fs: reduce dcache_inode_lock width in lru scanning
Nick Piggin [Fri, 7 Jan 2011 06:49:46 +0000 (17:49 +1100)]
Signed-off-by: Nick Piggin <npiggin@kernel.dk>

fs/dcache.c

index 1957063..fe8f28a 100644 (file)
@@ -621,7 +621,7 @@ static void shrink_dentry_list(struct list_head *list)
                dentry = list_entry(list->prev, struct dentry, d_lru);
 
                if (!spin_trylock(&dentry->d_lock)) {
-relock:
+relock1:
                        spin_unlock(&dcache_lru_lock);
                        cpu_relax();
                        spin_lock(&dcache_lru_lock);
@@ -638,20 +638,24 @@ relock:
                        spin_unlock(&dentry->d_lock);
                        continue;
                }
+               if (!spin_trylock(&dcache_inode_lock)) {
+relock2:
+                       spin_unlock(&dentry->d_lock);
+                       goto relock1;
+               }
                if (IS_ROOT(dentry))
                        parent = NULL;
                else
                        parent = dentry->d_parent;
                if (parent && !spin_trylock(&parent->d_lock)) {
-                       spin_unlock(&dentry->d_lock);
-                       goto relock;
+                       spin_unlock(&dcache_inode_lock);
+                       goto relock2;
                }
                __dentry_lru_del(dentry);
                spin_unlock(&dcache_lru_lock);
 
                prune_one_dentry(dentry, parent);
                /* dcache_inode_lock and dentry->d_lock dropped */
-               spin_lock(&dcache_inode_lock);
                spin_lock(&dcache_lru_lock);
        }
 }
@@ -672,7 +676,6 @@ static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
        LIST_HEAD(tmp);
        int cnt = *count;
 
-       spin_lock(&dcache_inode_lock);
 relock:
        spin_lock(&dcache_lru_lock);
        while (!list_empty(&sb->s_dentry_lru)) {
@@ -711,7 +714,6 @@ relock:
        if (!list_empty(&referenced))
                list_splice(&referenced, &sb->s_dentry_lru);
        spin_unlock(&dcache_lru_lock);
-       spin_unlock(&dcache_inode_lock);
 }
 
 /**
@@ -800,14 +802,12 @@ void shrink_dcache_sb(struct super_block *sb)
 {
        LIST_HEAD(tmp);
 
-       spin_lock(&dcache_inode_lock);
        spin_lock(&dcache_lru_lock);
        while (!list_empty(&sb->s_dentry_lru)) {
                list_splice_init(&sb->s_dentry_lru, &tmp);
                shrink_dentry_list(&tmp);
        }
        spin_unlock(&dcache_lru_lock);
-       spin_unlock(&dcache_inode_lock);
 }
 EXPORT_SYMBOL(shrink_dcache_sb);