ext4: let add_dir_entry handle inline data properly

This patch let add_dir_entry handle the inline data case. So the
dir is initialized as inline dir first and then we can try to add
some files to it, when the inline space can't hold all the entries,
a dir block will be created and the dir entry will be moved to it.

Also for an inlined dir, "." and ".." are removed and we only use
4 bytes to store the parent inode number. These 2 entries will be
added when we convert an inline dir to a block-based one.

[ Folded in patch from Dan Carpenter to remove an unused variable. ]

Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

fs/ext4/ext4.h

@@ -1616,6 +1616,11 @@ struct ext4_dir_entry_tail {
 	__le32	det_checksum;		/* crc32c(uuid+inum+dirblock) */
 };
 
+#define EXT4_DIRENT_TAIL(block, blocksize) \
+	((struct ext4_dir_entry_tail *)(((void *)(block)) + \
+					((blocksize) - \
+					 sizeof(struct ext4_dir_entry_tail))))
+
 /*
  * Ext4 directory file types.  Only the low 3 bits are used.  The
  * other bits are reserved for now.
@@ -2435,6 +2440,11 @@ extern struct ext4_dir_entry_2 *ext4_init_dot_dotdot(struct inode *inode,
 				 struct ext4_dir_entry_2 *de,
 				 int blocksize, int csum_size,
 				 unsigned int parent_ino, int dotdot_real_len);
+extern void initialize_dirent_tail(struct ext4_dir_entry_tail *t,
+				   unsigned int blocksize);
+extern int ext4_handle_dirty_dirent_node(handle_t *handle,
+					 struct inode *inode,
+					 struct buffer_head *bh);
 
 /* symlink.c */
 extern const struct inode_operations ext4_symlink_inode_operations;