diff options
| author | Ming Lei <ming.lei@redhat.com> | 2017-06-18 22:24:27 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-06-18 22:24:27 +0200 |
| commit | f4560ffe8cec1361b1021d81aca6a4173f8e7c87 (patch) | |
| tree | 957cae770ed234d2e03fef8a6e458296f011369e /block | |
| parent | blk-mq: use the introduced blk_mq_unquiesce_queue() (diff) | |
| download | linux-f4560ffe8cec1361b1021d81aca6a4173f8e7c87.tar.xz linux-f4560ffe8cec1361b1021d81aca6a4173f8e7c87.zip | |
blk-mq: use QUEUE_FLAG_QUIESCED to quiesce queue
It is required that no dispatch can happen any more once
blk_mq_quiesce_queue() returns, and we don't have such requirement
on APIs of stopping queue.
But blk_mq_quiesce_queue() still may not block/drain dispatch in the
the case of BLK_MQ_S_START_ON_RUN, so use the new introduced flag of
QUEUE_FLAG_QUIESCED and evaluate it inside RCU read-side critical
sections for fixing this issue.
Also blk_mq_quiesce_queue() is implemented via stopping queue, which
limits its uses, and easy to cause race, because any queue restart in
other paths may break blk_mq_quiesce_queue(). With the introduced
flag of QUEUE_FLAG_QUIESCED, we don't need to depend on stopping queue
for quiescing any more.
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Reviewed-by: Bart Van Assche <Bart.VanAssche@sandisk.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-mq-sched.c | 3 | ||||
| -rw-r--r-- | block/blk-mq.c | 11 |
2 files changed, 12 insertions, 2 deletions
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c index 254d1c164567..9f025289da63 100644 --- a/block/blk-mq-sched.c +++ b/block/blk-mq-sched.c @@ -58,7 +58,8 @@ void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx) bool did_work = false; LIST_HEAD(rq_list); - if (unlikely(blk_mq_hctx_stopped(hctx))) + /* RCU or SRCU read lock is needed before checking quiesced flag */ + if (unlikely(blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q))) return; hctx->run++; diff --git a/block/blk-mq.c b/block/blk-mq.c index 07785b5cf2bc..40b22c7f684e 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -170,6 +170,10 @@ void blk_mq_quiesce_queue(struct request_queue *q) __blk_mq_stop_hw_queues(q, true); + spin_lock_irq(q->queue_lock); + queue_flag_set(QUEUE_FLAG_QUIESCED, q); + spin_unlock_irq(q->queue_lock); + queue_for_each_hw_ctx(q, hctx, i) { if (hctx->flags & BLK_MQ_F_BLOCKING) synchronize_srcu(&hctx->queue_rq_srcu); @@ -190,6 +194,10 @@ EXPORT_SYMBOL_GPL(blk_mq_quiesce_queue); */ void blk_mq_unquiesce_queue(struct request_queue *q) { + spin_lock_irq(q->queue_lock); + queue_flag_clear(QUEUE_FLAG_QUIESCED, q); + spin_unlock_irq(q->queue_lock); + blk_mq_start_stopped_hw_queues(q, true); } EXPORT_SYMBOL_GPL(blk_mq_unquiesce_queue); @@ -1444,7 +1452,8 @@ static void __blk_mq_try_issue_directly(struct blk_mq_hw_ctx *hctx, blk_status_t ret; bool run_queue = true; - if (blk_mq_hctx_stopped(hctx)) { + /* RCU or SRCU read lock is needed before checking quiesced flag */ + if (blk_mq_hctx_stopped(hctx) || blk_queue_quiesced(q)) { run_queue = false; goto insert; } |