linux-kernel - Re: [PATCH 0/6] overlayfs + casefolding

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Message-ID: <oa6rl677vm3x4gl3jym4bh6ul56d5d6olrkylqpjnsnjbjxf5p@4pxem7egakqe>
Date: Tue, 27 May 2025 14:07:55 -0400
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Amir Goldstein <amir73il@...il.com>
Cc: linux-fsdevel@...r.kernel.org, linux-bcachefs@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-unionfs@...r.kernel.org, 
	Miklos Szeredi <miklos@...redi.hu>, Alexander Viro <viro@...iv.linux.org.uk>, 
	Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>
Subject: Re: [PATCH 0/6] overlayfs + casefolding

On Tue, May 27, 2025 at 10:57:05AM +0200, Amir Goldstein wrote:
> On Sun, May 25, 2025 at 8:27 PM Kent Overstreet
> <kent.overstreet@...ux.dev> wrote:
> >
> > On Sat, May 24, 2025 at 03:01:44PM +0200, Amir Goldstein wrote:
> > > On Fri, May 23, 2025 at 11:10 PM Kent Overstreet
> > > <kent.overstreet@...ux.dev> wrote:
> > > >
> > > > On Fri, May 23, 2025 at 10:30:16PM +0200, Amir Goldstein wrote:
> > > >
> > > > That makes fstests generic/631 pass.
> > >
> > > Yes, that is not very surprising.
> > > I meant if you could help test that:
> > >
> > > 1. mounting case folder upperdir/lowerdir fails
> > > 2. lookup a case folder subdir fails
> > > 3. lookup in a dir that was empty and became case folder while ovl was
> > > mounted fails
> > >
> > > For me, I do not have any setup with case folding subtrees
> > > so testing those use cases would take me time and
> > > I think that you must have tested all those scenarios with your patch set?
> > > and maybe already have some fstests for them?
> >
> > Unmount fauls after I test an overlayfs with a casefold subdir:
> >
> > Testing an overlayfs on a casefold fs with non-casefolded dirs
> > Test using casefolded dir - should fail
> > overlayfs: failed to resolve '/mnt/casefold': -2
> > mount: /mnt/merged: special device overlay does not exist.
> >        dmesg(1) may have more information after failed mount system call.
> 
> Test is using the wrong path:
> 
> 
> +    echo "Test using casefolded dir - should fail"
> +    ! mount -t overlay -o
> lowerdir=/mnt/lower,upperdir=/mnt/upper,workdir=/mnt/work overlay
> /mnt/merged
> +    ! mount -t overlay -o
> lowerdir=/mnt/casefold,upperdir=/mnt/casefold,workdir=/mnt/work
> overlay /mnt/merged
> 
> There is no "/mnt/casefold"

*nod*

> > Test using a dir with a casefold subdir - should mount
> > overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
> > overlayfs: workdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
> 
> Those warnings are because you have a stray mount command above:
> +    echo "Test using casefolded dir - should fail"
> +    ! mount -t overlay -o
> lowerdir=/mnt/lower,upperdir=/mnt/upper,workdir=/mnt/work overlay
> /mnt/merged
> 
> So a mount already exists. leftover?

*snort* - -ENOCAFFEINE, I presume.

The new warning doesn't fire after the last mount.

ls: cannot access '/mnt/merged/casefold': Object is remote

But nothing in dmesg. Adding a printk to ovl_mount_dir_check() shows
that it's never called for the 'ls /mnt/merged/casefold' call.