Re: [PATCH v6 4/6] fs: make vfs_fileattr_[get|set] return -EOPNOSUPP

Jan Kara
2025-10-06T15:39:53Z

On Mon 06-10-25 13:09:05, Jiri Slaby wrote:
> On 30. 06. 25, 18:20, Andrey Albershteyn wrote:
> > Future patches will add new syscalls which use these functions. As
> > this interface won't be used for ioctls only, the EOPNOSUPP is more
> > appropriate return code.
> >
> > This patch converts return code from ENOIOCTLCMD to EOPNOSUPP for
> > vfs_fileattr_get and vfs_fileattr_set. To save old behavior translate
> > EOPNOSUPP back for current users - overlayfs, encryptfs and fs/ioctl.c.
> >
> > Signed-off-by: Andrey Albershteyn <aalbersh@kernel.org>
> ...
> > @@ -292,6 +294,8 @@ int ioctl_setflags(struct file *file, unsigned int __user *argp)
> > fileattr_fill_flags(&fa, flags);
> > err = vfs_fileattr_set(idmap, dentry, &fa);
> > mnt_drop_write_file(file);
> > + if (err == -EOPNOTSUPP)
> > + err = -ENOIOCTLCMD;
>
> This breaks borg code (unit tests already) as it expects EOPNOTSUPP, not
> ENOIOCTLCMD/ENOTTY:
> https://github.com/borgbackup/borg/blob/1c6ef7a200c7f72f8d1204d727fea32168616ceb/src/borg/platform/linux.pyx#L147
>
> I.e. setflags now returns ENOIOCTLCMD/ENOTTY for cases where 6.16 used to
> return EOPNOTSUPP.
>
> This minimal testcase program doing ioctl(fd2, FS_IOC_SETFLAGS,
> &FS_NODUMP_FL):
> https://github.com/jirislaby/collected_sources/tree/master/ioctl_setflags
>
> dumps in 6.16:
> sf: ioctl: Operation not supported
>
> with the above patch:
> sf: ioctl: Inappropriate ioctl for device
>
> Is this expected?

No, that's a bug and a clear userspace regression so we need to fix it. I
think we need to revert this commit and instead convert ENOIOCTLCMD from
vfs_fileattr_get/set() to EOPNOTSUPP in appropriate places. Andrey?

Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR