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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 <xuejiufei@huawei.com>
Reviewed-by: Joseph Qi <joseph.qi@huawei.com>
Reviewed-by: Yiwen Jiang <jiangyiwen@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Xue jiufei 2016-01-14 15:17:18 -08:00 committed by Linus Torvalds
parent a84ac334dc
commit 30bee898f8
1 changed files with 8 additions and 1 deletions
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9
fs/ocfs2/dlm/dlmrecovery.c
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@ -1373,6 +1373,7 @@ int dlm_mig_lockres_handler(struct o2net_msg *msg, u32 len, void *data,
char *buf = NULL;
struct dlm_work_item *item = NULL;
struct dlm_lock_resource *res = NULL;
unsigned int hash;
if (!dlm_grab(dlm))
return -EINVAL;
@ -1400,7 +1401,10 @@ int dlm_mig_lockres_handler(struct o2net_msg *msg, u32 len, void *data,
/* lookup the lock to see if we have a secondary queue for this
* already... just add the locks in and this will have its owner
* and RECOVERY flag changed when it completes. */
res = dlm_lookup_lockres(dlm, mres->lockname, mres->lockname_len);
hash = dlm_lockid_hash(mres->lockname, mres->lockname_len);
spin_lock(&dlm->spinlock);
res = __dlm_lookup_lockres(dlm, mres->lockname, mres->lockname_len,
hash);
if (res) {
/* this will get a ref on res */
/* mark it as recovering/migrating and hash it */
@ -1421,13 +1425,16 @@ int dlm_mig_lockres_handler(struct o2net_msg *msg, u32 len, void *data,
mres->lockname_len, mres->lockname);
ret = -EFAULT;
spin_unlock(&res->spinlock);
spin_unlock(&dlm->spinlock);
dlm_lockres_put(res);
goto leave;
}
res->state |= DLM_LOCK_RES_MIGRATING;
}
spin_unlock(&res->spinlock);
spin_unlock(&dlm->spinlock);
} else {
spin_unlock(&dlm->spinlock);
/* need to allocate, just like if it was
* mastered here normally */
res = dlm_new_lockres(dlm, mres->lockname, mres->lockname_len);