Re: [f2fs-dev] [PATCH v2 2/2] f2fs: fix compat F2FS_IOC_{MOVE, GARBAGE_COLLECT}_RANGE

[Eric Biggers <ebiggers@kernel.org>]

On Wed, Nov 04, 2020 at 02:43:10PM +0800, Chao Yu wrote:
> +static int f2fs_ioc_gc_range(struct file *filp, unsigned long arg)
> +{
> +	struct f2fs_gc_range range;
> +	struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(filp));
> +
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EPERM;
> +	if (f2fs_readonly(sbi->sb))
> +		return -EROFS;
> +	if (copy_from_user(&range, (struct f2fs_gc_range __user *)arg,
> +							sizeof(range)))
> +		return -EFAULT;
> +
> +	return __f2fs_ioc_gc_range(filp, &range);
> +}
[...]
>  #ifdef CONFIG_COMPAT
> +static int f2fs_compat_ioc_gc_range(struct file *file, unsigned long arg)
> +{
> +	struct f2fs_sb_info *sbi = F2FS_I_SB(file_inode(file));
> +	struct compat_f2fs_gc_range __user *urange;
> +	struct f2fs_gc_range range;
> +	int err;
> +
> +	if (unlikely(f2fs_cp_error(sbi)))
> +		return -EIO;
> +	if (!f2fs_is_checkpoint_ready(sbi))
> +		return -ENOSPC;
> +	if (!capable(CAP_SYS_ADMIN))
> +		return -EPERM;
> +	if (f2fs_readonly(sbi->sb))
> +		return -EROFS;
> +
> +	urange = compat_ptr(arg);
> +	err = get_user(range.sync, &urange->sync);
> +	err |= get_user(range.start, &urange->start);
> +	err |= get_user(range.len, &urange->len);
> +	if (err)
> +		return -EFAULT;
> +
> +	return __f2fs_ioc_gc_range(file, &range);
> +}

It would be better to have __f2fs_ioc_gc_range() handle the f2fs_cp_error(),
f2fs_is_checkpoint_ready(), capable(), and f2fs_readonly() checks, so that they
don't have to be duplicated in the native and compat cases.

Similarly for "move range".

- Eric