On 25.02.21 23:43, Mike Rapoport wrote:
From: Mike Rapoport <rppt@xxxxxxxxxxxxx>
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);
in set_pfnblock_flags_mask() when called with a struct page from a range
other than E820_TYPE_RAM because there are pages in the range of ZONE_DMA32
but the unset zone link in struct page makes them appear as a part of
ZONE_DMA.
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. The holes between nodes will be prepended
to the zone/node above the hole and the trailing pages in the last section
that will be appended to the zone/node below.
Fixes: 73a6e474cb37 ("mm: memmap_init: iterate over memblock regions rather that check each PFN")
Signed-off-by: Mike Rapoport <rppt@xxxxxxxxxxxxx>
Reported-by: Qian Cai <cai@xxxxxx>
Reported-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Reviewed-by: Baoquan He <bhe@xxxxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
Reviewed-by: David Hildenbrand <david@xxxxxxxxxx>
Thanks Mike!
--
Thanks,
David / dhildenb
