From: Matthew Wilcox <willy@infradead.org>
To: Peter Maydell <peter.maydell@linaro.org>
Cc: Andreas Dilger <adilger@dilger.ca>,
Florian Weimer <fw@deneb.enyo.de>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
Linux API <linux-api@vger.kernel.org>,
Ext4 Developers List <linux-ext4@vger.kernel.org>,
Latchesar Ionkov <lucho@ionkov.net>,
libc-alpha@sourceware.org, Arnd Bergmann <arnd@arndb.de>,
Eric Van Hensbergen <ericvh@gmail.com>,
hpa@zytor.com,
lkml - Kernel Mailing List <linux-kernel@vger.kernel.org>,
QEMU Developers <qemu-devel@nongnu.org>,
rminnich@sandia.gov, v9fs-developer@lists.sourceforge.net
Subject: Re: [Qemu-devel] d_off field in struct dirent and 32-on-64 emulation
Date: Fri, 28 Dec 2018 17:54:54 -0800 [thread overview]
Message-ID: <20181229015453.GA6310@bombadil.infradead.org> (raw)
In-Reply-To: <CAFEAcA8Yq=CEyAUer1TcaSzuzcdNi3OUi4c67B6e+OkhmcKvbg@mail.gmail.com>
On Sat, Dec 29, 2018 at 12:12:27AM +0000, Peter Maydell wrote:
> On Fri, 28 Dec 2018 at 23:16, Andreas Dilger <adilger@dilger.ca> wrot
> > On Dec 28, 2018, at 4:18 AM, Peter Maydell <peter.maydell@linaro.org> wrote:
> > > The problem is that there is no 32-bit API in some cases
> > > (unless I have misunderstood the kernel code) -- not all
> > > host architectures implement compat syscalls or allow them
> > > to be called from 64-bit processes or implement all the older
> > > syscall variants that had smaller offets. If there was a guaranteed
> > > "this syscall always exists and always gives me 32-bit offsets"
> > > we could use it.
> >
> > The "32bitapi" mount option would use 32-bit hash for seekdir
> > and telldir, regardless of what kernel API was used. That would
> > just set the FMODE_32BITHASH flag in the file->f_mode for all files.
>
> A mount option wouldn't be much use to QEMU -- we can't tell
> our users how to mount their filesystems, which they're
> often doing lots of other things with besides running QEMU.
> (Otherwise we could just tell them "don't use ext4", which
> would also solve the problem :-)) We need something we can
> use at the individual-syscall level.
Could you use a prctl to set whether you were running in 32 or 64 bit
mode? Or do you change which kind of task you're emulating too often
to make this a good idea?
next prev parent reply other threads:[~2018-12-29 1:55 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-27 17:18 d_off field in struct dirent and 32-on-64 emulation Florian Weimer
2018-12-27 17:41 ` [Qemu-devel] " Peter Maydell
2018-12-28 0:23 ` Andreas Dilger
2018-12-28 11:18 ` Peter Maydell
2018-12-28 23:16 ` Andreas Dilger
2018-12-29 0:12 ` Peter Maydell
2018-12-29 1:54 ` Matthew Wilcox [this message]
2018-12-29 16:49 ` Andy Lutomirski
2018-12-30 13:59 ` Peter Maydell
2018-12-29 2:11 ` Theodore Y. Ts'o
2018-12-29 2:37 ` Dominique Martinet
2018-12-29 3:14 ` Theodore Y. Ts'o
2018-12-29 4:04 ` [V9fs-developer] " Dominique Martinet
[not found] ` <C65D3222-723F-4C0B-AF02-38488C302E84@amacapital.net>
2018-12-27 17:56 ` Florian Weimer
2018-12-27 17:58 ` Adhemerval Zanella
2018-12-27 18:09 ` Florian Weimer
2018-12-28 11:53 ` Adhemerval Zanella
2018-12-28 11:56 ` Florian Weimer
2018-12-28 12:01 ` Florian Weimer
2018-12-28 12:21 ` Adhemerval Zanella
2018-12-31 17:03 ` Joseph Myers
2019-01-02 13:16 ` Adhemerval Zanella
2018-12-28 2:23 ` Dmitry V. Levin
2018-12-28 7:38 ` Florian Weimer
2018-12-28 15:26 ` Andy Lutomirski
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