diff options
| author | Keith Busch <keith.busch@intel.com> | 2018-09-25 10:36:20 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-05-20 08:11:51 +0200 |
| commit | 4764810c454478029cb9acf0866d1aec3fccb689 (patch) | |
| tree | 3fbe99b31f03adec2a22f50290f612f188abc3e5 /block | |
| parent | fa9355afd5b07707e15a5f75b854f04a9c14a798 (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 | 7 |
1 files changed, 2 insertions, 5 deletions
diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c index bf356de30134..c1c654319287 100644 --- a/block/blk-mq-tag.c +++ b/block/blk-mq-tag.c @@ -484,11 +484,8 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, /* * Avoid potential races with things like queue removal. */ - 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; @@ -505,7 +502,7 @@ void blk_mq_queue_tag_busy_iter(struct request_queue *q, busy_iter_fn *fn, bt_for_each(hctx, &tags->bitmap_tags, tags->nr_reserved_tags, fn, priv, false); } - rcu_read_unlock(); + blk_queue_exit(q); } static unsigned int bt_unused_tags(struct blk_mq_bitmap_tags *bt) |