On Tue, Nov 27, 2018 at 05:20:03PM +0100, Oscar Salvador wrote: > From: Oscar Salvador <osalvador@xxxxxxxx> > > The current implementation accesses pages during hot-remove > stage in order to get the zone linked to this memory-range. > We use that zone for a) check if the zone is ZONE_DEVICE and > b) to shrink the zone's spanned pages. > > Accessing pages during this stage is problematic, as we might be > accessing pages that were not initialized if we did not get to > online the memory before removing it. > > The only reason to check for ZONE_DEVICE in __remove_pages > is to bypass the call to release_mem_region_adjustable(), > since these regions are removed with devm_release_mem_region. > > With patch#2, this is no longer a problem so we can safely > call release_mem_region_adjustable(). > release_mem_region_adjustable() will spot that the region > we are trying to remove was acquired by means of > devm_request_mem_region, and will back off safely. > > This allows us to remove all zone-related operations from > hot-remove stage. > > Because of this, zone's spanned pages are shrinked during > the offlining stage in shrink_zone_pgdat(). > It would have been great to decrease also the spanned page > for the node there, but we need them in try_offline_node(). > So we still decrease spanned pages for the node in the hot-remove > stage. > > The only particularity is that now > find_smallest_section_pfn/find_biggest_section_pfn, when called from > shrink_zone_span, will now check for online sections and not > valid sections instead. > To make this work with devm/HMM code, we need to call offline_mem_sections > and online_mem_sections in that code path when we are adding memory. > > Signed-off-by: Oscar Salvador <osalvador@xxxxxxx> > --- > arch/powerpc/mm/mem.c | 11 +---- > arch/sh/mm/init.c | 4 +- > arch/x86/mm/init_32.c | 3 +- > arch/x86/mm/init_64.c | 8 +--- > include/linux/memory_hotplug.h | 8 ++-- > kernel/memremap.c | 14 +++++-- > mm/memory_hotplug.c | 95 ++++++++++++++++++++++++------------------ > mm/sparse.c | 4 +- > 8 files changed, 76 insertions(+), 71 deletions(-) [ ... ] > /** > - * __remove_pages() - remove sections of pages from a zone > - * @zone: zone from which pages need to be removed > + * __remove_pages() - remove sections of pages from a nid > + * @nid: nid from which pages belong to Nit: the description sounds a bit awkward. Why not to keep the original one with s/zone/node/? > * @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 > @@ -547,35 +566,28 @@ 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(). > */ -- Sincerely yours, Mike.
