ocfs2/dlm: fix a race between purge and migration

We found a race between purge and migration when doing code review.
Node A put lockres to purgelist before receiving the migrate message
from node B which is the master.  Node A call dlm_mig_lockres_handler to
handle this message.

dlm_mig_lockres_handler
  dlm_lookup_lockres
  >>>>>> race window, dlm_run_purge_list may run and send
         deref message to master, waiting the response
  spin_lock(&res->spinlock);
  res->state |= DLM_LOCK_RES_MIGRATING;
  spin_unlock(&res->spinlock);
  dlm_mig_lockres_handler returns

  >>>>>> dlm_thread receives the response from master for the deref
  message and triggers the BUG because the lockres has the state
  DLM_LOCK_RES_MIGRATING with the following message:

dlm_purge_lockres:209 ERROR: 6633EB681FA7474A9C280A4E1A836F0F: res
M0000000000000000030c0300000000 in use after deref

Signed-off-by: Jiufei Xue <[email protected]>
Reviewed-by: Joseph Qi <[email protected]>
Reviewed-by: Yiwen Jiang <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

0 files changed, 0 insertions, 0 deletions