From: "Dmitry V. Levin" <ldv@altlinux.org>
To: Florian Weimer <fw@deneb.enyo.de>
Cc: linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
v9fs-developer@lists.sourceforge.net, libc-alpha@sourceware.org,
qemu-devel@nongnu.org, ericvh@gmail.com, rminnich@sandia.gov,
lucho@ionkov.net, hpa@zytor.com, arnd@arndb.de
Subject: Re: d_off field in struct dirent and 32-on-64 emulation
Date: Fri, 28 Dec 2018 05:23:39 +0300 [thread overview]
Message-ID: <20181228022338.GA27992@altlinux.org> (raw)
In-Reply-To: <87bm56vqg4.fsf@mid.deneb.enyo.de>
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On Thu, Dec 27, 2018 at 06:18:19PM +0100, Florian Weimer wrote:
> We have a bit of an interesting problem with respect to the d_off
> field in struct dirent.
>
> When running a 64-bit kernel on certain file systems, notably ext4,
> this field uses the full 63 bits even for small directories (strace -v
> output, wrapped here for readability):
>
> getdents(3, [
> {d_ino=1494304, d_off=3901177228673045825, d_reclen=40, d_name="authorized_keys", d_type=DT_REG},
> {d_ino=1494277, d_off=7491915799041650922, d_reclen=24, d_name=".", d_type=DT_DIR},
> {d_ino=1314655, d_off=9223372036854775807, d_reclen=24, d_name="..", d_type=DT_DIR}
> ], 32768) = 88
>
> When running in 32-bit compat mode, this value is somehow truncated to
> 31 bits, for both the getdents and the getdents64 (!) system call (at
> least on i386).
Why getdents64 system call is affected by this truncation,
isn't it a kernel bug that has to be fixed in the kernel instead?
--
ldv
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WARNING: multiple messages have this Message-ID (diff)
From: "Dmitry V. Levin" <ldv@altlinux.org>
To: Florian Weimer <fw@deneb.enyo.de>
Cc: linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org,
linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org,
v9fs-developer@lists.sourceforge.net, libc-alpha@sourceware.org,
qemu-devel@nongnu.org, ericvh@gmail.com, rminnich@sandia.gov,
lucho@ionkov.net, hpa@zytor.com, arnd@arndb.de
Subject: Re: [Qemu-devel] d_off field in struct dirent and 32-on-64 emulation
Date: Fri, 28 Dec 2018 05:23:39 +0300 [thread overview]
Message-ID: <20181228022338.GA27992@altlinux.org> (raw)
In-Reply-To: <87bm56vqg4.fsf@mid.deneb.enyo.de>
[-- Attachment #1: Type: text/plain, Size: 985 bytes --]
On Thu, Dec 27, 2018 at 06:18:19PM +0100, Florian Weimer wrote:
> We have a bit of an interesting problem with respect to the d_off
> field in struct dirent.
>
> When running a 64-bit kernel on certain file systems, notably ext4,
> this field uses the full 63 bits even for small directories (strace -v
> output, wrapped here for readability):
>
> getdents(3, [
> {d_ino=1494304, d_off=3901177228673045825, d_reclen=40, d_name="authorized_keys", d_type=DT_REG},
> {d_ino=1494277, d_off=7491915799041650922, d_reclen=24, d_name=".", d_type=DT_DIR},
> {d_ino=1314655, d_off=9223372036854775807, d_reclen=24, d_name="..", d_type=DT_DIR}
> ], 32768) = 88
>
> When running in 32-bit compat mode, this value is somehow truncated to
> 31 bits, for both the getdents and the getdents64 (!) system call (at
> least on i386).
Why getdents64 system call is affected by this truncation,
isn't it a kernel bug that has to be fixed in the kernel instead?
--
ldv
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next prev parent reply other threads:[~2018-12-28 2:23 UTC|newest]
Thread overview: 44+ 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 17:18 ` [Qemu-devel] " Florian Weimer
2018-12-27 17:38 ` Andy Lutomirski
2018-12-27 17:38 ` [Qemu-devel] " Andy Lutomirski
2018-12-27 17:56 ` Florian Weimer
2018-12-27 17:56 ` [Qemu-devel] " Florian Weimer
2018-12-27 17:41 ` 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
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 2:11 ` Theodore Y. Ts'o
2018-12-29 2:37 ` Dominique Martinet
2018-12-29 3:14 ` Theodore Y. Ts'o
2018-12-29 3:14 ` Theodore Y. Ts'o
2018-12-29 4:04 ` [V9fs-developer] " Dominique Martinet
2018-12-29 4:04 ` [Qemu-devel] [V9fs-developer] " Dominique Martinet
2018-12-27 17:58 ` Adhemerval Zanella
2018-12-27 17:58 ` [Qemu-devel] " Adhemerval Zanella
2018-12-27 18:09 ` Florian Weimer
2018-12-27 18:09 ` [Qemu-devel] " Florian Weimer
2018-12-28 11:53 ` Adhemerval Zanella
2018-12-28 11:53 ` [Qemu-devel] " Adhemerval Zanella
2018-12-28 11:56 ` Florian Weimer
2018-12-28 11:56 ` [Qemu-devel] " Florian Weimer
2018-12-28 12:01 ` Florian Weimer
2018-12-28 12:01 ` [Qemu-devel] " Florian Weimer
2018-12-28 12:21 ` Adhemerval Zanella
2018-12-28 12:21 ` [Qemu-devel] " Adhemerval Zanella
2018-12-31 17:03 ` Joseph Myers
2018-12-31 17:03 ` [Qemu-devel] " Joseph Myers
2018-12-31 17:03 ` Joseph Myers
2019-01-02 13:16 ` Adhemerval Zanella
2019-01-02 13:16 ` [Qemu-devel] " Adhemerval Zanella
2018-12-28 2:23 ` Dmitry V. Levin [this message]
2018-12-28 2:23 ` Dmitry V. Levin
2018-12-28 7:38 ` Florian Weimer
2018-12-28 7:38 ` [Qemu-devel] " Florian Weimer
2018-12-28 15:26 ` Andy Lutomirski
2018-12-28 15:26 ` [Qemu-devel] " Andy Lutomirski
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