linux-kernel - [PATCH] vfs: Revert spurious fix to spinning prevention in prune_icache

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Date:	Sat, 13 Apr 2013 16:03:06 -0700 (PDT)
From:	Hugh Dickins <hughd@...gle.com>
To:	Al Viro <viro@...iv.linux.org.uk>
cc:	Christoph Hellwig <hch@....de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Suleiman Souhlal <suleiman@...gle.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] vfs: Revert spurious fix to spinning prevention in
 prune_icache_sb

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

Revert v3.2's 62a3dde ("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>
Cc: stable@...r.kernel.org
---

 fs/inode.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
    
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -725,7 +725,7 @@ void prune_icache_sb(struct super_block *sb, int nr_to_scan, int priority)
 		 * 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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