f2fs: flush dirty data for bmap

Users expect bmap will give allocated block addresses.
Let's play likewise ext4.
Reviewed-by: NChao Yu <chao2.yu@samsung.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -1667,12 +1667,13 @@ static sector_t f2fs_bmap(struct address_space *mapping, sector_t block)
 {
 	struct inode *inode = mapping->host;
 
-	/* we don't need to use inline_data strictly */
-	if (f2fs_has_inline_data(inode)) {
-		int err = f2fs_convert_inline_inode(inode);
-		if (err)
-			return err;
-	}
+	if (f2fs_has_inline_data(inode))
+		return 0;
+
+	/* make sure allocating whole blocks */
+	if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY))
+		filemap_write_and_wait(mapping);
+
 	return generic_block_bmap(mapping, block, get_data_block_bmap);
 }