vfs: Revert spurious fix to spinning prevention in prune_icache_sb

Revert commit 62a3ddef6181 ("vfs: fix spinning prevention in prune_icache_sb").

This commit doesn't look right: since we are looking at the tail of the
list (sb->s_inode_lru.prev) if we want to skip an inode, we should put
it back at the head of the list instead of the tail, otherwise we will
keep spinning on it.

Discovered when investigating why prune_icache_sb came top in perf
reports of a swapping load.

Signed-off-by: Suleiman Souhlal <suleiman@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: stable@vger.kernel.org # v3.2+
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/inode.c b/fs/inode.c
index f5f7c06c36fb159f89a793510c62f3f9170c3e4d..a898b3d43ccf3990986d51be3305bdc3e6d665ef 100644 (file)
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -725,7 +725,7 @@ void prune_icache_sb(struct super_block *sb, int nr_to_scan)
                 * inode to the back of the list so we don't spin on it.
                 */
                if (!spin_trylock(&inode->i_lock)) {
-                       list_move_tail(&inode->i_lru, &sb->s_inode_lru);
+                       list_move(&inode->i_lru, &sb->s_inode_lru);
                        continue;
                }