Re: [patch 6/8] mm/page_alloc: fix memmap_init_zone pageblock alignment

On Sat, Mar 10, 2018 at 12:51 AM, akpm@linux-foundation.org wrote:

From: Daniel Vacek neelx@redhat.com Subject: mm/page_alloc: fix memmap_init_zone pageblock alignment

b92df1de5d28 ("mm: page_alloc: skip over regions of invalid pfns where possible") introduced a bug where move_freepages() triggers a VM_BUG_ON() on uninitialized page structure due to pageblock alignment. To fix this, simply align the skipped pfns in memmap_init_zone() the same way as in move_freepages_block().

diff -puN mm/page_alloc.c~mm-page_alloc-fix-memmap_init_zone-pageblock-alignment mm/page_alloc.c --- a/mm/page_alloc.c~mm-page_alloc-fix-memmap_init_zone-pageblock-alignment +++ a/mm/page_alloc.c @@ -5359,9 +5359,14 @@ void __meminit memmap_init_zone(unsigned /* * Skip to the pfn preceding the next valid one (or * end_pfn), such that we hit a valid pfn (or end_pfn)

•                    * on our next iteration of the loop.
  

•                    * on our next iteration of the loop. Note that it needs
  

•                    * to be pageblock aligned even when the region itself
  

•                    * is not. move_freepages_block() can shift ahead of
  

•                    * the valid region but still depends on correct page
  

•                    * metadata.
                     */
  

•                   pfn = memblock_next_valid_pfn(pfn, end_pfn) - 1;
  

•                   pfn = (memblock_next_valid_pfn(pfn, end_pfn) &
  

•                                   ~(pageblock_nr_pages-1)) - 1;
  

Again, end_pfn should be gone.

--nX

#endif continue; } _