linux-ext4 - Re: [PATCH] fcntl: Add 32bit filesystem mode

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Date:   Mon, 20 Apr 2020 15:16:14 +0100
From:   Peter Maydell <peter.maydell@...aro.org>
To:     Florian Weimer <fw@...eb.enyo.de>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        "Theodore Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Ext4 Developers List <linux-ext4@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        Linux API <linux-api@...r.kernel.org>,
        QEMU Developers <qemu-devel@...gnu.org>,
        Andy Lutomirski <luto@...nel.org>
Subject: Re: [PATCH] fcntl: Add 32bit filesystem mode

On Mon, 20 Apr 2020 at 12:38, Peter Maydell <peter.maydell@...aro.org> wrote:
> Whoops, good point. I was testing this via lkvm, so it's
> actually using a 9p filesystem... I'll see if I can figure
> out how to test with an ext3 fs, which I think is the one
> we most care about.

After some effort wrestling with kvmtool (which assumes that
if you provide it a disk image then you must have wanted that
to be your rootfs and can only be persuaded otherwise via
some undocumented and arcane options), I did a test with ext4:

bash-4.4# /qemu-no-fix /readdir-bug
dir=0x76108
readdir(dir)=(nil)
errno=75: Value too large for defined data type
bash-4.4# /qemu-fixed /readdir-bug
dir=0x76108
readdir(dir)=0x76128
errno=0: Success

(where the host kernel has Linus' fcntl patch, qemu-no-fix
is a current-git-master QEMU and qemu-fixed is one with
the patch in my previous email).

So for Linus' patch:

Tested-by: Peter Maydell <peter.maydell@...aro.org>

If 9pfs could be persuaded to honour the fcntl flag too
that would be really nice.

thanks
-- PMM