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[195.135.220.15]) by mx.google.com with ESMTPS id h17si1031745ejj.234.2019.02.12.00.33.31 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 12 Feb 2019 00:33:31 -0800 (PST) Received-SPF: softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) client-ip=195.135.220.15; Authentication-Results: mx.google.com; spf=softfail (google.com: domain of transitioning mhocko@kernel.org does not designate 195.135.220.15 as permitted sender) smtp.mailfrom=mhocko@kernel.org; dmarc=fail (p=NONE sp=NONE dis=NONE) header.from=kernel.org X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id 4EC3EAF17; Tue, 12 Feb 2019 08:33:31 +0000 (UTC) Date: Tue, 12 Feb 2019 09:33:29 +0100 From: Michal Hocko To: Oscar Salvador Cc: akpm@linux-foundation.org, david@redhat.com, anthony.yznaga@oracle.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm,memory_hotplug: Explicitly pass the head to isolate_huge_page Message-ID: <20190212083329.GN15609@dhcp22.suse.cz> References: <20190208090604.975-1-osalvador@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190208090604.975-1-osalvador@suse.de> User-Agent: Mutt/1.10.1 (2018-07-13) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri 08-02-19 10:06:04, Oscar Salvador wrote: > isolate_huge_page() expects we pass the head of hugetlb page to it: > > bool isolate_huge_page(...) > { > ... > VM_BUG_ON_PAGE(!PageHead(page), page); > ... > } > > While I really cannot think of any situation where we end up with a > non-head page between hands in do_migrate_range(), let us make sure > the code is as sane as possible by explicitly passing the Head. > Since we already got the pointer, it does not take us extra effort. > > Signed-off-by: Oscar Salvador Acked-by: Michal Hocko Btw. > --- > mm/memory_hotplug.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 656ff386ac15..d5f7afda67db 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -1378,12 +1378,12 @@ do_migrate_range(unsigned long start_pfn, unsigned long end_pfn) > > if (PageHuge(page)) { > struct page *head = compound_head(page); > - pfn = page_to_pfn(head) + (1< if (compound_order(head) > PFN_SECTION_SHIFT) { > ret = -EBUSY; > break; > } Why are we doing this, btw? > - isolate_huge_page(page, &source); > + pfn = page_to_pfn(head) + (1< + isolate_huge_page(head, &source); > continue; > } else if (PageTransHuge(page)) > pfn = page_to_pfn(compound_head(page)) > -- > 2.13.7 -- Michal Hocko SUSE Labs