linux-kernel - Re: [PATCH 2/2] mm,memory_hotplug: Fix shrink_{zone,node}

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:   Wed, 17 Jul 2019 10:08:03 +0200
From:   Oscar Salvador <osalvador@...e.de>
To:     David Hildenbrand <david@...hat.com>
Cc:     Dan Williams <dan.j.williams@...el.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@...ux.ibm.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Michal Hocko <mhocko@...e.com>, Linux MM <linux-mm@...ck.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mm,memory_hotplug: Fix shrink_{zone,node}_span

On Wed, Jul 17, 2019 at 10:01:01AM +0200, David Hildenbrand wrote:
> I'd also like to note that we should strive for making all zone-related
> changes when offlining in the future, not when removing memory. So
> ideally, any core changes we perform from now, should make that step
> (IOW implementing that) easier, not harder. Of course, BUGs have to be
> fixed.
> 
> The rough idea would be to also mark ZONE_DEVICE sections as ONLINE (or
> rather rename it to "ACTIVE" to generalize).
> 
> For each section we would then have
> 
> - pfn_valid(): We have a valid "struct page" / memmap
> - pfn_present(): We have actually added that memory via an oficial
>   interface to mm (e.g., arch_add_memory() )
> - pfn_online() / (or pfn_active()): Memory is active (online in "buddy"-
>   speak, or memory that was moved to the ZONE_DEVICE zone)
> 
> When resizing the zones (e.g., when offlining memory), we would then
> search for pfn_online(), not pfn_present().
> 
> In addition to move_pfn_range_to_zone(), we would have
> remove_pfn_range_from_zone(), called during offline_pages() / by
> devmem/hmm/pmem code before removing.
> 
> (I started to look into this, but I don't have any patches yet)

Yes, it seems like a good approach, and something that makes sense
to pursue.
FWIF, I sent a patchset [1] for that a long time ago, but I could not
follow-up due to time constraints.

[1] https://patchwork.kernel.org/cover/10700783/


-- 
Oscar Salvador
SUSE L3