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Message-Id: <1453926929-17663-76-git-send-email-kamal@canonical.com>
Date: Wed, 27 Jan 2016 12:32:16 -0800
From: Kamal Mostafa <kamal@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Stefan Bader <stefan.bader@...onical.com>,
Kent Overstreet <kent.overstreet@...il.com>,
Jens Axboe <axboe@...com>, Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 075/268] bcache: prevent crash on changing writeback_running
4.2.8-ckt3 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Stefan Bader <stefan.bader@...onical.com>
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@...onical.com>
Cc: Kent Overstreet <kent.overstreet@...il.com>
Signed-off-by: Jens Axboe <axboe@...com>
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
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 0a9dab1..073a042 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)
--
1.9.1
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