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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: George Spelvin <linux@horizon.com>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: Update of file offset on write() etc. is non-atomic with I/O
Date: Mon, 3 Mar 2014 13:52:13 -0800	[thread overview]
Message-ID: <CA+55aFwdEbMMTPyCEKop0Fukhxi90OCdvDieX7iB-dX9Ziovdg@mail.gmail.com> (raw)
In-Reply-To: <20140303212642.GJ18016@ZenIV.linux.org.uk>

On Mon, Mar 3, 2014 at 1:26 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> On Mon, Mar 03, 2014 at 04:03:59PM -0500, George Spelvin wrote:
>>
>> (If you want to use bits, why not use the two lsbits of the file pointer
>> for the purpose?  That would save a lot of space.)
>
> Most of the cases have it kept separately in registers, actually - there's
> a reason why fdget() and friends are inlined.

Yes. And bit test and set ops on registers are actually cheaper than
playing around with bytes.

That said, the "fget_light()" interface sucks - exactly because it
doesn't do the "return structure in two registers" thing. We should
get rid of it - there's just one remaining user in networking code,
and it should be rewritten in terms of fdget().

That's a separate issue, though.

Oh, and George, your email setup is broken. Gmail thinks your emails
are spam. I'm not sure why (the usual spf problems do not apply), but
it's possibly because your name and email looks made up.

              Linus

  reply	other threads:[~2014-03-03 21:52 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-03-03 21:03 Update of file offset on write() etc. is non-atomic with I/O George Spelvin
2014-03-03 21:26 ` Al Viro
2014-03-03 21:52   ` Linus Torvalds [this message]
2014-03-03 22:01     ` Al Viro
2014-03-03 22:17       ` Linus Torvalds
2014-03-03 23:28         ` Al Viro
2014-03-03 23:34           ` Linus Torvalds
2014-03-03 23:42             ` Al Viro
2014-03-03 23:59               ` Linus Torvalds
2014-03-04  0:23                 ` Al Viro
2014-03-04  0:42                   ` Linus Torvalds
2014-03-04  1:05                     ` Al Viro
2014-03-04 20:00                       ` Al Viro
2014-03-04 21:17                         ` Linus Torvalds
2014-03-05  0:04                           ` Al Viro
2014-03-10 15:55                             ` Al Viro
2014-03-03 22:55     ` Linus Torvalds
2014-03-03 23:23       ` Linus Torvalds
2014-03-03 23:39         ` Al Viro
2014-03-03 23:54           ` Linus Torvalds
2014-03-03 23:54           ` Al Viro
2014-03-04 20:11           ` Cedric Blancher
2014-03-04  0:07     ` George Spelvin
2014-05-04  7:04 ` Michael Kerrisk
     [not found] <a8df285f-de7f-4a3a-9a19-e0ad07ab3a5c@blur>
2014-02-20 18:15 ` Zuckerman, Boris
2014-02-20 18:29   ` Al Viro
2014-02-21  6:01     ` Michael Kerrisk (man-pages)
2014-02-23  1:18       ` Kevin Easton
2014-02-23  7:38         ` Michael Kerrisk (man-pages)
  -- strict thread matches above, loose matches on Subject: below --
2014-02-17 15:41 Michael Kerrisk (man-pages)
2014-02-18 13:00 ` Michael Kerrisk
2014-02-20 17:14 ` Linus Torvalds
2014-03-03 17:36   ` Linus Torvalds
2014-03-03 21:45     ` Al Viro
2014-03-03 21:56       ` Linus Torvalds
2014-03-03 22:09         ` Al Viro
2014-03-03 22:20           ` Linus Torvalds
2014-03-03 22:01       ` Linus Torvalds
2014-03-03 22:10         ` Al Viro
2014-03-03 22:22           ` Linus Torvalds
2014-03-06 15:03     ` Michael Kerrisk (man-pages)
2014-03-07  3:38       ` Yongzhi Pan

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