Commit ebe2e35e authored by David Hildenbrand's avatar David Hildenbrand Committed by Andrew Morton
Browse files

mm/rmap: introduce and use hugetlb_try_dup_anon_rmap() 

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.

Add sanity checks that we end up with the right folios in the right
functions.

Note that is_device_private_page() does not apply to hugetlb.

Link: https://lkml.kernel.org/r/20231220224504.646757-5-david@redhat.com


Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarYin Fengwei <fengwei.yin@intel.com>
Reviewed-by: default avatarRyan Roberts <ryan.roberts@arm.com>
Reviewed-by: default avatarMuchun Song <songmuchun@bytedance.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 44887f39

include/linux/mm.h

+9 −3
Original line number Diff line number Diff line
@@ -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));

}



/**

include/linux/rmap.h

+18 −0
Original line number Diff line number Diff line
@@ -211,6 +211,22 @@ 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_hugetlb(folio), folio);

	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_hugetlb(folio), folio);
@@ -228,6 +244,8 @@ static inline void hugetlb_remove_rmap(struct folio *folio) 


static inline void __page_dup_rmap(struct page *page, bool compound)

{

	VM_WARN_ON(folio_test_hugetlb(page_folio(page)));



	if (compound) {

		struct folio *folio = (struct folio *)page;

mm/hugetlb.c

+1 −2
Original line number Diff line number Diff line
@@ -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;