drbd: disambiguation, s/P_DISCARD_WRITE/P_SUPERSEDED/

To avoid confusion with REQ_DISCARD aka TRIM, rename our
"discard concurrent write acks" from P_DISCARD_WRITE to P_SUPERSEDED.

At the same time, rename the drbd request event DISCARD_WRITE
to CONFLICT_RESOLVED. It already triggers both successful completion
or restart of the request, depending on our RQ_POSTPONED flag.

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

5 files changed, 24 insertions, 23 deletions

diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index e5c98533c90c..91b73247f65d 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -197,7 +197,7 @@ enum drbd_packet {
         P_RECV_ACK            = 0x15, /* Used in protocol B */
         P_WRITE_ACK           = 0x16, /* Used in protocol C */
         P_RS_WRITE_ACK        = 0x17, /* Is a P_WRITE_ACK, additionally call set_in_sync(). */
-        P_DISCARD_WRITE       = 0x18, /* Used in proto C, two-primaries conflict detection */
+        P_SUPERSEDED          = 0x18, /* Used in proto C, two-primaries conflict detection */
         P_NEG_ACK             = 0x19, /* Sent if local disk is unusable */
         P_NEG_DREPLY          = 0x1a, /* Local disk is broken... */
         P_NEG_RS_DREPLY       = 0x1b, /* Local disk is broken... */
@@ -335,7 +335,7 @@ struct p_data {
  * commands which share a struct:
  *  p_block_ack:
  *   P_RECV_ACK (proto B), P_WRITE_ACK (proto C),
- *   P_DISCARD_WRITE (proto C, two-primaries conflict detection)
+ *   P_SUPERSEDED (proto C, two-primaries conflict detection)
  *  p_block_req:
  *   P_DATA_REQUEST, P_RS_DATA_REQUEST
  */
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 85d95ec405ef..328ce80fecfa 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -3339,7 +3339,7 @@ const char *cmdname(enum drbd_packet cmd)
                 [P_RECV_ACK]            = "RecvAck",
                 [P_WRITE_ACK]           = "WriteAck",
                 [P_RS_WRITE_ACK]        = "RSWriteAck",
-                [P_DISCARD_WRITE]        = "DiscardWrite",
+                [P_SUPERSEDED]          = "Superseded",
                 [P_NEG_ACK]             = "NegAck",
                 [P_NEG_DREPLY]          = "NegDReply",
                 [P_NEG_RS_DREPLY]       = "NegRSDReply",
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index d507700df85c..afab66bbc31f 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -425,7 +425,7 @@ static int drbd_finish_peer_reqs(struct drbd_conf *mdev)
                 drbd_free_net_peer_req(mdev, peer_req);
 
         /* possible callbacks here:
-         * e_end_block, and e_end_resync_block, e_send_discard_write.
+         * e_end_block, and e_end_resync_block, e_send_superseded.
          * all ignore the last argument.
          */
         list_for_each_entry_safe(peer_req, t, &work_list, w.list) {
@@ -1803,7 +1803,7 @@ static void restart_conflicting_writes(struct drbd_conf *mdev,
                         continue;
                 /* as it is RQ_POSTPONED, this will cause it to
                  * be queued on the retry workqueue. */
-                __req_mod(req, DISCARD_WRITE, NULL);
+                __req_mod(req, CONFLICT_RESOLVED, NULL);
         }
 }
 
@@ -1864,9 +1864,9 @@ static int e_send_ack(struct drbd_work *w, enum drbd_packet ack)
         return err;
 }
 
-static int e_send_discard_write(struct drbd_work *w, int unused)
+static int e_send_superseded(struct drbd_work *w, int unused)
 {
-        return e_send_ack(w, P_DISCARD_WRITE);
+        return e_send_ack(w, P_SUPERSEDED);
 }
 
 static int e_send_retry_write(struct drbd_work *w, int unused)
@@ -1874,7 +1874,7 @@ static int e_send_retry_write(struct drbd_work *w, int unused)
         struct drbd_tconn *tconn = w->mdev->tconn;
 
         return e_send_ack(w, tconn->agreed_pro_version >= 100 ?
-                             P_RETRY_WRITE : P_DISCARD_WRITE);
+                             P_RETRY_WRITE : P_SUPERSEDED);
 }
 
 static bool seq_greater(u32 a, u32 b)
@@ -2082,11 +2082,11 @@ static int handle_write_conflicts(struct drbd_conf *mdev,
                 if (resolve_conflicts) {
                         /*
                          * If the peer request is fully contained within the
-                         * overlapping request, it can be discarded; otherwise,
-                         * it will be retried once all overlapping requests
-                         * have completed.
+                         * overlapping request, it can be considered overwritten
+                         * and thus superseded; otherwise, it will be retried
+                         * once all overlapping requests have completed.
                          */
-                        bool discard = i->sector <= sector && i->sector +
+                        bool superseded = i->sector <= sector && i->sector +
                                        (i->size >> 9) >= sector + (size >> 9);
 
