ocfs2/dlm: fix race between convert and migration

commit e6f0c6e6170fec175fe676495f29029aecdf486c upstream.

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/fs/ocfs2/dlm/dlmconvert.c b/fs/ocfs2/dlm/dlmconvert.c
index f65bdcf..6d97883 100644 (file)
--- a/fs/ocfs2/dlm/dlmconvert.c
+++ b/fs/ocfs2/dlm/dlmconvert.c
@@ -265,7 +265,6 @@ 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);
@@ -332,7 +331,6 @@ 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
@@ -341,12 +339,14 @@ 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);