On 03.06.24 16:43, Matthew Wilcox wrote:
On Mon, Jun 03, 2024 at 10:07:45PM +0800, Lance Yang wrote:+++ b/mm/mlock.c @@ -307,26 +307,15 @@ void munlock_folio(struct folio *folio) static inline unsigned int folio_mlock_step(struct folio *folio, pte_t *pte, unsigned long addr, unsigned long end) { - unsigned int count, i, nr = folio_nr_pages(folio); - unsigned long pfn = folio_pfn(folio); + const fpb_t fpb_flags = FPB_IGNORE_DIRTY | FPB_IGNORE_SOFT_DIRTY; + unsigned int count = (end - addr) >> PAGE_SHIFT;This is a pre-existing bug, but ... what happens if you're on a 64-bit system and you mlock() a range that is exactly 2^44 bytes? Seems to me that count becomes 0. Why not use an unsigned long here and avoid the problem entirely? folio_pte_batch() also needs to take an unsigned long max_nr in that case, because you aren't restricting it to folio_nr_pages().
Yeah, likely we should also take a look at other folio_pte_batch() users like copy_present_ptes() that pass the count as an int. Nothing should really be broken, but we might not batch as much as we could, which is unfortunate.
-- Cheers, David / dhildenb
