linux-kernel - Re: [PATCH v5 0/9] ovl: Enable support for casefold layers

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Message-ID: <CAOQ4uxiOYFf_qUZAwCZ2DO0qemUdAbOWyUD2+oqewVPGn2+0cw@mail.gmail.com>
Date: Fri, 22 Aug 2025 19:21:36 +0200
From: Amir Goldstein <amir73il@...il.com>
To: André Almeida <andrealmeid@...lia.com>
Cc: Miklos Szeredi <miklos@...redi.hu>, Theodore Tso <tytso@....edu>, linux-unionfs@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, 
	Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, Jan Kara <jack@...e.cz>, 
	kernel-dev@...lia.com, Gabriel Krisman Bertazi <krisman@...nel.org>
Subject: Re: [PATCH v5 0/9] ovl: Enable support for casefold layers

On Fri, Aug 22, 2025 at 4:16 PM André Almeida <andrealmeid@...lia.com> wrote:
>
> Em 17/08/2025 12:03, Amir Goldstein escreveu:
> > On Fri, Aug 15, 2025 at 3:50 PM Amir Goldstein <amir73il@...il.com> wrote:
> >>
> >> On Fri, Aug 15, 2025 at 3:34 PM André Almeida <andrealmeid@...lia.com> wrote:
> >>>
> >>> Hi Amir,
> >>>
> >>> On 8/14/25 21:06, Amir Goldstein wrote:
> >>>> On Thu, Aug 14, 2025 at 7:30 PM André Almeida <andrealmeid@...lia.com> wrote:
> >>>>> Em 14/08/2025 14:22, André Almeida escreveu:
> >>>>>> Hi all,
> >>>>>>
> >>>>>> We would like to support the usage of casefold layers with overlayfs to
> >>>>>> be used with container tools. This use case requires a simple setup,
> >>>>>> where every layer will have the same encoding setting (i.e. Unicode
> >>>>>> version and flags), using one upper and one lower layer.
> >>>>>>
> >>>>> Amir,
> >>>>>
> >>>>> I tried to run your xfstest for casefolded ovl[1] but I can see that it
> >>>>> still requires some work. I tried to fix some of the TODO's but I didn't
> >>>>> managed to mkfs the base fs with casefold enabled...
> >>>> When you write mkfs the base fs, I suspect that you are running
> >>>> check -overlay or something.
> >>>>
> >>>> This is not how this test should be run.
> >>>> It should run as a normal test on ext4 or any other fs  that supports casefold.
> >>>>
> >>>> When you run check -g casefold, the generic test generic/556 will
> >>>> be run if the test fs supports casefold (e.g. ext4).
> >>>>
> >>>> The new added test belongs to the same group and should run
> >>>> if you run check -g casefold if the test fs supports casefold (e.g. ext4).
> >>>>
> >>> I see, I used `check -overlay` indeed, thanks!
> >>>
> >>
> >> Yeh that's a bit confusing I'll admit.
> >> It's an overlayfs test that "does not run on overlayfs"
> >> but requires extra overlayfs:
> >>
> >> _exclude_fs overlay
> >> _require_extra_fs overlay
> >>
> >> Because it does the overlayfs mount itself.
> >> That's the easiest way to test features (e.g. casefold) in basefs
> >>
> >
> > I tried to run the new test, which is able to mount an overlayfs
> > with layers with disabled casefolding with kernel 6.17-rc1.
> >
> > It does not even succeed in passing this simple test with
> > your patches, so something is clearly off.
>
> Apart from the other changes I had done for v6, I also had to change the
> test itself. The directories need to be empty to set the +F attribute,
> so I had to do this change:

Nice, so I suppose this test is passing with v6. I will try it.
Can you help to complete the TODO:

# TODO: test non-casefold subdir and casefold disabled after mount
The test now ends with the ofs->casefold == true mount,
but we need to test the error conditions same as the test cases
for ofs->casefold == false:

1. Casefold disabled after mount
2. Casefold disabled lower subdir

Those test cases are designed to trigger the "wrong parent casefold"
and "wrong child casefold" lookup warnings.

If you have an idea how to trigger the "wrong inherited casefold"
warning that would be nice.

Technically, test can delete the whiteout file inside $workdir/work
and remove casefold from $workdir/work and then trigger a copy up.
It may work. I am not sure if deleting the whietout file from work dir
is going to break something though.

Thanks,
Amir.