diff options
| author | Yufen Yu <yuyufen@huawei.com> | 2020-07-16 02:52:01 -0400 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2020-07-17 07:14:28 -0600 |
| commit | b5718d6c00afe51ce5327cf2beae4019da0c8e74 (patch) | |
| tree | 6737291920782b8fbaf65f97419c9d492a395326 | |
| parent | 943c4d9074aa05b86af89eec25330c1995e807c9 (diff) | |
block: defer flush request no matter whether we have elevator
Commit 7520872c0cf4 ("block: don't defer flushes on blk-mq + scheduling")
tried to fix deadlock for cycled wait between flush requests and data
request into flush_data_in_flight. The former holded all driver tags
and wait for data request completion, but the latter can not complete
for waiting free driver tags.
After commit 923218f6166a ("blk-mq: don't allocate driver tag upfront
for flush rq"), flush requests will not get driver tag before queuing
into flush queue.
* With elevator, flush request just get sched_tags before inserting
flush queue. It will not get driver tag until issue them to driver.
data request on list fq->flush_data_in_flight will complete in
the end.
* Without elevator, each flush request will get a driver tag when
allocate request. Then data request on fq->flush_data_in_flight
don't worry about lacking driver tag.
In both of these cases, cycled wait cannot be true. So we may allow
to defer flush request.
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | block/blk-flush.c | 9 |
1 files changed, 2 insertions, 7 deletions
diff --git a/block/blk-flush.c b/block/blk-flush.c index 71c7f520e040..6e1543c10493 100644 --- a/block/blk-flush.c +++ b/block/blk-flush.c @@ -283,13 +283,8 @@ static void blk_kick_flush(struct request_queue *q, struct blk_flush_queue *fq, if (fq->flush_pending_idx != fq->flush_running_idx || list_empty(pending)) return; - /* C2 and C3 - * - * For blk-mq + scheduling, we can risk having all driver tags - * assigned to empty flushes, and we deadlock if we are expecting - * other requests to make progress. Don't defer for that case. - */ - if (!list_empty(&fq->flush_data_in_flight) && q->elevator && + /* C2 and C3 */ + if (!list_empty(&fq->flush_data_in_flight) && time_before(jiffies, fq->flush_pending_since + FLUSH_PENDING_TIMEOUT)) return; |