Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2962 insertions, 0 deletions

diff --git a/fs/gfs2/glock.c b/fs/gfs2/glock.c
new file mode 100644
index 000000000..235a0948f
--- /dev/null
+++ b/fs/gfs2/glock.c
@@ -0,0 +1,2962 @@
+// 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 <linux/pid_namespace.h>
+#include <linux/fdtable.h>
+#include <linux/file.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 void __gfs2_glock_dq(struct gfs2_holder *gh);
+static void handle_callback(struct gfs2_glock *gl, unsigned int state,
+			    unsigned long delay, bool remote);
+
+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) {
+		struct gfs2_glock_aspace *gla =
+			container_of(gl, struct gfs2_glock_aspace, glock);
+		kmem_cache_free(gfs2_glock_aspace_cachep, gla);
+	} 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;
+	/*
+	 * Note that demote_ok is used for the lru process of disposing of
+	 * glocks. For this purpose, we don't care if the glock's holders
+	 * have the HIF_MAY_DEMOTE flag set or not. If someone is using
+	 * them, don't demote.
+	 */
+	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_move_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_empty(mapping));
+	}
+	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 it's ok to grant a new lock
+ * @gl: The glock
+ * @current_gh: One of the current holders of @gl
+ * @gh: The lock request which we wish to grant
+ *
+ * With our current compatibility rules, if a glock has one or more active
+ * holders (HIF_HOLDER flag set), any of those holders can be passed in as
+ * @current_gh; they are all the same as far as compatibility with the new @gh
+ * goes.
+ *
+ * Returns true if it's ok to grant the lock.
+ */
+
+static inline bool may_grant(struct gfs2_glock *gl,
+			     struct gfs2_holder *current_gh,
+			     struct gfs2_holder *gh)
+{
+	if (current_gh) {
+		GLOCK_BUG_ON(gl, !test_bit(HIF_HOLDER, &current_gh->gh_iflags));
+
+		switch(current_gh->gh_state) {
+		case LM_ST_EXCLUSIVE:
+			/*
+			 * Here we make a special exception to grant holders
+			 * who agree to share the EX lock with other holders
+			 * who also have the bit set. If the original holder
+			 * has the LM_FLAG_NODE_SCOPE bit set, we grant more
+			 * holders with the bit set.
+			 */
+			return gh->gh_state == LM_ST_EXCLUSIVE &&
+			       (current_gh->gh_flags & LM_FLAG_NODE_SCOPE) &&
+			       (gh->gh_flags & LM_FLAG_NODE_SCOPE);
+
+		case LM_ST_SHARED:
+		case LM_ST_DEFERRED:
+			return gh->gh_state == current_gh->gh_state;
+
+		default:
+			return false;
+		}
+	}
+
+	if (gl->gl_state == gh->gh_state)
+		return true;
+	if (gh->gh_flags & GL_EXACT)
+		return false;
+	if (gl->gl_state == LM_ST_EXCLUSIVE) {
+		return gh->gh_state == LM_ST_SHARED ||
+		       gh->gh_state == LM_ST_DEFERRED;
+	}
+	if (gh->gh_flags & LM_FLAG_ANY)
+		return gl->gl_state != LM_ST_UNLOCKED;
+	return false;
+}
+
+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
+ * @gl: The glock
+ * @ret: The status from the DLM
+ */
+
+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_WAIT, &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);
+	}
+}
+
+/**
+ * demote_incompat_holders - demote incompatible demoteable holders
+ * @gl: the glock we want to promote
+ * @current_gh: the newly promoted holder
+ *
+ * We're passing the newly promoted holder in @current_gh, but actually, any of
+ * the strong holders would do.
+ */
+static void demote_incompat_holders(struct gfs2_glock *gl,
+				    struct gfs2_holder *current_gh)
+{
+	struct gfs2_holder *gh, *tmp;
+
+	/*
+	 * Demote incompatible holders before we make ourselves eligible.
+	 * (This holder may or may not allow auto-demoting, but we don't want
+	 * to demote the new holder before it's even granted.)
