linux-kernel - Re: [Patch 1/2] ia32: use generic sys

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Message-ID: <20090918094642.GA26833@elte.hu>
Date:	Fri, 18 Sep 2009 11:46:42 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Amerigo Wang <amwang@...hat.com>, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [Patch 1/2] ia32: use generic sys_pipe()


* Al Viro <viro@...IV.linux.org.uk> wrote:

> On Tue, Aug 04, 2009 at 02:24:32PM +0200, Ingo Molnar wrote:
> 
> > Please _ALWAYS_ mention the change in behavior in the changelog, 
> > just in case someone ends up bisecting it. I only found out when i 
> > reviewed the two syscalls out of caution.
> > 
> > The syscall you remove kept stale fd's around in case of -EFAULT 
> > from copy_to_user(). The generic version does an explicit close of 
> > those files:
> > 
> >                         sys_close(fd[0]);
> >                         sys_close(fd[1]);
> >                         error = -EFAULT;
> 
> > The generic version looks like the better choice to me but this 
> > difference should be mentioned in the changelog nevertheless, just 
> > in case some buggy app runs into this issue.
> 
> It's not a matter of QOI, actually - sys32_pipe() is supposed to do 
> what sys_pipe() would do on i386 host.  So any difference in handling 
> of an error case is simply wrong.
> 
> Whether we want those sys_close() in sys_pipe() or not is a separate 
> question, but we definitely want the same behaviour when 32bit process 
> is run natively and when it's run on amd64.  So sys32_pipe() has no 
> business existing at all.

I generally agree except the notion that we 'must' do this change.

This is a (small) past ABI sin of ours and we have to live with the 
consequences without breaking apps. We didnt break any it appears so 
it's all good.

	Ingo
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