ocfs2/dlm: fix race between convert and recovery

There is a race window between dlmconvert_remote and
dlm_move_lockres_to_recovery_list, which will cause a lock with
OCFS2_LOCK_BUSY in grant list, thus system hangs.

dlmconvert_remote
{
        spin_lock(&res->spinlock);
        list_move_tail(&lock->list, &res->converting);
        lock->convert_pending = 1;
        spin_unlock(&res->spinlock);

        status = dlm_send_remote_convert_request();
        >>>>>> race window, master has queued ast and return DLM_NORMAL,
               and then down before sending ast.
               this node detects master down and calls
               dlm_move_lockres_to_recovery_list, which will revert the
               lock to grant list.
               Then OCFS2_LOCK_BUSY won't be cleared as new master won't
               send ast any more because it thinks already be authorized.

        spin_lock(&res->spinlock);
        lock->convert_pending = 0;
        if (status != DLM_NORMAL)
                dlm_revert_pending_convert(res, lock);
        spin_unlock(&res->spinlock);
}

In this case, check if res->state has DLM_LOCK_RES_RECOVERING bit set
(res is still in recovering) or res master changed (new master has
finished recovery), reset the status to DLM_RECOVERING, then it will
retry convert.

Signed-off-by: Joseph Qi <joseph.qi@huawei.com>
Reported-by: Yiwen Jiang <jiangyiwen@huawei.com>
Reviewed-by: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Tariq Saeed <tariq.x.saeed@oracle.com>
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, 10 insertions, 1 deletions

diff --git a/fs/ocfs2/dlm/dlmconvert.c b/fs/ocfs2/dlm/dlmconvert.c
index e36d63ff1783..84de55ed865a 100644
--- a/fs/ocfs2/dlm/dlmconvert.c
+++ b/fs/ocfs2/dlm/dlmconvert.c
@@ -262,6 +262,7 @@ 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);
@@ -316,11 +317,19 @@ 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 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
+         * DLM_RECOVERING and retry convert */
         if (status != DLM_NORMAL) {
                 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);
+                status = DLM_RECOVERING;
         }
 bail:
         spin_unlock(&res->spinlock);