PAGE_CLEAR_DIRTY and PAGE_SET_WRITEBACK are two macros used in
__process_pages_contig(), to inform the function to clear page dirty and
then set page writeback.

However page write back and dirty are two conflict status (at least for
sector size == PAGE_SIZE case), this means those two macros are always
called together.

This means we can merge PAGE_CLEAR_DIRTY and PAGE_SET_WRITEBACK, into
one macro, PAGE_START_WRITEBACK.

Signed-off-by: Qu Wenruo <redacted>
---
  fs/btrfs/extent_io.c |  4 ++--
  fs/btrfs/extent_io.h | 12 ++++++------
  fs/btrfs/inode.c     | 28 ++++++++++------------------
  3 files changed, 18 insertions(+), 26 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 3442f1746683..a816ba4a8537 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c

@@ -1970,10 +1970,10 @@ static int __process_pages_contig(struct address_space *mapping,
  			if (page_ops & PAGE_SET_PRIVATE2)
  				SetPagePrivate2(pages[i]);
  
-			if (page_ops & PAGE_CLEAR_DIRTY)
+			if (page_ops & PAGE_START_WRITEBACK) {
  				clear_page_dirty_for_io(pages[i]);
-			if (page_ops & PAGE_SET_WRITEBACK)
  				set_page_writeback(pages[i]);
+			}
  			if (page_ops & PAGE_SET_ERROR)
  				SetPageError(pages[i]);
  			if (page_ops & PAGE_END_WRITEBACK)

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 19221095c635..bedf761a0300 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h

@@ -35,12 +35,12 @@ enum {
  
  /* these are flags for __process_pages_contig */
  #define PAGE_UNLOCK		(1 << 0)
-#define PAGE_CLEAR_DIRTY	(1 << 1)
-#define PAGE_SET_WRITEBACK	(1 << 2)
-#define PAGE_END_WRITEBACK	(1 << 3)
-#define PAGE_SET_PRIVATE2	(1 << 4)
-#define PAGE_SET_ERROR		(1 << 5)
-#define PAGE_LOCK		(1 << 6)
+/* This one will clera page dirty and then set paeg writeback */