1 files changed, 4 insertions, 2 deletions

diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 8b1bf8d3d4a2..894e5d125de6 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -81,11 +81,14 @@ struct buffer_head {
 /*
  * macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
  * and buffer_foo() functions.
+ * To avoid reset buffer flags that are already set, because that causes
+ * a costly cache line transition, check the flag first.
  */
 #define BUFFER_FNS(bit, name)                                           \
 static __always_inline void set_buffer_##name(struct buffer_head *bh)   \
 {                                                                       \
-        set_bit(BH_##bit, &(bh)->b_state);                              \
+        if (!test_bit(BH_##bit, &(bh)->b_state))                        \
+                set_bit(BH_##bit, &(bh)->b_state);                      \
 }                                                                       \
 static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
 {                                                                       \
@@ -151,7 +154,6 @@ void buffer_check_dirty_writeback(struct page *page,
 
 void mark_buffer_dirty(struct buffer_head *bh);
 void mark_buffer_write_io_error(struct buffer_head *bh);
-void init_buffer(struct buffer_head *, bh_end_io_t *, void *);
 void touch_buffer(struct buffer_head *bh);
 void set_bh_page(struct buffer_head *bh,
                 struct page *page, unsigned long offset);