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    Subject[PATCH 4.4 080/113] RAID10 BUG_ON in raise_barrier when force is true and conf->barrier is 0
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    drivers/md/raid10.c | 5 ++++-
    1 file changed, 4 insertions(+), 1 deletion(-)

    --- a/drivers/md/raid10.c
    +++ b/drivers/md/raid10.c
    @@ -4336,11 +4336,12 @@ static sector_t reshape_request(struct m
    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 @@ bio_full:
    if (sector_nr <= last)
    goto read_more;

    + lower_barrier(conf);
    +
    /* Now that we have done the whole section we can
    * update reshape_progress
    */

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