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Subject[PATCH 3.16 308/346] ocfs2/dlm: fix race between convert and migration
3.16.39-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Joseph Qi <joseph.qi@huawei.com>

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>
---
fs/ocfs2/dlm/dlmconvert.c | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)

--- a/fs/ocfs2/dlm/dlmconvert.c
+++ b/fs/ocfs2/dlm/dlmconvert.c
@@ -262,7 +262,6 @@ enum dlm_status dlmconvert_remote(struct
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);
@@ -329,7 +328,6 @@ enum dlm_status dlmconvert_remote(struct

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
@@ -338,12 +336,14 @@ enum dlm_status dlmconvert_remote(struct
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);

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