From: Li Xinhai <lixinhai.lxh@xxxxxxxxx> Subject: mm, isolation: avoid checking unmovable pages across pageblock boundary In has_unmovable_pages(), the page parameter would not always be the first page within a pageblock (see how the page pointer is passed in from start_isolate_page_range() after call __first_valid_page()), so that would cause checking unmovable pages span two pageblocks. After this patch, the checking is enforced within one pageblock no matter the page is first one or not, and obey the semantics of this function. This issue is found by code inspection. Michal said "this might lead to false negatives when an unrelated block would cause an isolation failure". Link: https://lkml.kernel.org/r/20200824065811.383266-1-lixinhai.lxh@xxxxxxxxx Signed-off-by: Li Xinhai <lixinhai.lxh@xxxxxxxxx> Reviewed-by: Oscar Salvador <osalvador@xxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Cc: David Hildenbrand <david@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) --- a/mm/page_alloc.c~mm-isolation-avoid-checking-unmovable-pages-across-pageblock-boundary +++ a/mm/page_alloc.c @@ -8234,6 +8234,7 @@ struct page *has_unmovable_pages(struct { unsigned long iter = 0; unsigned long pfn = page_to_pfn(page); + unsigned long offset = pfn % pageblock_nr_pages; if (is_migrate_cma_page(page)) { /* @@ -8247,7 +8248,7 @@ struct page *has_unmovable_pages(struct return page; } - for (; iter < pageblock_nr_pages; iter++) { + for (; iter < pageblock_nr_pages - offset; iter++) { if (!pfn_valid_within(pfn + iter)) continue; _
