dm: inherit QUEUE_FLAG_SG_GAPS flags from underlying queues

A DM device must inherit the QUEUE_FLAG_SG_GAPS flags from its
underlying block devices' request queues.

This fixes problems when submitting cloned requests to multipathed
devices requiring virtually contiguous buffers.

Signed-off-by: Keith Busch <keith.busch@intel.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 14954d844668..6554d9148927 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1389,6 +1389,14 @@ static int queue_supports_sg_merge(struct dm_target *ti, struct dm_dev *dev,
         return q && !test_bit(QUEUE_FLAG_NO_SG_MERGE, &q->queue_flags);
 }
 
+static int queue_supports_sg_gaps(struct dm_target *ti, struct dm_dev *dev,
+                                  sector_t start, sector_t len, void *data)
+{
+        struct request_queue *q = bdev_get_queue(dev->bdev);
+
+        return q && !test_bit(QUEUE_FLAG_SG_GAPS, &q->queue_flags);
+}
+
 static bool dm_table_all_devices_attribute(struct dm_table *t,
                                            iterate_devices_callout_fn func)
 {
@@ -1509,6 +1517,11 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
         else
                 queue_flag_set_unlocked(QUEUE_FLAG_NO_SG_MERGE, q);
 
+        if (dm_table_all_devices_attribute(t, queue_supports_sg_gaps))
+                queue_flag_clear_unlocked(QUEUE_FLAG_SG_GAPS, q);
+        else
+                queue_flag_set_unlocked(QUEUE_FLAG_SG_GAPS, q);
+
         dm_table_set_integrity(t);
 
         /*