On 4/9/18 4:54 PM, Bart Van Assche wrote:
> On Mon, 2018-04-09 at 14:54 +0800, Joseph Qi wrote:
>> The oops happens during generic_make_request_checks(), in
>> blk_throtl_bio() exactly.
>> So if we want to bypass dying queue, we have to check this before
>> generic_make_request_checks(), I think.
>
> How about something like the patch below?
>
> Thanks,
>
> Bart.
>
> Subject: [PATCH] blk-mq: Avoid that submitting a bio concurrently with device
> removal triggers a crash
>
> 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 a blk_queue_enter() / blk_queue_exit() pair.
>
> ---
> block/blk-core.c | 17 ++++++++++++++++-
> 1 file changed, 16 insertions(+), 1 deletion(-)
>
> diff --git a/block/blk-core.c b/block/blk-core.c
> index d69888ff52f0..0c48bef8490f 100644
> --- a/block/blk-core.c
> +++ b/block/blk-core.c
> @@ -2388,9 +2388,24 @@ 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;
> + bool check_result;
> blk_qc_t ret = BLK_QC_T_NONE;
>
> - if (!generic_make_request_checks(bio))
> + if (blk_queue_enter(q, flags) < 0) {
> + if (!blk_queue_dying(q) && (bio->bi_opf & REQ_NOWAIT))
> + bio_wouldblock_error(bio);
> + else
> + bio_io_error(bio);
> + return ret;
> + }
> +
> + check_result = generic_make_request_checks(bio);
> + blk_queue_exit(q);
This ends up being nutty in the generic_make_request() case, where we
do the exact same enter/exit logic right after. That needs to get unified.
Maybe move the queue enter into generic_make_request_checks(), and exit
in the caller?
--
Jens Axboe
