drbd: discard_zeroes_if_aligned allows "thin" resync for discard_zeroes_data=0

Even if discard_zeroes_data != 0,
if discard_zeroes_if_aligned is set, we assume we can reliably
zero-out/discard using the drbd_issue_peer_discard() helper.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index e5fdcc6c2e67..169e3e15a30e 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1408,9 +1408,12 @@ static void sanitize_disk_conf(struct drbd_device *device, struct disk_conf *dis
         if (disk_conf->al_extents > drbd_al_extents_max(nbc))
                 disk_conf->al_extents = drbd_al_extents_max(nbc);
 
-        if (!blk_queue_discard(q) || !q->limits.discard_zeroes_data) {
-                disk_conf->rs_discard_granularity = 0; /* disable feature */
-                drbd_info(device, "rs_discard_granularity feature disabled\n");
+        if (!blk_queue_discard(q)
+            || (!q->limits.discard_zeroes_data && !disk_conf->discard_zeroes_if_aligned)) {
+                if (disk_conf->rs_discard_granularity) {
+                        disk_conf->rs_discard_granularity = 0; /* disable feature */
+                        drbd_info(device, "rs_discard_granularity feature disabled\n");
+                }
         }
 
         if (disk_conf->rs_discard_granularity) {