fs: move code out of buffer.c

Move invalidate_bdev, block_sync_page into fs/block_dev.c.  Export
kill_bdev as well, so brd doesn't have to open code it.  Reduce
buffer_head.h requirement accordingly.

Removed a rather large comment from invalidate_bdev, as it looked a bit
obsolete to bother moving.  The small comment replacing it says enough.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

2 files changed, 1 insertions, 2 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 50f08241f981..8616ef3025a4 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -32,7 +32,7 @@
 #include <linux/sysctl.h>
 #include <linux/cpu.h>
 #include <linux/syscalls.h>
-#include <linux/buffer_head.h>
+#include <linux/buffer_head.h> /* __set_page_dirty_buffers */
 #include <linux/pagevec.h>
 #include <trace/events/writeback.h>
 
diff --git a/mm/swap_state.c b/mm/swap_state.c
index 78cc4d1f6cce..ea6b32d61873 100644
--- a/mm/swap_state.c
+++ b/mm/swap_state.c
@@ -13,7 +13,6 @@
 #include <linux/swapops.h>
 #include <linux/init.h>
 #include <linux/pagemap.h>
-#include <linux/buffer_head.h>
 #include <linux/backing-dev.h>
 #include <linux/pagevec.h>
 #include <linux/migrate.h>