linux-kernel - Re: [git pull] cpus4096 tree, part 3

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Message-ID: <alpine.LFD.2.00.0901261107280.5284@localhost.localdomain>
Date:	Mon, 26 Jan 2009 11:09:59 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Nick Piggin <npiggin@...e.de>, mingo@...e.hu,
	linux-arch@...r.kernel.org, rusty@...tcorp.com.au, travis@....com,
	linux-kernel@...r.kernel.org, venkatesh.pallipadi@...el.com,
	suresh.b.siddha@...el.com, arjan@...radead.org, hpa@...or.com,
	tglx@...utronix.de
Subject: Re: [git pull] cpus4096 tree, part 3



On Mon, 26 Jan 2009, Andrew Morton wrote:
> > +	write = error_code & PF_WRITE;
> 
> What's going on here?  We set `error_code' to PF_WRITE, which is some
> x86-specific thing.

No. We set "write" to non-zero if it was a write fault.

> >  	fault = handle_mm_fault(mm, vma, address, write);
> 
> and then pass it into handle_mm_fault(), which is expecting a bunch of
> flags in the FAULT_FLAG_foo domain.

No. "handle_mm_fault()" takes an integer that is non-zero if it's a write, 
zero if it's a read. That's how it has _always_ worked.

I don't see where you find that FAULT_FLAG_foo thing. That's much deeper 
down, when people do things like

        unsigned int flags = FAULT_FLAG_NONLINEAR |
                                (write_access ? FAULT_FLAG_WRITE : 0);

based on that whole "write_access" flag.

		Linus
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