drbd: fix hang on local read errors while disconnected

"canceled" w_read_retry_remote never completed, if they have been
canceled after drbd_disconnect connection teardown cleanup has already
run (or we are currently not connected anyways).

Fixed by not queueing a remote retry if we already know it won't work
(pdsk not uptodate), and cleanup ourselves on "cancel", in case we hit a
race with drbd_disconnect.

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

3 files changed, 16 insertions, 13 deletions

diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index e6c4d579eaba..8915644af722 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -452,20 +452,21 @@ void __req_mod(struct drbd_request *req, enum drbd_req_event what,
 
                 dev_alert(DEV, "Local READ failed sec=%llus size=%u\n",
                       (unsigned long long)req->sector, req->size);
-                /* _req_mod(req,to_be_send); oops, recursion... */
                 D_ASSERT(!(req->rq_state & RQ_NET_MASK));
-                req->rq_state |= RQ_NET_PENDING;
-                inc_ap_pending(mdev);
 
                 __drbd_chk_io_error(mdev, FALSE);
                 put_ldev(mdev);
-                /* NOTE: if we have no connection,
-                 * or know the peer has no good data either,
-                 * then we don't actually need to "queue_for_net_read",
-                 * but we do so anyways, since the drbd_io_error()
-                 * and the potential state change to "Diskless"
-                 * needs to be done from process context */
 
+                /* no point in retrying if there is no good remote data,
+                 * or we have no connection. */
+                if (mdev->state.pdsk != D_UP_TO_DATE) {
+                        _req_may_be_done(req, m);
+                        break;
+                }
+
+                /* _req_mod(req,to_be_send); oops, recursion... */
+                req->rq_state |= RQ_NET_PENDING;
+                inc_ap_pending(mdev);
                 /* fall through: _req_mod(req,queue_for_net_read); */
 
         case queue_for_net_read:
@@ -575,6 +576,9 @@ void __req_mod(struct drbd_request *req, enum drbd_req_event what,
                 _req_may_be_done(req, m);
                 break;
 
+        case read_retry_remote_canceled:
+                req->rq_state &= ~RQ_NET_QUEUED;
+                /* fall through, in case we raced with drbd_disconnect */
         case connection_lost_while_pending:
                 /* transfer log cleanup after connection loss */
                 /* assert something? */
diff --git a/drivers/block/drbd/drbd_req.h b/drivers/block/drbd/drbd_req.h
index 16119d7056cc..02d575d24518 100644
--- a/drivers/block/drbd/drbd_req.h
+++ b/drivers/block/drbd/drbd_req.h
@@ -91,6 +91,7 @@ enum drbd_req_event {
         send_failed,
         handed_over_to_network,
         connection_lost_while_pending,
+        read_retry_remote_canceled,
         recv_acked_by_peer,
         write_acked_by_peer,
         write_acked_by_peer_and_sis, /* and set_in_sync */
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index a12b447bafbd..67371fcbc5aa 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -266,10 +266,8 @@ int w_read_retry_remote(struct drbd_conf *mdev, struct drbd_work *w, int cancel)
          * to give the disk the chance to relocate that block */
 
         spin_lock_irq(&mdev->req_lock);
-        if (cancel ||
-            mdev->state.conn < C_CONNECTED ||
-            mdev->state.pdsk <= D_INCONSISTENT) {
-                _req_mod(req, send_canceled);
+        if (cancel || mdev->state.pdsk != D_UP_TO_DATE) {
+                _req_mod(req, read_retry_remote_canceled);
                 spin_unlock_irq(&mdev->req_lock);
                 dev_alert(DEV, "WE ARE LOST. Local IO failure, no peer.\n");
                 return 1;