[PATCH v2 3/3] vfs: Use per-cpu list for superblock's inode list

From: Waiman Long
Date: Fri Feb 19 2016 - 16:12:18 EST

When many threads are trying to add or delete inode to or from
a superblock's s_inodes list, spinlock contention on the list can
become a performance bottleneck.

This patch changes the s_inodes field to become a per-cpu list with
per-cpu spinlocks.

With an exit microbenchmark that creates a large number of threads,
attachs many inodes to them and then exits. The runtimes of that
microbenchmark with 1000 threads before and after the patch on a
4-socket Intel E7-4820 v3 system (40 cores, 80 threads) were as
follows:

Kernel Elapsed Time System Time
------ ------------ -----------
Vanilla 4.5-rc4 65.29s 82m14s
Patched 4.5-rc4 22.81s 23m03s

Before the patch, spinlock contention at the inode_sb_list_add()
function at the startup phase and the inode_sb_list_del() function at
the exit phase were about 79% and 93% of total CPU time respectively
(as measured by perf). After the patch, the percpu_list_add()
function consumed only about 0.04% of CPU time at startup phase. The
percpu_list_del() function consumed about 0.4% of CPU time at exit
phase. There were still some spinlock contention, but they happened
elsewhere.

Signed-off-by: Waiman Long <Waiman.Long@xxxxxxx>
---
fs/block_dev.c | 40 +++++++++++--------
fs/drop_caches.c | 31 ++++++++-------
fs/fs-writeback.c | 30 ++++++++------
fs/inode.c | 99 ++++++++++++++++++++++++-----------------------
fs/notify/inode_mark.c | 43 ++++++++++-----------
fs/quota/dquot.c | 83 ++++++++++++++++++++++------------------
fs/super.c | 7 ++-
include/linux/fs.h | 37 ++++++++++++++++--
8 files changed, 211 insertions(+), 159 deletions(-)

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 6eaeedf..5992a1f 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1862,21 +1862,27 @@ int __invalidate_device(struct block_device *bdev, bool kill_dirty)
}
EXPORT_SYMBOL(__invalidate_device);

-static inline void
-__iterate_bdev(spinlock_t *lock, struct inode *inode, struct inode **old_inode,
- void (*func)(struct block_device *, void *), void *arg)
+/*
+ * iterate_bdev_iter - iteration function for each inode of a block
+ * device superblock
+ */
+SB_INODES_ITER_FUNC(iterate_bdev, pcpu_lock,
+ struct inode *old_inode;
+ void (*func)(struct block_device *, void *);
+ void *arg)
{
+ SB_INODES_ITER_ARGS(iterate_bdev, inode, arg);
struct address_space *mapping = inode->i_mapping;

spin_lock(&inode->i_lock);
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW) ||
mapping->nrpages == 0) {
spin_unlock(&inode->i_lock);
- return;
+ return 0;
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(lock);
+ spin_unlock(pcpu_lock);
/*
* We hold a reference to 'inode' so it couldn't have been
* removed from s_inodes list while we dropped the
@@ -1884,23 +1890,23 @@ __iterate_bdev(spinlock_t *lock, struct inode *inode, struct inode **old_inode,
* be holding the last reference and we cannot iput it under
* pcpu_lock. So we keep the reference and iput it later.
*/
- iput(*old_inode);
- *old_inode = inode;
+ iput(arg->old_inode);
+ arg->old_inode = inode;

- func(I_BDEV(inode), arg);
+ arg->func(I_BDEV(inode), arg->arg);

- spin_lock(lock);
+ spin_lock(pcpu_lock);
+ return 0;
}

-void iterate_bdevs(void (*func)(struct block_device *, void *), void *arg)
+void iterate_bdevs(void (*func)(struct block_device *, void *), void *f_arg)
{
- struct inode *inode, *old_inode = NULL;
+ struct iterate_bdev_arg arg;

- spin_lock(&blockdev_superblock->s_inode_list_lock);
- list_for_each_entry(inode, &blockdev_superblock->s_inodes, i_sb_list)
- __iterate_bdev(&blockdev_superblock->s_inode_list_lock,
- inode, &old_inode, func, arg);
+ arg.arg = f_arg;
+ arg.func = func;
+ arg.old_inode = NULL;

