RAID10 BUG_ON in raise_barrier when force is true and conf->barrier is 0

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>

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 9818980..d6f7978 100644 (file)
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -4529,11 +4529,12 @@ 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;
@@ -4629,6 +4630,8 @@ read_more:
        if (sector_nr <= last)
                goto read_more;
 
+       lower_barrier(conf);
+
        /* Now that we have done the whole section we can
         * update reshape_progress
         */