Patch "ocfs2/dlm: fix race between convert and migration" has been added to the 4.7-stable tree

This is a note to let you know that I've just added the patch titled

ocfs2/dlm: fix race between convert and migration

to the 4.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ocfs2-dlm-fix-race-between-convert-and-migration.patch
and it can be found in the queue-4.7 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Joseph Qi <[email protected]>
Date: Mon, 19 Sep 2016 14:43:55 -0700
Subject: ocfs2/dlm: fix race between convert and migration

From: Joseph Qi <[email protected]>

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.

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

@@ -268,7 +268,6 @@ 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);

@@ -335,7 +334,6 @@ 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

@@ -344,12 +342,14 @@ 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);
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.7/ocfs2-fix-start-offset-to-ocfs2_zero_range_for_truncate.patch queue-4.7/ocfs2-dlm-fix-race-between-convert-and-migration.patch queue-4.7/revert-ocfs2-bump-up-o2cb-network-protocol-version.patch