- spin_unlock(&blockdev_superblock->s_inode_list_lock);
- iput(old_inode);
+ SB_INODES_ITER_CALL(iterate_bdev, blockdev_superblock);
+ iput(arg.old_inode);
}
diff --git a/fs/drop_caches.c b/fs/drop_caches.c
index d3449d5..63b1842 100644
--- a/fs/drop_caches.c
+++ b/fs/drop_caches.c
@@ -13,37 +13,40 @@
/* A global variable is a bit ugly, but it keeps the code simple */
int sysctl_drop_caches;

-static inline void __drop_pagecache_sb(spinlock_t *lock, struct inode *inode,
- struct inode **toput_inode)
+/*
+ * drop_pagecache_iter - iteration function for each inode of a superblock
+ */
+SB_INODES_ITER_FUNC(drop_pagecache, pcpu_lock,
+ struct inode *toput_inode)
{
+ SB_INODES_ITER_ARGS(drop_pagecache, inode, arg);
+
spin_lock(&inode->i_lock);
if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
(inode->i_mapping->nrpages == 0)) {
spin_unlock(&inode->i_lock);
- return;
+ return 0;
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(lock);
+ spin_unlock(pcpu_lock);

invalidate_mapping_pages(inode->i_mapping, 0, -1);
- iput(*toput_inode);
- *toput_inode = inode;
+ iput(arg->toput_inode);
+ arg->toput_inode = inode;

- spin_lock(lock);
+ spin_lock(pcpu_lock);
+ return 0;
}

static void drop_pagecache_sb(struct super_block *sb, void *unused)
{
- struct inode *inode, *toput_inode = NULL;
+ struct drop_pagecache_arg arg;

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list)
- __drop_pagecache_sb(&sb->s_inode_list_lock, inode,
- &toput_inode);
+ arg.toput_inode = NULL;

- spin_unlock(&sb->s_inode_list_lock);
- iput(toput_inode);
+ SB_INODES_ITER_CALL(drop_pagecache, sb);
+ iput(arg.toput_inode);
}

int drop_caches_sysctl_handler(struct ctl_table *table, int write,
diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 5ad6eda..080bae5 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -2095,20 +2095,24 @@ out_unlock_inode:
}
EXPORT_SYMBOL(__mark_inode_dirty);

-static inline void __wait_sb_inode(spinlock_t *lock, struct inode *inode,
- struct inode **old_inode)
+/*
+ * wait_sb_inode_iter - iteration function for each inode of a superblock
+ */
+SB_INODES_ITER_FUNC(wait_sb_inode, pcpu_lock,
+ struct inode *old_inode)
{
+ SB_INODES_ITER_ARGS(wait_sb_inode, inode, arg);
struct address_space *mapping = inode->i_mapping;

spin_lock(&inode->i_lock);
if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
(mapping->nrpages == 0)) {
spin_unlock(&inode->i_lock);
- return;
+ return 0;
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(lock);
+ spin_unlock(pcpu_lock);

/*
* We hold a reference to 'inode' so it couldn't have been
@@ -2117,8 +2121,8 @@ static inline void __wait_sb_inode(spinlock_t *lock, struct inode *inode,
* be holding the last reference and we cannot iput it under
* pcpu_lock. So we keep the reference and iput it later.
*/
- iput(*old_inode);
- *old_inode = inode;
+ iput(arg->old_inode);
+ arg->old_inode = inode;

/*
* We keep the error status of individual mapping so that
@@ -2129,7 +2133,8 @@ static inline void __wait_sb_inode(spinlock_t *lock, struct inode *inode,

cond_resched();

- spin_lock(lock);
+ spin_lock(pcpu_lock);
+ return 0;
}

/*
@@ -2143,7 +2148,9 @@ static inline void __wait_sb_inode(spinlock_t *lock, struct inode *inode,
*/
static void wait_sb_inodes(struct super_block *sb)
{
- struct inode *inode, *old_inode = NULL;
+ struct wait_sb_inode_arg arg;
+
+ arg.old_inode = NULL;

/*
* We need to be protected against the filesystem going from
@@ -2152,7 +2159,6 @@ static void wait_sb_inodes(struct super_block *sb)
WARN_ON(!rwsem_is_locked(&sb->s_umount));

mutex_lock(&sb->s_sync_lock);
- spin_lock(&sb->s_inode_list_lock);

