[PATCH AUTOSEL 4.4 07/18] RAID10 BUG_ON in raise_barrier when force is true and conf->barrier is 0

From: Sasha Levin <Alexander.Levin@microsoft.com>
To: "stable@vger.kernel.org" <stable@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Xiao Ni <xni@redhat.com>, Shaohua Li <shli@fb.com>,
	Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL 4.4 07/18] RAID10 BUG_ON in raise_barrier when force is true and conf->barrier is 0
Date: Mon, 24 Sep 2018 14:49:48 +0000	[thread overview]
Message-ID: <20180924144942.164688-7-alexander.levin@microsoft.com> (raw)
In-Reply-To: <20180924144942.164688-1-alexander.levin@microsoft.com>

From: Xiao Ni <xni@redhat.com>

[ Upstream commit 1d0ffd264204eba1861865560f1f7f7a92919384 ]

In raid10 reshape_request it gets max_sectors in read_balance. If the underlayer disks
have bad blocks, the max_sectors is less than last. It will call goto read_more many
times. It calls raise_barrier(conf, sectors_done != 0) every time. In this condition
sectors_done is not 0. So the value passed to the argument force of raise_barrier is
true.

In raise_barrier it checks conf->barrier when force is true. If force is true and
conf->barrier is 0, it panic. In this case reshape_request submits bio to under layer
disks. And in the callback function of the bio it calls lower_barrier. If the bio
finishes before calling raise_barrier again, it can trigger the BUG_ON.

Add one pair of raise_barrier/lower_barrier to fix this bug.

Signed-off-by: Xiao Ni <xni@redhat.com>
Suggested-by: Neil Brown <neilb@suse.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
---
 drivers/md/raid10.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 8a731bdd268e..89111d455b71 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4336,11 +4336,12 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
 		allow_barrier(conf);
 	}
 
+	raise_barrier(conf, 0);
 read_more:
 	/* Now schedule reads for blocks from sector_nr to last */
 	r10_bio = mempool_alloc(conf->r10buf_pool, GFP_NOIO);
 	r10_bio->state = 0;
-	raise_barrier(conf, sectors_done != 0);
+	raise_barrier(conf, 1);
 	atomic_set(&r10_bio->remaining, 0);
 	r10_bio->mddev = mddev;
 	r10_bio->sector = sector_nr;
@@ -4445,6 +4446,8 @@ static sector_t reshape_request(struct mddev *mddev, sector_t sector_nr,
 	if (sector_nr <= last)
 		goto read_more;
 
+	lower_barrier(conf);
+
 	/* Now that we have done the whole section we can
 	 * update reshape_progress
 	 */
-- 
2.17.1