+	 */
+	list_for_each_entry_safe(gh, tmp, &gl->gl_holders, gh_list) {
+		/*
+		 * Since holders are at the front of the list, we stop when we
+		 * find the first non-holder.
+		 */
+		if (!test_bit(HIF_HOLDER, &gh->gh_iflags))
+			return;
+		if (gh == current_gh)
+			continue;
+		if (test_bit(HIF_MAY_DEMOTE, &gh->gh_iflags) &&
+		    !may_grant(gl, current_gh, gh)) {
+			/*
+			 * We should not recurse into do_promote because
+			 * __gfs2_glock_dq only calls handle_callback,
+			 * gfs2_glock_add_to_lru and __gfs2_glock_queue_work.
+			 */
+			__gfs2_glock_dq(gh);
+		}
+	}
+}
+
+/**
+ * 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;
+}
+
+/**
+ * find_first_strong_holder - find the first non-demoteable holder
+ * @gl: the glock
+ *
+ * Find the first holder that doesn't have the HIF_MAY_DEMOTE flag set.
+ */
+static inline struct gfs2_holder *
+find_first_strong_holder(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 NULL;
+		if (!test_bit(HIF_MAY_DEMOTE, &gh->gh_iflags))
+			return gh;
+	}
+	return NULL;
+}
+
+/*
+ * gfs2_instantiate - Call the glops instantiate function
+ * @gh: The glock holder
+ *
+ * Returns: 0 if instantiate was successful, or error.
+ */
+int gfs2_instantiate(struct gfs2_holder *gh)
+{
+	struct gfs2_glock *gl = gh->gh_gl;
+	const struct gfs2_glock_operations *glops = gl->gl_ops;
+	int ret;
+
+again:
+	if (!test_bit(GLF_INSTANTIATE_NEEDED, &gl->gl_flags))
+		goto done;
+
+	/*
+	 * Since we unlock the lockref lock, we set a flag to indicate
+	 * instantiate is in progress.
+	 */
+	if (test_and_set_bit(GLF_INSTANTIATE_IN_PROG, &gl->gl_flags)) {
+		wait_on_bit(&gl->gl_flags, GLF_INSTANTIATE_IN_PROG,
+			    TASK_UNINTERRUPTIBLE);
+		/*
+		 * Here we just waited for a different instantiate to finish.
+		 * But that may not have been successful, as when a process
+		 * locks an inode glock _before_ it has an actual inode to
+		 * instantiate into. So we check again. This process might
+		 * have an inode to instantiate, so might be successful.
+		 */
+		goto again;
+	}
+
+	ret = glops->go_instantiate(gl);
+	if (!ret)
+		clear_bit(GLF_INSTANTIATE_NEEDED, &gl->gl_flags);
+	clear_and_wake_up_bit(GLF_INSTANTIATE_IN_PROG, &gl->gl_flags);
+	if (ret)
+		return ret;
+
+done:
+	if (glops->go_held)
+		return glops->go_held(gh);
+	return 0;
+}
+
+/**
+ * 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
+ */
+
+static int do_promote(struct gfs2_glock *gl)
+{
+	struct gfs2_holder *gh, *current_gh;
+	bool incompat_holders_demoted = false;
+
+	current_gh = find_first_strong_holder(gl);
+	list_for_each_entry(gh, &gl->gl_holders, gh_list) {
+		if (test_bit(HIF_HOLDER, &gh->gh_iflags))
+			continue;
+		if (!may_grant(gl, current_gh, gh)) {
+			/*
+			 * If we get here, it means we may not grant this
+			 * holder for some reason. If this holder is at the
+			 * head of the list, it means we have a blocked holder
+			 * at the head, so return 1.
