blk-mq: Allow blocking queue tag iter callbacks
A recent commit runs tag iterator callbacks under the rcu read lock,
but existing callbacks do not satisfy the non-blocking requirement.
The commit intended to prevent an iterator from accessing a queue that's
being modified. This patch fixes the original issue by taking a queue
reference instead of reading it, which allows callbacks to make blocking
calls.
Fixes: f5bbbbe4d6
("blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter")
Acked-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
parent
b57e99b4b8
commit
530ca2c9bd
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@ -322,16 +322,11 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
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/*
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/*
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* __blk_mq_update_nr_hw_queues will update the nr_hw_queues and
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* __blk_mq_update_nr_hw_queues will update the nr_hw_queues and
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* queue_hw_ctx after freeze the queue. So we could use q_usage_counter
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* queue_hw_ctx after freeze the queue, so we use q_usage_counter
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* to avoid race with it. __blk_mq_update_nr_hw_queues will users
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* to avoid race with it.
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* synchronize_rcu to ensure all of the users go out of the critical
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* section below and see zeroed q_usage_counter.
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*/
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*/
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rcu_read_lock();
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if (!percpu_ref_tryget(&q->q_usage_counter))
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if (percpu_ref_is_zero(&q->q_usage_counter)) {
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rcu_read_unlock();
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return;
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return;
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}
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queue_for_each_hw_ctx(q, hctx, i) {
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queue_for_each_hw_ctx(q, hctx, i) {
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struct blk_mq_tags *tags = hctx->tags;
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struct blk_mq_tags *tags = hctx->tags;
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@ -347,7 +342,7 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn,
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bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
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bt_for_each(hctx, &tags->breserved_tags, fn, priv, true);
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bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
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bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false);
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}
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}
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rcu_read_unlock();
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blk_queue_exit(q);
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}
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}
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static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
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static int bt_alloc(struct sbitmap_queue *bt, unsigned int depth,
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