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

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Message-ID: <ozxxm5fglq5kuoiteqr34wghaqhxgue4kshz2jnnk7oopmhxk6@a2lo6weivsyz>
Date: Tue, 1 Jul 2025 14:51:51 +0200
From: Jan Kara <jack@...e.cz>
To: Amir Goldstein <amir73il@...il.com>
Cc: Andrey Albershteyn <aalbersh@...hat.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 Tue 01-07-25 08:05:45, Amir Goldstein wrote:
> On Mon, Jun 30, 2025 at 6:20 PM Andrey Albershteyn <aalbersh@...hat.com> 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>
...
> > --- a/fs/overlayfs/inode.c
> > +++ b/fs/overlayfs/inode.c
> > @@ -721,7 +721,7 @@ int ovl_real_fileattr_get(const struct path *realpath, struct fileattr *fa)
> >                 return err;
> >
> >         err = vfs_fileattr_get(realpath->dentry, fa);
> > -       if (err == -ENOIOCTLCMD)
> > +       if (err == -EOPNOTSUPP)
> >                 err = -ENOTTY;
> >         return err;
> >  }
> 
> That's the wrong way, because it hides the desired -EOPNOTSUPP
> return code from ovl_fileattr_get().
> 
> The conversion to -ENOTTY was done for
> 5b0a414d06c3 ("ovl: fix filattr copy-up failure"),
> so please do this instead:
> 
> --- a/fs/overlayfs/inode.c
> +++ b/fs/overlayfs/inode.c
> @@ -722,7 +722,7 @@ int ovl_real_fileattr_get(const struct path
> *realpath, struct fileattr *fa)
> 
>         err = vfs_fileattr_get(realpath->dentry, fa);
>         if (err == -ENOIOCTLCMD)
> -               err = -ENOTTY;
> +               err = -EOPNOTSUPP;

Is this really needed? AFAICS nobody returns ENOIOCTLCMD after this
patch...

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