linux-ext4 - Re: [PATCH] ext4: Give 32bit personalities 32bit hashes

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Date:   Tue, 24 Mar 2020 22:17:46 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     Peter Maydell <peter.maydell@...aro.org>,
        "Suzuki K. Poulose" <suzuki.poulose@....com>,
        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>,
        Florian Weimer <fw@...eb.enyo.de>,
        Andy Lutomirski <luto@...nel.org>,
        stable <stable@...r.kernel.org>
Subject: Re: [PATCH] ext4: Give 32bit personalities 32bit hashes

On Tue, Mar 24, 2020 at 7:48 PM Theodore Y. Ts'o <tytso@....edu> wrote:
> On Tue, Mar 24, 2020 at 09:29:58AM +0000, Peter Maydell wrote:
> >
> > On the contrary, that would be a much better interface for QEMU.
> > We always know when we're doing an open-syscall on behalf
> > of the guest, and it would be trivial to make the fcntl() call then.
> > That would ensure that we don't accidentally get the
> > '32-bit semantics' on file descriptors QEMU opens for its own
> > purposes, and wouldn't leave us open to the risk in future that
> > setting the PER_LINUX32 flag for all of QEMU causes
> > unexpected extra behaviour in future kernels that would be correct
> > for the guest binary but wrong/broken for QEMU's own internals.
>
> If using a flag set by fcntl is better for qemu, then by all means
> let's go with that instead of using a personality flag/number.
>
> Linus, do you have what you need to do a respin of the patch?

Absolutely, I'm a bit occupied this week but I will try to get to it
early next week!

Thanks a lot for the directions here, it's highly valuable.

Yours,
Linus Walleij