linux-kernel - [RFC -v2 8/8] btrfs: use __GFP_NOFAIL in alloc_btrfs

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Message-ID: <20150818104116.GG5033@dhcp22.suse.cz>
Date:	Tue, 18 Aug 2015 12:41:16 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	LKML <linux-kernel@...r.kernel.org>
Cc:	linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Johannes Weiner <hannes@...xchg.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	Dave Chinner <david@...morbit.com>,
	Theodore Ts'o <tytso@....edu>, linux-btrfs@...r.kernel.org,
	linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz>
Subject: [RFC -v2 8/8] btrfs: use __GFP_NOFAIL in alloc_btrfs_bio

From: Michal Hocko <mhocko@...e.com>

alloc_btrfs_bio is relying on GFP_NOFS to allocate a bio but since "mm:
page_alloc: do not lock up GFP_NOFS allocations upon OOM" this is
allowed to fail which can lead to
[   37.928625] kernel BUG at fs/btrfs/extent_io.c:4045

This is clearly undesirable and the nofail behavior should be explicit
if the allocation failure cannot be tolerated.

Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 fs/btrfs/volumes.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 53af23f2c087..42b9949dd71d 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4914,9 +4914,7 @@ static struct btrfs_bio *alloc_btrfs_bio(int total_stripes, int real_stripes)
 		 * and the stripes
 		 */
 		sizeof(u64) * (total_stripes),
-		GFP_NOFS);
-	if (!bbio)
-		return NULL;
+		GFP_NOFS|__GFP_NOFAIL);
 
 	atomic_set(&bbio->error, 0);
 	atomic_set(&bbio->refs, 1);
-- 
2.5.0

-- 
Michal Hocko
SUSE Labs
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