2 files changed, 18 insertions, 1 deletions

diff --git a/include/linux/wait_bit.h b/include/linux/wait_bit.h
index 9318b2166439..2b0072fa5e92 100644
--- a/include/linux/wait_bit.h
+++ b/include/linux/wait_bit.h
@@ -305,4 +305,21 @@ do {									\
         __ret;                                                          \
 })
 
+/**
+ * clear_and_wake_up_bit - clear a bit and wake up anyone waiting on that bit
+ *
+ * @bit: the bit of the word being waited on
+ * @word: the word being waited on, a kernel virtual address
+ *
+ * You can use this helper if bitflags are manipulated atomically rather than
+ * non-atomically under a lock.
+ */
+static inline void clear_and_wake_up_bit(int bit, void *word)
+{
+        clear_bit_unlock(bit, word);
+        /* See wake_up_bit() for which memory barrier you need to use. */
+        smp_mb__after_atomic();
+        wake_up_bit(word, bit);
+}
+
 #endif /* _LINUX_WAIT_BIT_H */
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 023190c69dce..fa5e6d7406d1 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -383,7 +383,7 @@ static void wb_shutdown(struct bdi_writeback *wb)
          * the barrier provided by test_and_clear_bit() above.
          */
         smp_wmb();
-        clear_bit(WB_shutting_down, &wb->state);
+        clear_and_wake_up_bit(WB_shutting_down, &wb->state);
 }
 
 static void wb_exit(struct bdi_writeback *wb)