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[209.132.183.28]) by mx.google.com with ESMTPS id y198si7907799qka.85.2019.06.25.03.29.06 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 25 Jun 2019 03:29:06 -0700 (PDT) Received-SPF: pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7AAA43098558; Tue, 25 Jun 2019 10:29:00 +0000 (UTC) Received: from [10.36.117.83] (ovpn-117-83.ams2.redhat.com [10.36.117.83]) by smtp.corp.redhat.com (Postfix) with ESMTP id 52C67600C7; Tue, 25 Jun 2019 10:28:57 +0000 (UTC) Subject: Re: [PATCH v2 3/5] mm,memory_hotplug: Introduce Vmemmap page helpers To: Oscar Salvador , akpm@linux-foundation.org Cc: mhocko@suse.com, dan.j.williams@intel.com, pasha.tatashin@soleen.com, Jonathan.Cameron@huawei.com, anshuman.khandual@arm.com, vbabka@suse.cz, "linux-mm@kvack.org" , Matthew Wilcox References: <20190625075227.15193-1-osalvador@suse.de> <20190625075227.15193-4-osalvador@suse.de> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <20190625075227.15193-4-osalvador@suse.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Tue, 25 Jun 2019 10:29:05 +0000 (UTC) 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 25.06.19 09:52, Oscar Salvador wrote: > Introduce a set of functions for Vmemmap pages. > Set of functions: > > - {Set,Clear,Check} Vmemmap flag > - Given a vmemmap page, get its vmemmap-head > - Get #nr of vmemmap pages taking into account the current position > of the page > > These functions will be used for the code handling Vmemmap pages. > > Signed-off-by: Oscar Salvador > --- > include/linux/page-flags.h | 34 ++++++++++++++++++++++++++++++++++ > mm/util.c | 2 ++ > 2 files changed, 36 insertions(+) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index b848517da64c..a8b9b57162b3 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -466,6 +466,40 @@ static __always_inline int __PageMovable(struct page *page) > PAGE_MAPPING_MOVABLE; > } > > +#define VMEMMAP_PAGE (~PAGE_MAPPING_FLAGS) > +static __always_inline int PageVmemmap(struct page *page) > +{ > + return PageReserved(page) && (unsigned long)page->mapping == VMEMMAP_PAGE; > +} > + > +static __always_inline int __PageVmemmap(struct page *page) > +{ > + return (unsigned long)page->mapping == VMEMMAP_PAGE; > +} > + > +static __always_inline void __ClearPageVmemmap(struct page *page) > +{ Should we VM_BUG_ON in case !PG_reserved || pg->mapping != VMEMMAP_PAGE ? > + __ClearPageReserved(page); > + page->mapping = NULL; > +} > + > +static __always_inline void __SetPageVmemmap(struct page *page) > +{ Should we VM_BUG_ON in case PG_reserved || pg->mapping != NULL ? > + __SetPageReserved(page); > + page->mapping = (void *)VMEMMAP_PAGE; > +} > + > +static __always_inline struct page *vmemmap_get_head(struct page *page) > +{ > + return (struct page *)page->freelist; freelist is a "slab, slob and slub" concept (reading include/linux/mm_types.h). page->mapping is a "Page cache and anonymous pages" concept. Hmmm... > +} > + > +static __always_inline unsigned long get_nr_vmemmap_pages(struct page *page) > +{ > + struct page *head = vmemmap_get_head(page); > + return head->private - (page - head); > +} > + > #ifdef CONFIG_KSM > /* > * A KSM page is one of those write-protected "shared pages" or "merged pages" > diff --git a/mm/util.c b/mm/util.c > index 021648a8a3a3..5e20563cdef6 100644 > --- a/mm/util.c > +++ b/mm/util.c > @@ -607,6 +607,8 @@ struct address_space *page_mapping(struct page *page) > mapping = page->mapping; > if ((unsigned long)mapping & PAGE_MAPPING_ANON) > return NULL; > + if ((unsigned long)mapping == VMEMMAP_PAGE) > + return NULL; > > return (void *)((unsigned long)mapping & ~PAGE_MAPPING_FLAGS); > } > I wonder if using a page type would be appropriate here instead. Then, define a new sub-structure within "struct page" that describes what you actually want (instead of reusing ->private and ->mapping). Just an idea, we have to find out if that is possible. vmemmap_get_head() smells like __GFP_COMP, but of course, these vmemmap pages never saw the buddy. But sounds like you want a similar concept. -- Thanks, David / dhildenb