On Sun, Feb 17, 2019 at 04:37:29PM +0100, Thibaut Sautereau wrote:

On Wed, Jan 30, 2019 at 08:54:09AM -0700, Jens Axboe wrote:

...

On 1/30/19 2:01 AM, Jianchao Wang wrote:

...

Florian reported a io hung issue when fsync(). It should be triggered by following race condition.

data + post flush a flush

blk_flush_complete_seq case REQ_FSEQ_DATA blk_flush_queue_rq issued to driver blk_mq_dispatch_rq_list try to issue a flush req failed due to NON-NCQ command .queue_rq return BLK_STS_DEV_RESOURCE

request completion req->end_io // doesn't check RESTART mq_flush_data_end_io case REQ_FSEQ_POSTFLUSH blk_kick_flush do nothing because previous flush has not been completed blk_mq_run_hw_queue insert rq to hctx->dispatch due to RESTART is still set, do nothing

To fix this, replace the blk_mq_run_hw_queue in mq_flush_data_end_io with blk_mq_sched_restart to check and clear the RESTART flag.

Applied, thanks.

-- Jens Axboe

Can this be applied to stable kernels please?

It's commit 85bd6e61f34dffa8ec2dc75ff3c02ee7b2f1cbce upstream.

I've queued it for 4.20, 4.19 and 4.14.

-- Thanks, Sasha