/*
* Data integrity sync. Must wait for all pages under writeback,
@@ -2161,11 +2167,9 @@ static void wait_sb_inodes(struct super_block *sb)
* In which case, the inode may not be on the dirty list, but
* we still have to wait for that writeout.
*/
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list)
- __wait_sb_inode(&sb->s_inode_list_lock, inode, &old_inode);
+ SB_INODES_ITER_CALL(wait_sb_inode, sb);

- spin_unlock(&sb->s_inode_list_lock);
- iput(old_inode);
+ iput(arg.old_inode);
mutex_unlock(&sb->s_sync_lock);
}

diff --git a/fs/inode.c b/fs/inode.c
index 6dd609e..0f2fba4 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -28,7 +28,7 @@
* inode->i_state, inode->i_hash, __iget()
* Inode LRU list locks protect:
* inode->i_sb->s_inode_lru, inode->i_lru
- * inode->i_sb->s_inode_list_lock protects:
+ * inode->i_sb->s_inodes->lock protects:
* inode->i_sb->s_inodes, inode->i_sb_list
* bdi->wb.list_lock protects:
* bdi->wb.b_{dirty,io,more_io,dirty_time}, inode->i_io_list
@@ -37,7 +37,7 @@
*
* Lock ordering:
*
- * inode->i_sb->s_inode_list_lock
+ * inode->i_sb->s_inodes->lock
* inode->i_lock
* Inode LRU list locks
*
@@ -45,7 +45,7 @@
* inode->i_lock
*
* inode_hash_lock
- * inode->i_sb->s_inode_list_lock
+ * inode->i_sb->s_inodes->lock
* inode->i_lock
*
* iunique_lock
@@ -424,19 +424,14 @@ static void inode_lru_list_del(struct inode *inode)
*/
void inode_sb_list_add(struct inode *inode)
{
- spin_lock(&inode->i_sb->s_inode_list_lock);
- list_add(&inode->i_sb_list, &inode->i_sb->s_inodes);
- spin_unlock(&inode->i_sb->s_inode_list_lock);
+ pcpu_list_add(&inode->i_sb_list, inode->i_sb->s_inodes);
}
EXPORT_SYMBOL_GPL(inode_sb_list_add);

static inline void inode_sb_list_del(struct inode *inode)
{
- if (!list_empty(&inode->i_sb_list)) {
- spin_lock(&inode->i_sb->s_inode_list_lock);
- list_del_init(&inode->i_sb_list);
- spin_unlock(&inode->i_sb->s_inode_list_lock);
- }
+ if (!list_empty(&inode->i_sb_list.list))
+ pcpu_list_del(&inode->i_sb_list);
}

static unsigned long hash(struct super_block *sb, unsigned long hashval)
@@ -579,9 +574,15 @@ static void dispose_list(struct list_head *head)
}
}

-static inline int __evict_inode(spinlock_t *lock, struct inode *inode,
- struct list_head *dispose)
+/*
+ * evict_inode_iter - iteration function for each inode of a superblock
+ */
+SB_INODES_ITER_FUNC(evict_inode, pcpu_lock,
+ struct list_head dispose;
+ bool iter_again)
{
+ SB_INODES_ITER_ARGS(evict_inode, inode, arg);
+
if (atomic_read(&inode->i_count))
return 0;

@@ -594,7 +595,7 @@ static inline int __evict_inode(spinlock_t *lock, struct inode *inode,
inode->i_state |= I_FREEING;
inode_lru_list_del(inode);
spin_unlock(&inode->i_lock);
- list_add(&inode->i_lru, dispose);
+ list_add(&inode->i_lru, &arg->dispose);

