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Subject[PATCH 13/13] dcache: convert to use new lru list infrastructure
Date
From: Dave Chinner <dchinner@redhat.com>

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/dcache.c | 142 +++++++++++++++++++++-------------------------------
fs/super.c | 10 ++--
include/linux/fs.h | 14 +++--
3 files changed, 71 insertions(+), 95 deletions(-)
diff --git a/fs/dcache.c b/fs/dcache.c
index 79bf47c..382cd27 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -36,6 +36,7 @@
#include <linux/bit_spinlock.h>
#include <linux/rculist_bl.h>
#include <linux/prefetch.h>
+#include <linux/list_lru.h>
#include "internal.h"

/*
@@ -239,42 +240,17 @@ static void dentry_unlink_inode(struct dentry * dentry)
*/
static void dentry_lru_add(struct dentry *dentry)
{
- if (list_empty(&dentry->d_lru)) {
- 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++;
+ if (list_empty(&dentry->d_lru) &&
+ list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru))
this_cpu_inc(nr_dentry_unused);
- spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
- }
}

-static void __dentry_lru_del(struct dentry *dentry)
-{
- list_del_init(&dentry->d_lru);
- dentry->d_sb->s_nr_dentry_unused--;
- this_cpu_dec(nr_dentry_unused);
-}

static void dentry_lru_del(struct dentry *dentry)
{
- if (!list_empty(&dentry->d_lru)) {
- spin_lock(&dentry->d_sb->s_dentry_lru_lock);
- __dentry_lru_del(dentry);
- spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
- }
-}
-
-static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
-{
- spin_lock(&dentry->d_sb->s_dentry_lru_lock);
- if (list_empty(&dentry->d_lru)) {
- list_add_tail(&dentry->d_lru, list);
- } else {
- list_move_tail(&dentry->d_lru, list);
- dentry->d_sb->s_nr_dentry_unused--;
+ if (!list_empty(&dentry->d_lru) &&
+ list_lru_del(&dentry->d_sb->s_dentry_lru, &dentry->d_lru))
this_cpu_dec(nr_dentry_unused);
- }
- spin_unlock(&dentry->d_sb->s_dentry_lru_lock);
}

/**
@@ -756,6 +732,50 @@ static void shrink_dentry_list(struct list_head *list)
rcu_read_unlock();
}

+static int dentry_lru_isolate(struct list_head *item, spinlock_t *lru_lock,
+ void *arg)
+{
+ struct list_head *freeable = arg;
+ struct dentry *dentry = container_of(item, struct dentry, d_lru);
+
+
+ /*
+ * we are inverting the lru lock/dentry->d_lock here,
+ * so use a trylock. If we fail to get the lock, just skip
+ * it
+ */
+ if (!spin_trylock(&dentry->d_lock))
+ return 2;
+
+ /*
+ * Referenced dentries are still in use. If they have active
+ * counts, just remove them from the LRU. Otherwise give them
+ * another pass through the LRU.
+ */
+ if (dentry->d_count) {
+ list_del_init(&dentry->d_lru);
+ spin_unlock(&dentry->d_lock);
+ return 0;
+ }
+
+ if (dentry->d_flags & DCACHE_REFERENCED) {
+ dentry->d_flags &= ~DCACHE_REFERENCED;
+ spin_unlock(&dentry->d_lock);
+
+ /*
+ * XXX: this list move should be be done under d_lock. Need to
+ * determine if it is safe just to do it under the lru lock.
+ */
+ return 1;
+ }
+
+ list_move_tail(&dentry->d_lru, freeable);
+ this_cpu_dec(nr_dentry_unused);
+ spin_unlock(&dentry->d_lock);
+
+ return 0;
+}
+
/**
* prune_dcache_sb - shrink the dcache
* @sb: superblock
@@ -770,44 +790,13 @@ static void shrink_dentry_list(struct list_head *list)
*/
long prune_dcache_sb(struct super_block *sb, long nr_to_scan)
{
- struct dentry *dentry;
- LIST_HEAD(referenced);
- LIST_HEAD(tmp);
+ LIST_HEAD(dispose);
long freed = 0;

-relock:
- 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(&sb->s_dentry_lru_lock);
- cpu_relax();
- goto relock;
- }
+ freed = list_lru_walk(&sb->s_dentry_lru, dentry_lru_isolate,
+ &dispose, nr_to_scan);

