On Tue, Apr 10, 2018 at 02:45:54PM -0600, Bart Van Assche wrote:
> Because blkcg_exit_queue() is now called from inside blk_cleanup_queue()
> it is no longer safe to access cgroup information during or after the
> blk_cleanup_queue() call. Hence protect the generic_make_request_checks()
> call with blk_queue_enter() / blk_queue_exit().
>
> Reported-by: Ming Lei <ming....@redhat.com>
> Fixes: a063057d7c73 ("block: Fix a race between request queue removal and the
> block cgroup controller")
> Signed-off-by: Bart Van Assche <bart.vanass...@wdc.com>
> Cc: Ming Lei <ming....@redhat.com>
> Cc: Joseph Qi <joseph...@linux.alibaba.com>
> ---
>
> Changes compared to v1: changed the blk_queue_exit() inside the loop with "if
> (q)".
>
> block/blk-core.c | 33 +++++++++++++++++++++++++++------
> 1 file changed, 27 insertions(+), 6 deletions(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index 34e2f2227fd9..181b1a688a5b 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -2386,8 +2386,19 @@ blk_qc_t generic_make_request(struct bio *bio)
> * yet.
> */
> struct bio_list bio_list_on_stack[2];
> + blk_mq_req_flags_t flags = bio->bi_opf & REQ_NOWAIT ?
> + BLK_MQ_REQ_NOWAIT : 0;
> + struct request_queue *q = bio->bi_disk->queue;
> blk_qc_t ret = BLK_QC_T_NONE;
>
> + if (blk_queue_enter(q, flags) < 0) {
Same issue with V1, the queue pointer has to be checked before calling
blk_queue_enter().
--
Ming
