%-10s %8s:", gfs2_gltype[index],
  		   (index == 0) ? "cpu": gfs2_stype[subindex]);
  
  	for_each_possible_cpu(i) {
                  const struct gfs2_pcpu_lkstats *lkstats = per_cpu_ptr(sdp->sd_lkstats, i);
  
  		if (index == 0)
  			seq_printf(seq, " %15u", i);
  		else
  			seq_printf(seq, " %15llu", (unsigned long long)lkstats->
  				   lkstats[index - 1].stats[subindex]);
  	}
  	seq_putc(seq, '\n');
  	return 0;
  }
  
  int __init gfs2_glock_init(void)
  {
  	int i, ret;
  
  	ret = rhashtable_init(&gl_hash_table, &ht_parms);
  	if (ret < 0)
  		return ret;
  
  	glock_workqueue = alloc_workqueue("glock_workqueue", WQ_MEM_RECLAIM |
  					  WQ_HIGHPRI | WQ_FREEZABLE, 0);
  	if (!glock_workqueue) {
  		rhashtable_destroy(&gl_hash_table);
  		return -ENOMEM;
  	}
  	gfs2_delete_workqueue = alloc_workqueue("delete_workqueue",
  						WQ_MEM_RECLAIM | WQ_FREEZABLE,
  						0);
  	if (!gfs2_delete_workqueue) {
  		destroy_workqueue(glock_workqueue);
  		rhashtable_destroy(&gl_hash_table);
  		return -ENOMEM;
  	}
  
  	ret = register_shrinker(&glock_shrinker);
  	if (ret) {
  		destroy_workqueue(gfs2_delete_workqueue);
  		destroy_workqueue(glock_workqueue);
  		rhashtable_destroy(&gl_hash_table);
  		return ret;
  	}
  
  	for (i = 0; i < GLOCK_WAIT_TABLE_SIZE; i++)
  		init_waitqueue_head(glock_wait_table + i);
  
  	return 0;
  }
  
  void gfs2_glock_exit(void)
  {
  	unregister_shrinker(&glock_shrinker);
  	rhashtable_destroy(&gl_hash_table);
  	destroy_workqueue(glock_workqueue);
  	destroy_workqueue(gfs2_delete_workqueue);
  }
  
  static void gfs2_glock_iter_next(struct gfs2_glock_iter *gi, loff_t n)
  {
  	struct gfs2_glock *gl = gi->gl;
  
  	if (gl) {
  		if (n == 0)
  			return;
  		if (!lockref_put_not_zero(&gl->gl_lockref))
  			gfs2_glock_queue_put(gl);
  	}
  	for (;;) {
  		gl = rhashtable_walk_next(&gi->hti);
  		if (IS_ERR_OR_NULL(gl)) {
  			if (gl == ERR_PTR(-EAGAIN)) {
  				n = 1;
  				continue;
  			}
  			gl = NULL;
  			break;
  		}
  		if (gl->gl_name.ln_sbd != gi->sdp)
  			continue;
  		if (n <= 1) {
  			if (!lockref_get_not_dead(&gl->gl_lockref))
  				continue;
  			break;
  		} else {
  			if (__lockref_is_dead(&gl->gl_lockref))
  				continue;
  			n--;
  		}
  	}
  	gi->gl = gl;
  }
  
  static void *gfs2_glock_seq_start(struct seq_file *seq, loff_t *pos)
  	__acquires(RCU)
  {
  	struct gfs2_glock_iter *gi = seq->private;
  	loff_t n;
  
  	/*
  	 * We can either stay where we are, skip to the next hash table
  	 * entry, or start from the beginning.
  	 */
  	if (*pos < gi->last_pos) {
  		rhashtable_walk_exit(&gi->hti);
  		rhashtable_walk_enter(&gl_hash_table, &gi->hti);
  		n = *pos + 1;
  	} else {
  		n = *pos - gi->last_pos;
  	}
  
  	rhashtable_walk_start(&gi->hti);
  
  	gfs2_glock_iter_next(gi, n);
  	gi->last_pos = *pos;
  	return gi->gl;
  }
  
  static void *gfs2_glock_seq_next(struct seq_file *seq, void *iter_ptr,
  				 loff_t *pos)
  {
  	struct gfs2_glock_iter *gi = seq->private;
  