+			 */
+			if (list_is_first(&gh->gh_list, &gl->gl_holders))
+				return 1;
+			do_error(gl, 0);
+			break;
+		}
+		set_bit(HIF_HOLDER, &gh->gh_iflags);
+		trace_gfs2_promote(gh);
+		gfs2_holder_wake(gh);
+		if (!incompat_holders_demoted) {
+			current_gh = gh;
+			demote_incompat_holders(gl, current_gh);
+			incompat_holders_demoted = true;
+		}
+	}
+	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;
+
+	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 && (ret & LM_OUT_CANCELED))
+			gfs2_holder_wake(gh);
+		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) {
+			int rv;
+
+			spin_unlock(&gl->gl_lockref.lock);
+			rv = glops->go_xmote_bh(gl);
+			spin_lock(&gl->gl_lockref.lock);
+			if (rv) {
+				do_error(gl, rv);
+				goto out;
+			}
+		}
+		do_promote(gl);
+	}
+out:
+	clear_bit(GLF_LOCK, &gl->gl_flags);
+	spin_unlock(&gl->gl_lockref.lock);
+}
+
+static bool is_system_glock(struct gfs2_glock *gl)
+{
+	struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
+	struct gfs2_inode *m_ip = GFS2_I(sdp->sd_statfs_inode);
+
+	if (gl == m_ip->i_gl)
+		return true;
+	return false;
+}
+
+/**
+ * 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))
+		goto skip_inval;
+
+	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.
+	 *
+	 * We make a special exception for some system glocks, such as the
+	 * system statfs inode glock, which needs to be granted before the
+	 * gfs2_quotad daemon can exit, and that exit needs to finish before
+	 * we can unmount the withdrawn file system.
+	 *
+	 * 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) &&
+	    (target != LM_ST_UNLOCKED ||
+	     test_bit(SDF_WITHDRAW_RECOVERY, &sdp->sd_flags))) {
+		if (!is_system_glock(gl)) {
+			handle_callback(gl, LM_ST_UNLOCKED, 0, false); /* sets demote */
+			/*
+			 * Ordinarily, we would call dlm and its callback would call
+			 * finish_xmote, which would call state_change() to the new state.
+			 * Since we withdrew, we won't call dlm, so call state_change
+			 * manually, but to the UNLOCKED state we desire.
+			 */
+			state_change(gl, LM_ST_UNLOCKED);
+			/*
+			 * We skip telling dlm to do the locking, so we won't get a
+			 * reply that would otherwise clear GLF_LOCK. So we clear it here.
+			 */
+			clear_bit(GLF_LOCK, &gl->gl_flags);
+			clear_bit(GLF_DEMOTE_IN_PROGRESS, &gl->gl_flags);
+			gfs2_glock_queue_work(gl, GL_GLOCK_DFT_HOLD);
+			goto out;
+		} else {
+			clear_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags);
+		}
+	}
+
+	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);
+}
+
+/**
+ * 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;
+
+	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);
+		if (do_promote(gl) == 0)
+			goto out_unlock;
+		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);
+	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, _RET_IP_);
+	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 (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(inode)) {
+		if (PTR_ERR(inode) == -EAGAIN &&
+			(gfs2_queue_delete_work(gl, 5 * HZ)))
+				return;
+	} else {
+		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;
+	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) {
+		struct gfs2_glock_aspace *gla =
+			kmem_cache_alloc(gfs2_glock_aspace_cachep, GFP_NOFS);
+		if (!gla)
+			return -ENOMEM;
+		gl = &gla->glock;
+	} else {
+		gl = kmem_cache_alloc(gfs2_glock_cachep, GFP_NOFS);
+		if (!gl)
+			return -ENOMEM;
+	}
+	memset(&gl->gl_lksb, 0, sizeof(struct dlm_lksb));
+	gl->gl_ops = glops;
+
+	if (glops->go_flags & GLOF_LVB) {
+		gl->gl_lksb.sb_lvbptr = kzalloc(GDLM_LVB_SIZE, GFP_NOFS);
+		if (!gl->gl_lksb.sb_lvbptr) {
+			gfs2_glock_dealloc(&gl->gl_rcu);
+			return -ENOMEM;
+		}
+	}
+
+	atomic_inc(&sdp->sd_glock_disposal);
+	gl->gl_node.next = NULL;
+	gl->gl_flags = glops->go_instantiate ? BIT(GLF_INSTANTIATE_NEEDED) : 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_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:
+	gfs2_glock_dealloc(&gl->gl_rcu);
+	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, unsigned long ip)
+{
+	INIT_LIST_HEAD(&gh->gh_list);
+	gh->gh_gl = gl;
+	gh->gh_ip = ip;
+	gh->gh_owner_pid = get_pid(task_pid(current));
+	gh->gh_state = state;
+	gh->gh_flags = flags;
+	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_holder_ready - holder is ready and its error code can be collected
+ * @gh: the glock holder
+ *
+ * Called when a glock holder no longer needs to be waited for because it is
+ * now either held (HIF_HOLDER set; gh_error == 0), or acquiring the lock has
+ * failed (gh_error != 0).
