allow in-inode EAs on ext4 root inode

The ext3 root inode was treated specially with respect
to in-inode extended attributes, for reasons detailed
in the removed comment below.  The first mkfs-created
inodes would not get extra_i_size or the EXT3_STATE_XATTR
flag set in ext3_read_inode, which disallowed reading or
setting in-inode EAs on the root.

However, in ext4, ext4_mark_inode_dirty calls
ext4_expand_extra_isize for all inodes; once this is done
EAs may be placed in the root ext4 inode body.

But for reasons above, it won't be found after a reboot.

testcase:

setfattr -n user.name -v value mntpt/
setfattr -n user.name2 -v value2 mntpt/
umount mntpt/; remount mntpt/
getfattr -d mntpt/

name2/value2 has gone missing; debugfs shows it in the
inode body, but it is not found there by getattr.

The following fixes it up; newer mkfs appears to properly
zero the inodes, so this workaround isn't needed for ext4.
Signed-off-by: NEric Sandeen <sandeen@redhat.com>
Signed-off-by: NTheodore Ts'o <tytso@mit.edu>

fs/ext4/inode.c

@@ -2758,13 +2758,7 @@ struct inode *ext4_iget(struct super_block *sb, unsigned long ino)
 		ei->i_data[block] = raw_inode->i_block[block];
 	INIT_LIST_HEAD(&ei->i_orphan);
 
-	if (inode->i_ino >= EXT4_FIRST_INO(inode->i_sb) + 1 &&
-	    EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
-		/*
-		 * When mke2fs creates big inodes it does not zero out
-		 * the unused bytes above EXT4_GOOD_OLD_INODE_SIZE,
-		 * so ignore those first few inodes.
-		 */
+	if (EXT4_INODE_SIZE(inode->i_sb) > EXT4_GOOD_OLD_INODE_SIZE) {
 		ei->i_extra_isize = le16_to_cpu(raw_inode->i_extra_isize);
 		if (EXT4_GOOD_OLD_INODE_SIZE + ei->i_extra_isize >
 		    EXT4_INODE_SIZE(inode->i_sb)) {