linux-kernel - Re: [PATCH v3 07/15] mm/memory_hotplug: Introduce offline_and_remove

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Date:   Thu, 7 May 2020 13:24:38 +0200
From:   David Hildenbrand <david@...hat.com>
To:     "Michael S. Tsirkin" <mst@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        virtio-dev@...ts.oasis-open.org,
        virtualization@...ts.linux-foundation.org, kvm@...r.kernel.org,
        Michal Hocko <mhocko@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Pankaj Gupta <pankaj.gupta.linux@...il.com>,
        Oscar Salvador <osalvador@...e.com>,
        Pavel Tatashin <pasha.tatashin@...een.com>,
        Wei Yang <richard.weiyang@...il.com>,
        Dan Williams <dan.j.williams@...el.com>, Qian Cai <cai@....pw>
Subject: Re: [PATCH v3 07/15] mm/memory_hotplug: Introduce
 offline_and_remove_memory()

On 07.05.20 12:46, Michael S. Tsirkin wrote:
> On Thu, May 07, 2020 at 12:31:11PM +0200, David Hildenbrand wrote:
>> virtio-mem wants to offline and remove a memory block once it unplugged
>> all subblocks (e.g., using alloc_contig_range()). Let's provide
>> an interface to do that from a driver. virtio-mem already supports to
>> offline partially unplugged memory blocks. Offlining a fully unplugged
>> memory block will not require to migrate any pages. All unplugged
>> subblocks are PageOffline() and have a reference count of 0 - so
>> offlining code will simply skip them.
>>
>> All we need is an interface to offline and remove the memory from kernel
>> module context, where we don't have access to the memory block devices
>> (esp. find_memory_block() and device_offline()) and the device hotplug
>> lock.
>>
>> To keep things simple, allow to only work on a single memory block.
>>
>> Acked-by: Michal Hocko <mhocko@...e.com>
>> Tested-by: Pankaj Gupta <pankaj.gupta.linux@...il.com>
>> Cc: Andrew Morton <akpm@...ux-foundation.org>
>> Cc: David Hildenbrand <david@...hat.com>
>> Cc: Oscar Salvador <osalvador@...e.com>
>> Cc: Michal Hocko <mhocko@...e.com>
>> Cc: Pavel Tatashin <pasha.tatashin@...een.com>
>> Cc: Wei Yang <richard.weiyang@...il.com>
>> Cc: Dan Williams <dan.j.williams@...el.com>
>> Cc: Qian Cai <cai@....pw>
>> Signed-off-by: David Hildenbrand <david@...hat.com>
> 
> 
> didn't you lose Andrew Morton's ack here?

Yeah, thanks for noticing.

> 
>> ---
>>  include/linux/memory_hotplug.h |  1 +
>>  mm/memory_hotplug.c            | 37 ++++++++++++++++++++++++++++++++++
>>  2 files changed, 38 insertions(+)
> 
> I get:
> 
> error: sha1 information is lacking or useless (mm/memory_hotplug.c).
> error: could not build fake ancestor
> 
> which version is this against? Pls post patches on top of some tag
> in Linus' tree if possible.

As the cover states, latest linux-next. To be precise

commit 6b43f715b6379433e8eb30aa9bcc99bd6a585f77 (tag: next-20200507,
next/master)
Author: Stephen Rothwell <sfr@...b.auug.org.au>
Date:   Thu May 7 18:11:31 2020 +1000

    Add linux-next specific files for 20200507


-- 
Thanks,

David / dhildenb