/*
* We can have a ton of inodes to evict at unmount time given
@@ -602,9 +603,10 @@ static inline int __evict_inode(spinlock_t *lock, struct inode *inode,
* bit so we don't livelock.
*/
if (need_resched()) {
- spin_unlock(lock);
+ spin_unlock(pcpu_lock);
cond_resched();
- dispose_list(dispose);
+ dispose_list(&arg->dispose);
+ arg->iter_again = true;
return 1; /* Redo it again */
}
return 0;
@@ -621,47 +623,53 @@ static inline int __evict_inode(spinlock_t *lock, struct inode *inode,
*/
void evict_inodes(struct super_block *sb)
{
- struct inode *inode, *next;
- LIST_HEAD(dispose);
+ struct evict_inode_arg arg;
+
+ INIT_LIST_HEAD(&arg.dispose);

again:
- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
- if (__evict_inode(&sb->s_inode_list_lock, inode, &dispose))
- goto again;
- }
- spin_unlock(&sb->s_inode_list_lock);
+ arg.iter_again = false;
+ SB_INODES_ITER_CALL_SAFE(evict_inode, sb, NULL);
+ if (arg.iter_again)
+ goto again;

- dispose_list(&dispose);
+ dispose_list(&arg.dispose);
}

-static inline void __invalidate_inode(struct inode *inode, bool kill_dirty,
- struct list_head *dispose, int *busy)
+/*
+ * invalidate_inode_iter - attempt to free an inode on a superblock
+ */
+SB_INODES_ITER_FUNC(invalidate_inode, pcpu_lock,
+ struct list_head dispose;
+ bool busy;
+ bool kill_dirty)
{
+ SB_INODES_ITER_ARGS(invalidate_inode, inode, arg);
+
spin_lock(&inode->i_lock);
if (inode->i_state & (I_NEW | I_FREEING | I_WILL_FREE)) {
spin_unlock(&inode->i_lock);
- return;
+ return 0;
}

- if (inode->i_state & I_DIRTY_ALL && !kill_dirty) {
+ if (inode->i_state & I_DIRTY_ALL && !arg->kill_dirty) {
spin_unlock(&inode->i_lock);
- *busy = 1;
- return;
+ arg->busy = 1;
+ return 0;
}

if (atomic_read(&inode->i_count)) {
spin_unlock(&inode->i_lock);
- *busy = 1;
- return;
+ arg->busy = 1;
+ return 0;
}

inode->i_state |= I_FREEING;
inode_lru_list_del(inode);
spin_unlock(&inode->i_lock);
- list_add(&inode->i_lru, dispose);
+ list_add(&inode->i_lru, &arg->dispose);
+ return 0;
}
-
/**
* invalidate_inodes - attempt to free all inodes on a superblock
* @sb: superblock to operate on
@@ -674,19 +682,16 @@ static inline void __invalidate_inode(struct inode *inode, bool kill_dirty,
*/
int invalidate_inodes(struct super_block *sb, bool kill_dirty)
{
- int busy = 0;
- struct inode *inode, *next;
- LIST_HEAD(dispose);
+ struct invalidate_inode_arg arg;

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list)
- __invalidate_inode(inode, kill_dirty, &dispose, &busy);
+ arg.kill_dirty = kill_dirty;
+ arg.busy = 0;
+ INIT_LIST_HEAD(&arg.dispose);

- spin_unlock(&sb->s_inode_list_lock);
+ SB_INODES_ITER_CALL_SAFE(invalidate_inode, sb, NULL);
+ dispose_list(&arg.dispose);

- dispose_list(&dispose);
-
- return busy;
+ return arg.busy;
}

/*
@@ -897,7 +902,7 @@ struct inode *new_inode_pseudo(struct super_block *sb)
spin_lock(&inode->i_lock);
inode->i_state = 0;
spin_unlock(&inode->i_lock);
- INIT_LIST_HEAD(&inode->i_sb_list);
+ init_pcpu_list_node(&inode->i_sb_list);
}
return inode;
}
@@ -918,8 +923,6 @@ struct inode *new_inode(struct super_block *sb)
{
struct inode *inode;

- spin_lock_prefetch(&sb->s_inode_list_lock);
-
inode = new_inode_pseudo(sb);
if (inode)
inode_sb_list_add(inode);
diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
index ec52dcb..1fd1daf 100644
--- a/fs/notify/inode_mark.c
+++ b/fs/notify/inode_mark.c
@@ -141,13 +141,15 @@ int fsnotify_add_inode_mark(struct fsnotify_mark *mark,
return ret;
}

