4 files changed, 26 insertions, 3 deletions

diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index edd0227f4b43..822fb3d42356 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -1087,7 +1087,11 @@ void drbd_gen_and_send_sync_uuid(struct drbd_conf *mdev)
 
         D_ASSERT(mdev->state.disk == D_UP_TO_DATE);
 
-        uuid = mdev->ldev->md.uuid[UI_BITMAP] + UUID_NEW_BM_OFFSET;
+        uuid = mdev->ldev->md.uuid[UI_BITMAP];
+        if (uuid && uuid != UUID_JUST_CREATED)
+                uuid = uuid + UUID_NEW_BM_OFFSET;
+        else
+                get_random_bytes(&uuid, sizeof(u64));
         drbd_uuid_set(mdev, UI_BITMAP, uuid);
         drbd_print_uuids(mdev, "updated sync UUID");
         drbd_md_sync(mdev);
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 16c3710e1b9c..c50c1753aa9a 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1666,7 +1666,9 @@ static int adm_detach(struct drbd_conf *mdev, int force)
         }
 
         drbd_suspend_io(mdev); /* so no-one is stuck in drbd_al_begin_io */
+        drbd_md_get_buffer(mdev); /* make sure there is no in-flight meta-data IO */
         retcode = drbd_request_state(mdev, NS(disk, D_FAILED));
+        drbd_md_put_buffer(mdev);
         /* D_FAILED will transition to DISKLESS. */
         ret = wait_event_interruptible(mdev->misc_wait,
                         mdev->state.disk != D_FAILED);
diff --git a/drivers/block/drbd/drbd_state.c b/drivers/block/drbd/drbd_state.c
index 4075bd2d2515..dffc6973e2b5 100644
--- a/drivers/block/drbd/drbd_state.c
+++ b/drivers/block/drbd/drbd_state.c
@@ -1231,6 +1231,11 @@ static void after_state_ch(struct drbd_conf *mdev, union drbd_state os,
         }
 
         if (ns.pdsk < D_INCONSISTENT && get_ldev(mdev)) {
+                if (os.peer == R_SECONDARY && ns.peer == R_PRIMARY &&
+                    mdev->ldev->md.uuid[UI_BITMAP] == 0 && ns.disk >= D_UP_TO_DATE) {
+                        drbd_uuid_new_current(mdev);
+                        drbd_send_uuids(mdev);
+                }
                 /* D_DISKLESS Peer becomes secondary */
                 if (os.peer == R_PRIMARY && ns.peer == R_SECONDARY)
                         /* We may still be Primary ourselves.
diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index 34a6065d95e6..bc2cfd6c600f 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -74,10 +74,21 @@ void drbd_md_io_complete(struct bio *bio, int error)
 
         md_io->error = error;
 
+        /* We grabbed an extra reference in _drbd_md_sync_page_io() to be able
+         * to timeout on the lower level device, and eventually detach from it.
+         * If this io completion runs after that timeout expired, this
+         * drbd_md_put_buffer() may allow us to finally try and re-attach.
+         * During normal operation, this only puts that extra reference
+         * down to 1 again.
+         * Make sure we first drop the reference, and only then signal
+         * completion, or we may (in drbd_al_read_log()) cycle so fast into the
+         * next drbd_md_sync_page_io(), that we trigger the
+         * ASSERT(atomic_read(&mdev->md_io_in_use) == 1) there.
+         */
+        drbd_md_put_buffer(mdev);
         md_io->done = 1;
         wake_up(&mdev->misc_wait);
         bio_put(bio);
-        drbd_md_put_buffer(mdev);
         put_ldev(mdev);
 }
 
@@ -1581,12 +1592,13 @@ void drbd_start_resync(struct drbd_conf *mdev, enum drbd_conns side)
         }
         clear_bit(B_RS_H_DONE, &mdev->flags);
 
+        write_lock_irq(&global_state_lock);
         if (!get_ldev_if_state(mdev, D_NEGOTIATING)) {
+                write_unlock_irq(&global_state_lock);
                 mutex_unlock(mdev->state_mutex);
                 return;
         }
 
-        write_lock_irq(&global_state_lock);
         ns = drbd_read_state(mdev);
 
         ns.aftr_isp = !_drbd_may_sync_now(mdev);