linux-kernel - Re: [PATCH v6 4/6] fs: make vfs_fileattr

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Message-ID: <jp3vopwtpik7bj77aejuknaziecuml6x2l2dr3oe2xoats6tls@yskzvehakmkv>
Date: Mon, 6 Oct 2025 17:39:46 +0200
From: Jan Kara <jack@...e.cz>
To: Jiri Slaby <jirislaby@...nel.org>
Cc: Andrey Albershteyn <aalbersh@...hat.com>, 
	Amir Goldstein <amir73il@...il.com>, Arnd Bergmann <arnd@...db.de>, 
	Casey Schaufler <casey@...aufler-ca.com>, Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
	Pali Rohár <pali@...nel.org>, Paul Moore <paul@...l-moore.com>, linux-api@...r.kernel.org, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org, 
	selinux@...r.kernel.org, Andrey Albershteyn <aalbersh@...nel.org>
Subject: Re: [PATCH v6 4/6] fs: make vfs_fileattr_[get|set] return -EOPNOSUPP

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@...nel.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@...e.com>
SUSE Labs, CR