-static inline void
-__fsnotify_unmount_inode(spinlock_t *lock, struct inode *inode,
- struct list_head *head, struct inode **pnext,
- struct inode **need_iput)
+/*
+ * unmount_inode_iter - iteration function for each inode of a SB
+ */
+SB_INODES_ITER_FUNC(unmount_inode, pcpu_lock,
+ struct inode *need_iput;
+ struct list_head *percpu_head)
{
+ SB_INODES_ITER_ARGS_SAFE(unmount_inode, inode, next_i, arg);
struct inode *need_iput_tmp;
- struct inode *next_i = *pnext;

/*
* We cannot __iget() an inode in state I_FREEING,
@@ -157,7 +159,7 @@ __fsnotify_unmount_inode(spinlock_t *lock, struct inode *inode,
spin_lock(&inode->i_lock);
if (inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) {
spin_unlock(&inode->i_lock);
- return;
+ return 0;
}

/*
@@ -168,11 +170,11 @@ __fsnotify_unmount_inode(spinlock_t *lock, struct inode *inode,
*/
if (!atomic_read(&inode->i_count)) {
spin_unlock(&inode->i_lock);
- return;
+ return 0;
}

- need_iput_tmp = *need_iput;
- *need_iput = NULL;
+ need_iput_tmp = arg->need_iput;
+ arg->need_iput = NULL;

/* In case fsnotify_inode_delete() drops a reference. */
if (inode != need_iput_tmp)
@@ -182,19 +184,19 @@ __fsnotify_unmount_inode(spinlock_t *lock, struct inode *inode,
spin_unlock(&inode->i_lock);

/* In case the dropping of a reference would nuke next_i. */
- while (&next_i->i_sb_list != head) {
+ while (&next_i->i_sb_list.list != arg->percpu_head) {
spin_lock(&next_i->i_lock);
if (!(next_i->i_state & (I_FREEING | I_WILL_FREE)) &&
atomic_read(&next_i->i_count)) {
__iget(next_i);
- *need_iput = next_i;
+ arg->need_iput = next_i;
spin_unlock(&next_i->i_lock);
break;
}
spin_unlock(&next_i->i_lock);
- next_i = list_next_entry(next_i, i_sb_list);
+ next_i = pcpu_list_next_entry(next_i, i_sb_list);
}
- *pnext = next_i;
+ SB_INODES_ITER_SET_PCPU_LIST_NEXT(next_i);

/*
* We can safely drop pcpu_lock here because either
@@ -202,7 +204,7 @@ __fsnotify_unmount_inode(spinlock_t *lock, struct inode *inode,
* end of list. Also no new inodes will be added since the
* umount has begun.
*/
- spin_unlock(lock);
+ spin_unlock(pcpu_lock);

if (need_iput_tmp)
iput(need_iput_tmp);
@@ -214,7 +216,8 @@ __fsnotify_unmount_inode(spinlock_t *lock, struct inode *inode,

iput(inode);

- spin_lock(lock);
+ spin_lock(pcpu_lock);
+ return 0;
}

/**
@@ -227,12 +230,8 @@ __fsnotify_unmount_inode(spinlock_t *lock, struct inode *inode,
*/
void fsnotify_unmount_inodes(struct super_block *sb)
{
- struct inode *inode, *next_i, *need_iput = NULL;
-
- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry_safe(inode, next_i, &sb->s_inodes, i_sb_list)
- __fsnotify_unmount_inode(&sb->s_inode_list_lock, inode,
- &sb->s_inodes, &next_i, &need_iput);
+ struct unmount_inode_arg arg;

- spin_unlock(&sb->s_inode_list_lock);
+ arg.need_iput = NULL;
+ SB_INODES_ITER_CALL_SAFE(unmount_inode, sb, &arg.percpu_head);
}
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 143183b..6aa593e 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -920,30 +920,33 @@ static int dqinit_needed(struct inode *inode, int type)
return 0;
}

-static inline void
-__add_dquot_ref(spinlock_t *lock, struct inode *inode, int type,
-#ifdef CONFIG_QUOTA_DEBUG
- int *reserved,
-#endif
- struct inode **old_inode)
+/*
+ * add_dquot_iter - iteration function for each inode of a superblock
+ */
+SB_INODES_ITER_FUNC(add_dquot, pcpu_lock,
+ struct inode *old_inode;
+ int type;
+ int reserved)
{
+ SB_INODES_ITER_ARGS(add_dquot, inode, arg);
+
spin_lock(&inode->i_lock);
if ((inode->i_state & (I_FREEING|I_WILL_FREE|I_NEW)) ||
!atomic_read(&inode->i_writecount) ||
- !dqinit_needed(inode, type)) {
+ !dqinit_needed(inode, arg->type)) {
spin_unlock(&inode->i_lock);
- return;
+ return 0;
}
__iget(inode);
spin_unlock(&inode->i_lock);
- spin_unlock(lock);
+ spin_unlock(pcpu_lock);

