1 files changed, 78 insertions, 92 deletions

diff --git a/fs/dcache.c b/fs/dcache.c
index 77d466b13fef..38a4a03499a2 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -37,6 +37,7 @@
 #include <linux/rculist_bl.h>
 #include <linux/prefetch.h>
 #include <linux/ratelimit.h>
+#include <linux/list_lru.h>
 #include "internal.h"
 #include "mount.h"
 
@@ -356,28 +357,17 @@ static void dentry_unlink_inode(struct dentry * dentry)
 }
 
 /*
- * dentry_lru_(add|del|move_list) must be called with d_lock held.
+ * dentry_lru_(add|del)_list) must be called with d_lock held.
  */
 static void dentry_lru_add(struct dentry *dentry)
 {
         if (unlikely(!(dentry->d_flags & DCACHE_LRU_LIST))) {
-                spin_lock(&dentry->d_sb->s_dentry_lru_lock);
+                if (list_lru_add(&dentry->d_sb->s_dentry_lru, &dentry->d_lru))
+                        this_cpu_inc(nr_dentry_unused);
                 dentry->d_flags |= DCACHE_LRU_LIST;
-                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(&dentry->d_sb->s_dentry_lru_lock);
         }
 }
 
-static void __dentry_lru_del(struct dentry *dentry)
-{
-        list_del_init(&dentry->d_lru);
-        dentry->d_flags &= ~DCACHE_LRU_LIST;
-        dentry->d_sb->s_nr_dentry_unused--;
-        this_cpu_dec(nr_dentry_unused);
-}
-
 /*
  * Remove a dentry with references from the LRU.
  *
@@ -393,27 +383,9 @@ static void dentry_lru_del(struct dentry *dentry)
                 return;
         }
 
-        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)
-{
-        BUG_ON(dentry->d_flags & DCACHE_SHRINK_LIST);
-
-        spin_lock(&dentry->d_sb->s_dentry_lru_lock);
-        if (list_empty(&dentry->d_lru)) {
-                dentry->d_flags |= DCACHE_LRU_LIST;
-                list_add_tail(&dentry->d_lru, list);
-        } else {
-                list_move_tail(&dentry->d_lru, list);
-                dentry->d_sb->s_nr_dentry_unused--;
+        if (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);
+        dentry->d_flags &= ~DCACHE_LRU_LIST;
 }
 
 /**
@@ -901,12 +873,72 @@ static void shrink_dentry_list(struct list_head *list)
         rcu_read_unlock();
 }
 
+static enum lru_status
+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 LRU_SKIP;
+
+        /*
+         * 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_lockref.count) {
+                list_del_init(&dentry->d_lru);
+                spin_unlock(&dentry->d_lock);
+                return LRU_REMOVED;
+        }
+
+        if (dentry->d_flags & DCACHE_REFERENCED) {
+                dentry->d_flags &= ~DCACHE_REFERENCED;
+                spin_unlock(&dentry->d_lock);
+
+                /*
+                 * The list move itself will be made by the common LRU code. At
+                 * this point, we've dropped the dentry->d_lock but keep the
+                 * lru lock. This is safe to do, since every list movement is
+                 * protected by the lru lock even if both locks are held.
+                 *
+                 * This is guaranteed by the fact that all LRU management
+                 * functions are intermediated by the LRU API calls like
+                 * list_lru_add and list_lru_del. List movement in this file
+                 * only ever occur through this functions or through callbacks
+                 * like this one, that are called from the LRU API.
+                 *
+                 * The only exceptions to this are functions like
+                 * shrink_dentry_list, and code that first checks for the
+                 * DCACHE_SHRINK_LIST flag.  Those are guaranteed to be
+                 * operating only with stack provided lists after they are
+                 * properly isolated from the main list.  It is thus, always a
+                 * local access.
+                 */
+                return LRU_ROTATE;
+        }
+
+        dentry->d_flags |= DCACHE_SHRINK_LIST;
+        list_move_tail(&dentry->d_lru, freeable);
+        this_cpu_dec(nr_dentry_unused);
+        spin_unlock(&dentry->d_lock);
+
+        return LRU_REMOVED;
+}
+
 /**
  * prune_dcache_sb - shrink the dcache
  * @sb: superblock
- * @count: number of entries to try to free
+ * @nr_to_scan : number of entries to try to free
  *
- * Attempt to shrink the superblock dcache LRU by @count entries. This is
+ * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is
  * done when we need more memory an called from the superblock shrinker
  * function.
  *
@@ -915,45 +947,12 @@ static void shrink_dentry_list(struct list_head *list)
  */
 long prune_dcache_sb(struct super_block *sb, unsigned long nr_to_scan)
 {
-        struct dentry *dentry;
-        LIST_HEAD(referenced);
-        LIST_HEAD(tmp);
-        long freed = 0;
+        LIST_HEAD(dispose);
+        long freed;
 
-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;
-                }
-
-                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(&dentry->d_lru, &tmp);
-                        dentry->d_flags |= DCACHE_SHRINK_LIST;
-                        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);
+        freed = list_lru_walk(&sb->s_dentry_lru, dentry_lru_isolate,
+                              &dispose, nr_to_scan);
+        shrink_dentry_list(&dispose);
         return freed;
 }
 
@@ -987,24 +986,10 @@ shrink_dcache_list(
  */
 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)) {
-                /*
-                 * account for removal here so we don't need to handle it later
-                 * even though the dentry is no longer on the lru list.
-                 */
-                list_splice_init(&sb->s_dentry_lru, &tmp);
-                this_cpu_sub(nr_dentry_unused, sb->s_nr_dentry_unused);
-                sb->s_nr_dentry_unused = 0;
-                spin_unlock(&sb->s_dentry_lru_lock);
+        long disposed;
 
-                shrink_dcache_list(&tmp);
-
-                spin_lock(&sb->s_dentry_lru_lock);
-        }
-        spin_unlock(&sb->s_dentry_lru_lock);
+        disposed = list_lru_dispose_all(&sb->s_dentry_lru, shrink_dcache_list);
+        this_cpu_sub(nr_dentry_unused, disposed);
 }
 EXPORT_SYMBOL(shrink_dcache_sb);
 
@@ -1366,7 +1351,8 @@ static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
         if (dentry->d_lockref.count) {
                 dentry_lru_del(dentry);
         } else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
-                dentry_lru_move_list(dentry, &data->dispose);
+                dentry_lru_del(dentry);
+                list_add_tail(&dentry->d_lru, &data->dispose);
                 dentry->d_flags |= DCACHE_SHRINK_LIST;
                 data->found++;
                 ret = D_WALK_NORETRY;