drbd: announce FLUSH/FUA capability to upper layers

Unconditionally announce FLUSH/FUA to upper layers.
If the lower layers on either node do not actually support this,
generic_make_request() will deal with it.

If this causes performance regressions on your setup,
make sure there are no volatile caches involved,
and mount -o nobarrier or equivalent.

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

1 files changed, 1 insertions, 2 deletions

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 1f4b2dbb7d4a..910335c30927 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -1111,13 +1111,12 @@ void drbd_make_request(struct request_queue *q, struct bio *bio)
         /*
          * what we "blindly" assume:
          */
-        D_ASSERT(bio->bi_size > 0);
         D_ASSERT((bio->bi_size & 0x1ff) == 0);
 
         /* to make some things easier, force alignment of requests within the
          * granularity of our hash tables */
         s_enr = bio->bi_sector >> HT_SHIFT;
-        e_enr = (bio->bi_sector+(bio->bi_size>>9)-1) >> HT_SHIFT;
+        e_enr = bio->bi_size ? (bio->bi_sector+(bio->bi_size>>9)-1) >> HT_SHIFT : s_enr;
 
         if (likely(s_enr == e_enr)) {
                 do {