From: Mel Gorman <mgorman@suse.de>
Date: Wed, 24 Aug 2011 23:46:59 +0000 (+1000)
Subject: Direct reclaim should never writeback pages.  For now, handle the
X-Git-Tag: next-20110912~1^2~77
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=7b84eac8368ceb7989aff82ce6e72c75a8930b2a;p=karo-tx-linux.git

Direct reclaim should never writeback pages.  For now, handle the
situation and warn about it.  Ultimately, this will be a BUG_ON.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Johannes Weiner <jweiner@redhat.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Alex Elder <aelder@sgi.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 46bba3e0af47..444853aff021 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -895,11 +895,11 @@ xfs_vm_writepage(
 	 * random callers for direct reclaim or memcg reclaim.  We explicitly
 	 * allow reclaim from kswapd as the stack usage there is relatively low.
 	 *
-	 * This should really be done by the core VM, but until that happens
-	 * filesystems like XFS, btrfs and ext4 have to take care of this
-	 * by themselves.
+	 * This should never happen except in the case of a VM regression so
+	 * warn about it.
 	 */
-	if ((current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC)
+	if (WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
+			PF_MEMALLOC))
 		goto redirty;
 
 	/*