linux-kernel - [PATCH] bcache: Fix a sleep-in-atomic bug

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Date:   Wed, 31 May 2017 15:23:40 +0800
From:   Jia-Ju Bai <baijiaju1990@....com>
To:     kent.overstreet@...il.com, shli@...nel.org, axboe@...com,
        mchristi@...hat.com, git@...ux.ewheeler.net, colyli@...e.de,
        akpm@...ux-foundation.org, wangyijing@...wei.com, mingo@...nel.org,
        mhocko@...e.com
Cc:     linux-bcache@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jia-Ju Bai <baijiaju1990@....com>
Subject: [PATCH] bcache: Fix a sleep-in-atomic bug

The driver may sleep under a spin lock, and the function call path is:
journal_wait_for_write (acquire the lock by spin_lock)
  closure_sync
    schedule --> may sleep

To fix it, the lock is released before "closure_sync", and the lock is 
acquired again after this function.

Signed-off-by: Jia-Ju Bai <baijiaju1990@....com>
---
 drivers/md/bcache/journal.c |    1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/md/bcache/journal.c b/drivers/md/bcache/journal.c
index 1198e53..ad47c36 100644
--- a/drivers/md/bcache/journal.c
+++ b/drivers/md/bcache/journal.c
@@ -724,6 +724,7 @@ static struct journal_write *journal_wait_for_write(struct cache_set *c,
 			btree_flush_write(c);
 		}
 
+		spin_unlock(&c->journal.lock);
 		closure_sync(&cl);
 		spin_lock(&c->journal.lock);
 		wait = true;
-- 
1.7.9.5