[PATCH v1 04/39] mm/rmap: introduce and use hugetlb_try_dup_anon_rmap()

David Hildenbrand
2023-12-11T15:57:43Z

hugetlb rmap handling differs quite a lot from "ordinary" rmap code.
For example, hugetlb currently only supports entire mappings, and treats
any mapping as mapped using a single "logical PTE". Let's move it out
of the way so we can overhaul our "ordinary" rmap.
implementation/interface.

So let's introduce and use hugetlb_try_dup_anon_rmap() to make all
hugetlb handling use dedicated hugetlb_* rmap functions.

Note that is_device_private_page() does not apply to hugetlb.

Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/mm.h | 12 +++++++++---
include/linux/rmap.h | 15 +++++++++++++++
mm/hugetlb.c | 3 +--
3 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index b72bf25a45cf..ae547b62f325 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1964,15 +1964,21 @@ static inline bool page_maybe_dma_pinned(struct page *page)
*
* The caller has to hold the PT lock and the vma->vm_mm->->write_protect_seq.
*/
-static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma,
- struct page *page)
+static inline bool folio_needs_cow_for_dma(struct vm_area_struct *vma,
+ struct folio *folio)
{
VM_BUG_ON(!(raw_read_seqcount(&vma->vm_mm->write_protect_seq) & 1));

if (!test_bit(MMF_HAS_PINNED, &vma->vm_mm->flags))
return false;

- return page_maybe_dma_pinned(page);
+ return folio_maybe_dma_pinned(folio);
+}
+
+static inline bool page_needs_cow_for_dma(struct vm_area_struct *vma,
+ struct page *page)
+{
+ return folio_needs_cow_for_dma(vma, page_folio(page));
}

/**
diff --git a/include/linux/rmap.h b/include/linux/rmap.h
index 91178d1aa028..ca42b3db5688 100644
--- a/include/linux/rmap.h
+++ b/include/linux/rmap.h
@@ -213,6 +213,21 @@ void hugetlb_add_anon_rmap(struct folio *, struct vm_area_struct *,
void hugetlb_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
unsigned long address);

+/* See page_try_dup_anon_rmap() */
+static inline int hugetlb_try_dup_anon_rmap(struct folio *folio,
+ struct vm_area_struct *vma)
+{
+ VM_WARN_ON_FOLIO(!folio_test_anon(folio), folio);
+
+ if (PageAnonExclusive(&folio->page)) {
+ if (unlikely(folio_needs_cow_for_dma(vma, folio)))
+ return -EBUSY;
+ ClearPageAnonExclusive(&folio->page);
+ }
+ atomic_inc(&folio->_entire_mapcount);
+ return 0;
+}
+
static inline void hugetlb_add_file_rmap(struct folio *folio)
{
VM_WARN_ON_FOLIO(folio_test_anon(folio), folio);
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 57e898187931..378e460a6ab4 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5409,8 +5409,7 @@ int copy_hugetlb_page_range(struct mm_struct *dst, struct mm_struct *src,
*/
if (!folio_test_anon(pte_folio)) {
hugetlb_add_file_rmap(pte_folio);
- } else if (page_try_dup_anon_rmap(&pte_folio->page,
- true, src_vma)) {
+ } else if (hugetlb_try_dup_anon_rmap(pte_folio, src_vma)) {
pte_t src_pte_old = entry;
struct folio *new_folio;

--
2.43.0