f2fs: optimize the flow of f2fs_map_blocks

check map->m_len right after it changes to avoid excess call
to update dnode_of_data.
Signed-off-by: NFan li <fanofcode.li@samsung.com>
Reviewed-by: NChao Yu <chao2.yu@samsung.com>
Signed-off-by: NJaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -573,6 +573,7 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
 	int err = 0, ofs = 1;
 	struct extent_info ei;
 	bool allocated = false;
+	block_t blkaddr;
 
 	map->m_len = 0;
 	map->m_flags = 0;
@@ -636,6 +637,9 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
 	pgofs++;
 
 get_next:
+	if (map->m_len >= maxblocks)
+		goto sync_out;
+
 	if (dn.ofs_in_node >= end_offset) {
 		if (allocated)
 			sync_inode_page(&dn);
@@ -653,8 +657,7 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
 		end_offset = ADDRS_PER_PAGE(dn.node_page, F2FS_I(inode));
 	}
 
-	if (maxblocks > map->m_len) {
-		block_t blkaddr = datablock_addr(dn.node_page, dn.ofs_in_node);
+	blkaddr = datablock_addr(dn.node_page, dn.ofs_in_node);
 
 	if (blkaddr == NEW_ADDR || blkaddr == NULL_ADDR) {
 		if (create) {
@@ -690,7 +693,7 @@ int f2fs_map_blocks(struct inode *inode, struct f2fs_map_blocks *map,
 		map->m_len++;
 		goto get_next;
 	}
-	}
+
 sync_out:
 	if (allocated)
 		sync_inode_page(&dn);