On 03.06.24 17:08, Lance Yang wrote:
On Mon, Jun 3, 2024 at 10:56 PM David Hildenbrand <david@xxxxxxxxxx> wrote:
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.
Could I change folio_pte_batch() to take an unsigned long max_nr?
It might be more future proof; see my other mail, I think currently all
is fine, because "end" is not the end of the VMA but the end of the PMD.
Please double-check.
--
Cheers,
David / dhildenb
