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From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Oscar Salvador <osalvador@suse.de>,
	"mike.kravetz@oracle.com" <mike.kravetz@oracle.com>,
	"linux-mm@kvack.org" <linux-mm@kvack.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH v2 02/16] mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED
Date: Mon, 21 Oct 2019 07:02:55 +0000
Message-ID: <20191021070254.GB8782@hori.linux.bs1.fc.nec.co.jp> (raw)
In-Reply-To: <20191018115227.GL5017@dhcp22.suse.cz>

On Fri, Oct 18, 2019 at 01:52:27PM +0200, Michal Hocko wrote:
> On Thu 17-10-19 16:21:09, Oscar Salvador wrote:
> > From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> > 
> > The call to get_user_pages_fast is only to get the pointer to a struct
> > page of a given address, pinning it is memory-poisoning handler's job,
> > so drop the refcount grabbed by get_user_pages_fast
> > 
> > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> > Signed-off-by: Oscar Salvador <osalvador@suse.de>
> > ---
> >  mm/madvise.c | 24 ++++++++++++------------
> >  1 file changed, 12 insertions(+), 12 deletions(-)
> > 
> > diff --git a/mm/madvise.c b/mm/madvise.c
> > index 2be9f3fdb05e..89ed9a22ff4f 100644
> > --- a/mm/madvise.c
> > +++ b/mm/madvise.c
> > @@ -878,16 +878,24 @@ static int madvise_inject_error(int behavior,
> >  		 */
> >  		order = compound_order(compound_head(page));
> >  
> > -		if (PageHWPoison(page)) {
> > -			put_page(page);
> > +		/*
> > +		 * The get_user_pages_fast() is just to get the pfn of the
> > +		 * given address, and the refcount has nothing to do with
> > +		 * what we try to test, so it should be released immediately.
> > +		 * This is racy but it's intended because the real hardware
> > +		 * errors could happen at any moment and memory error handlers
> > +		 * must properly handle the race.
> > +		 */
> > +		put_page(page);
> > +
> > +		if (PageHWPoison(page))
> >  			continue;
> > -		}
> >  
> >  		if (behavior == MADV_SOFT_OFFLINE) {
> >  			pr_info("Soft offlining pfn %#lx at process virtual address %#lx\n",
> >  					pfn, start);
> >  
> > -			ret = soft_offline_page(page, MF_COUNT_INCREASED);
> > +			ret = soft_offline_page(page, 0);
> 
> What does prevent this struct page to go away completely?

Nothing does it.  Memory error handler tries to pin by itself and
then determines what state the page is in now.

Thanks,
Naoya Horiguchi

> 
> >  			if (ret)
> >  				return ret;
> >  			continue;
> > @@ -895,14 +903,6 @@ static int madvise_inject_error(int behavior,
> >  
> >  		pr_info("Injecting memory failure for pfn %#lx at process virtual address %#lx\n",
> >  				pfn, start);
> > -
> > -		/*
> > -		 * Drop the page reference taken by get_user_pages_fast(). In
> > -		 * the absence of MF_COUNT_INCREASED the memory_failure()
> > -		 * routine is responsible for pinning the page to prevent it
> > -		 * from being released back to the page allocator.
> > -		 */
> > -		put_page(page);
> >  		ret = memory_failure(pfn, 0);
> >  		if (ret)
> >  			return ret;
> > -- 
> > 2.12.3
> > 
> 
> -- 
> Michal Hocko
> SUSE Labs
> 