- if (dentry->d_flags & DCACHE_REFERENCED) {
- dentry->d_flags &= ~DCACHE_REFERENCED;
- list_move(&dentry->d_lru, &referenced);
- spin_unlock(&dentry->d_lock);
- } else {
- list_move_tail(&dentry->d_lru, &tmp);
- this_cpu_dec(nr_dentry_unused);
- sb->s_nr_dentry_unused--;
- spin_unlock(&dentry->d_lock);
- freed++;
- if (!--nr_to_scan)
- break;
- }
- cond_resched_lock(&sb->s_dentry_lru_lock);
- }
- if (!list_empty(&referenced))
- list_splice(&referenced, &sb->s_dentry_lru);
- spin_unlock(&sb->s_dentry_lru_lock);
-
- shrink_dentry_list(&tmp);
+ shrink_dentry_list(&dispose);
return freed;
}

@@ -820,24 +809,10 @@ relock:
*/
void shrink_dcache_sb(struct super_block *sb)
{
- LIST_HEAD(tmp);
-
- spin_lock(&sb->s_dentry_lru_lock);
- while (!list_empty(&sb->s_dentry_lru)) {
- list_splice_init(&sb->s_dentry_lru, &tmp);
+ long freed;

- /*
- * account for removal here so we don't need to handle it later
- * even though the dentry is no longer on the lru list.
- */
- this_cpu_sub(nr_dentry_unused, sb->s_nr_dentry_unused);
- sb->s_nr_dentry_unused = 0;
-
- spin_unlock(&sb->s_dentry_lru_lock);
- shrink_dentry_list(&tmp);
- spin_lock(&sb->s_dentry_lru_lock);
- }
- spin_unlock(&sb->s_dentry_lru_lock);
+ freed = list_lru_dispose_all(&sb->s_dentry_lru, shrink_dentry_list);
+ this_cpu_sub(nr_dentry_unused, freed);
}
EXPORT_SYMBOL(shrink_dcache_sb);

@@ -1094,11 +1069,10 @@ resume:
/*
* move only zero ref count dentries to the dispose list.
*/
+ dentry_lru_del(dentry);
if (!dentry->d_count) {
- dentry_lru_move_list(dentry, dispose);
+ list_add_tail(&dentry->d_lru, dispose);
found++;
- } else {
- dentry_lru_del(dentry);
}

/*
diff --git a/fs/super.c b/fs/super.c
index bc0e101..cc96fdf 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -70,10 +70,11 @@ static long super_cache_scan(struct shrinker *shrink, struct shrink_control *sc)
fs_objects = sb->s_op->nr_cached_objects(sb);

inodes = list_lru_count(&sb->s_inode_lru);
- total_objects = sb->s_nr_dentry_unused + inodes + fs_objects + 1;
+ dentries = list_lru_count(&sb->s_dentry_lru);
+ total_objects = dentries + inodes + fs_objects + 1;

/* proportion the scan between the caches */
- dentries = (sc->nr_to_scan * sb->s_nr_dentry_unused) / total_objects;
+ dentries = (sc->nr_to_scan * dentries) / total_objects;
inodes = (sc->nr_to_scan * inodes) / total_objects;

/*
@@ -105,7 +106,7 @@ static long super_cache_count(struct shrinker *shrink, struct shrink_control *sc
if (sb->s_op && sb->s_op->nr_cached_objects)
total_objects = sb->s_op->nr_cached_objects(sb);

- total_objects += sb->s_nr_dentry_unused;
+ total_objects += list_lru_count(&sb->s_dentry_lru);
total_objects += list_lru_count(&sb->s_inode_lru);

total_objects = (total_objects / 100) * sysctl_vfs_cache_pressure;
@@ -151,8 +152,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
INIT_LIST_HEAD(&s->s_instances);
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);
+ list_lru_init(&s->s_dentry_lru);
list_lru_init(&s->s_inode_lru);
init_rwsem(&s->s_umount);
mutex_init(&s->s_lock);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 80beb62..fd458f9 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1411,12 +1411,6 @@ struct super_block {
#else
struct list_head s_files;
#endif
- 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 dentries on lru */
-
- struct list_lru s_inode_lru ____cacheline_aligned_in_smp;
-
struct block_device *s_bdev;
struct backing_dev_info *s_bdi;
struct mtd_info *s_mtd;
@@ -1461,6 +1455,14 @@ struct super_block {
int cleancache_poolid;

struct shrinker s_shrink; /* per-sb shrinker handle */
+
+ /*
+ * keep the lru lists last in the structure so they always sit on their
+ * own individual cachelines.
+ */
+ struct list_lru s_dentry_lru ____cacheline_aligned_in_smp;
+ struct list_lru s_inode_lru ____cacheline_aligned_in_smp;
+
};

extern struct timespec current_fs_time(struct super_block *sb);
--
1.7.5.4


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