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

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Message-ID: <CAOQ4uxgfKcey301gZRBHf=2YfWmNg5zkj7Bh+DwVwpztMR1uOg@mail.gmail.com>
Date: Fri, 15 Aug 2025 15:50:09 +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 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

You should also run check -overlay -g overlay/quick,
but that's only to verify your patches did not regress any
non-casefolded test.


> >> but we might as
> >> well discuss this in a dedicated xfstest email thread if you want to
> >> send a RFC for the test.
> >>
> >> [1]
> >> https://github.com/amir73il/xfstests/commit/03b3facf60e14cab9fc563ad54893563b4cb18e4
> >>
> >>
> > Can you point me to a branch with your ovl patches, so I can pull it
> > for testing?
>
> You can find my branch here, based on top of vfs.all:
> https://gitlab.freedesktop.org/andrealmeid/linux/-/commits/ovl_casefold
>
> I fixed the following minor issues:
>
> - 4/9: dropped the `kfree(cf_name);` - 6/9: fixed kernel robot warning
> `unused variable 'ofs'` - 8/9: change pr_warn_ratelimited() string
>

Cool. Let me know when the test is passing (regardless of TODOs).
I'll try to test it next week.

Thanks,
Amir.