linux-kernel - [42/75] vfs: Revert spurious fix to spinning prevention in prune_icache

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Date:	Mon, 22 Apr 2013 15:25:59 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org,
	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Hugh Dickins" <hughd@...gle.com>,
	"Suleiman Souhlal" <suleiman@...gle.com>
Subject: [42/75] vfs: Revert spurious fix to spinning prevention in
 prune_icache_sb

3.2.44-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Suleiman Souhlal <suleiman@...gle.com>

commit 5b55d708335a9e3e4f61f2dadf7511502205ccd1 upstream.

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@...gle.com>
Signed-off-by: Hugh Dickins <hughd@...gle.com>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 fs/inode.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/inode.c
+++ b/fs/inode.c
@@ -634,7 +634,7 @@ void prune_icache_sb(struct super_block
 		 * 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;
 		}
 

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