[PATCH v2 2/2] mm: use aligned address in copy_user_gigantic_page()

Kefeng Wang
2024-10-26T05:43:24Z

When copying gigantic page, it copies page from the first page to the
last page, if directly passing addr_hint which maybe not the address
of the first page of folio, then some archs could flush the wrong cache
if it does use the addr_hint as a hint. For non-gigantic page, it
calculates the base address inside, even passed the wrong addr_hint, it
only has performance impact as the process_huge_page() wants to process
target page last to keep its cache lines hot), no functional impact.

Let's pass the real accessed address to copy_user_large_folio() and use
the aligned address in copy_user_gigantic_page() to fix it.

Fixes: 530dd9926dc1 ("mm: memory: improve copy_user_large_folio()")
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
v2:
- update changelog to clarify the impact, per Andrew

mm/hugetlb.c | 5 ++---
mm/memory.c | 1 +
2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 2c8c5da0f5d3..15b5d46d49d2 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5338,7 +5338,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
break;
}
ret = copy_user_large_folio(new_folio, pte_folio,
- ALIGN_DOWN(addr, sz), dst_vma);
+ addr, dst_vma);
folio_put(pte_folio);
if (ret) {
folio_put(new_folio);
@@ -6641,8 +6641,7 @@ int hugetlb_mfill_atomic_pte(pte_t *dst_pte,
*foliop = NULL;
goto out;
}
- ret = copy_user_large_folio(folio, *foliop,
- ALIGN_DOWN(dst_addr, size), dst_vma);
+ ret = copy_user_large_folio(folio, *foliop, dst_addr, dst_vma);
folio_put(*foliop);
*foliop = NULL;
if (ret) {
diff --git a/mm/memory.c b/mm/memory.c
index ef47b7ea5ddd..e5284bab659d 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -6860,6 +6860,7 @@ static int copy_user_gigantic_page(struct folio *dst, struct folio *src,
struct page *dst_page;
struct page *src_page;

+ addr = ALIGN_DOWN(addr, folio_size(dst));
for (i = 0; i < nr_pages; i++) {
dst_page = folio_page(dst, i);
src_page = folio_page(src, i);
--
2.27.0