[PATCH] f2fs: fix to wait on page writeback in __clone_blkaddrs()

[Chao Yu]

In below race condition, dst page may become writeback status
in __clone_blkaddrs(), it needs to wait writeback before update,
fix it.

Thread A				GC Thread
- f2fs_move_file_range
  - filemap_write_and_wait_range(dst)
					- gc_data_segment
					 - f2fs_down_write(dst)
					 - move_data_page
					  - set_page_writeback(dst_page)
					  - f2fs_submit_page_write
					 - f2fs_up_write(dst)
  - f2fs_down_write(dst)
  - __exchange_data_block
   - __clone_blkaddrs
    - f2fs_get_new_data_page
    - memcpy_page

Fixes: 0a2aa8fbb969 ("f2fs: refactor __exchange_data_block for speed up")
Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
 fs/f2fs/file.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index f6edc2fdaafe..911b074f808c 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1328,6 +1328,9 @@ static int __clone_blkaddrs(struct inode *src_inode, struct inode *dst_inode,
 				f2fs_put_page(psrc, 1);
 				return PTR_ERR(pdst);
 			}
+
+			f2fs_wait_on_page_writeback(pdst, DATA, true, true);
+
 			memcpy_page(pdst, 0, psrc, 0, PAGE_SIZE);
 			set_page_dirty(pdst);
 			set_page_private_gcing(pdst);
-- 
2.40.1