[PATCH 2/8] xfs: Warn if direct reclaim tries to writeback pages

[Mel Gorman <mgorman@xxxxxxx>]

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@xxxxxxx>
---
 fs/xfs/linux-2.6/xfs_aops.c |    9 +++++----
 1 files changed, 5 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index 79ce38b..c33a439 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -930,12 +930,13 @@ 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 ((current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC) {
+               WARN_ON_ONCE(1);
                goto redirty;
+       }
 
        /*
         * We need a transaction if there are delalloc or unwritten buffers
-- 
1.7.3.4