ocfs2: fix slot overwritten if storage link down during mount

The following case will lead to slot overwritten.

N1                               N2
mount ocfs2 volume, find and
allocate slot 0, then set
osb->slot_num to 0, begin to
write slot info to disk
                                 mount ocfs2 volume, wait for super lock
write block fail because of
storage link down, unlock
super lock
                                 got super lock and also allocate slot 0
                                 then unlock super lock

mount fail and then dismount,
since osb->slot_num is 0, try to
put invalid slot to disk. And it
will succeed if storage link
restores.
                                 N2 slot info is now overwritten

Once another node say N3 mount, it will find and allocate slot 0 again,
which will lead to mount hung because journal has already been locked by
N2.  so when write slot info failed, invalidate slot in advance to avoid
overwrite slot.

[akpm@linux-foundation.org: coding-style fixes]
Signed-off-by: Yiwen Jiang <jiangyiwen@huawei.com>
Reviewed-by: Joseph Qi <joseph.qi@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>
(cherry picked from commit 1247017f43a93eae3d64b7c25f3637dc545f5a47)

Orabug: 24939243

Signed-off-by: Junxiao Bi <junxiao.bi@oracle.com>

diff --git a/fs/ocfs2/slot_map.c b/fs/ocfs2/slot_map.c
index e78a203d44c832d8d638782984752cfc87e924b8..7b05c18b4eeaa0dab8e0746cfffb839d4f22c75c 100644 (file)
--- a/fs/ocfs2/slot_map.c
+++ b/fs/ocfs2/slot_map.c
@@ -503,8 +503,17 @@ int ocfs2_find_slot(struct ocfs2_super *osb)
        trace_ocfs2_find_slot(osb->slot_num);
 
        status = ocfs2_update_disk_slot(osb, si, osb->slot_num);
-       if (status < 0)
+       if (status < 0) {
                mlog_errno(status);
+               /*
+                * if write block failed, invalidate slot to avoid overwrite
+                * slot during dismount in case another node rightly has mounted
+                */
+               spin_lock(&osb->osb_lock);
+               ocfs2_invalidate_slot(si, osb->slot_num);
+               osb->slot_num = OCFS2_INVALID_SLOT;
+               spin_unlock(&osb->osb_lock);
+       }
 
 bail:
        return status;