diff options
| author | Keith Busch <keith.busch@intel.com> | 2018-09-25 10:36:20 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-04-13 10:32:52 +0200 |
| commit | d4d74449367e1ca68078db17dedd764916740cca (patch) | |
| tree | 5e95fd6e7799936e94eb0a9500024e1b4d50666e /block | |
| parent | f530afb974c2e82047bd6220303a2dbe30eff304 (diff) | |
blk-mq: Allow blocking queue tag iter callbacks
commit 530ca2c9bd6949c72c9b5cfc330cb3dbccaa3f5b upstream.
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: f5bbbbe4d6357 ("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>
Signed-off-by: Giuliano Procida <gprocida@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-mq-tag.c | 13 |
1 files changed, 4 insertions, 9 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index 0861f15ec0df..89bb6250633d 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -338,16 +338,11 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, /* * __blk_mq_update_nr_hw_queues will update the nr_hw_queues and - * queue_hw_ctx after freeze the queue. So we could use q_usage_counter - * to avoid race with it. __blk_mq_update_nr_hw_queues will users - * synchronize_rcu to ensure all of the users go out of the critical - * section below and see zeroed q_usage_counter. + * queue_hw_ctx after freeze the queue, so we use q_usage_counter + * to avoid race with it. */ - rcu_read_lock(); - if (percpu_ref_is_zero(&q->q_usage_counter)) { - rcu_read_unlock(); + if (!percpu_ref_tryget(&q->q_usage_counter)) return; - } queue_for_each_hw_ctx(q, hctx, i) { struct blk_mq_tags *tags = hctx->tags; @@ -363,7 +358,7 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, bt_for_each(hctx, &tags->breserved_tags, fn, priv, true); bt_for_each(hctx, &tags->bitmap_tags, fn, priv, false); } - rcu_read_unlock(); + blk_queue_exit(q); } static unsigned int bt_unused_tags(const struct sbitmap_queue *bt) |