[PATCH 2/2] fs: xfs: use BUG_ON if writepage call comes from direct reclaim

[Yang Shi]

direct reclaim doesn't write out filesystem page, only kswapd could do
this. So, if it is called from direct relaim, it is definitely a bug.

And, Mel Gorman mentioned "Ultimately, this will be a BUG_ON." in commit
94054fa3fca1fd78db02cb3d68d5627120f0a1d4 ("xfs: warn if direct reclaim
tries to writeback pages"),

It has been many years since that commit, so it should be safe to
elevate WARN_ON to BUG_ON now.

Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
Cc: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Yang Shi <yang.shi@xxxxxxxxxxxxxxxxx>
---
 fs/xfs/xfs_aops.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 8eb3ba3..7efc2d2 100644
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -1080,11 +1080,9 @@ static inline int xfs_bio_add_buffer(struct bio *bio, struct buffer_head *bh)
 	 * allow reclaim from kswapd as the stack usage there is relatively low.
 	 *
 	 * This should never happen except in the case of a VM regression so
-	 * warn about it.
+	 * BUG about it.
 	 */
-	if (WARN_ON_ONCE((current->flags & (PF_MEMALLOC|PF_KSWAPD)) ==
-			PF_MEMALLOC))
-		goto redirty;
+	BUG_ON((current->flags & (PF_MEMALLOC|PF_KSWAPD)) == PF_MEMALLOC);
 
 	/*
 	 * Given that we do not allow direct reclaim to call us, we should
-- 
1.8.3.1