Patch "bcache: stop writeback thread after detaching" has been added to the 4.4-stable tree

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

bcache: stop writeback thread after detaching

to the 4.4-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:
bcache-stop-writeback-thread-after-detaching.patch
and it can be found in the queue-4.4 subdirectory.

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

From: Tang Junhui <[email protected]>
Date: Mon, 8 Jan 2018 12:21:19 -0800
Subject: bcache: stop writeback thread after detaching

From: Tang Junhui <[email protected]>

[ Upstream commit 8d29c4426b9f8afaccf28de414fde8a722b35fdf ]

Currently, when a cached device detaching from cache, writeback thread is not stopped, and writeback_rate_update work is not canceled. For example, after the following command:
echo 1 >/sys/block/sdb/bcache/detach
you can still see the writeback thread. Then you attach the device to the cache again, bcache will create another writeback thread, for example, after below command:
echo ba0fb5cd-658a-4533-9806-6ce166d883b9 > /sys/block/sdb/bcache/attach then you will see 2 writeback threads.
This patch stops writeback thread and cancels writeback_rate_update work when cached device detaching from cache.

Compare with patch v1, this v2 patch moves code down into the register lock for safety in case of any future changes as Coly and Mike suggested.

[edit by mlyle: commit log spelling/formatting]

---
 drivers/md/bcache/super.c |    6 ++++++
 1 file changed, 6 insertions(+)

@@ -890,6 +890,12 @@ static void cached_dev_detach_finish(str
 
 	mutex_lock(&bch_register_lock);
 
+	cancel_delayed_work_sync(&dc->writeback_rate_update);
+	if (!IS_ERR_OR_NULL(dc->writeback_thread)) {
+		kthread_stop(dc->writeback_thread);
+		dc->writeback_thread = NULL;
+	}
+
 	memset(&dc->sb.set_uuid, 0, 16);
 	SET_BDEV_STATE(&dc->sb, BDEV_STATE_NONE);
 

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

queue-4.4/bcache-segregate-flash-only-volume-write-streams.patch queue-4.4/bcache-stop-writeback-thread-after-detaching.patch