blk-mq: fix race condition in active queue accounting
If multiple CPUs are sharing the same hardware queue, it can
cause leak in the active queue counter tracking when __blk_mq_tag_busy()
is executed simultaneously.
Fixes: ee78ec1077
("blk-mq: blk_mq_tag_busy is no need to return a value")
Signed-off-by: Tian Lan <tian.lan@twosigma.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Link: https://lore.kernel.org/r/20230522210555.794134-1-tilan7663@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
parent
8a2b20a997
commit
3e94d54e83
@ -39,16 +39,20 @@ void __blk_mq_tag_busy(struct blk_mq_hw_ctx *hctx)
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{
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unsigned int users;
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/*
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* calling test_bit() prior to test_and_set_bit() is intentional,
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* it avoids dirtying the cacheline if the queue is already active.
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*/
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if (blk_mq_is_shared_tags(hctx->flags)) {
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struct request_queue *q = hctx->queue;
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if (test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
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if (test_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags) ||
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test_and_set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags))
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return;
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set_bit(QUEUE_FLAG_HCTX_ACTIVE, &q->queue_flags);
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} else {
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if (test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
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if (test_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state) ||
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test_and_set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state))
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return;
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set_bit(BLK_MQ_S_TAG_ACTIVE, &hctx->state);
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}
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users = atomic_inc_return(&hctx->tags->active_queues);
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