linux-kernel - Re: [PATCH 5/5] mm, memory_hotplug: be more verbose for memory offline failures

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Message-ID: <20181116112218.GH14706@dhcp22.suse.cz>
Date:   Fri, 16 Nov 2018 12:22:18 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     osalvador <osalvador@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Baoquan He <bhe@...hat.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        linux-mm@...ck.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 5/5] mm, memory_hotplug: be more verbose for memory
 offline failures

On Fri 16-11-18 11:47:01, osalvador wrote:
> On Fri, 2018-11-16 at 09:30 +0100, Michal Hocko wrote:
> > From: Michal Hocko <mhocko@...e.com>
> > diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> > index a919ba5cb3c8..ec2c7916dc2d 100644
> > --- a/mm/page_alloc.c
> > +++ b/mm/page_alloc.c
> > @@ -7845,6 +7845,7 @@ bool has_unmovable_pages(struct zone *zone,
> > struct page *page, int count,
> >  	return false;
> >  unmovable:
> >  	WARN_ON_ONCE(zone_idx(zone) == ZONE_MOVABLE);
> > +	dump_page(pfn_to_page(pfn+iter), "unmovable page");
> 
> Would not be enough to just do:
> 
> dump_page(page, "unmovable page".
> 
> Unless I am missing something, page should already have the
> right pfn?

What if pfn_valid_within fails? You could have a pointer to the previous
page.

> 
> <---
> unsigned long check = pfn + iter;
> page = pfn_to_page(check);
> --->
> 
> The rest looks good to me
> 
> Reviewed-by: Oscar Salvador <osalvador@...e.de>

Thanks!

-- 
Michal Hocko
SUSE Labs