From: Michael Kerrisk <mtk.manpages@gmail.com>
To: Andreas Dilger <adilger@dilger.ca>
Cc: Josef Bacik <josef@redhat.com>,
Eric Gouriou <egouriou@google.com>,
inux-man@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org,
Lucian Adrian Grijincu <lucian.grijincu@gmail.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Dave Chinner <dchinner@redhat.com>
Subject: Re: [PATCH] fallocate.2: add FALLOC_FL_PUNCH_HOLE flag definition
Date: Wed, 21 Sep 2011 07:49:33 +0200 [thread overview]
Message-ID: <CAKgNAkiGp7stGdxFPgH973gaEwSN28H0uEx4NkNq-ub96Xw=tA@mail.gmail.com> (raw)
In-Reply-To: <804BB4B7-E19F-41EE-81A3-25D4389B54B9@dilger.ca>
Hello Andreas,
On Wed, Sep 21, 2011 at 7:25 AM, Andreas Dilger <adilger@dilger.ca> wrote:
> On 2011-09-20, at 10:11 PM, Michael Kerrisk wrote:
>> Thanks for this patch. As noted in another mail, Lucian also sent a
>> patch for FALLOC_FL_PUNCH_HOLE, and I applied his patch first, and
>> then added some pieces from yours, as well as some of my own edits.
>>
>> However, the addition of a second class of operation to the man page
>> made it clear that some significant restructuring of the page is
>> required. So I substantially reworked the page, including the
>> preexisting material on the default "file allocation" operation (Dave
>> C please note).
>>
>> .TP
>> .B EINVAL
>> .I offset
>> was less than 0, or
>> .I len
>> was less than or equal to 0.
>
> I wasn't sure if this is a bug in the manpage or actually how it is done
> in the kernel, but it seems this is a kernel implementation issue...
>
> Does it make sense to return an error if len == 0? That just adds extra
> complexity on the part of the application, and doesn't reduce complexity
> in the kernel (whether the kernel checks for len == 0 and returns 0 or
> -EINVAL is not any different). read() and write() and malloc() all allow
> a length of zero to succeed, since applications may compute this length
> and sometimes it is zero.
Good point. I agree: for comfort of userspace application writers and
for consistency with related interfaces, len == 0 shouldn't be an
error.
Cheers,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
prev parent reply other threads:[~2011-09-21 5:49 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-11-15 17:07 [PATCH] fallocate.2: add FALLOC_FL_PUNCH_HOLE flag definition Josef Bacik
2011-09-19 5:08 ` Michael Kerrisk
2011-09-19 6:32 ` Dave Chinner
2011-09-21 4:11 ` Michael Kerrisk
2011-09-21 5:25 ` Andreas Dilger
2011-09-21 5:49 ` Michael Kerrisk [this message]
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