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android-kvm / linux / d75663868d60f74bda33135fd737a7967532c357 / . / fs / gfs2 / glock.c
blob: b7123de7c180eb3ebc2affdf66132bdf9a411035 [file] [log] [blame]
// 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);
if (gl->gl_ops->go_flags & GLOF_ASPACE) {
kmem_cache_free(gfs2_glock_aspace_cachep, gl);
} else {
kfree(gl->gl_lksb.sb_lvbptr);
kmem_cache_free(gfs2_glock_cachep, gl);
}
}
void gfs2_glock_free(struct gfs2_glock *gl)
{
struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
BUG_ON(atomic_read(&gl->gl_revokes));
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));
GLOCK_BUG_ON(gl, mapping && mapping->nrpages);
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_entry(gl->gl_holders.next, 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 (held1 && held2 && list_empty(&gl->gl_holders))
clear_bit(GLF_QUEUED, &gl->gl_flags);
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_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 (unlikely(gfs2_withdrawn(sdp)) &&
target != LM_ST_UNLOCKED)
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)
glops->go_sync(gl);
if (test_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags))
glops->go_inval(gl, target == LM_ST_DEFERRED ? 0 : DIO_METADATA);
clear_bit(GLF_INVALIDATE_IN_PROGRESS, &gl->gl_flags);
gfs2_glock_hold(gl);
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);
}
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_entry(gl->gl_holders.next, 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;
}
static void delete_work_func(struct work_struct *work)
{
struct gfs2_glock *gl = container_of(work, 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;
/* 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;
inode = gfs2_lookup_by_inum(sdp, no_addr, NULL, 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);
set_bit(GLF_DEMOTE, &gl->gl_flags);
}
}
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(GFS2_MIN_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;
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);
INIT_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);
atomic_dec(&sdp->sd_glock_disposal);
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)
{
int bit = delay ? GLF_PENDING_DEMOTE : GLF_DEMOTE;
set_bit(bit, &gl->gl_flags);
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;
}
set_bit(GLF_QUEUED, &gl->gl_flags);
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_entry(gl->gl_holders.next, 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;
struct gfs2_sbd *sdp = gl->gl_name.ln_sbd;
int error = 0;
if (unlikely(gfs2_withdrawn(sdp)))
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;
const struct gfs2_glock_operations *glops = gl->gl_ops;
unsigned delay = 0;
int fast_path = 0;
spin_lock(&gl->gl_lockref.lock);
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 (glops->go_unlock) {
GLOCK_BUG_ON(gl, test_and_set_bit(GLF_LOCK, &gl->gl_flags));
spin_unlock(&gl->gl_lockref.lock);
glops->go_unlock(gh);
spin_lock(&gl->gl_lockref.lock);
clear_bit(GLF_LOCK, &gl->gl_flags);
}
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);
holdtime = gl->gl_tchange + gl->gl_hold_time;
if (test_bit(GLF_QUEUED, &gl->gl_flags) &&
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;
}
spin_lock(&gl->gl_lockref.lock);
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_entry(list->next, 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_entry(lru_list.next, 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,
};
/**
* examine_bucket - Call a function for glock in a hash bucket
* @examiner: the function
* @sdp: the filesystem
* @bucket: the bucket
*
* 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);
}
/**
* 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_assert_withdraw(gl->gl_name.ln_sbd, 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 (test_bit(GLF_QUEUED, gflags))
*p++ = 'q';
if (test_bit(GLF_LRU, gflags))
*p++ = 'L';
if (gl->gl_object)
*p++ = 'o';
if (test_bit(GLF_BLOCKING, gflags))
*p++ = 'b';
*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];
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\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);
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_seq_ops = {
.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 int gfs2_sbstats_open(struct inode *inode, struct file *file)
{
int ret = seq_open(file, &gfs2_sbstats_seq_ops);
if (ret == 0) {
struct seq_file *seq = file->private_data;
seq->private = inode->i_private; /* sdp */
}
return ret;
}
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,
};
static const struct file_operations gfs2_sbstats_fops = {
.owner = THIS_MODULE,
.open = gfs2_sbstats_open,
.read = seq_read,
.llseek = seq_lseek,
.release = seq_release,
};
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;
}