writeback: fix bad _bh spinlock nesting

Fix a bug where a lock is _bh nested within another _bh lock,
but forgets to use the _bh variant for unlock.

Further more, it's not necessary to test _bh locks, the inner lock
can just use spin_lock(). So fix up the bug by making that change.

Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 0b8ee66993dd..08d357522e78 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -415,7 +415,8 @@ static int bdi_forker_thread(void *ptr)
                                 break;
                         }
 
-                        spin_lock_bh(&bdi->wb_lock);
+                        spin_lock(&bdi->wb_lock);
+
                         /*
                          * If there is no work to do and the bdi thread was
                          * inactive long enough - kill it. The wb_lock is taken
@@ -432,7 +433,7 @@ static int bdi_forker_thread(void *ptr)
                                 action = KILL_THREAD;
                                 break;
                         }
-                        spin_unlock_bh(&bdi->wb_lock);
+                        spin_unlock(&bdi->wb_lock);
                 }
                 spin_unlock_bh(&bdi_lock);