f2fs: support the inline xattrs

0. modified inode structure
--------------------------------------
metadata (e.g., i_mtime, i_ctime, etc)
--------------------------------------
direct pointers [0 ~ 873]

inline xattrs (200 bytes by default)

indirect pointers [0 ~ 4]
--------------------------------------
node footer
--------------------------------------

1. setxattr flow
 - read_all_xattrs copies all the xattrs from inline and xattr node block.
 - handle xattr entries
 - write_all_xattrs copies modified xattrs into inline and xattr node block.

2. getxattr flow
 - read_all_xattrs copies all the xattrs from inline and xattr node block.
 - check target entries

3. Usage
 # mount -t f2fs -o inline_xattr $DEV $MNT

 Once mounted with the inline_xattr option, f2fs marks all the newly created
 files to reserve an amount of inline xattr space explicitly inside the inode
 block. Without the mount option, f2fs will not touch any existing files and
 newly created files as well.

Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/f2fs.h

@@ -940,6 +940,22 @@ static inline unsigned int addrs_per_inode(struct f2fs_inode_info *fi)
 	return DEF_ADDRS_PER_INODE;
 }
 
+static inline void *inline_xattr_addr(struct page *page)
+{
+	struct f2fs_inode *ri;
+	ri = (struct f2fs_inode *)page_address(page);
+	return (void *)&(ri->i_addr[DEF_ADDRS_PER_INODE -
+					F2FS_INLINE_XATTR_ADDRS]);
+}
+
+static inline int inline_xattr_size(struct inode *inode)
+{
+	if (is_inode_flag_set(F2FS_I(inode), FI_INLINE_XATTR))
+		return F2FS_INLINE_XATTR_ADDRS << 2;
+	else
+		return 0;
+}
+
 static inline int f2fs_readonly(struct super_block *sb)
 {
 	return sb->s_flags & MS_RDONLY;

fs/f2fs/node.c

@@ -787,6 +787,10 @@ int truncate_xattr_node(struct inode *inode, struct page *page)
 		return PTR_ERR(npage);
 
 	F2FS_I(inode)->i_xattr_nid = 0;
+
+	/* need to do checkpoint during fsync */
+	F2FS_I(inode)->xattr_ver = cur_cp_version(F2FS_CKPT(sbi));
+
 	set_new_dnode(&dn, inode, page, npage, nid);
 
 	if (page)
@@ -1464,6 +1468,9 @@ void alloc_nid_failed(struct f2fs_sb_info *sbi, nid_t nid)
 	struct f2fs_nm_info *nm_i = NM_I(sbi);
 	struct free_nid *i;
 
+	if (!nid)
+		return;
+
 	spin_lock(&nm_i->free_nid_list_lock);
 	i = __lookup_free_nid_list(nid, &nm_i->free_nid_list);
 	BUG_ON(!i || i->state != NID_ALLOC);