linux-kernel - Re: splice vs O

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Message-ID: <alpine.LFD.2.00.0810091218300.3210@nehalem.linux-foundation.org>
Date:	Thu, 9 Oct 2008 12:22:23 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Miklos Szeredi <miklos@...redi.hu>
cc:	jens.axboe@...cle.com, linux-kernel@...r.kernel.org,
	linux-fsdevel@...r.kernel.org
Subject: Re: splice vs O_APPEND

On Thu, 9 Oct 2008, Miklos Szeredi wrote:
> 
> We know that nobody is currently relying on O_APPEND semantics with
> splice, so this should be OK.

Having now realized that apparently you can't rely on O_APPEND for 
anything but plain write _anyway_ (ie pwrite shouldn't honor it), I'm 
going to drop this thing as "let's think about it more".

Maybe the right thing to do is to just say that O_APPEND (and IS_APPEND) 
is really not as reliable as people might expect, and just say that the 
only thing it affects is a plain write() system call. 

Of course, I think POSIX is crazy, and we probably _should_ always honor 
O_APPEND, and returning -EINVAL is the right thing for both pwrite and 
splice, but this is all a murkier issue than it looked like originally, 
and any possible "security" implications are dubious in that you cannot 
really depend on O_APPEND/IS_APPEND anyway.

		Linus
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