linux-kernel - Re: Update of file offset on write() etc. is non-atomic with I/O

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Date:	Mon, 3 Mar 2014 15:34:43 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Al Viro <viro@...iv.linux.org.uk>
Cc:	George Spelvin <linux@...izon.com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Update of file offset on write() etc. is non-atomic with I/O

On Mon, Mar 3, 2014 at 3:28 PM, Al Viro <viro@...iv.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)

              Linus
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