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| author |   Jianchao Wang <jianchao.w.wang@oracle.com> | 2018-08-21 15:15:04 +0800 |
|---|---|---|
| committer |   Jens Axboe <axboe@kernel.dk> | 2018-08-21 09:02:56 -0600 |
| commit | f5bbbbe4d63577026f908a809f22f5fd5a90ea1f (patch) | |
| tree | a6d8a1e7329b4160285b79a0565a45b53a2809f6 /block/blk-mq.c | |
| parent | blk-mq: init hctx sched after update ctx and hctx mapping (diff) | |
| download | linux-dev-f5bbbbe4d63577026f908a809f22f5fd5a90ea1f.tar.xz linux-dev-f5bbbbe4d63577026f908a809f22f5fd5a90ea1f.zip | |
blk-mq: sync the update nr_hw_queues with blk_mq_queue_tag_busy_iter
For blk-mq, part_in_flight/rw will invoke blk_mq_in_flight/rw to
account the inflight requests. It will access the queue_hw_ctx and
nr_hw_queues w/o any protection. When updating nr_hw_queues and
blk_mq_in_flight/rw occur concurrently, panic comes up.
Before update nr_hw_queues, the q will be frozen. So we could use
q_usage_counter to avoid the race. percpu_ref_is_zero is used here
so that we will not miss any in-flight request. The access to
nr_hw_queues and queue_hw_ctx in blk_mq_queue_tag_busy_iter are
under rcu critical section, __blk_mq_update_nr_hw_queues could use
synchronize_rcu to ensure the zeroed q_usage_counter to be globally
visible.
Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq.c')
| -rw-r--r-- | block/blk-mq.c | 4 |
1 files changed, 4 insertions, 0 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index 9c8c8c71a13f..81cb84b17b73 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2977,6 +2977,10 @@ static void __blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, list_for_each_entry(q, &set->tag_list, tag_set_list) blk_mq_freeze_queue(q); /* + * Sync with blk_mq_queue_tag_busy_iter. + */ + synchronize_rcu(); + /* * Switch IO scheduler to 'none', cleaning up the data associated * with the previous scheduler. We will switch back once we are done * updating the new sw to hw queue mappings. |