  	(*pos)++;
  	gi->last_pos = *pos;
  	gfs2_glock_iter_next(gi, 1);
  	return gi->gl;
  }
  
  static void gfs2_glock_seq_stop(struct seq_file *seq, void *iter_ptr)
  	__releases(RCU)
  {
  	struct gfs2_glock_iter *gi = seq->private;
  
  	rhashtable_walk_stop(&gi->hti);
  }
  
  static int gfs2_glock_seq_show(struct seq_file *seq, void *iter_ptr)
  {
  	dump_glock(seq, iter_ptr, false);
  	return 0;
  }
  
  static void *gfs2_sbstats_seq_start(struct seq_file *seq, loff_t *pos)
  {
  	preempt_disable();
  	if (*pos >= GFS2_NR_SBSTATS)
  		return NULL;
  	return pos;
  }
  
  static void *gfs2_sbstats_seq_next(struct seq_file *seq, void *iter_ptr,
  				   loff_t *pos)
  {
  	(*pos)++;
  	if (*pos >= GFS2_NR_SBSTATS)
  		return NULL;
  	return pos;
  }
  
  static void gfs2_sbstats_seq_stop(struct seq_file *seq, void *iter_ptr)
  {
  	preempt_enable();
  }
  
  static const struct seq_operations gfs2_glock_seq_ops = {
  	.start = gfs2_glock_seq_start,
  	.next  = gfs2_glock_seq_next,
  	.stop  = gfs2_glock_seq_stop,
  	.show  = gfs2_glock_seq_show,
  };
  
  static const struct seq_operations gfs2_glstats_seq_ops = {
  	.start = gfs2_glock_seq_start,
  	.next  = gfs2_glock_seq_next,
  	.stop  = gfs2_glock_seq_stop,
  	.show  = gfs2_glstats_seq_show,
  };
  
  static const struct seq_operations gfs2_sbstats_sops = {
  	.start = gfs2_sbstats_seq_start,
  	.next  = gfs2_sbstats_seq_next,
  	.stop  = gfs2_sbstats_seq_stop,
  	.show  = gfs2_sbstats_seq_show,
  };
  
  #define GFS2_SEQ_GOODSIZE min(PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER, 65536UL)
  
  static int __gfs2_glocks_open(struct inode *inode, struct file *file,
  			      const struct seq_operations *ops)
  {
  	int ret = seq_open_private(file, ops, sizeof(struct gfs2_glock_iter));
  	if (ret == 0) {
  		struct seq_file *seq = file->private_data;
  		struct gfs2_glock_iter *gi = seq->private;
  
  		gi->sdp = inode->i_private;
  		seq->buf = kmalloc(GFS2_SEQ_GOODSIZE, GFP_KERNEL | __GFP_NOWARN);
  		if (seq->buf)
  			seq->size = GFS2_SEQ_GOODSIZE;
  		/*
  		 * Initially, we are "before" the first hash table entry; the
  		 * first call to rhashtable_walk_next gets us the first entry.
  		 */
  		gi->last_pos = -1;
  		gi->gl = NULL;
  		rhashtable_walk_enter(&gl_hash_table, &gi->hti);
  	}
  	return ret;
  }
  
  static int gfs2_glocks_open(struct inode *inode, struct file *file)
  {
  	return __gfs2_glocks_open(inode, file, &gfs2_glock_seq_ops);
  }
  
  static int gfs2_glocks_release(struct inode *inode, struct file *file)
  {
  	struct seq_file *seq = file->private_data;
  	struct gfs2_glock_iter *gi = seq->private;
  
  	if (gi->gl)
  		gfs2_glock_put(gi->gl);
  	rhashtable_walk_exit(&gi->hti);
  	return seq_release_private(inode, file);
  }
  
  static int gfs2_glstats_open(struct inode *inode, struct file *file)
  {
  	return __gfs2_glocks_open(inode, file, &gfs2_glstats_seq_ops);
  }
  
  static const struct file_operations gfs2_glocks_fops = {
  	.owner   = THIS_MODULE,
  	.open    = gfs2_glocks_open,
  	.read    = seq_read,
  	.llseek  = seq_lseek,
  	.release = gfs2_glocks_release,
  };
  
  static const struct file_operations gfs2_glstats_fops = {
  	.owner   = THIS_MODULE,
  	.open    = gfs2_glstats_open,
  	.read    = seq_read,
  	.llseek  = seq_lseek,
  	.release = gfs2_glocks_release,
  };
  
  DEFINE_SEQ_ATTRIBUTE(gfs2_sbstats);
  
  void gfs2_create_debugfs_file(struct gfs2_sbd *sdp)
  {
  	sdp->debugfs_dir = debugfs_create_dir(sdp->sd_table_name, gfs2_root);
  
  	debugfs_create_file("glocks", S_IFREG | S_IRUGO, sdp->debugfs_dir, sdp,
  			    &gfs2_glocks_fops);
  
  	debugfs_create_file("glstats", S_IFREG | S_IRUGO, sdp->debugfs_dir, sdp,
  			    &gfs2_glstats_fops);
  
  	debugfs_create_file("sbstats", S_IFREG | S_IRUGO, sdp->debugfs_dir, sdp,
  			    &gfs2_sbstats_fops);
  }
  
  void gfs2_delete_debugfs_file(struct gfs2_sbd *sdp)
  {
  	debugfs_remove_recursive(sdp->debugfs_dir);
  	sdp->debugfs_dir = NULL;
  }
  
  void gfs2_register_debugfs(void)
  {
  	gfs2_root = debugfs_create_dir("gfs2", NULL);
  }
  
  void gfs2_unregister_debugfs(void)
  {
  	debugfs_remove(gfs2_root);
  	gfs2_root = NULL;
  }
  