  reply index

Thread overview: 57+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-17 14:21 [RFC PATCH v2 00/16] Hwpoison rework {hard,soft}-offline Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 01/16] mm,hwpoison: cleanup unused PageHuge() check Oscar Salvador
2019-10-18 11:48   ` Michal Hocko
2019-10-21  7:00     ` Naoya Horiguchi
2019-10-21 12:16       ` Michal Hocko
2019-11-12 12:22       ` Aneesh Kumar K.V
2019-11-13  6:02         ` Naoya Horiguchi
2019-10-17 14:21 ` [RFC PATCH v2 02/16] mm,madvise: call soft_offline_page() without MF_COUNT_INCREASED Oscar Salvador
2019-10-18 11:52   ` Michal Hocko
2019-10-21  7:02     ` Naoya Horiguchi [this message]
2019-10-21 12:20       ` Michal Hocko
2019-10-17 14:21 ` [RFC PATCH v2 03/16] mm,madvise: Refactor madvise_inject_error Oscar Salvador
2019-10-21  7:03   ` Naoya Horiguchi
2019-10-17 14:21 ` [RFC PATCH v2 04/16] mm,hwpoison-inject: don't pin for hwpoison_filter Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 05/16] mm,hwpoison: Un-export get_hwpoison_page and make it static Oscar Salvador
2019-10-21  7:03   ` Naoya Horiguchi
2019-10-17 14:21 ` [RFC PATCH v2 06/16] mm,hwpoison: Kill put_hwpoison_page Oscar Salvador
2019-10-21  7:04   ` Naoya Horiguchi
2019-10-17 14:21 ` [RFC PATCH v2 07/16] mm,hwpoison: remove MF_COUNT_INCREASED Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 08/16] mm,hwpoison: remove flag argument from soft offline functions Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 09/16] mm,hwpoison: Unify THP handling for hard and soft offline Oscar Salvador
2019-10-21  7:04   ` Naoya Horiguchi
2019-10-21  9:51     ` [PATCH 17/16] mm,hwpoison: introduce MF_MSG_UNSPLIT_THP Naoya Horiguchi
2019-10-22  8:00       ` Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 10/16] mm,hwpoison: Rework soft offline for free pages Oscar Salvador
2019-10-18 12:06   ` Michal Hocko
2019-10-21 12:58     ` Oscar Salvador
2019-10-21 15:41       ` Michal Hocko
2019-10-22  7:46         ` Oscar Salvador
2019-10-22  8:26           ` Michal Hocko
2019-10-22  8:35             ` Oscar Salvador
2019-10-22  9:22               ` Michal Hocko
2019-10-22  9:58                 ` Oscar Salvador
2019-10-22 10:24                   ` Michal Hocko
2019-10-22 10:33                     ` Oscar Salvador
2019-10-23  2:15                       ` Naoya Horiguchi
2019-10-23  2:01                   ` Naoya Horiguchi
2019-10-21  7:45   ` Naoya Horiguchi
2019-10-22  8:00     ` Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 11/16] mm,hwpoison: Rework soft offline for in-use pages Oscar Salvador
2019-10-18 12:39   ` Michal Hocko
2019-10-21 13:48     ` Oscar Salvador
2019-10-21 14:06       ` Michal Hocko
2019-10-22  7:56         ` Oscar Salvador
2019-10-22  8:30           ` Michal Hocko
2019-10-22  9:40             ` Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 12/16] mm,hwpoison: Refactor soft_offline_huge_page and __soft_offline_page Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 13/16] mm,hwpoison: Take pages off the buddy when hard-offlining Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 14/16] mm,hwpoison: Return 0 if the page is already poisoned in soft-offline Oscar Salvador
2019-10-21  9:20   ` Naoya Horiguchi
2019-10-17 14:21 ` [RFC PATCH v2 15/16] mm/hwpoison-inject: Rip off duplicated checks Oscar Salvador
2019-10-21  9:40   ` David Hildenbrand
2019-10-22  7:57     ` Oscar Salvador
2019-10-17 14:21 ` [RFC PATCH v2 16/16] mm, soft-offline: convert parameter to pfn Oscar Salvador
2019-10-18  8:15   ` David Hildenbrand
2020-06-11 16:43 ` [RFC PATCH v2 00/16] Hwpoison rework {hard,soft}-offline Dmitry Yakunin
2020-06-15  6:19   ` HORIGUCHI NAOYA(堀口 直也)

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