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

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Message-ID: <CAOQ4uxg0-ZJYDMfMLNVm=YfA9CdjY2WaaXYdv+i8nWNgqPgpuw@mail.gmail.com>
Date: Tue, 27 May 2025 10:57:05 +0200
From: Amir Goldstein <amir73il@...il.com>
To: Kent Overstreet <kent.overstreet@...ux.dev>
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 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"

> 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?

> ls: cannot access '/mnt/merged/dir/casefold': No such file or directory
> umount: /mnt: target is busy.

Not sure about that, but could be due to the aforementioned stay mount.

>
> https://evilpiepirate.org/git/ktest.git/commit/?id=47d1f2a04d79bc4cbc843f81e71eb7d821fb8384

Please fix the test and report Tested-by if all works as expected.
Please include dmesg so we can see the new warnings.

Thanks,
Amir.