On 18.01.24 12:10, Barry Song wrote:
From: Barry Song <v-songbaohua@xxxxxxxx> In do_swap_page(), while supporting large folio swap-in, we are using the helper folio_add_anon_rmap_ptes. This is triggerring a WARN_ON in __folio_add_anon_rmap. We can make the warning quiet by two ways 1. in do_swap_page, we call folio_add_new_anon_rmap() if we are sure the large folio is new allocated one; we call folio_add_anon_rmap_ptes() if we find the large folio in swapcache. 2. we always call folio_add_anon_rmap_ptes() in do_swap_page but weaken the WARN_ON in __folio_add_anon_rmap() by letting the WARN_ON less sensitive. Option 2 seems to be better for do_swap_page() as it can use unified code for all cases. Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx> Tested-by: Chuanhua Han <hanchuanhua@xxxxxxxx> --- mm/rmap.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/rmap.c b/mm/rmap.c index f5d43edad529..469fcfd32317 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1304,7 +1304,10 @@ static __always_inline void __folio_add_anon_rmap(struct folio *folio, * page. */ VM_WARN_ON_FOLIO(folio_test_large(folio) && - level != RMAP_LEVEL_PMD, folio); + level != RMAP_LEVEL_PMD && + (!IS_ALIGNED(address, nr_pages * PAGE_SIZE) || + (folio_test_swapcache(folio) && !IS_ALIGNED(folio->index, nr_pages)) || + page != &folio->page), folio); __folio_set_anon(folio, vma, address, !!(flags & RMAP_EXCLUSIVE)); } else if (likely(!folio_test_ksm(folio))) {
I have on my todo list to move all that !anon handling out of folio_add_anon_rmap_ptes(), and instead make swapin code call add folio_add_new_anon_rmap(), where we'll have to pass an exclusive flag then (-> whole new folio exclusive).
That's the cleaner approach. -- Cheers, David / dhildenb