[PATCH 020/102] xfs: warn if direct reclaim tries to writeback pages

Dave Chinner
2012-08-23T05:03:11Z

From: Mel Gorman <mgorman@suse.de>

Upstream commit: 94054fa3fca1fd78db02cb3d68d5627120f0a1d4

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>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
fs/xfs/linux-2.6/xfs_aops.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index f16207b..4ff2404 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -943,11 +943,11 @@ 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;

/*