[PATCH 4.14 49/62] dm kcopyd: always complete failed jobs

From: Greg Kroah-Hartman
Date: Tue Aug 27 2019 - 04:16:31 EST

From: Dmitry Fomichev <dmitry.fomichev@xxxxxxx>

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@xxxxxxxxxxxxxxx
Signed-off-by: Dmitry Fomichev <dmitry.fomichev@xxxxxxx>
Reviewed-by: Damien Le Moal <damien.lemoal@xxxxxxx>
Signed-off-by: Mike Snitzer <snitzer@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

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
@@ -545,8 +545,10 @@ 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;
+ }


@@ -598,6 +600,7 @@ static int process_jobs(struct list_head
job->read_err = 1;
push(&kc->complete_jobs, job);
+ wake(kc);