#ifdef CONFIG_QUOTA_DEBUG
if (unlikely(inode_get_rsv_space(inode) > 0))
- *reserved = 1;
+ arg->reserved = 1;
#endif
- iput(*old_inode);
- __dquot_initialize(inode, type);
+ iput(arg->old_inode);
+ __dquot_initialize(inode, arg->type);

/*
* We hold a reference to 'inode' so it couldn't have been
@@ -952,30 +955,27 @@ __add_dquot_ref(spinlock_t *lock, struct inode *inode, int type,
* holding the last reference and we cannot iput it under
* pcpu_lock. So we keep the reference and iput it later.
*/
- *old_inode = inode;
- spin_lock(lock);
+ arg->old_inode = inode;
+ spin_lock(pcpu_lock);
+ return 0;
}

/* This routine is guarded by dqonoff_mutex mutex */
static void add_dquot_ref(struct super_block *sb, int type)
{
- struct inode *inode, *old_inode = NULL;
-#ifdef CONFIG_QUOTA_DEBUG
- int reserved = 0;
-#endif
+ struct add_dquot_arg arg;

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list)
- __add_dquot_ref(&sb->s_inode_list_lock, inode, type,
#ifdef CONFIG_QUOTA_DEBUG
- &reserved,
+ arg.reserved = 0;
#endif
- &old_inode);
- spin_unlock(&sb->s_inode_list_lock);
- iput(old_inode);
+ arg.old_inode = NULL;
+ arg.type = type;
+
+ SB_INODES_ITER_CALL(add_dquot, sb);
+ iput(arg.old_inode);

#ifdef CONFIG_QUOTA_DEBUG
- if (reserved) {
+ if (arg.reserved) {
quota_error(sb, "Writes happened before quota was turned on "
"thus quota information is probably inconsistent. "
"Please run quotacheck(8)");
@@ -1034,10 +1034,16 @@ static void put_dquot_list(struct list_head *tofree_head)
}
}

-static inline void
-__remove_dquot_ref(struct inode *inode, int type,
- struct list_head *tofree_head, int *reserved)
+/*
+ * add_dquot_iter - iteration function for each inode of a superblock
+ */
+SB_INODES_ITER_FUNC(remove_dquot, pcpu_lock,
+ struct list_head *tofree_head;
+ int type;
+ int reserved)
{
+ SB_INODES_ITER_ARGS(remove_dquot, inode, arg);
+
/*
* We have to scan also I_NEW inodes because they can already
* have quota pointer initialized. Luckily, we need to touch
@@ -1047,25 +1053,26 @@ __remove_dquot_ref(struct inode *inode, int type,
spin_lock(&dq_data_lock);
if (!IS_NOQUOTA(inode)) {
if (unlikely(inode_get_rsv_space(inode) > 0))
- *reserved = 1;
- remove_inode_dquot_ref(inode, type, tofree_head);
+ arg->reserved = 1;
+ remove_inode_dquot_ref(inode, arg->type, arg->tofree_head);
}
spin_unlock(&dq_data_lock);
+ return 0;
}

static void remove_dquot_ref(struct super_block *sb, int type,
struct list_head *tofree_head)
{
- struct inode *inode;
- int reserved = 0;
+ struct remove_dquot_arg arg;
+
+ arg.reserved = 0;
+ arg.type = type;
+ arg.tofree_head = tofree_head;

- spin_lock(&sb->s_inode_list_lock);
- list_for_each_entry(inode, &sb->s_inodes, i_sb_list)
- __remove_dquot_ref(inode, type, tofree_head, &reserved);
+ SB_INODES_ITER_CALL(remove_dquot, sb);

