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

[Amir Goldstein]

On Tue, Jul 1, 2025 at 2:51 PM Jan Kara <jack@xxxxxxx> wrote:
>
> On Tue 01-07-25 08:05:45, Amir Goldstein wrote:
> > On Mon, Jun 30, 2025 at 6:20 PM Andrey Albershteyn <aalbersh@xxxxxxxxxx> 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@xxxxxxxxxx>
> ...
> > > --- 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.
From 85d097f639518670c57827513b02f497950071de Mon Sep 17 00:00:00 2001
From: Amir Goldstein <amir73il@xxxxxxxxx>
Date: Tue, 1 Jul 2025 16:06:44 +0200
Subject: [PATCH] fuse: return -EOPNOTSUPP from ->fileattr_[gs]et() instead of
 -ENOTTY

As part of changing calling convenstion of ->fileattr_[gs]et()
to return -EOPNOTSUPP and fix related overlayfs code.

Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxx>
---
 fs/fuse/ioctl.c        | 4 ++++
 fs/overlayfs/copy_up.c | 2 +-
 fs/overlayfs/inode.c   | 2 +-
 3 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/fuse/ioctl.c b/fs/fuse/ioctl.c
index 2d9abf48828f..f2692f7d5932 100644
--- a/fs/fuse/ioctl.c
+++ b/fs/fuse/ioctl.c
@@ -536,6 +536,8 @@ int fuse_fileattr_get(struct dentry *dentry, struct fileattr *fa)
 cleanup:
 	fuse_priv_ioctl_cleanup(inode, ff);
 
+	if (err == -ENOTTY)
+		err = -EOPNOTSUPP;
 	return err;
 }
 
@@ -572,5 +574,7 @@ int fuse_fileattr_set(struct mnt_idmap *idmap,
 cleanup:
 	fuse_priv_ioctl_cleanup(inode, ff);
 
+	if (err == -ENOTTY)
+		err = -EOPNOTSUPP;
 	return err;
 }
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index d7310fcf3888..2c646b7076d0 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -178,7 +178,7 @@ static int ovl_copy_fileattr(struct inode *inode, const struct path *old,
 	err = ovl_real_fileattr_get(old, &oldfa);
 	if (err) {
 		/* Ntfs-3g returns -EINVAL for "no fileattr support" */
-		if (err == -ENOTTY || err == -EINVAL)
+		if (err == -EOPNOTSUPP || err == -EINVAL)
 			return 0;
 		pr_warn("failed to retrieve lower fileattr (%pd2, err=%i)\n",
 			old->dentry, err);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 6f0e15f86c21..92754749f316 100644
--- 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;
 	return err;
 }
 
-- 
2.43.0