f2fs: clean up with is_valid_blkaddr()

- rename is_valid_blkaddr() to is_valid_meta_blkaddr() for readability.
- introduce is_valid_blkaddr() for cleanup.

No logic change in this patch.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 62ce499..67b3e89 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -379,8 +379,7 @@ static void set_node_addr(struct f2fs_sb_info *sbi, struct node_info *ni,
 			new_blkaddr == NULL_ADDR);
 	f2fs_bug_on(sbi, nat_get_blkaddr(e) == NEW_ADDR &&
 			new_blkaddr == NEW_ADDR);
-	f2fs_bug_on(sbi, nat_get_blkaddr(e) != NEW_ADDR &&
-			nat_get_blkaddr(e) != NULL_ADDR &&
+	f2fs_bug_on(sbi, is_valid_blkaddr(nat_get_blkaddr(e)) &&
 			new_blkaddr == NEW_ADDR);
 
 	/* increment version no as node is removed */
@@ -391,7 +390,7 @@ static void set_node_addr(struct f2fs_sb_info *sbi, struct node_info *ni,
 
 	/* change address */
 	nat_set_blkaddr(e, new_blkaddr);
-	if (new_blkaddr == NEW_ADDR || new_blkaddr == NULL_ADDR)
+	if (!is_valid_blkaddr(new_blkaddr))
 		set_nat_flag(e, IS_CHECKPOINTED, false);
 	__set_nat_cache_dirty(nm_i, e);