drbd: Finish requests that completed while IO was frozen

Requests of an acked epoch are stored on the barrier_acked_requests list. In
case the private bio of such a request completes while IO on the drbd device
is suspended [req_mod(completed_ok)] then the request stays there.

When thawing IO because the fence_peer handler returned, then we use
tl_clear() to apply the connection_lost_while_pending event to all requests
on the transfer-log and the barrier_acked_requests list.

Up to now the connection_lost_while_pending event was not applied
on requests on the barrier_acked_requests list. Fixed that.

I.e. now the connection_lost_while_pending and resend events are
applied to requests on the barrier_acked_requests list. For that
it is necessary that the resend event finishes (local only)
READS correctly.

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

2 files changed, 18 insertions, 16 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 2e0e7fc1dbba..136db95b212d 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -79,6 +79,7 @@ static int w_md_sync(struct drbd_conf *mdev, struct drbd_work *w, int unused);
 static void md_sync_timer_fn(unsigned long data);
 static int w_bitmap_io(struct drbd_conf *mdev, struct drbd_work *w, int unused);
 static int w_go_diskless(struct drbd_conf *mdev, struct drbd_work *w, int unused);
+static void _tl_clear(struct drbd_conf *mdev);
 
 MODULE_AUTHOR("Philipp Reisner <phil@linbit.com>, "
               "Lars Ellenberg <lars@linbit.com>");
@@ -432,19 +433,10 @@ static void _tl_restart(struct drbd_conf *mdev, enum drbd_req_event what)
 
         /* Actions operating on the disk state, also want to work on
            requests that got barrier acked. */
-        switch (what) {
-        case fail_frozen_disk_io:
-        case restart_frozen_disk_io:
-                list_for_each_safe(le, tle, &mdev->barrier_acked_requests) {
-                        req = list_entry(le, struct drbd_request, tl_requests);
-                        _req_mod(req, what);
-                }
 
-        case connection_lost_while_pending:
-        case resend:
-                break;
-        default:
-                dev_err(DEV, "what = %d in _tl_restart()\n", what);
+        list_for_each_safe(le, tle, &mdev->barrier_acked_requests) {
+                req = list_entry(le, struct drbd_request, tl_requests);
+                _req_mod(req, what);
         }
 }
 
@@ -459,11 +451,16 @@ static void _tl_restart(struct drbd_conf *mdev, enum drbd_req_event what)
  */
 void tl_clear(struct drbd_conf *mdev)
 {
+        spin_lock_irq(&mdev->req_lock);
+        _tl_clear(mdev);
+        spin_unlock_irq(&mdev->req_lock);
+}
+
+static void _tl_clear(struct drbd_conf *mdev)
+{
         struct list_head *le, *tle;
         struct drbd_request *r;
 
-        spin_lock_irq(&mdev->req_lock);
-
         _tl_restart(mdev, connection_lost_while_pending);
 
         /* we expect this list to be empty. */
@@ -482,7 +479,6 @@ void tl_clear(struct drbd_conf *mdev)
 
         memset(mdev->app_reads_hash, 0, APP_R_HSIZE*sizeof(void *));
 
-        spin_unlock_irq(&mdev->req_lock);
 }
 
 void tl_restart(struct drbd_conf *mdev, enum drbd_req_event what)
@@ -1476,12 +1472,12 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
         if (ns.susp_fen) {
                 /* case1: The outdate peer handler is successful: */
                 if (os.pdsk > D_OUTDATED  && ns.pdsk <= D_OUTDATED) {
-                        tl_clear(mdev);
                         if (test_bit(NEW_CUR_UUID, &mdev->flags)) {
                                 drbd_uuid_new_current(mdev);
                                 clear_bit(NEW_CUR_UUID, &mdev->flags);
                         }
                         spin_lock_irq(&mdev->req_lock);
+                        _tl_clear(mdev);
                         _drbd_set_state(_NS(mdev, susp_fen, 0), CS_VERBOSE, NULL);
                         spin_unlock_irq(&mdev->req_lock);
                 }
diff --git a/drivers/block/drbd/drbd_req.c b/drivers/block/drbd/drbd_req.c
index 0bb1e41f136f..01b2ac641c7b 100644
--- a/drivers/block/drbd/drbd_req.c
+++ b/drivers/block/drbd/drbd_req.c
@@ -695,6 +695,12 @@ int __req_mod(struct drbd_request *req, enum drbd_req_event what,
                 break;
 
         case resend:
+                /* Simply complete (local only) READs. */
+                if (!(req->rq_state & RQ_WRITE) && !req->w.cb) {
+                        _req_may_be_done(req, m);
+                        break;
+                }
+
                 /* If RQ_NET_OK is already set, we got a P_WRITE_ACK or P_RECV_ACK
                    before the connection loss (B&C only); only P_BARRIER_ACK was missing.
                    Trowing them out of the TL here by pretending we got a BARRIER_ACK