# Re: \[PATCH 3/6\] fs-verity: add FS\_IOC\_READ\_VERITY\_METADATA ioctl

- From: Eric Biggers \<ebiggers@kernel.org\>
- Date: 2021-02-07 08:02:35 
- List: linux-api
- Page: https://ratatoskr.run/linux-api/2021/02/199437
- Thread: https://ratatoskr.run/linux-fscrypt/2021/01/197428/t.md

```text
On Sun, Feb 07, 2021 at 03:46:43PM +0800, Chao Yu wrote:
> Hi Eric,
> 
> On 2021/1/16 2:18, Eric Biggers wrote:
> > +static int f2fs_ioc_read_verity_metadata(struct file *filp, unsigned long arg)
> > +{
> > +	if (!f2fs_sb_has_verity(F2FS_I_SB(file_inode(filp))))
> > +		return -EOPNOTSUPP;
> 
> One case is after we update kernel image, f2fs module may no longer support
> compress algorithm which current file was compressed with, to avoid triggering
> IO with empty compress engine (struct f2fs_compress_ops pointer):
> 
> It needs to add f2fs_is_compress_backend_ready() check condition here?
> 
> Thanks,
> 
> > +
> > +	return fsverity_ioctl_read_metadata(filp, (const void __user *)arg);
> > +}

In that case it wouldn't have been possible to open the file, because
f2fs_file_open() checks for it.  So it's not necessary to repeat the same check
in every operation on the file descriptor.

- Eric
```