linux-kernel - Re: [RFC][PATCH] HWPOISON: remove the unsafe __set_page

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Message-ID: <Pine.LNX.4.64.0909272251180.4402@sister.anvils>
Date:	Sun, 27 Sep 2009 22:57:29 +0100 (BST)
From:	Hugh Dickins <hugh.dickins@...cali.co.uk>
To:	Nick Piggin <npiggin@...e.de>
cc:	Andi Kleen <andi@...stfloor.org>,
	Wu Fengguang <fengguang.wu@...el.com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC][PATCH] HWPOISON: remove the unsafe __set_page_locked()

On Sun, 27 Sep 2009, Nick Piggin wrote:
> On Sun, Sep 27, 2009 at 05:26:25PM +0100, Hugh Dickins wrote:
> > 
> > I don't particularly like adding a GFP_LOCKED just for this, and I
> > don't particularly like having to remember to unlock the thing on the
> > various(?) error paths between getting the page and adding it to cache.
> 
> God no, please no more crazy branches in the page allocator.
> 
> I'm going to resubmit my patches to allow 0-ref page allocations,
> so the pagecache will be able to work with those to do what we
> want here.
>  
> > But it is a good idea, and if doing it that way would really close a
> > race window which checking page->mapping (or whatever) cannot (I'm
> > simply not sure about that), then it would seem the best way to go.
> 
> Yep, seems reasonable: the ordering is no technical burden, and a
> simple comment pointing to hwpoison will keep it maintainable.

You move from "God no" to "Yep, seems reasonable"!

I think perhaps you couldn't bring yourself to believe that I was
giving any support to Andi's GFP_LOCKED idea.  Pretend I did not!

I'll assume we stick with the "God no", and we'll see how what
you come up with affects what they want.

Hugh
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