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, 10 insertions, 0 deletions

diff --git a/drivers/md/dm-zoned.h b/drivers/md/dm-zoned.h
index ed8de49c9a08..93a64529f219 100644
--- a/drivers/md/dm-zoned.h
+++ b/drivers/md/dm-zoned.h
@@ -56,6 +56,8 @@ struct dmz_dev {
 
 	unsigned int		nr_zones;
 
+	unsigned int		flags;
+
 	sector_t		zone_nr_sectors;
 	unsigned int		zone_nr_sectors_shift;
 
@@ -67,6 +69,9 @@ struct dmz_dev {
 				 (dev)->zone_nr_sectors_shift)
 #define dmz_chunk_block(dev, b)	((b) & ((dev)->zone_nr_blocks - 1))
 
+/* Device flags. */
+#define DMZ_BDEV_DYING		(1 << 0)
+
 /*
  * Zone descriptor.
  */
@@ -245,4 +250,9 @@ void dmz_resume_reclaim(struct dmz_reclaim *zrc);
 void dmz_reclaim_bio_acc(struct dmz_reclaim *zrc);
 void dmz_schedule_reclaim(struct dmz_reclaim *zrc);
 
+/*
+ * Functions defined in dm-zoned-target.c
+ */
+bool dmz_bdev_is_dying(struct dmz_dev *dmz_dev);
+
 #endif /* DM_ZONED_H */