writeback: Fix issue on make htmldocs

Document the @reason parameter to make "make htmldocs" happy.
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Marcos Paulo de Souza <marcos.mage@gmail.com>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>

fs/fs-writeback.c

@@ -156,6 +156,7 @@ __bdi_start_writeback(struct backing_dev_info *bdi, long nr_pages,
  * bdi_start_writeback - start writeback
  * @bdi: the backing device to write from
  * @nr_pages: the number of pages to write
+ * @reason: reason why some writeback work was initiated
  *
  * Description:
  *   This does WB_SYNC_NONE opportunistic writeback. The IO is only
@@ -1223,6 +1224,7 @@ static void wait_sb_inodes(struct super_block *sb)
  * writeback_inodes_sb_nr -	writeback dirty inodes from given super_block
  * @sb: the superblock
  * @nr: the number of pages to write
+ * @reason: reason why some writeback work initiated
  *
  * Start writeback on some inodes on this super_block. No guarantees are made
  * on how many (if any) will be written, and this function does not wait
@@ -1251,6 +1253,7 @@ EXPORT_SYMBOL(writeback_inodes_sb_nr);
 /**
  * writeback_inodes_sb	-	writeback dirty inodes from given super_block
  * @sb: the superblock
+ * @reason: reason why some writeback work was initiated
  *
  * Start writeback on some inodes on this super_block. No guarantees are made
  * on how many (if any) will be written, and this function does not wait
@@ -1265,6 +1268,7 @@ EXPORT_SYMBOL(writeback_inodes_sb);
 /**
  * writeback_inodes_sb_if_idle	-	start writeback if none underway
  * @sb: the superblock
+ * @reason: reason why some writeback work was initiated
  *
  * Invoke writeback_inodes_sb if no writeback is currently underway.
  * Returns 1 if writeback was started, 0 if not.
@@ -1285,6 +1289,7 @@ EXPORT_SYMBOL(writeback_inodes_sb_if_idle);
  * writeback_inodes_sb_if_idle	-	start writeback if none underway
  * @sb: the superblock
  * @nr: the number of pages to write
+ * @reason: reason why some writeback work was initiated
  *
  * Invoke writeback_inodes_sb if no writeback is currently underway.
  * Returns 1 if writeback was started, 0 if not.