linux-ext4 - Re: [PATCH -RFC] ext4: add feature file to advertise that ext4 supports idmapped mounts

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Date:   Thu, 15 Apr 2021 07:54:08 +0200
From:   Christoph Hellwig <hch@....de>
To:     Theodore Ts'o <tytso@....edu>
Cc:     Christian Brauner <christian.brauner@...ntu.com>,
        Eryu Guan <guan@...u.me>,
        Christian Brauner <brauner@...nel.org>,
        fstests@...r.kernel.org, Christoph Hellwig <hch@....de>,
        linux-ext4@...r.kernel.org, "Darrick J . Wong" <djwong@...nel.org>,
        David Howells <dhowells@...hat.com>,
        Amir Goldstein <amir73il@...il.com>
Subject: Re: [PATCH -RFC] ext4: add feature file to advertise that ext4
 supports idmapped mounts

On Wed, Apr 14, 2021 at 04:47:10PM -0400, Theodore Ts'o wrote:
> On Mon, Apr 12, 2021 at 06:41:20PM -0400, Theodore Ts'o wrote:
> > In the ideal world, if the kernel wasn't compiled with the necessary
> > CONFIG options enabled, it's desirable of the test can detect that
> > fact and skip running the test instead failing and forcing the person
> > running the test to try to figure out whether this is a legitmate file
> > system bug or a just a test setup bug.
> 
> So it would make it easier for me to manage running xfstests on ext4
> if I had added something like this to ext4 and sent it to Linus before
> v5.12 is released.  What do folks think?

Completely stupid.  This is a VFS-level feature and we need to have
proper VFS-level testing (which we have through creating a mount
with the option), not fs-specific band aids.