On Thu 01-03-18 13:47:45, Daniel Vacek wrote:
> In move_freepages() a BUG_ON() can be triggered on uninitialized page structures
> due to pageblock alignment. Aligning the skipped pfns in memmap_init_zone() the
> same way as in move_freepages_block() simply fixes those crashes.
This changelog doesn't describe how the fix works. Why doesn't
memblock_next_valid_pfn return the first valid pfn as one would expect?
It would be also good put the panic info in the changelog.
> Fixes: b92df1de5d28 ("[mm] page_alloc: skip over regions of invalid pfns where possible")
> Signed-off-by: Daniel Vacek <neelx@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> ---
> mm/page_alloc.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index cb416723538f..9edee36e6a74 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -5359,9 +5359,14 @@ void __meminit memmap_init_zone(unsigned long size, int nid, unsigned long zone,
> /*
> * 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 as 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;
> #endif
> continue;
> }
> --
> 2.16.2
>
--
Michal Hocko
SUSE Labs