drbd: abort start of resync early, if it raced with connection breakage

We've seen a spurious full resync, because a connection breakage
raced with drbd_start_resync(, C_SYNC_TARGET),
and the resulting state change request intended to start the resync
ended up looking like a local invalidate.

Fix:
Double check the state inside the lock,
and don't even request that state change,
if we had connection or IO problems.

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>

1 files changed, 3 insertions, 1 deletions

diff --git a/drivers/block/drbd/drbd_worker.c b/drivers/block/drbd/drbd_worker.c
index f41e224caa7c..7f51f88b0a80 100644
--- a/drivers/block/drbd/drbd_worker.c
+++ b/drivers/block/drbd/drbd_worker.c
@@ -1653,7 +1653,9 @@ 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)) {
+        /* Did some connection breakage or IO error race with us? */
+        if (mdev->state.conn < C_CONNECTED
+        || !get_ldev_if_state(mdev, D_NEGOTIATING)) {
                 write_unlock_irq(&global_state_lock);
                 mutex_unlock(mdev->state_mutex);
                 return;