+static void blk_queue_discard_granularity(struct request_queue *q, unsigned int granularity)
+{
+ q->limits.discard_granularity = granularity;
+}
+static void decide_on_discard_support(struct drbd_device *device,
+ struct request_queue *q,
+ struct request_queue *b,
+ bool discard_zeroes_if_aligned)
+{
+ /* q = drbd device queue (device->rq_queue)
+ * b = backing device queue (device->ldev->backing_bdev->bd_disk->queue),
+ * or NULL if diskless
+ */
+ struct drbd_connection *connection = first_peer_device(device)->connection;
+ bool can_do = b ? blk_queue_discard(b) : true;
+
+ if (can_do && b && !b->limits.discard_zeroes_data && !discard_zeroes_if_aligned) {
+ can_do = false;
+ drbd_info(device, "discard_zeroes_data=0 and discard_zeroes_if_aligned=no: disabling discards\n");
+ }
+ if (can_do && connection->cstate >= C_CONNECTED && !(connection->agreed_features & FF_TRIM)) {
+ can_do = false;
+ drbd_info(connection, "peer DRBD too old, does not support TRIM: disabling discards\n");
+ }
+ if (can_do) {
+ /* We don't care for the granularity, really.
+ * Stacking limits below should fix it for the local
+ * device. Whether or not it is a suitable granularity
+ * on the remote device is not our problem, really. If
+ * you care, you need to use devices with similar
+ * topology on all peers. */
+ blk_queue_discard_granularity(q, 512);
+ q->limits.max_discard_sectors = DRBD_MAX_DISCARD_SECTORS;
+ queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
+ } else {
+ queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
+ blk_queue_discard_granularity(q, 0);
+ q->limits.max_discard_sectors = 0;
+ }
+}
+
+static void fixup_discard_if_not_supported(struct request_queue *q)
+{
+ /* To avoid confusion, if this queue does not support discard, clear
+ * max_discard_sectors, which is what lsblk -D reports to the user.
+ * Older kernels got this wrong in "stack limits".
+ * */
+ if (!blk_queue_discard(q)) {
+ blk_queue_max_discard_sectors(q, 0);
+ blk_queue_discard_granularity(q, 0);
+ }
+}
+