linux-kernel - [PATCH AUTOSEL 4.18 46/76] RAID10 BUG_ON in raise_barrier when force is true and conf->barrier is 0

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Date:   Mon, 24 Sep 2018 14:48:30 +0000
From:   Sasha Levin <Alexander.Levin@...rosoft.com>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     Xiao Ni <xni@...hat.com>, Shaohua Li <shli@...com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
Subject: [PATCH AUTOSEL 4.18 46/76] RAID10 BUG_ON in raise_barrier when force
 is true and conf->barrier is 0

From: Xiao Ni <xni@...hat.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@...hat.com>
Suggested-by: Neil Brown <neilb@...e.com>
Signed-off-by: Shaohua Li <shli@...com>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.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 35bd3a62451b..8c93d44a052c 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4531,11 +4531,12 @@ 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 = raid10_alloc_init_r10buf(conf);
 	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;
@@ -4631,6 +4632,8 @@ 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