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From: Al Viro <viro@ZenIV.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
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 23:42:07 +0000	[thread overview]
Message-ID: <20140303234207.GQ18016@ZenIV.linux.org.uk> (raw)
In-Reply-To: <CA+55aFyEXgMh61P3cmjZzw3RxitiL0oymWSyUsiMp96iJ+98Og@mail.gmail.com>

On Mon, Mar 03, 2014 at 03:34:43PM -0800, Linus Torvalds wrote:
> On Mon, Mar 3, 2014 at 3:28 PM, Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> > Umm...   I would be very surprised if that worked well.  You have just
> > forced fdget() to comply to the ABI.  And unless that has such structs
> > returned in register pairs, there's no way for compiler to do about
> > that.
> 
> Register pairs are very much a common return model.
> 
> And we've relied on that before. For example, 64-bit pte's on x86-32
> very much does that whole thing with the "pte_t" union.
> 
> So you can now commence being surprised.
> 
> (Side note: I think sparc or something doesn't support it, and may
> return things in memory. I can't really seem to find it in myself to
> care)

sparc64 actually does support that.  So does amd64, and, with explicit
flag, i386.  No other more or less general purpose architecture does.

Not ppc.  Not mips.  Not arm.  I think that some of those are worth
caring about...

  reply	other threads:[~2014-03-03 23:42 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
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 [this message]
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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