Commit d1fef414 authored Aug 05, 2019 by Dmitry Fomichev Committed by Mike Snitzer Aug 15, 2019

dm kcopyd: always complete failed jobs



This patch fixes a problem in dm-kcopyd that may leave jobs in
complete queue indefinitely in the event of backing storage failure.

This behavior has been observed while running 100% write file fio
workload against an XFS volume created on top of a dm-zoned target
device. If the underlying storage of dm-zoned goes to offline state
under I/O, kcopyd sometimes never issues the end copy callback and
dm-zoned reclaim work hangs indefinitely waiting for that completion.

This behavior was traced down to the error handling code in
process_jobs() function that places the failed job to complete_jobs
queue, but doesn't wake up the job handler. In case of backing device
failure, all outstanding jobs may end up going to complete_jobs queue
via this code path and then stay there forever because there are no
more successful I/O jobs to wake up the job handler.

This patch adds a wake() call to always wake up kcopyd job wait queue
for all I/O jobs that fail before dm_io() gets called for that job.

The patch also sets the write error status in all sub jobs that are
failed because their master job has failed.

Fixes: b73c67c2 ("dm kcopyd: add sequential write feature")
Cc: stable@vger.kernel.org
Signed-off-by: Dmitry Fomichev <dmitry.fomichev@wdc.com>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

parent cf3591ef

drivers/md/dm-kcopyd.c

+4 −1

Original line number	Diff line number	Diff line
		@@ -566,8 +566,10 @@ static int run_io_job(struct kcopyd_job *job)
		* no point in continuing.
		*/
		if (test_bit(DM_KCOPYD_WRITE_SEQ, &job->flags) &&
		job->master_job->write_err)
		job->master_job->write_err) {
		job->write_err = job->master_job->write_err;
		return -EIO;
		}

		io_job_start(job->kc->throttle);

		@@ -619,6 +621,7 @@ static int process_jobs(struct list_head jobs, struct dm_kcopyd_client kc,
		else
		job->read_err = 1;
		push(&kc->complete_jobs, job);
		wake(kc);
		break;
		}

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