drbd: Create the protocol feature THIN_RESYNC

If thinly provisioned volumes are used, during a resync the sync source
tries to find out if a block is deallocated. If it is deallocated, then
the resync target uses block_dev_issue_zeroout() on the range in
question.

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>

3 files changed, 17 insertions, 2 deletions

diff --git a/drivers/block/drbd/drbd_protocol.h b/drivers/block/drbd/drbd_protocol.h
index ce0e72ca47ec..95ca4586af59 100644
--- a/drivers/block/drbd/drbd_protocol.h
+++ b/drivers/block/drbd/drbd_protocol.h
@@ -165,6 +165,7 @@ struct p_block_req {
  */
 
 #define FF_TRIM      1
+#define FF_THIN_RESYNC 2
 
 struct p_connection_features {
         u32 protocol_min;
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index f5eef97ec47d..a50cc99aaf3b 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -48,7 +48,7 @@
 #include "drbd_req.h"
 #include "drbd_vli.h"
 
-#define PRO_FEATURES (FF_TRIM)
+#define PRO_FEATURES (FF_TRIM | FF_THIN_RESYNC)
 
 struct packet_info {
         enum drbd_packet cmd;
@@ -4991,6 +4991,9 @@ static int drbd_do_features(struct drbd_connection *connection)
         drbd_info(connection, "Agreed to%ssupport TRIM on protocol level\n",
                   connection->agreed_features & FF_TRIM ? " " : " not ");
 
+        drbd_info(connection, "Agreed to%ssupport THIN_RESYNC on protocol level\n",
+                  connection->agreed_features & FF_THIN_RESYNC ? " " : " not ");
+
         return 1;
 
  incompat:
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index dd85433315d2..154dbfc61aff 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -583,6 +583,7 @@ static int make_resync_request(struct drbd_device *const device, int cancel)
         int number, rollback_i, size;
         int align, requeue = 0;
         int i = 0;
+        int discard_granularity = 0;
 
         if (unlikely(cancel))
                 return 0;
@@ -602,6 +603,12 @@ static int make_resync_request(struct drbd_device *const device, int cancel)
                 return 0;
         }
 
+        if (connection->agreed_features & FF_THIN_RESYNC) {
+                rcu_read_lock();
+                discard_granularity = rcu_dereference(device->ldev->disk_conf)->rs_discard_granularity;
+                rcu_read_unlock();
+        }
+
         max_bio_size = queue_max_hw_sectors(device->rq_queue) << 9;
         number = drbd_rs_number_requests(device);
         if (number <= 0)
@@ -666,6 +673,9 @@ next_sector:
                         if (sector & ((1<<(align+3))-1))
                                 break;
 
+                        if (discard_granularity && size == discard_granularity)
+                                break;
+
                         /* do not cross extent boundaries */
                         if (((bit+1) & BM_BLOCKS_PER_BM_EXT_MASK) == 0)
                                 break;
@@ -712,7 +722,8 @@ next_sector:
                         int err;
 
                         inc_rs_pending(device);
-                        err = drbd_send_drequest(peer_device, P_RS_DATA_REQUEST,
+                        err = drbd_send_drequest(peer_device,
+                                                 size == discard_granularity ? P_RS_THIN_REQ : P_RS_DATA_REQUEST,
                                                  sector, size, ID_SYNCER);
                         if (err) {
                                 drbd_err(device, "drbd_send_drequest() failed, aborting...\n");