f2fs: fix to update page flag

This patch fixes to update page flag (e.g. Uptodate/cold flag) in
->write_begin.

Otherwise, page will be non-uptodate when we try to write entire
page, and cold data flag in page will not be clean when gced page
is being rewritten.
Signed-off-by: NChao Yu <chao2.yu@samsung.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -1790,8 +1790,10 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
 	f2fs_put_dnode(&dn);
 	f2fs_unlock_op(sbi);
 
-	if ((len == PAGE_CACHE_SIZE) || PageUptodate(page))
-		return 0;
+	if (len == PAGE_CACHE_SIZE)
+		goto out_update;
+	if (PageUptodate(page))
+		goto out_clear;
 
 	f2fs_wait_on_page_writeback(page, DATA);
 
@@ -1801,7 +1803,7 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
 
 		/* Reading beyond i_size is simple: memset to zero */
 		zero_user_segments(page, 0, start, end, PAGE_CACHE_SIZE);
-		goto out;
+		goto out_update;
 	}
 
 	if (dn.data_blkaddr == NEW_ADDR) {
@@ -1839,8 +1841,9 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
 			}
 		}
 	}
-out:
+out_update:
 	SetPageUptodate(page);
+out_clear:
 	clear_cold_data(page);
 	return 0;