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SubjectRe: [RFC PATCH 2/3] mm/memory_hotplug: Create __shrink_pages and move it to offline_pages
On Tue 07-08-18 09:52:21, Jerome Glisse wrote:
> On Tue, Aug 07, 2018 at 03:37:56PM +0200, osalvador@techadventures.net wrote:
> > From: Oscar Salvador <osalvador@suse.de>
>
> [...]
>
> > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> > index 9bd629944c91..e33555651e46 100644
> > --- a/mm/memory_hotplug.c
> > +++ b/mm/memory_hotplug.c
>
> [...]
>
> > /**
> > * __remove_pages() - remove sections of pages from a zone
> > - * @zone: zone from which pages need to be removed
> > + * @nid: node which pages belong to
> > * @phys_start_pfn: starting pageframe (must be aligned to start of a section)
> > * @nr_pages: number of pages to remove (must be multiple of section size)
> > * @altmap: alternative device page map or %NULL if default memmap is used
> > @@ -548,7 +557,7 @@ static int __remove_section(struct zone *zone, struct mem_section *ms,
> > * sure that pages are marked reserved and zones are adjust properly by
> > * calling offline_pages().
> > */
> > -int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
> > +int __remove_pages(int nid, unsigned long phys_start_pfn,
> > unsigned long nr_pages, struct vmem_altmap *altmap)
> > {
> > unsigned long i;
> > @@ -556,10 +565,9 @@ int __remove_pages(struct zone *zone, unsigned long phys_start_pfn,
> > int sections_to_remove, ret = 0;
> >
> > /* In the ZONE_DEVICE case device driver owns the memory region */
> > - if (is_dev_zone(zone)) {
> > - if (altmap)
> > - map_offset = vmem_altmap_offset(altmap);
> > - } else {
> > + if (altmap)
> > + map_offset = vmem_altmap_offset(altmap);
> > + else {
>
> This will break ZONE_DEVICE at least for HMM. While i think that
> altmap -> ZONE_DEVICE (ie altmap imply ZONE_DEVICE) the reverse
> is not true ie ZONE_DEVICE does not necessarily imply altmap. So
> with the above changes you change the expected behavior.

Could you be more specific what is the expected behavior here?
Is this about calling release_mem_region_adjustable? Why does is it not
suitable for zone device ranges?
--
Michal Hocko
SUSE Labs

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