ocfs2/dlm: fix race between convert and migration

Commit ac7cf246dfdb ("ocfs2/dlm: fix race between convert and recovery")
checks if lockres master has changed to identify whether new master has
finished recovery or not.  This will introduce a race that right after
old master does umount ( means master will change), a new convert
request comes.

In this case, it will reset lockres state to DLM_RECOVERING and then
retry convert, and then fail with lockres->l_action being set to
OCFS2_AST_INVALID, which will cause inconsistent lock level between
ocfs2 and dlm, and then finally BUG.

Since dlm recovery will clear lock->convert_pending in
dlm_move_lockres_to_recovery_list, we can use it to correctly identify
the race case between convert and recovery.  So fix it.

Fixes: ac7cf246dfdb ("ocfs2/dlm: fix race between convert and recovery")
Link: http://lkml.kernel.org/r/57CE1569.8010704@huawei.com
Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Signed-off-by: Jun Piao <piaojun@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 6 insertions, 6 deletions

diff --git a/fs/ocfs2/dlm/dlmconvert.c b/fs/ocfs2/dlm/dlmconvert.c
index cdeafb4e7ed6..0bb128659d4b 100644
--- a/fs/ocfs2/dlm/dlmconvert.c
+++ b/fs/ocfs2/dlm/dlmconvert.c
@@ -268,7 +268,6 @@ enum dlm_status dlmconvert_remote(struct dlm_ctxt *dlm,
                                   struct dlm_lock *lock, int flags, int type)
 {
         enum dlm_status status;
-        u8 old_owner = res->owner;
 
         mlog(0, "type=%d, convert_type=%d, busy=%d\n", lock->ml.type,
              lock->ml.convert_type, res->state & DLM_LOCK_RES_IN_PROGRESS);
@@ -335,7 +334,6 @@ enum dlm_status dlmconvert_remote(struct dlm_ctxt *dlm,
 
         spin_lock(&res->spinlock);
         res->state &= ~DLM_LOCK_RES_IN_PROGRESS;
-        lock->convert_pending = 0;
         /* if it failed, move it back to granted queue.
          * if master returns DLM_NORMAL and then down before sending ast,
          * it may have already been moved to granted queue, reset to
@@ -344,12 +342,14 @@ enum dlm_status dlmconvert_remote(struct dlm_ctxt *dlm,
                 if (status != DLM_NOTQUEUED)
                         dlm_error(status);
                 dlm_revert_pending_convert(res, lock);
-        } else if ((res->state & DLM_LOCK_RES_RECOVERING) ||
-                        (old_owner != res->owner)) {
-                mlog(0, "res %.*s is in recovering or has been recovered.\n",
-                                res->lockname.len, res->lockname.name);
+        } else if (!lock->convert_pending) {
+                mlog(0, "%s: res %.*s, owner died and lock has been moved back "
+                                "to granted list, retry convert.\n",
+                                dlm->name, res->lockname.len, res->lockname.name);
                 status = DLM_RECOVERING;
         }
+
+        lock->convert_pending = 0;
 bail:
         spin_unlock(&res->spinlock);