drbd: only fail empty flushes if no good data is reachable

We completed empty flushes (blkdev_issue_flush()) with IO error
if we lost the local disk, even if we still have an established
replication link to a healthy remote disk.

Fix this to only report errors to upper layers,
if neither local nor remote data is reachable.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 9f7ff1cb46ff4cd2a034eb43fa56277d7c49742c..beefe65764ffc258aeaf6dc4108b2d1babf4e189 100644 (file)
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -263,8 +263,7 @@ void drbd_req_complete(struct drbd_request *req, struct bio_and_error *m)
                else
                        root = &mdev->read_requests;
                drbd_remove_request_interval(root, req);
-       } else if (!(s & RQ_POSTPONED))
-               D_ASSERT((s & (RQ_NET_MASK & ~RQ_NET_DONE)) == 0);
+       }
 
        /* Before we can signal completion to the upper layers,
         * we may need to close the current transfer log epoch.
@@ -755,6 +754,11 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                D_ASSERT(req->rq_state & RQ_NET_PENDING);
                mod_rq_state(req, m, RQ_NET_PENDING, RQ_NET_OK|RQ_NET_DONE);
                break;
+
+       case QUEUE_AS_DRBD_BARRIER:
+               start_new_tl_epoch(mdev->tconn);
+               mod_rq_state(req, m, 0, RQ_NET_OK|RQ_NET_DONE);
+               break;
        };
 
        return rv;
@@ -975,8 +979,8 @@ static int drbd_process_write_request(struct drbd_request *req)
                /* The only size==0 bios we expect are empty flushes. */
                D_ASSERT(req->master_bio->bi_rw & REQ_FLUSH);
                if (remote)
-                       start_new_tl_epoch(mdev->tconn);
-               return 0;
+                       _req_mod(req, QUEUE_AS_DRBD_BARRIER);
+               return remote;
        }
 
        if (!remote && !send_oos)

diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index c08d22964d06784024481cd0005784306341b891..978cb1addc98845fb8ca49838cfb5ec2478170f7 100644 (file)
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -88,6 +88,14 @@ enum drbd_req_event {
        QUEUE_FOR_NET_READ,
        QUEUE_FOR_SEND_OOS,
 
+       /* An empty flush is queued as P_BARRIER,
+        * which will cause it to complete "successfully",
+        * even if the local disk flush failed.
+        *
+        * Just like "real" requests, empty flushes (blkdev_issue_flush()) will
+        * only see an error if neither local nor remote data is reachable. */
+       QUEUE_AS_DRBD_BARRIER,
+
        SEND_CANCELED,
        SEND_FAILED,
        HANDED_OVER_TO_NETWORK,