                         if (!equal)
@@ -2095,10 +2095,10 @@ static int handle_write_conflicts(struct drbd_conf *mdev,
                                                "assuming %s came first\n",
                                           (unsigned long long)i->sector, i->size,
                                           (unsigned long long)sector, size,
-                                          discard ? "local" : "remote");
+                                          superseded ? "local" : "remote");
 
                         inc_unacked(mdev);
-                        peer_req->w.cb = discard ? e_send_discard_write :
+                        peer_req->w.cb = superseded ? e_send_superseded :
                                                    e_send_retry_write;
                         list_add_tail(&peer_req->w.list, &mdev->done_ee);
                         wake_asender(mdev->tconn);
@@ -2119,8 +2119,9 @@ static int handle_write_conflicts(struct drbd_conf *mdev,
                             !(req->rq_state & RQ_POSTPONED)) {
                                 /*
                                  * Wait for the node with the discard flag to
-                                 * decide if this request will be discarded or
-                                 * retried.  Requests that are discarded will
+                                 * decide if this request has been superseded
+                                 * or needs to be retried.
+                                 * Requests that have been superseded will
                                  * disappear from the write_requests tree.
                                  *
                                  * In addition, wait for the conflicting
@@ -4994,8 +4995,8 @@ static int got_BlockAck(struct drbd_tconn *tconn, struct packet_info *pi)
         case P_RECV_ACK:
                 what = RECV_ACKED_BY_PEER;
                 break;
-        case P_DISCARD_WRITE:
-                what = DISCARD_WRITE;
+        case P_SUPERSEDED:
+                what = CONFLICT_RESOLVED;
                 break;
         case P_RETRY_WRITE:
                 what = POSTPONE_WRITE;
@@ -5220,7 +5221,7 @@ static struct asender_cmd asender_tbl[] = {
         [P_RECV_ACK]        = { sizeof(struct p_block_ack), got_BlockAck },
         [P_WRITE_ACK]       = { sizeof(struct p_block_ack), got_BlockAck },
         [P_RS_WRITE_ACK]    = { sizeof(struct p_block_ack), got_BlockAck },
-        [P_DISCARD_WRITE]   = { sizeof(struct p_block_ack), got_BlockAck },
+        [P_SUPERSEDED]   = { sizeof(struct p_block_ack), got_BlockAck },
         [P_NEG_ACK]         = { sizeof(struct p_block_ack), got_NegAck },
         [P_NEG_DREPLY]      = { sizeof(struct p_block_ack), got_NegDReply },
         [P_NEG_RS_DREPLY]   = { sizeof(struct p_block_ack), got_NegRSDReply },
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 67768570141a..266ef24b3c74 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -611,13 +611,13 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                                 RQ_NET_DONE);
                 break;
 
-        case DISCARD_WRITE:
-                /* for discarded conflicting writes of multiple primaries,
+        case CONFLICT_RESOLVED:
+                /* for superseded conflicting writes of multiple primaries,
                  * there is no need to keep anything in the tl, potential
                  * node crashes are covered by the activity log.
                  *
                  * If this request had been marked as RQ_POSTPONED before,
-                 * it will actually not be discarded, but "restarted",
+                 * it will actually not be completed, but "restarted",
                  * resubmitted from the retry worker context. */
                 D_ASSERT(req->rq_state & RQ_NET_PENDING);
                 D_ASSERT(req->rq_state & RQ_EXP_WRITE_ACK);
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index 9611713c3580..016de6b8bb57 100644
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -97,7 +97,7 @@ enum drbd_req_event {
         RECV_ACKED_BY_PEER,
         WRITE_ACKED_BY_PEER,
         WRITE_ACKED_BY_PEER_AND_SIS, /* and set_in_sync */
-        DISCARD_WRITE,
+        CONFLICT_RESOLVED,
         POSTPONE_WRITE,
         NEG_ACKED,
         BARRIER_ACKED, /* in protocol A and B */