[PATCH v6 03/31] dentry: move to per-sb LRU locks

Glauber Costa
2013-05-12T18:13:24Z

From: Dave Chinner <dchinner@redhat.com>

With the dentry LRUs being per-sb structures, there is no real need
for a global dentry_lru_lock. The locking can be made more
fine-grained by moving to a per-sb LRU lock, isolating the LRU
operations of different filesytsems completely from each other.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Acked-by: Mel Gorman <mgorman@suse.de>
---
fs/dcache.c | 33 ++++++++++++++++-----------------
fs/super.c | 1 +
include/linux/fs.h | 4 +++-
3 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/fs/dcache.c b/fs/dcache.c
index cb304f4..795c15d 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -48,7 +48,7 @@
* - the dcache hash table
* s_anon bl list spinlock protects:
* - the s_anon list (see __d_drop)
- * dcache_lru_lock protects:
+ * dentry->d_sb->s_dentry_lru_lock protects:
* - the dcache lru lists and counters
* d_lock protects:
* - d_flags
@@ -63,7 +63,7 @@
* Ordering:
* dentry->d_inode->i_lock
* dentry->d_lock
- * dcache_lru_lock
+ * dentry->d_sb->s_dentry_lru_lock
* dcache_hash_bucket lock
* s_anon lock
*
@@ -81,7 +81,6 @@
int sysctl_vfs_cache_pressure __read_mostly = 100;
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);

-static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);

EXPORT_SYMBOL(rename_lock);
@@ -321,11 +320,11 @@ static void dentry_unlink_inode(struct dentry * dentry)
static void dentry_lru_add(struct dentry *dentry)
{
if (list_empty(&dentry->d_lru)) {
- spin_lock(&dcache_lru_lock);
+ spin_lock(&dentry->d_sb->s_dentry_lru_lock);
list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
dentry->d_sb->s_nr_dentry_unused++;
this_cpu_inc(nr_dentry_unused);
- spin_unlock(&dcache_lru_lock);
+ spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
}
}

@@ -343,15 +342,15 @@ static void __dentry_lru_del(struct dentry *dentry)
static void dentry_lru_del(struct dentry *dentry)
{
if (!list_empty(&dentry->d_lru)) {
- spin_lock(&dcache_lru_lock);
+ spin_lock(&dentry->d_sb->s_dentry_lru_lock);
__dentry_lru_del(dentry);
- spin_unlock(&dcache_lru_lock);
+ spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
}
}

static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
{
- spin_lock(&dcache_lru_lock);
+ spin_lock(&dentry->d_sb->s_dentry_lru_lock);
if (list_empty(&dentry->d_lru)) {
list_add_tail(&dentry->d_lru, list);
dentry->d_sb->s_nr_dentry_unused++;
@@ -359,7 +358,7 @@ static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
} else {
list_move_tail(&dentry->d_lru, list);
}
- spin_unlock(&dcache_lru_lock);
+ spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
}

/**
@@ -839,14 +838,14 @@ void prune_dcache_sb(struct super_block *sb, int count)
LIST_HEAD(tmp);

relock:
- spin_lock(&dcache_lru_lock);
+ spin_lock(&sb->s_dentry_lru_lock);
while (!list_empty(&sb->s_dentry_lru)) {
dentry = list_entry(sb->s_dentry_lru.prev,
struct dentry, d_lru);
BUG_ON(dentry->d_sb != sb);

if (!spin_trylock(&dentry->d_lock)) {
- spin_unlock(&dcache_lru_lock);
+ spin_unlock(&sb->s_dentry_lru_lock);
cpu_relax();
goto relock;
}
@@ -862,11 +861,11 @@ relock:
if (!--count)
break;
}
- cond_resched_lock(&dcache_lru_lock);
+ cond_resched_lock(&sb->s_dentry_lru_lock);
}
if (!list_empty(&referenced))
list_splice(&referenced, &sb->s_dentry_lru);
- spin_unlock(&dcache_lru_lock);
+ spin_unlock(&sb->s_dentry_lru_lock);

shrink_dentry_list(&tmp);
}
@@ -882,14 +881,14 @@ void shrink_dcache_sb(struct super_block *sb)
{
LIST_HEAD(tmp);

- spin_lock(&dcache_lru_lock);
+ spin_lock(&sb->s_dentry_lru_lock);
while (!list_empty(&sb->s_dentry_lru)) {
list_splice_init(&sb->s_dentry_lru, &tmp);
- spin_unlock(&dcache_lru_lock);
+ spin_unlock(&sb->s_dentry_lru_lock);
shrink_dentry_list(&tmp);
- spin_lock(&dcache_lru_lock);
+ spin_lock(&sb->s_dentry_lru_lock);
}
- spin_unlock(&dcache_lru_lock);
+ spin_unlock(&sb->s_dentry_lru_lock);
}
EXPORT_SYMBOL(shrink_dcache_sb);

diff --git a/fs/super.c b/fs/super.c
index 2a37fd6..0be75fb 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -182,6 +182,7 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags)
INIT_HLIST_BL_HEAD(&s->s_anon);
INIT_LIST_HEAD(&s->s_inodes);
INIT_LIST_HEAD(&s->s_dentry_lru);
+ spin_lock_init(&s->s_dentry_lru_lock);
INIT_LIST_HEAD(&s->s_inode_lru);
spin_lock_init(&s->s_inode_lru_lock);
INIT_LIST_HEAD(&s->s_mounts);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 0a9a6766..67e1040 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1263,7 +1263,9 @@ struct super_block {
struct list_head s_files;
#endif
struct list_head s_mounts; /* list of mounts; _not_ for fs use */
- /* s_dentry_lru, s_nr_dentry_unused protected by dcache.c lru locks */
+
+ /* s_dentry_lru_lock protects s_dentry_lru and s_nr_dentry_unused */
+ spinlock_t s_dentry_lru_lock ____cacheline_aligned_in_smp;
struct list_head s_dentry_lru; /* unused dentry lru */
int s_nr_dentry_unused; /* # of dentry on lru */

--
1.8.1.4