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blk-mq: don't touch ->tagset in blk_mq_get_sq_hctx

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blk_mq_run_hw_queues() could be run when there isn't queued request and
after queue is cleaned up, at that time tagset is freed, because tagset
lifetime is covered by driver, and often freed after blk_cleanup_queue()
returns.

So don't touch ->tagset for figuring out current default hctx by the mapping
built in request queue, so use-after-free on tagset can be avoided. Meantime
this way should be fast than retrieving mapping from tagset.

Cc: "yukuai (C)" <yukuai3@huawei.com>
Cc: Jan Kara <jack@suse.cz>
Fixes: b6e68ee825 ("blk-mq: Improve performance of non-mq IO schedulers with multiple HW queues")
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220522122350.743103-1-ming.lei@redhat.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei 2022-05-22 20:23:50 +08:00 committed by Jens Axboe
parent 2aaf516084
commit 5d05426e2d
1 changed files with 3 additions and 4 deletions
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7
block/blk-mq.c
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@ -2130,8 +2130,7 @@ static bool blk_mq_has_sqsched(struct request_queue *q)
*/
static struct blk_mq_hw_ctx *blk_mq_get_sq_hctx(struct request_queue *q)
{
struct blk_mq_hw_ctx *hctx;
struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
/*
* If the IO scheduler does not respect hardware queues when
* dispatching, we just don't bother with multiple HW queues and
@ -2139,8 +2138,8 @@ static struct blk_mq_hw_ctx *blk_mq_get_sq_hctx(struct request_queue *q)
* just causes lock contention inside the scheduler and pointless cache
* bouncing.
*/
hctx = blk_mq_map_queue_type(q, HCTX_TYPE_DEFAULT,
raw_smp_processor_id());
struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, 0, ctx);
if (!blk_mq_hctx_stopped(hctx))
return hctx;
return NULL;