mm: add end_buffer_read helper function

Move duplicated code from end_buffer_read_XXX methods to separate helper
function.
Signed-off-by: NDmitry Monakhov <dmonakhov@openvz.org>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

fs/buffer.c

@@ -110,10 +110,14 @@ static void buffer_io_error(struct buffer_head *bh)
 }
 
 /*
- * Default synchronous end-of-IO handler..  Just mark it up-to-date and
- * unlock the buffer. This is what ll_rw_block uses too.
+ * End-of-IO handler helper function which does not touch the bh after
+ * unlocking it.
+ * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
+ * a race there is benign: unlock_buffer() only use the bh's address for
+ * hashing after unlocking the buffer, so it doesn't actually touch the bh
+ * itself.
  */
-void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
+static void __end_buffer_read_notouch(struct buffer_head *bh, int uptodate)
 {
 	if (uptodate) {
 		set_buffer_uptodate(bh);
@@ -122,6 +126,15 @@ void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
 		clear_buffer_uptodate(bh);
 	}
 	unlock_buffer(bh);
+}
+
+/*
+ * Default synchronous end-of-IO handler..  Just mark it up-to-date and
+ * unlock the buffer. This is what ll_rw_block uses too.
+ */
+void end_buffer_read_sync(struct buffer_head *bh, int uptodate)
+{
+	__end_buffer_read_notouch(bh, uptodate);
 	put_bh(bh);
 }
 
@@ -2245,21 +2258,10 @@ block_page_mkwrite(struct vm_area_struct *vma, struct page *page,
  * nobh_prepare_write()'s prereads are special: the buffer_heads are freed
  * immediately, while under the page lock.  So it needs a special end_io
  * handler which does not touch the bh after unlocking it.
- *
- * Note: unlock_buffer() sort-of does touch the bh after unlocking it, but
- * a race there is benign: unlock_buffer() only use the bh's address for
- * hashing after unlocking the buffer, so it doesn't actually touch the bh
- * itself.
  */
 static void end_buffer_read_nobh(struct buffer_head *bh, int uptodate)
 {
-	if (uptodate) {
-		set_buffer_uptodate(bh);
-	} else {
-		/* This happens, due to failed READA attempts. */
-		clear_buffer_uptodate(bh);
-	}
-	unlock_buffer(bh);
+	__end_buffer_read_notouch(bh, uptodate);
 }
 
 /*