+ */
+
+int gfs2_glock_holder_ready(struct gfs2_holder *gh)
+{
+	if (gh->gh_error || (gh->gh_flags & GL_SKIP))
+		return gh->gh_error;
+	gh->gh_error = gfs2_instantiate(gh);
+	if (gh->gh_error)
+		gfs2_glock_dq(gh);
+	return gh->gh_error;
+}
+
+/**
+ * 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 gfs2_glock_holder_ready(gh);
+}
+
+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;
+
+	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;
+
+	if (!wait_event_timeout(sdp->sd_async_glock_wait,
+				!glocks_pending(num_gh, ghs), timeout)) {
+		ret = -ESTALE; /* request timed out. */
+		goto out;
+	}
+
+	for (i = 0; i < num_gh; i++) {
+		struct gfs2_holder *gh = &ghs[i];
+		int ret2;
+
+		if (test_bit(HIF_HOLDER, &gh->gh_iflags)) {
+			gfs2_glock_update_hold_time(gh->gh_gl,
+						    start_time);
+		}
+		ret2 = gfs2_glock_holder_ready(gh);
+		if (!ret)
+			ret = ret2;
+	}
+
+out:
+	if (ret) {
+		for (i = 0; i < num_gh; i++) {
+			struct gfs2_holder *gh = &ghs[i];
+
+			gfs2_glock_dq(gh);
+		}
+	}
+	return ret;
+}
+
+/**
+ * handle_callback - process a demote request
+ * @gl: the glock
+ * @state: the state the caller wants us to change to
+ * @delay: zero to demote immediately; otherwise pending demote
+ * @remote: true if this came from a different cluster node
+ *
+ * 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);
+}
+
+static inline bool pid_is_meaningful(const struct gfs2_holder *gh)
+{
+        if (!(gh->gh_flags & GL_NOPID))
+                return true;
+        if (gh->gh_state == LM_ST_UNLOCKED)
+                return true;
+        return false;
+}
+
+/**
+ * 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)) {
+			struct gfs2_holder *current_gh;
+
+			current_gh = find_first_strong_holder(gl);
+			try_futile = !may_grant(gl, current_gh, gh);
+		}
+		if (test_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags))
+			goto fail;
+	}
+
+	list_for_each_entry(gh2, &gl->gl_holders, gh_list) {
+		if (likely(gh2->gh_owner_pid != gh->gh_owner_pid))
+			continue;
+		if (gh->gh_gl->gl_ops->go_type == LM_TYPE_FLOCK)
+			continue;
+		if (test_bit(HIF_MAY_DEMOTE, &gh2->gh_iflags))
+			continue;
+		if (!pid_is_meaningful(gh2))
+			continue;
+		goto trap_recursive;
+	}
+	list_for_each_entry(gh2, &gl->gl_holders, gh_list) {
+		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);
+
+	gh->gh_error = 0;
+	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;
+}
+
+static inline bool needs_demote(struct gfs2_glock *gl)
+{
+	return (test_bit(GLF_DEMOTE, &gl->gl_flags) ||
+		test_bit(GLF_PENDING_DEMOTE, &gl->gl_flags));
+}
+
+static 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;
+
+	/*
+	 * This while loop is similar to function demote_incompat_holders:
+	 * If the glock is due to be demoted (which may be from another node
+	 * or even if this holder is GL_NOCACHE), the weak holders are
+	 * demoted as well, allowing the glock to be demoted.
