drbd: fix race between drbdadm invalidate/verify and finishing resync

When a resync or online verify is finished or aborted,
drbd does a bulk write-out of changed bitmap pages.

If *in that very moment* a new verify or resync is triggered,
this can race:
 ASSERT( !test_bit(BITMAP_IO, &mdev->flags) ) in drbd_main.c
 FIXME going to queue 'set_n_write from StartingSync' but 'write from resync_finished' still pending?
and similar.

This can be observed with e.g. tight invalidate loops in test scripts,
and probably has no real-life implication.

Still, that race can be solved by first quiescen the device,
before starting a new resync or verify.

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

1 files changed, 6 insertions, 0 deletions

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 308beb8c0c1..867bf1d8298 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -1963,6 +1963,7 @@ static int drbd_nl_invalidate(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nl
 
         /* If there is still bitmap IO pending, probably because of a previous
          * resync just being finished, wait for it before requesting a new resync. */
+        drbd_suspend_io(mdev);
         wait_event(mdev->misc_wait, !test_bit(BITMAP_IO, &mdev->flags));
 
         retcode = _drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T), CS_ORDERED);
@@ -1981,6 +1982,7 @@ static int drbd_nl_invalidate(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nl
 
                 retcode = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_T));
         }
+        drbd_resume_io(mdev);
 
         reply->ret_code = retcode;
         return 0;
@@ -2002,6 +2004,7 @@ static int drbd_nl_invalidate_peer(struct drbd_conf *mdev, struct drbd_nl_cfg_re
 
         /* If there is still bitmap IO pending, probably because of a previous
          * resync just being finished, wait for it before requesting a new resync. */
+        drbd_suspend_io(mdev);
         wait_event(mdev->misc_wait, !test_bit(BITMAP_IO, &mdev->flags));
 
         retcode = _drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_S), CS_ORDERED);
@@ -2020,6 +2023,7 @@ static int drbd_nl_invalidate_peer(struct drbd_conf *mdev, struct drbd_nl_cfg_re
                 } else
                         retcode = drbd_request_state(mdev, NS(conn, C_STARTING_SYNC_S));
         }
+        drbd_resume_io(mdev);
 
         reply->ret_code = retcode;
         return 0;
@@ -2192,11 +2196,13 @@ static int drbd_nl_start_ov(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp,
 
         /* If there is still bitmap IO pending, e.g. previous resync or verify
          * just being finished, wait for it before requesting a new resync. */
+        drbd_suspend_io(mdev);
         wait_event(mdev->misc_wait, !test_bit(BITMAP_IO, &mdev->flags));
 
         /* w_make_ov_request expects position to be aligned */
         mdev->ov_start_sector = args.start_sector & ~BM_SECT_PER_BIT;
         reply->ret_code = drbd_request_state(mdev,NS(conn,C_VERIFY_S));
+        drbd_resume_io(mdev);
         return 0;
 }