[PATCH 20/30] drbd: discard_zeroes_if_aligned allows "thin" resync for discard_zeroes_data=0

[Philipp Reisner]

From: Lars Ellenberg <l...@linbit.com>

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.reis...@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenb...@linbit.com>
---
 drivers/block/drbd/drbd_nl.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index a703a0e..48fa6c3 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) {
-- 
1.9.1