+	 */
+	while (gh) {
+		/*
+		 * 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++;
+			spin_unlock(&gl->gl_lockref.lock);
+			might_sleep();
+			wait_on_bit(&sdp->sd_flags, SDF_WITHDRAW_RECOVERY,
+				    TASK_UNINTERRUPTIBLE);
+			spin_lock(&gl->gl_lockref.lock);
+		}
+
+		/*
+		 * This holder should not be cached, so mark it for demote.
+		 * Note: this should be done before the check for needs_demote
+		 * below.
+		 */
+		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);
+		trace_gfs2_glock_queue(gh, 0);
+
+		/*
+		 * If there hasn't been a demote request we are done.
+		 * (Let the remaining holders, if any, keep holding it.)
+		 */
+		if (!needs_demote(gl)) {
+			if (list_empty(&gl->gl_holders))
+				fast_path = 1;
+			break;
+		}
+		/*
+		 * If we have another strong holder (we cannot auto-demote)
+		 * we are done. It keeps holding it until it is done.
+		 */
+		if (find_first_strong_holder(gl))
+			break;
+
+		/*
+		 * If we have a weak holder at the head of the list, it
+		 * (and all others like it) must be auto-demoted. If there
+		 * are no more weak holders, we exit the while loop.
+		 */
+		gh = find_first_holder(gl);
+	}
+
+	if (!test_bit(GLF_LFLUSH, &gl->gl_flags) && demote_ok(gl))
+		gfs2_glock_add_to_lru(gl);
+
+	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);
+	}
+}
+
+/**
+ * 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;
+
+	spin_lock(&gl->gl_lockref.lock);
+	if (list_is_first(&gh->gh_list, &gl->gl_holders) &&
+	    !test_bit(HIF_HOLDER, &gh->gh_iflags)) {
+		spin_unlock(&gl->gl_lockref.lock);
+		gl->gl_name.ln_sbd->sd_lockstruct.ls_ops->lm_cancel(gl);
+		wait_on_bit(&gh->gh_iflags, HIF_WAIT, TASK_UNINTERRUPTIBLE);
+		spin_lock(&gl->gl_lockref.lock);
+	}
+
+	__gfs2_glock_dq(gh);
+	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 - synchronously acquire more than one glock in deadlock free order
+ * @num_gh: the number of structures
+ * @ghs: an array of struct gfs2_holder structures
+ * @p: placeholder for the holder structure to pass back
+ *
+ * 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++) {
+		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:
+		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;
+	}
+	/*
+	 * Note 1: We cannot call demote_incompat_holders from handle_callback
+	 * or gfs2_set_demote due to recursion problems like: gfs2_glock_dq ->
+	 * handle_callback -> demote_incompat_holders -> gfs2_glock_dq
+	 * Plus, we only want to demote the holders if the request comes from
+	 * a remote cluster node because local holder conflicts are resolved
+	 * elsewhere.
+	 *
+	 * Note 2: if a remote node wants this glock in EX mode, lock_dlm will
+	 * request that we set our state to UNLOCKED. Here we mock up a holder
+	 * to make it look like someone wants the lock EX locally. Any SH
+	 * and DF requests should be able to share the lock without demoting.
+	 *
+	 * Note 3: We only want to demote the demoteable holders when there
+	 * are no more strong holders. The demoteable holders might as well
+	 * keep the glock until the last strong holder is done with it.
+	 */
+	if (!find_first_strong_holder(gl)) {
+		struct gfs2_holder mock_gh = {
+			.gh_gl = gl,
+			.gh_state = (state == LM_ST_UNLOCKED) ?
