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

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Message-ID: <CAOQ4uxj22du-+8vmkSq3V8C22y7hEGhOHqryAck9yuB1V3spow@mail.gmail.com>
Date: Tue, 1 Jul 2025 16:16:13 +0200
From: Amir Goldstein <amir73il@...il.com>
To: Jan Kara <jack@...e.cz>
Cc: Andrey Albershteyn <aalbersh@...hat.com>, Arnd Bergmann <arnd@...db.de>, 
	Casey Schaufler <casey@...aufler-ca.com>, Christian Brauner <brauner@...nel.org>, 
	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, Jul 1, 2025 at 2:51 PM Jan Kara <jack@...e.cz> wrote:
>
> 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...

you are right it is not needed

Attaching the patch with missing bits of fuse and overlayfs to make this
conversion complete.

Christian, please squash my patch
and afterward make sure there is no conversion remaining in
ovl_real_fileattr_get() as well as in ecryptfs_fileattr_get()
Both those helpers should return the value they
got from vfs_fileattr_get() as is.

Thanks,
Amir.

View attachment "0001-fuse-return-EOPNOTSUPP-from-fileattr_-gs-et-instead-.patch" of type "text/x-patch" (2017 bytes)