From: Doug Berger <opendmb@xxxxxxxxx> Subject: mm/page_alloc: don't corrupt pcppage_migratetype When placing pages on a pcp list, migratetype values over MIGRATE_PCPTYPES get added to the MIGRATE_MOVABLE pcp list. However, the actual migratetype is preserved in the page and should not be changed to MIGRATE_MOVABLE or the page may end up on the wrong free_list. The impact is that HIGHATOMIC or CMA pages getting bulk freed from the PCP lists could potentially end up on the wrong buddy list. There are various consequences but minimally NR_FREE_CMA_PAGES accounting could get screwed up. [mgorman@xxxxxxxxxxxxxxxxxxx: changelog update] Link: https://lkml.kernel.org/r/20210811182917.2607994-1-opendmb@xxxxxxxxx Fixes: df1acc856923 ("mm/page_alloc: avoid conflating IRQs disabled with zone->lock") Signed-off-by: Doug Berger <opendmb@xxxxxxxxx> Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Acked-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-) --- a/mm/page_alloc.c~mm-page_alloc-dont-corrupt-pcppage_migratetype +++ a/mm/page_alloc.c @@ -3453,19 +3453,10 @@ void free_unref_page_list(struct list_he * comment in free_unref_page. */ migratetype = get_pcppage_migratetype(page); - if (unlikely(migratetype >= MIGRATE_PCPTYPES)) { - if (unlikely(is_migrate_isolate(migratetype))) { - list_del(&page->lru); - free_one_page(page_zone(page), page, pfn, 0, - migratetype, FPI_NONE); - continue; - } - - /* - * Non-isolated types over MIGRATE_PCPTYPES get added - * to the MIGRATE_MOVABLE pcp list. - */ - set_pcppage_migratetype(page, MIGRATE_MOVABLE); + if (unlikely(is_migrate_isolate(migratetype))) { + list_del(&page->lru); + free_one_page(page_zone(page), page, pfn, 0, migratetype, FPI_NONE); + continue; } set_page_private(page, pfn); @@ -3475,7 +3466,15 @@ void free_unref_page_list(struct list_he list_for_each_entry_safe(page, next, list, lru) { pfn = page_private(page); set_page_private(page, 0); + + /* + * Non-isolated types over MIGRATE_PCPTYPES get added + * to the MIGRATE_MOVABLE pcp list. + */ migratetype = get_pcppage_migratetype(page); + if (unlikely(migratetype >= MIGRATE_PCPTYPES)) + migratetype = MIGRATE_MOVABLE; + trace_mm_page_free_batched(page); free_unref_page_commit(page, pfn, migratetype, 0); _
