From: Shan Hai <[email protected]>

The writeback thread would exit with a lock held when the cache device is
detached via sysfs interface, fix it by releasing the held lock before exiting
the while-loop.

Fixes: fadd94e05c02 (bcache: quit dc->writeback_thread when 
BCACHE_DEV_DETACHING is set)
Signed-off-by: Shan Hai <[email protected]>
Signed-off-by: Coly Li <[email protected]>
Tested-by: Shenghui Wang <[email protected]>
Cc: [email protected] #4.17+
---
Changelog:
v2: add Fixes tag by Coly Li.
v1: initial patch from Shan Hai.

 drivers/md/bcache/writeback.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/md/bcache/writeback.c b/drivers/md/bcache/writeback.c
index 6be05bd7ca67..08c3a9f9676c 100644
--- a/drivers/md/bcache/writeback.c
+++ b/drivers/md/bcache/writeback.c
@@ -685,8 +685,10 @@ static int bch_writeback_thread(void *arg)
                         * data on cache. BCACHE_DEV_DETACHING flag is set in
                         * bch_cached_dev_detach().
                         */
-                       if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags))
+                       if (test_bit(BCACHE_DEV_DETACHING, &dc->disk.flags)) {
+                               up_write(&dc->writeback_lock);
                                break;
+                       }
                }
 
                up_write(&dc->writeback_lock);
-- 
2.18.0

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