drbd: application writes may set-in-sync in protocol != C

If "dirty" blocks are written to during resync,
that brings them in-sync.

By explicitly requesting write-acks during resync even in protocol != C,
we now can actually respect this.

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

4 files changed, 49 insertions, 31 deletions

diff --git a/drivers/block/drbd/drbd_interval.h b/drivers/block/drbd/drbd_interval.h
index f38fcb00c10d..f210543f05f4 100644
--- a/drivers/block/drbd/drbd_interval.h
+++ b/drivers/block/drbd/drbd_interval.h
@@ -10,7 +10,9 @@ struct drbd_interval {
         unsigned int size;      /* size in bytes */
         sector_t end;           /* highest interval end in subtree */
         int local:1             /* local or remote request? */;
-        int waiting:1;
+        int waiting:1;          /* someone is waiting for this to complete */
+        int completed:1;        /* this has been completed already;
+                                 * ignore for conflict detection */
 };
 
 static inline void drbd_clear_interval(struct drbd_interval *i)
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 7c060243ae46..7ada5d363064 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1639,7 +1639,10 @@ int drbd_send_dblock(struct drbd_peer_device *peer_device, struct drbd_request *
         if (peer_device->connection->agreed_pro_version >= 100) {
                 if (req->rq_state & RQ_EXP_RECEIVE_ACK)
                         dp_flags |= DP_SEND_RECEIVE_ACK;
-                if (req->rq_state & RQ_EXP_WRITE_ACK)
+                /* During resync, request an explicit write ack,
+                 * even in protocol != C */
+                if (req->rq_state & RQ_EXP_WRITE_ACK
+                || (dp_flags & DP_MAY_SET_IN_SYNC))
                         dp_flags |= DP_SEND_WRITE_ACK;
         }
         p->dp_flags = cpu_to_be32(dp_flags);
diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index b89e6fb468c6..3a3c4893ea26 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -1930,6 +1930,7 @@ static int e_end_block(struct drbd_work *w, int cancel)
                 }
                 dec_unacked(device);
         }
+
         /* we delete from the conflict detection hash _after_ we sent out the
          * P_WRITE_ACK / P_NEG_ACK, to get the sequence number right.  */
         if (peer_req->flags & EE_IN_INTERVAL_TREE) {
@@ -2156,6 +2157,8 @@ static int handle_write_conflicts(struct drbd_device *device,
         drbd_for_each_overlap(i, &device->write_requests, sector, size) {
                 if (i == &peer_req->i)
                         continue;
+                if (i->completed)
+                        continue;
 
                 if (!i->local) {
                         /*
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 1ee735590b61..f07a724998ea 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -92,6 +92,19 @@ static struct drbd_request *drbd_req_new(struct drbd_device *device,
         return req;
 }
 
+static void drbd_remove_request_interval(struct rb_root *root,
+                                         struct drbd_request *req)
+{
+        struct drbd_device *device = req->device;
+        struct drbd_interval *i = &req->i;
+
+        drbd_remove_interval(root, i);
+
+        /* Wake up any processes waiting for this request to complete.  */
+        if (i->waiting)
+                wake_up(&device->misc_wait);
+}
+
 void drbd_req_destroy(struct kref *kref)
 {
         struct drbd_request *req = container_of(kref, struct drbd_request, kref);
@@ -115,6 +128,20 @@ void drbd_req_destroy(struct kref *kref)
          * here unconditionally */
         list_del_init(&req->tl_requests);
 
+        /* finally remove the request from the conflict detection
+         * respective block_id verification interval tree. */
+        if (!drbd_interval_empty(&req->i)) {
+                struct rb_root *root;
+
+                if (s & RQ_WRITE)
+                        root = &device->write_requests;
+                else
+                        root = &device->read_requests;
+                drbd_remove_request_interval(root, req);
+        } else if (s & (RQ_NET_MASK & ~RQ_NET_DONE) && req->i.size != 0)
+                drbd_err(device, "drbd_req_destroy: Logic BUG: interval empty, but: rq_state=0x%x, sect=%llu, size=%u\n",
+                        s, (unsigned long long)req->i.sector, req->i.size);
+
         /* if it was a write, we may have to set the corresponding
          * bit(s) out-of-sync first. If it had a local part, we need to
          * release the reference to the activity log. */
@@ -188,19 +215,6 @@ void complete_master_bio(struct drbd_device *device,
 }
 
 
-static void drbd_remove_request_interval(struct rb_root *root,
-                                         struct drbd_request *req)
-{
-        struct drbd_device *device = req->device;
-        struct drbd_interval *i = &req->i;
-
-        drbd_remove_interval(root, i);
-
-        /* Wake up any processes waiting for this request to complete.  */
-        if (i->waiting)
-                wake_up(&device->misc_wait);
-}
-
 /* Helper for __req_mod().
  * Set m->bio to the master bio, if it is fit to be completed,
  * or leave it alone (it is initialized to NULL in __req_mod),
@@ -254,18 +268,6 @@ void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
         ok = (s & RQ_LOCAL_OK) || (s & RQ_NET_OK);
         error = PTR_ERR(req->private_bio);
 
-        /* remove the request from the conflict detection
-         * respective block_id verification hash */
-        if (!drbd_interval_empty(&req->i)) {
-                struct rb_root *root;
-
-                if (rw == WRITE)
-                        root = &device->write_requests;
-                else
-                        root = &device->read_requests;
-                drbd_remove_request_interval(root, req);
-        }
-
         /* Before we can signal completion to the upper layers,
          * we may need to close the current transfer log epoch.
          * We are within the request lock, so we can simply compare
@@ -301,7 +303,15 @@ void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
                 m->error = ok ? 0 : (error ?: -EIO);
                 m->bio = req->master_bio;
                 req->master_bio = NULL;
+                /* We leave it in the tree, to be able to verify later
+                 * write-acks in protocol != C during resync.
+                 * But we mark it as "complete", so it won't be counted as
+                 * conflict in a multi-primary setup. */
+                req->i.completed = true;
         }
+
+        if (req->i.waiting)
+                wake_up(&device->misc_wait);
 }
 
 static int drbd_req_put_completion_ref(struct drbd_request *req, struct bio_and_error *m, int put)
@@ -660,12 +670,13 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
         case WRITE_ACKED_BY_PEER_AND_SIS:
                 req->rq_state |= RQ_NET_SIS;
         case WRITE_ACKED_BY_PEER:
-                D_ASSERT(device, req->rq_state & RQ_EXP_WRITE_ACK);
-                /* protocol C; successfully written on peer.
+                /* Normal operation protocol C: successfully written on peer.
+                 * During resync, even in protocol != C,
+                 * we requested an explicit write ack anyways.
+                 * Which means we cannot even assert anything here.
                  * Nothing more to do here.
                  * We want to keep the tl in place for all protocols, to cater
                  * for volatile write-back caches on lower level devices. */
-
                 goto ack_common;
         case RECV_ACKED_BY_PEER:
                 D_ASSERT(device, req->rq_state & RQ_EXP_RECEIVE_ACK);
@@ -673,7 +684,6 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                  * see also notes above in HANDED_OVER_TO_NETWORK about
                  * protocol != C */
         ack_common:
-                D_ASSERT(device, req->rq_state & RQ_NET_PENDING);
                 mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK);
                 break;