Messages in this thread | | | Subject | Re: [PATCH v6 1/1] mm/page_alloc.c: refactor initialization of struct page for holes in memory layout | From | David Hildenbrand <> | Date | Tue, 23 Feb 2021 09:04:19 +0100 |
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On 22.02.21 11:57, Mike Rapoport wrote: > From: Mike Rapoport <rppt@linux.ibm.com> > > There could be struct pages that are not backed by actual physical memory. > This can happen when the actual memory bank is not a multiple of > SECTION_SIZE or when an architecture does not register memory holes > reserved by the firmware as memblock.memory. > > Such pages are currently initialized using init_unavailable_mem() function > that iterates through PFNs in holes in memblock.memory and if there is a > struct page corresponding to a PFN, the fields of this page are set to > default values and it is marked as Reserved. > > init_unavailable_mem() does not take into account zone and node the page > belongs to and sets both zone and node links in struct page to zero. > > Before commit 73a6e474cb37 ("mm: memmap_init: iterate over memblock regions > rather that check each PFN") the holes inside a zone were re-initialized > during memmap_init() and got their zone/node links right. However, after > that commit nothing updates the struct pages representing such holes. > > On a system that has firmware reserved holes in a zone above ZONE_DMA, for > instance in a configuration below: > > # grep -A1 E820 /proc/iomem > 7a17b000-7a216fff : Unknown E820 type > 7a217000-7bffffff : System RAM > > unset zone link in struct page will trigger > > VM_BUG_ON_PAGE(!zone_spans_pfn(page_zone(page), pfn), page); > > because there are pages in both ZONE_DMA32 and ZONE_DMA (unset zone link > in struct page) in the same pageblock. > > Interleave initialization of the unavailable pages with the normal > initialization of memory map, so that zone and node information will be > properly set on struct pages that are not backed by the actual memory. > > With this change the pages for holes inside a zone will get proper > zone/node links and the pages that are not spanned by any node will get > links to the adjacent zone/node.
Does this include pages in the last section has handled by ... ... > - /* > - * Early sections always have a fully populated memmap for the whole > - * section - see pfn_valid(). If the last section has holes at the > - * end and that section is marked "online", the memmap will be > - * considered initialized. Make sure that memmap has a well defined > - * state. > - */ > - pgcnt += init_unavailable_range(PFN_DOWN(next), > - round_up(max_pfn, PAGES_PER_SECTION)); > -
^ this code?
Or how is that case handled now?
-- Thanks,
David / dhildenb
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