On 9/2/20 7:25 PM, Mike Kravetz wrote: > On 9/2/20 3:49 AM, Vlastimil Babka wrote: >> On 9/1/20 3:46 AM, Wei Yang wrote: >>> The page allocated from buddy is not on any list, so just use list_add() >>> is enough. >>> >>> Signed-off-by: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx> >>> Reviewed-by: Baoquan He <bhe@xxxxxxxxxx> >>> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> >>> --- >>> mm/hugetlb.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>> index 441b7f7c623e..c9b292e664c4 100644 >>> --- a/mm/hugetlb.c >>> +++ b/mm/hugetlb.c >>> @@ -2405,7 +2405,7 @@ struct page *alloc_huge_page(struct vm_area_struct *vma, >>> h->resv_huge_pages--; >>> } >>> spin_lock(&hugetlb_lock); >>> - list_move(&page->lru, &h->hugepage_activelist); >>> + list_add(&page->lru, &h->hugepage_activelist); >> >> Hmm, how does that list_move() actually not crash today? >> Page has been taken from free lists, thus there was list_del() and page->lru >> should be poisoned. >> list_move() does __list_del_entry() which will either detect the poison with >> CONFIG_DEBUG_LIST, or crash accessing the poison, no? >> Am I missing something or does it mean this code is actually never executed in wild? >> > > There is not enough context in the diff, but the hugetlb page was not taken > from the free list. Rather, it was just created by a call to > alloc_buddy_huge_page_with_mpol(). As part of the allocation/creation > prep_new_huge_page will be called which will INIT_LIST_HEAD(&page->lru). Ah so indeed I was missing something :) Thanks. Then this is indeed a an optimization and not a bugfix and doesn't need stable@. Sorry for the noise.
