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

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Message-Id: <1438768284-30927-9-git-send-email-mhocko@kernel.org>
Date:	Wed,  5 Aug 2015 11:51:24 +0200
From:	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>,
	Michal Hocko <mhocko@...e.com>
Subject: [RFC 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 | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 53af23f2c087..57a99d19533d 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -4914,7 +4914,7 @@ static struct btrfs_bio *alloc_btrfs_bio(int total_stripes, int real_stripes)
 		 * and the stripes
 		 */
 		sizeof(u64) * (total_stripes),
-		GFP_NOFS);
+		GFP_NOFS|__GFP_NOFAIL);
 	if (!bbio)
 		return NULL;
 
-- 
2.5.0

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