dm zoned: properly handle backing device failure

dm-zoned is observed to lock up or livelock in case of hardware
failure or some misconfiguration of the backing zoned device.

This patch adds a new dm-zoned target function that checks the status of
the backing device. If the request queue of the backing device is found
to be in dying state or the SCSI backing device enters offline state,
the health check code sets a dm-zoned target flag prompting all further
incoming I/O to be rejected. In order to detect backing device failures
timely, this new function is called in the request mapping path, at the
beginning of every reclaim run and before performing any metadata I/O.

The proper way out of this situation is to do

dmsetup remove <dm-zoned target>

and recreate the target when the problem with the backing device
is resolved.

Fixes: 3b1a94c88b79 ("dm zoned: drive-managed zoned block device target")
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>

1 files changed, 16 insertions, 2 deletions

diff --git a/drivers/md/dm-zoned-reclaim.c b/drivers/md/dm-zoned-reclaim.c
index e381354dc136..9470b8f77a33 100644
--- a/drivers/md/dm-zoned-reclaim.c
+++ b/drivers/md/dm-zoned-reclaim.c
@@ -37,7 +37,7 @@ enum {
 /*
  * Number of seconds of target BIO inactivity to consider the target idle.
  */
-#define DMZ_IDLE_PERIOD		(10UL * HZ)
+#define DMZ_IDLE_PERIOD			(10UL * HZ)
 
 /*
  * Percentage of unmapped (free) random zones below which reclaim starts
@@ -134,6 +134,9 @@ static int dmz_reclaim_copy(struct dmz_reclaim *zrc,
 		set_bit(DM_KCOPYD_WRITE_SEQ, &flags);
 
 	while (block < end_block) {
+		if (dev->flags & DMZ_BDEV_DYING)
+			return -EIO;
+
 		/* Get a valid region from the source zone */
 		ret = dmz_first_valid_block(zmd, src_zone, &block);
 		if (ret <= 0)
@@ -451,6 +454,9 @@ static void dmz_reclaim_work(struct work_struct *work)
 	unsigned int p_unmap_rnd;
 	int ret;
 
+	if (dmz_bdev_is_dying(zrc->dev))
+		return;
+
 	if (!dmz_should_reclaim(zrc)) {
 		mod_delayed_work(zrc->wq, &zrc->work, DMZ_IDLE_PERIOD);
 		return;
@@ -480,8 +486,16 @@ static void dmz_reclaim_work(struct work_struct *work)
 		      p_unmap_rnd, nr_unmap_rnd, nr_rnd);
 
 	ret = dmz_do_reclaim(zrc);
-	if (ret)
+	if (ret) {
 		dmz_dev_debug(zrc->dev, "Reclaim error %d\n", ret);
+		if (ret == -EIO)
+			/*
+			 * LLD might be performing some error handling sequence
+			 * at the underlying device. To not interfere, do not
+			 * attempt to schedule the next reclaim run immediately.
+			 */
+			return;
+	}
 
 	dmz_schedule_reclaim(zrc);
 }