On 13.06.24 02:07, Barry Song wrote:
From: Barry Song <v-songbaohua@xxxxxxxx>
For the !folio_test_anon(folio) case, we can now invoke folio_add_new_anon_rmap()
with the rmap flags set to either EXCLUSIVE or non-EXCLUSIVE. This action will
suppress the VM_WARN_ON_FOLIO check within __folio_add_anon_rmap() while initiating
the process of bringing up mTHP swapin.
static __always_inline void __folio_add_anon_rmap(struct folio *folio,
struct page *page, int nr_pages, struct vm_area_struct *vma,
unsigned long address, rmap_t flags, enum rmap_level level)
{
...
if (unlikely(!folio_test_anon(folio))) {
VM_WARN_ON_FOLIO(folio_test_large(folio) &&
level != RMAP_LEVEL_PMD, folio);
}
...
}
It also enhances the code’s readability.
Suggested-by: David Hildenbrand <david@xxxxxxxxxx>
Signed-off-by: Barry Song <v-songbaohua@xxxxxxxx>
---
mm/memory.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/mm/memory.c b/mm/memory.c
index 2f94921091fb..9c962f62f928 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4339,6 +4339,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
if (unlikely(folio != swapcache && swapcache)) {
folio_add_new_anon_rmap(folio, vma, address, RMAP_EXCLUSIVE);
folio_add_lru_vma(folio, vma);
+ } else if (!folio_test_anon(folio)) {
+ folio_add_new_anon_rmap(folio, vma, address, rmap_flags);
So, with large folio swapin, we would never end up here if any swp PTE
is !exclusive, because we would make sure to allocate a large folio only
for suitable regions, correct?
It can certainly happen during swapout + refault with large folios. But
there, we will always have folio_test_anon() still set and wouldn't run
into this code path.
(it will all be better with per-folio PAE bit, but that will take some
more time until I actually get to implement it properly, handling all
the nasty corner cases)
Better add a comment regarding why we are sure that the complete thing
is exclusive (e.g., currently only small folios).
} else {
folio_add_anon_rmap_ptes(folio, page, nr_pages, vma, address,
rmap_flags);
--
Cheers,
David / dhildenb
