From: Neil Brown <neilb@suse.de>
To: Christoph Hellwig <hch@infradead.org>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
viro@zeniv.linux.org.uk, adilger@sun.com, corbet@lwn.net,
npiggin@suse.de, hooanon05@yahoo.co.jp, bfields@fieldses.org,
miklos@szeredi.hu, linux-fsdevel@vger.kernel.org,
sfrench@us.ibm.com, philippe.deniel@CEA.FR,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH -V18 05/13] vfs: Support null pathname in readlink
Date: Fri, 20 Aug 2010 20:04:01 +1000 [thread overview]
Message-ID: <20100820200401.1b824be5@notabene> (raw)
In-Reply-To: <20100820083213.GB10039@infradead.org>
On Fri, 20 Aug 2010 04:32:13 -0400
Christoph Hellwig <hch@infradead.org> wrote:
> Changing the interfaces of existing system calls to accept a NULL name
> which previously wasn't acceptable is not valid. Even for new system
> calls I think it's a bad idea. utimensat already has the most ugly
> code of all fs related system calls because of that.
Again, you have made an assertion without justifying it.
I disagree, I think it is perfectly valid.
The function would still return an error in every case that it previously
returned an error, because in every previous case the fd would not have
referred to a symlink so the new version will have nothing to perform a
readlink on when NULL is passed. The error would probably be EINVAL rather
than EFAULT but even that difference could be avoided if it was really
important (I doubt it is).
You only get different behaviour if the path name is NULL and the fd refers
to a symlink. This is a completely new situation for which there is no
precedent for how the syscall should behave. We are free to create whatever
behaviour is most consistent. I believe the proposed behaviour is the
correct one.
The code may be ugly, but I'm sure it can be tidied up, particularly if
several system-calls adopted the same calling convention.
NeilBrown
next prev parent reply other threads:[~2010-08-20 10:04 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-20 1:51 [PATCH -V18 0/13] Generic name to handle and open by handle syscalls Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 01/13] exportfs: Return the minimum required handle size Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 02/13] vfs: Add name to file handle conversion support Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 03/13] vfs: Add open by file handle support Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 04/13] vfs: Allow handle based open on symlinks Aneesh Kumar K.V
2010-08-20 2:13 ` Aneesh Kumar K. V
2010-08-20 6:53 ` Aneesh Kumar K. V
2010-08-20 8:30 ` Christoph Hellwig
2010-08-20 9:53 ` Neil Brown
2010-08-20 11:51 ` Al Viro
2010-08-21 0:09 ` Neil Brown
2010-08-21 7:13 ` Andreas Dilger
2010-08-21 9:32 ` Aneesh Kumar K. V
2010-08-22 23:06 ` Neil Brown
2010-08-23 1:24 ` Aneesh Kumar K. V
2010-08-23 1:52 ` Neil Brown
2010-08-24 10:40 ` Aneesh Kumar K. V
2010-08-23 2:49 ` Aneesh Kumar K. V
2010-08-25 2:06 ` Neil Brown
2010-08-24 9:41 ` Bastien ROUCARIES
2010-08-25 2:04 ` Neil Brown
2010-08-25 9:13 ` Bastien ROUCARIES
2010-08-21 8:30 ` Nick Piggin
2010-08-21 9:42 ` Aneesh Kumar K. V
2010-08-22 2:02 ` Aneesh Kumar K. V
2010-08-24 7:21 ` Nick Piggin
2010-08-24 10:34 ` Aneesh Kumar K. V
2010-08-24 13:19 ` J. Bruce Fields
2010-08-22 23:17 ` Neil Brown
2010-08-24 7:29 ` Nick Piggin
2010-08-21 9:31 ` Aneesh Kumar K. V
2010-08-20 13:25 ` Peter Zijlstra
2010-08-20 23:47 ` Neil Brown
2010-08-20 14:38 ` Aneesh Kumar K. V
2010-08-20 1:51 ` [PATCH -V18 05/13] vfs: Support null pathname in readlink Aneesh Kumar K.V
2010-08-20 8:32 ` Christoph Hellwig
2010-08-20 10:04 ` Neil Brown [this message]
2010-08-20 14:43 ` Aneesh Kumar K. V
2010-08-20 1:51 ` [PATCH -V18 06/13] vfs: Support null pathname in faccessat Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 07/13] vfs: Support null pathname in linkat Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 08/13] x86: Add new syscalls for x86_32 Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 09/13] x86: Add new syscalls for x86_64 Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 10/13] unistd.h: Add new syscalls numbers to asm-generic Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 11/13] vfs: Export file system uuid via /proc/<pid>/mountinfo Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 12/13] ext3: Copy fs UUID to superblock Aneesh Kumar K.V
2010-08-20 1:51 ` [PATCH -V18 13/13] ext4: " Aneesh Kumar K.V
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