On 08.10.19 16:36, lantianyu1986@xxxxxxxxx wrote: > From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx> > > If size of offline memory region passed to offline_pages() is > not aligned with PAGES_PER_SECTION, memory section will be set > to offline in the offline_mem_sections() with some pages of > memory section online. Fix it, Update memory section status after > marking offline pages as "reserved" in __offline_isolated_pages() > and check all pages in memory are reserved or not before setting > memory section offline. > > Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx> > --- > This patch is to prepare for hot remove memory function in Hyper-V > balloon driver. It requests to offline memory with random size. I proposed roughly the same a while ago. See https://lkml.org/lkml/2018/4/30/207 Memory onlining/offlining works in memory block granularity only. Sub-sections, you have to emulate it on top, similar to how hyper-v balloon handles it already. E.g., have a look how virtio-mem handles it using alloc_contig_range/free_contig_range and PG_offline extensions. https://lkml.org/lkml/2018/4/30/207 So a clear NACK from my side. > --- > mm/page_alloc.c | 3 ++- > mm/sparse.c | 10 ++++++++++ > 2 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index dbd0d5cbbcbb..cc02866924ae 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -8540,7 +8540,6 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn) > if (pfn == end_pfn) > return offlined_pages; > > - offline_mem_sections(pfn, end_pfn); > zone = page_zone(pfn_to_page(pfn)); > spin_lock_irqsave(&zone->lock, flags); > pfn = start_pfn; > @@ -8576,6 +8575,8 @@ __offline_isolated_pages(unsigned long start_pfn, unsigned long end_pfn) > } > spin_unlock_irqrestore(&zone->lock, flags); > > + offline_mem_sections(pfn, end_pfn); > + > return offlined_pages; > } > #endif > diff --git a/mm/sparse.c b/mm/sparse.c > index fd13166949b5..eb5860487b84 100644 > --- a/mm/sparse.c > +++ b/mm/sparse.c > @@ -571,6 +571,7 @@ void online_mem_sections(unsigned long start_pfn, unsigned long end_pfn) > void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn) > { > unsigned long pfn; > + int i; > > for (pfn = start_pfn; pfn < end_pfn; pfn += PAGES_PER_SECTION) { > unsigned long section_nr = pfn_to_section_nr(pfn); > @@ -583,6 +584,15 @@ void offline_mem_sections(unsigned long start_pfn, unsigned long end_pfn) > if (WARN_ON(!valid_section_nr(section_nr))) > continue; > > + /* > + * Check whether all pages in the section are reserverd before > + * setting setction offline. > + */ > + for (i = 0; i < PAGES_PER_SECTION; i++) > + if (!PageReserved(pfn_to_page( > + SECTION_ALIGN_DOWN(pfn + i)))) > + continue; > + > ms = __nr_to_section(section_nr); > ms->section_mem_map &= ~SECTION_IS_ONLINE; > } > -- Thanks, David / dhildenb
