linux-kernel - Re: [PATCH v13 4/5] mm: support reporting free page blocks

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Tue, 08 Aug 2017 14:12:56 +0800
From:   Wei Wang <wei.w.wang@...el.com>
To:     Michal Hocko <mhocko@...nel.org>
CC:     linux-kernel@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        linux-mm@...ck.org, mst@...hat.com, mawilcox@...rosoft.com,
        akpm@...ux-foundation.org, virtio-dev@...ts.oasis-open.org,
        david@...hat.com, cornelia.huck@...ibm.com,
        mgorman@...hsingularity.net, aarcange@...hat.com,
        amit.shah@...hat.com, pbonzini@...hat.com,
        liliang.opensource@...il.com, yang.zhang.wz@...il.com,
        quan.xu@...yun.com
Subject: Re: [PATCH v13 4/5] mm: support reporting free page blocks

On 08/03/2017 05:11 PM, Michal Hocko wrote:
> On Thu 03-08-17 14:38:18, Wei Wang wrote:
> This is just too ugly and wrong actually. Never provide struct page
> pointers outside of the zone->lock. What I've had in mind was to simply
> walk free lists of the suitable order and call the callback for each one.
> Something as simple as
>
> 	for (i = 0; i < MAX_NR_ZONES; i++) {
> 		struct zone *zone = &pgdat->node_zones[i];
>
> 		if (!populated_zone(zone))
> 			continue;

Can we directly use for_each_populated_zone(zone) here?


> 		spin_lock_irqsave(&zone->lock, flags);
> 		for (order = min_order; order < MAX_ORDER; ++order) {


This appears to be covered by for_each_migratetype_order(order, mt) below.


> 			struct free_area *free_area = &zone->free_area[order];
> 			enum migratetype mt;
> 			struct page *page;
>
> 			if (!free_area->nr_pages)
> 				continue;
>
> 			for_each_migratetype_order(order, mt) {
> 				list_for_each_entry(page,
> 						&free_area->free_list[mt], lru) {
>
> 					pfn = page_to_pfn(page);
> 					visit(opaque2, prn, 1<<order);
> 				}
> 			}
> 		}
>
> 		spin_unlock_irqrestore(&zone->lock, flags);
> 	}
>
> [...]
>

What do you think if we further simply the above implementation like this:

for_each_populated_zone(zone) {
                 for_each_migratetype_order_decend(1, order, mt) {
                         spin_lock_irqsave(&zone->lock, flags);
                         list_for_each_entry(page,
&zone->free_area[order].free_list[mt], lru) {
                                 pfn = page_to_pfn(page);
                                 visit(opaque1, pfn, 1 << order);
                         }
                         spin_unlock_irqrestore(&zone->lock, flags);
                 }
         }


Best,
Wei