+				    LM_ST_EXCLUSIVE : state,
+			.gh_iflags = BIT(HIF_HOLDER)
+		};
+
+		demote_incompat_holders(gl, &mock_gh);
+	}
+	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, const struct list_head *a,
+		     const 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);
+		clear_bit(GLF_LRU, &gl->gl_flags);
+		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);
+			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)
+				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(&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);
+		}
+	}
+}
+
+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))
+		return;
+	if (!lockref_get_not_dead(&gl->gl_lockref))
+		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 (!__lockref_is_dead(&gl->gl_lockref)) {
+		gl->gl_lockref.count++;
+		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);
+}
+
+static void withdraw_dq(struct gfs2_glock *gl)
+{
+	spin_lock(&gl->gl_lockref.lock);
+	if (!__lockref_is_dead(&gl->gl_lockref) &&
+	    glock_blocked_by_withdraw(gl))
+		do_error(gl, LM_OUT_ERROR); /* remove pending waiters */
+	spin_unlock(&gl->gl_lockref.lock);
+}
+
+void gfs2_gl_dq_holders(struct gfs2_sbd *sdp)
+{
+	glock_hash_walk(withdraw_dq, sdp);
+}
+
+/**
+ * gfs2_gl_hash_clear - Empty out the glock hash table
+ * @sdp: the filesystem
+ *
+ * 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);
+}
+
+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 & LM_FLAG_NODE_SCOPE)
+		*p++ = 'n';
+	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_MAY_DEMOTE, &iflags))
+		*p++ = 'D';
+	if (flags & GL_SKIP)
+		*p++ = 's';
+	*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)
+{
+	const char *comm = "(none)";
+	pid_t owner_pid = 0;
+	char flags_buf[32];
+
+	rcu_read_lock();
+	if (pid_is_meaningful(gh)) {
+		struct task_struct *gh_owner;
+
+		comm = "(ended)";
+		owner_pid = pid_nr(gh->gh_owner_pid);
+		gh_owner = pid_task(gh->gh_owner_pid, PIDTYPE_PID);
+		if (gh_owner)
+			comm = gh_owner->comm;
+	}
+	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, (long)owner_pid, comm, (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_PENDING_DELETE, gflags))
+		*p++ = 'P';
+	if (test_bit(GLF_FREEING, gflags))
+		*p++ = 'x';
+	if (test_bit(GLF_INSTANTIATE_NEEDED, gflags))
+		*p++ = 'n';
+	if (test_bit(GLF_INSTANTIATE_IN_PROG, gflags))
+		*p++ = 'N';
+	*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, "gfs2-glock");
+	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,
+};
+
+struct gfs2_glockfd_iter {
+	struct super_block *sb;
+	unsigned int tgid;
+	struct task_struct *task;
+	unsigned int fd;
+	struct file *file;
+};
+
+static struct task_struct *gfs2_glockfd_next_task(struct gfs2_glockfd_iter *i)
+{
+	struct pid_namespace *ns = task_active_pid_ns(current);
+	struct pid *pid;
+
+	if (i->task)
+		put_task_struct(i->task);
+
+	rcu_read_lock();
+retry:
+	i->task = NULL;
+	pid = find_ge_pid(i->tgid, ns);
+	if (pid) {
+		i->tgid = pid_nr_ns(pid, ns);
+		i->task = pid_task(pid, PIDTYPE_TGID);
+		if (!i->task) {
+			i->tgid++;
+			goto retry;
+		}
+		get_task_struct(i->task);
+	}
+	rcu_read_unlock();
+	return i->task;
+}
+
+static struct file *gfs2_glockfd_next_file(struct gfs2_glockfd_iter *i)
