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From: Peter Maydell <peter.maydell@linaro.org>
To: Andreas Dilger <adilger@dilger.ca>
Cc: Florian Weimer <fw@deneb.enyo.de>,
	Linus Walleij <linus.walleij@linaro.org>,
	"Theodore Ts'o" <tytso@mit.edu>,
	Ext4 Developers List <linux-ext4@vger.kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux API <linux-api@vger.kernel.org>,
	QEMU Developers <qemu-devel@nongnu.org>,
	Andy Lutomirski <luto@kernel.org>
Subject: Re: [PATCH] fcntl: Add 32bit filesystem mode
Date: Tue, 21 Apr 2020 14:02:39 +0100	[thread overview]
Message-ID: <CAFEAcA9kktJd8EJ1VCp4a0XikPS9mxmag2GFv0NvwobubQLABw@mail.gmail.com> (raw)
In-Reply-To: <FA73C1DA-B07F-43D5-A9A8-FBC0BAE400CA@dilger.ca>

On Tue, 21 Apr 2020 at 00:51, Andreas Dilger <adilger@dilger.ca> wrote:
> Another question I had here is whether the filesystem needs to provide
> 32-bit values for other syscalls, such as stat() and statfs()?  For
> ext4, stat() is not going to return a 64-bit inode number, but other
> filesystems might (e.g. Lustre has a mode to do this).  Similarly,
> should statfs() scale up f_bsize until it can return a 32-bit f_blocks
> value?  We also had to do this ages ago for Lustre when 32-bit clients
> couldn't handle > 16TB filesystems, but that is a single disk today.
>
> Should that be added into F_SET_FILE_32BIT_FS also?

Interesting question. The directory-offset is the thing that's
got peoples' attention because it's what has actually been hit
in real-world situations, but other syscalls have the same
potential problem too. The closest I can think of to a 'general
rule' (in terms of what QEMU would like) would be "behave the
same way you would for a compat32 syscall if you had one, or
how you would behave on an actual 32-bit host".

thanks
-- PMM

WARNING: multiple messages have this Message-ID (diff)
From: Peter Maydell <peter.maydell@linaro.org>
To: Andreas Dilger <adilger@dilger.ca>
Cc: Theodore Ts'o <tytso@mit.edu>,
	Linux API <linux-api@vger.kernel.org>,
	Linus Walleij <linus.walleij@linaro.org>,
	QEMU Developers <qemu-devel@nongnu.org>,
	Florian Weimer <fw@deneb.enyo.de>,
	Andy Lutomirski <luto@kernel.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Ext4 Developers List <linux-ext4@vger.kernel.org>
Subject: Re: [PATCH] fcntl: Add 32bit filesystem mode
Date: Tue, 21 Apr 2020 14:02:39 +0100	[thread overview]
Message-ID: <CAFEAcA9kktJd8EJ1VCp4a0XikPS9mxmag2GFv0NvwobubQLABw@mail.gmail.com> (raw)
In-Reply-To: <FA73C1DA-B07F-43D5-A9A8-FBC0BAE400CA@dilger.ca>

On Tue, 21 Apr 2020 at 00:51, Andreas Dilger <adilger@dilger.ca> wrote:
> Another question I had here is whether the filesystem needs to provide
> 32-bit values for other syscalls, such as stat() and statfs()?  For
> ext4, stat() is not going to return a 64-bit inode number, but other
> filesystems might (e.g. Lustre has a mode to do this).  Similarly,
> should statfs() scale up f_bsize until it can return a 32-bit f_blocks
> value?  We also had to do this ages ago for Lustre when 32-bit clients
> couldn't handle > 16TB filesystems, but that is a single disk today.
>
> Should that be added into F_SET_FILE_32BIT_FS also?

Interesting question. The directory-offset is the thing that's
got peoples' attention because it's what has actually been hit
in real-world situations, but other syscalls have the same
potential problem too. The closest I can think of to a 'general
rule' (in terms of what QEMU would like) would be "behave the
same way you would for a compat32 syscall if you had one, or
how you would behave on an actual 32-bit host".

thanks
-- PMM


  reply	other threads:[~2020-04-21 13:02 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-03-31 13:35 [PATCH] fcntl: Add 32bit filesystem mode Linus Walleij
2020-03-31 13:35 ` Linus Walleij
2020-04-20 11:19 ` Peter Maydell
2020-04-20 11:19   ` Peter Maydell
2020-04-20 11:23   ` Florian Weimer
2020-04-20 11:23     ` Florian Weimer
2020-04-20 11:38     ` Peter Maydell
2020-04-20 11:38       ` Peter Maydell
2020-04-20 14:16       ` Peter Maydell
2020-04-20 14:16         ` Peter Maydell
2020-04-20 23:51       ` Andreas Dilger
2020-04-20 23:51         ` Andreas Dilger
2020-04-21 13:02         ` Peter Maydell [this message]
2020-04-21 13:02           ` Peter Maydell
2020-04-20 15:13 ` Theodore Y. Ts'o
2020-04-20 15:13   ` Theodore Y. Ts'o
2020-04-20 15:23   ` Eric Blake
2020-04-20 15:29     ` Peter Maydell
2020-04-20 15:29       ` Peter Maydell
2020-04-20 17:01       ` Theodore Y. Ts'o
2020-04-20 17:01         ` Theodore Y. Ts'o

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