btrfs: defrag: enable defrag for subpage case

With the new infrastructure which has taken subpage into consideration,
now we should be safe to allow defrag to work for subpage case.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/ioctl.c

@@ -3080,12 +3080,6 @@ static int btrfs_ioctl_defrag(struct file *file, void __user *argp)
 		goto out;
 	}
 
-	/* Subpage defrag will be supported in later commits */
-	if (root->fs_info->sectorsize < PAGE_SIZE) {
-		ret = -ENOTTY;
-		goto out;
-	}
-
 	switch (inode->i_mode & S_IFMT) {
 	case S_IFDIR:
 		if (!capable(CAP_SYS_ADMIN)) {