Re: [PATCH v2 27/29] mm/memory_hotplug: extend offline_and_remove_memory() to handle more than one memory block

[David Hildenbrand]

On 18.11.20 05:53, Andrew Morton wrote:
> On Thu, 12 Nov 2020 14:38:13 +0100 David Hildenbrand <david@xxxxxxxxxx> wrote:
>
> > virtio-mem soon wants to use offline_and_remove_memory() memory that
> > exceeds a single Linux memory block (memory_block_size_bytes()). Let's
> > remove that restriction.
> >
> > Let's remember the old state and try to restore that if anything goes
> > wrong. While re-onlining can, in general, fail, it's highly unlikely to
> > happen (usually only when a notifier fails to allocate memory, and these
> > are rather rare).
> >
> > This will be used by virtio-mem to offline+remove memory ranges that are
> > bigger than a single memory block - for example, with a device block
> > size of 1 GiB (e.g., gigantic pages in the hypervisor) and a Linux memory
> > block size of 128MB.
> >
> > While we could compress the state into 2 bit, using 8 bit is much
> > easier.
> >
> > This handling is similar, but different to acpi_scan_try_to_offline():
> >
> > a) We don't try to offline twice. I am not sure if this CONFIG_MEMCG
> > optimization is still relevant - it should only apply to ZONE_NORMAL
> > (where we have no guarantees). If relevant, we can always add it.
> >
> > b) acpi_scan_try_to_offline() simply onlines all memory in case
> > something goes wrong. It doesn't restore previous online type. Let's do
> > that, so we won't overwrite what e.g., user space configured.
> >
> > ...
>
> uint8_t is a bit of a mouthful.  u8 is less typing ;)  Doesn't matter.

In case I have to resend, I'll change it :)

> Acked-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>

Thanks!


--
Thanks,

David / dhildenb