mbcache: fix shrinker function return value

The shrinker function is supposed to return the number of cache
entries after shrinking, not before shrinking.  Fix that.

Based on a patch from Wang Sheng-Hui <crosslonelyover@gmail.com>.
Signed-off-by: NAndreas Gruenbacher <agruen@suse.de>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

fs/mbcache.c

@@ -176,22 +176,12 @@ static int
 mb_cache_shrink_fn(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask)
 {
 	LIST_HEAD(free_list);
-	struct list_head *l, *ltmp;
+	struct mb_cache *cache;
+	struct mb_cache_entry *entry, *tmp;
 	int count = 0;
 
-	spin_lock(&mb_cache_spinlock);
-	list_for_each(l, &mb_cache_list) {
-		struct mb_cache *cache =
-			list_entry(l, struct mb_cache, c_cache_list);
-		mb_debug("cache %s (%d)", cache->c_name,
-			  atomic_read(&cache->c_entry_count));
-		count += atomic_read(&cache->c_entry_count);
-	}
 	mb_debug("trying to free %d entries", nr_to_scan);
-	if (nr_to_scan == 0) {
-		spin_unlock(&mb_cache_spinlock);
-		goto out;
-	}
+	spin_lock(&mb_cache_spinlock);
 	while (nr_to_scan-- && !list_empty(&mb_cache_lru_list)) {
 		struct mb_cache_entry *ce =
 			list_entry(mb_cache_lru_list.next,
@@ -199,12 +189,15 @@ mb_cache_shrink_fn(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask)
 		list_move_tail(&ce->e_lru_list, &free_list);
 		__mb_cache_entry_unhash(ce);
 	}
+	list_for_each_entry(cache, &mb_cache_list, c_cache_list) {
+		mb_debug("cache %s (%d)", cache->c_name,
+			  atomic_read(&cache->c_entry_count));
+		count += atomic_read(&cache->c_entry_count);
+	}
 	spin_unlock(&mb_cache_spinlock);
-	list_for_each_safe(l, ltmp, &free_list) {
-		__mb_cache_entry_forget(list_entry(l, struct mb_cache_entry,
-						   e_lru_list), gfp_mask);
+	list_for_each_entry_safe(entry, tmp, &free_list, e_lru_list) {
+		__mb_cache_entry_forget(entry, gfp_mask);
 	}
-out:
 	return (count / 100) * sysctl_vfs_cache_pressure;
 }