linux-kernel - [PATCH 3.16 308/346] ocfs2/dlm: fix race between convert and migration

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Message-ID: <lsq.1479082460.887718538@decadent.org.uk>
Date:   Mon, 14 Nov 2016 00:14:20 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Joel Becker" <jlbec@...lplan.org>,
        "Jun Piao" <piaojun@...wei.com>,
        "Joseph Qi" <joseph.qi@...wei.com>,
        "Mark Fasheh" <mfasheh@...e.de>,
        "Junxiao Bi" <junxiao.bi@...cle.com>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>
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@...wei.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@...wei.com>
Signed-off-by: Jun Piao <piaojun@...wei.com>
Cc: Mark Fasheh <mfasheh@...e.de>
Cc: Joel Becker <jlbec@...lplan.org>
Cc: Junxiao Bi <junxiao.bi@...cle.com>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Ben Hutchings <ben@...adent.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);