linux-kernel - Re: [PATCH 1/3] HWPOISON, hugetlbfs: fix warning on freeing hwpoisoned hugepage

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Message-Id: <1354846694-6101-1-git-send-email-n-horiguchi@ah.jp.nec.com>
Date:	Thu,  6 Dec 2012 21:18:14 -0500
From:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
To:	Tony Luck <tony.luck@...el.com>
Cc:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andi Kleen <andi.kleen@...el.com>,
	Wu Fengguang <fengguang.wu@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 1/3] HWPOISON, hugetlbfs: fix warning on freeing hwpoisoned hugepage

On Wed, Dec 05, 2012 at 10:13:42PM +0000, Luck, Tony wrote:
> > This patch fixes the warning from __list_del_entry() which is triggered
> > when a process tries to do free_huge_page() for a hwpoisoned hugepage.
> 
> Ultimately it would be nice to avoid poisoning huge pages. Generally we know the
> location of the poison to a cache line granularity (but sometimes only to a 4K
> granularity) ... and it is rather inefficient to take an entire 2M page out of service.
> With 1G pages things would be even worse!!

Thanks for the comment.
And yes, it's remaining work to be done.

> It also makes life harder for applications that would like to catch the SIGBUS
> and try to take their own recovery actions. Losing more data than they really
> need to will make it less likely that they can do something to work around the
> loss.
> 
> Has anyone looked at how hard it might be to have the code in memory-failure.c
> break up a huge page and only poison the 4K that needs to be taken out of service?

This work is one of my interest and became a bit easier than used to be,
because now transparent hugepage works commonly and some of code can be
copied from or shared with it.

Thanks,
Naoya
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