linux-kernel - Re: [PATCH] fat: ignore .. subdir and always add a link to dirs

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Message-ID: <874jdzpov7.fsf@mail.parknet.co.jp>
Date: Fri, 23 Feb 2024 17:27:08 +0900
From: OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To: Thadeu Lima de Souza Cascardo <cascardo@...lia.com>
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        Gwendal
 Grignou <gwendal@...omium.org>, dlunev@...omium.org
Subject: Re: [PATCH] fat: ignore .. subdir and always add a link to dirs

Thadeu Lima de Souza Cascardo <cascardo@...lia.com> writes:

> On Fri, Feb 23, 2024 at 10:52:12AM +0900, OGAWA Hirofumi wrote:
>> Thadeu Lima de Souza Cascardo <cascardo@...lia.com> writes:
>> 
>> > The tools used for creating images for the Lego Mindstrom EV3 are not
>> > adding '.' and '..' entry in the 'Projects' directory.
>> >
>> > Without this fix, the kernel can not fill the inode structure for
>> > 'Projects' directory.
>> >
>> > See https://github.com/microsoft/pxt-ev3/issues/980
>> > And https://github.com/microsoft/uf2-linux/issues/6
>> >
>> > When counting the number of subdirs, ignore .. subdir and add one when
>> > setting the initial link count for directories. This way, when .. is
>> > present, it is still accounted for, and when neither . or .. are present, a
>> > single link is still done, as it should, since this link would be the one
>> > from the parent directory.
>> >
>> > With this fix applied, we can mount an image with such empty directories,
>> > access them, create subdirectories and remove them.
>> 
>> This looks like the bug of those tools, isn't it?
>> 
>> Thanks.
>> -- 
>> OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
>
> Which they refused to fix, arguing that there are already filesystems out there
> in the world like that. Also, there is argument that this works on Windows,
> though I haven't been able to test this.
>
> https://github.com/microsoft/pxt-ev3/issues/980
> https://github.com/microsoft/uf2-linux/issues/6

OK.

If you want to add the workaround for this, it must emulate the correct
format. I.e. sane link count even if without "."/"..". And furthermore
it works for any operations.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>