From: Stefan Bader <stefan.bader@xxxxxxxxxxxxx>
This patch does NOT apply to the 3.12 stable tree. If you still want
it applied, please provide a backport.
===============
commit 8d16ce540c94c9d366eb36fc91b7154d92d6397b upstream.
Added a safeguard in the shutdown case. At least while not being
attached it is also possible to trigger a kernel bug by writing into
writeback_running. This change adds the same check before trying to
wake up the thread for that case.
Signed-off-by: Stefan Bader <stefan.bader@xxxxxxxxxxxxx>
Cc: Kent Overstreet <kent.overstreet@xxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jens Axboe <axboe@xxxxxx>
---
drivers/md/bcache/writeback.h | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/md/bcache/writeback.h b/drivers/md/bcache/writeback.h
index 0a9dab187b79..073a042aed24 100644
--- a/drivers/md/bcache/writeback.h
+++ b/drivers/md/bcache/writeback.h
@@ -63,7 +63,8 @@ static inline bool should_writeback(struct cached_dev *dc, struct bio *bio,
static inline void bch_writeback_queue(struct cached_dev *dc)
{
- wake_up_process(dc->writeback_thread);
+ if (!IS_ERR_OR_NULL(dc->writeback_thread))
+ wake_up_process(dc->writeback_thread);
}
static inline void bch_writeback_add(struct cached_dev *dc)
--
2.7.2
--
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