linux-kernel - [PATCH 4.19 75/98] dm kcopyd: always complete failed jobs

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Message-Id: <20190827072722.114406263@linuxfoundation.org>
Date:   Tue, 27 Aug 2019 09:50:54 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Dmitry Fomichev <dmitry.fomichev@....com>,
        Damien Le Moal <damien.lemoal@....com>,
        Mike Snitzer <snitzer@...hat.com>
Subject: [PATCH 4.19 75/98] dm kcopyd: always complete failed jobs

From: Dmitry Fomichev <dmitry.fomichev@....com>

commit d1fef41465f0e8cae0693fb184caa6bfafb6cd16 upstream.

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: b73c67c2cbb00 ("dm kcopyd: add sequential write feature")
Cc: stable@...r.kernel.org
Signed-off-by: Dmitry Fomichev <dmitry.fomichev@....com>
Reviewed-by: Damien Le Moal <damien.lemoal@....com>
Signed-off-by: Mike Snitzer <snitzer@...hat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/md/dm-kcopyd.c |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

--- a/drivers/md/dm-kcopyd.c
+++ b/drivers/md/dm-kcopyd.c
@@ -548,8 +548,10 @@ static int run_io_job(struct kcopyd_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);

@@ -601,6 +603,7 @@ static int process_jobs(struct list_head
 			else
 				job->read_err = 1;
 			push(&kc->complete_jobs, job);
+			wake(kc);
 			break;
 		}