+{
+	if (i->file) {
+		fput(i->file);
+		i->file = NULL;
+	}
+
+	rcu_read_lock();
+	for(;; i->fd++) {
+		struct inode *inode;
+
+		i->file = task_lookup_next_fd_rcu(i->task, &i->fd);
+		if (!i->file) {
+			i->fd = 0;
+			break;
+		}
+		inode = file_inode(i->file);
+		if (inode->i_sb != i->sb)
+			continue;
+		if (get_file_rcu(i->file))
+			break;
+	}
+	rcu_read_unlock();
+	return i->file;
+}
+
+static void *gfs2_glockfd_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	struct gfs2_glockfd_iter *i = seq->private;
+
+	if (*pos)
+		return NULL;
+	while (gfs2_glockfd_next_task(i)) {
+		if (gfs2_glockfd_next_file(i))
+			return i;
+		i->tgid++;
+	}
+	return NULL;
+}
+
+static void *gfs2_glockfd_seq_next(struct seq_file *seq, void *iter_ptr,
+				   loff_t *pos)
+{
+	struct gfs2_glockfd_iter *i = seq->private;
+
+	(*pos)++;
+	i->fd++;
+	do {
+		if (gfs2_glockfd_next_file(i))
+			return i;
+		i->tgid++;
+	} while (gfs2_glockfd_next_task(i));
+	return NULL;
+}
+
+static void gfs2_glockfd_seq_stop(struct seq_file *seq, void *iter_ptr)
+{
+	struct gfs2_glockfd_iter *i = seq->private;
+
+	if (i->file)
+		fput(i->file);
+	if (i->task)
+		put_task_struct(i->task);
+}
+
+static void gfs2_glockfd_seq_show_flock(struct seq_file *seq,
+					struct gfs2_glockfd_iter *i)
+{
+	struct gfs2_file *fp = i->file->private_data;
+	struct gfs2_holder *fl_gh = &fp->f_fl_gh;
+	struct lm_lockname gl_name = { .ln_type = LM_TYPE_RESERVED };
+
+	if (!READ_ONCE(fl_gh->gh_gl))
+		return;
+
+	spin_lock(&i->file->f_lock);
+	if (gfs2_holder_initialized(fl_gh))
+		gl_name = fl_gh->gh_gl->gl_name;
+	spin_unlock(&i->file->f_lock);
+
+	if (gl_name.ln_type != LM_TYPE_RESERVED) {
+		seq_printf(seq, "%d %u %u/%llx\n",
+			   i->tgid, i->fd, gl_name.ln_type,
+			   (unsigned long long)gl_name.ln_number);
+	}
+}
+
+static int gfs2_glockfd_seq_show(struct seq_file *seq, void *iter_ptr)
+{
+	struct gfs2_glockfd_iter *i = seq->private;
+	struct inode *inode = file_inode(i->file);
+	struct gfs2_glock *gl;
+
+	inode_lock_shared(inode);
+	gl = GFS2_I(inode)->i_iopen_gh.gh_gl;
+	if (gl) {
+		seq_printf(seq, "%d %u %u/%llx\n",
+			   i->tgid, i->fd, gl->gl_name.ln_type,
+			   (unsigned long long)gl->gl_name.ln_number);
+	}
+	gfs2_glockfd_seq_show_flock(seq, i);
+	inode_unlock_shared(inode);
+	return 0;
+}
+
+static const struct seq_operations gfs2_glockfd_seq_ops = {
+	.start = gfs2_glockfd_seq_start,
+	.next  = gfs2_glockfd_seq_next,
+	.stop  = gfs2_glockfd_seq_stop,
+	.show  = gfs2_glockfd_seq_show,
+};
+
+static int gfs2_glockfd_open(struct inode *inode, struct file *file)
+{
+	struct gfs2_glockfd_iter *i;
+	struct gfs2_sbd *sdp = inode->i_private;
+
+	i = __seq_open_private(file, &gfs2_glockfd_seq_ops,
+			       sizeof(struct gfs2_glockfd_iter));
+	if (!i)
+		return -ENOMEM;
+	i->sb = sdp->sd_vfs;
+	return 0;
+}
+
+static const struct file_operations gfs2_glockfd_fops = {
+	.owner   = THIS_MODULE,
+	.open    = gfs2_glockfd_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = seq_release_private,
+};
+
+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("glockfd", S_IFREG | S_IRUGO, sdp->debugfs_dir, sdp,
+			    &gfs2_glockfd_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;
+}