- spin_unlock(&sb->s_inode_list_lock);
#ifdef CONFIG_QUOTA_DEBUG
- if (reserved) {
+ if (arg.reserved) {
printk(KERN_WARNING "VFS (%s): Writes happened after quota"
" was disabled thus quota information is probably "
"inconsistent. Please run quotacheck(8).\n", sb->s_id);
diff --git a/fs/super.c b/fs/super.c
index 1182af8..7d44fad 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -163,6 +163,7 @@ static void destroy_super(struct super_block *s)
{
list_lru_destroy(&s->s_dentry_lru);
list_lru_destroy(&s->s_inode_lru);
+ free_pcpu_list_head(&s->s_inodes);
security_sb_free(s);
WARN_ON(!list_empty(&s->s_mounts));
kfree(s->s_subtype);
@@ -204,9 +205,9 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
INIT_HLIST_NODE(&s->s_instances);
INIT_HLIST_BL_HEAD(&s->s_anon);
mutex_init(&s->s_sync_lock);
- INIT_LIST_HEAD(&s->s_inodes);
- spin_lock_init(&s->s_inode_list_lock);

+ if (init_pcpu_list_head(&s->s_inodes))
+ goto fail;
if (list_lru_init_memcg(&s->s_dentry_lru))
goto fail;
if (list_lru_init_memcg(&s->s_inode_lru))
@@ -426,7 +427,7 @@ void generic_shutdown_super(struct super_block *sb)
if (sop->put_super)
sop->put_super(sb);

- if (!list_empty(&sb->s_inodes)) {
+ if (!pcpu_list_empty(sb->s_inodes)) {
printk("VFS: Busy inodes after unmount of %s. "
"Self-destruct in 5 seconds. Have a nice day...\n",
sb->s_id);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ae68100..c30cdb6 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -27,6 +27,7 @@
#include <linux/migrate_mode.h>
#include <linux/uidgid.h>
#include <linux/lockdep.h>
+#include <linux/percpu-list.h>
#include <linux/percpu-rwsem.h>
#include <linux/blk_types.h>
#include <linux/workqueue.h>
@@ -648,7 +649,7 @@ struct inode {
u16 i_wb_frn_history;
#endif
struct list_head i_lru; /* inode LRU list */
- struct list_head i_sb_list;
+ struct pcpu_list_node i_sb_list;
union {
struct hlist_head i_dentry;
struct rcu_head i_rcu;
@@ -1397,11 +1398,39 @@ struct super_block {
*/
int s_stack_depth;

- /* s_inode_list_lock protects s_inodes */
- spinlock_t s_inode_list_lock ____cacheline_aligned_in_smp;
- struct list_head s_inodes; /* all inodes */
+ /* The percpu locks protect s_inodes */
+ struct pcpu_list_head __percpu *s_inodes; /* all inodes */
};

+/*
+ * Superblock's inode list iterator function and arguments macros
+ */
+#define SB_INODES_ITER_FUNC(name, lock, struct_fields) \
+ struct name ## _arg { \
+ struct_fields; \
+ }; \
+ static int name ## _iter(struct pcpu_list_node *_node, \
+ struct pcpu_list_node **_pnext, \
+ spinlock_t *lock, void *_arg)
+
+#define SB_INODES_ITER_ARGS(name, i, a) \
+ struct inode *i = container_of(_node, struct inode, i_sb_list); \
+ struct name ## _arg *a = (struct name ## _arg *)_arg
+
+#define SB_INODES_ITER_ARGS_SAFE(name, i, n, a) \
+ struct inode *i = container_of(_node, struct inode, i_sb_list); \
+ struct inode *n = container_of(*_pnext, struct inode, i_sb_list);\
+ struct name ## _arg *a = (struct name ## _arg *)_arg
+
+#define SB_INODES_ITER_SET_PCPU_LIST_NEXT(n) \
+ { *_pnext = &(n)->i_sb_list; }
+
+#define SB_INODES_ITER_CALL(name, sb) \
+ pcpu_list_iterate(sb->s_inodes, false, NULL, name ## _iter, &arg)
+
+#define SB_INODES_ITER_CALL_SAFE(name, sb, phead) \
+ pcpu_list_iterate(sb->s_inodes, true, phead, name ## _iter, &arg)
+
extern struct timespec current_fs_time(struct super_block *sb);

/*
--
1.7.1