+ mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap.patch added to mm-unstable branch

+ mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap.patch added to mm-unstable branch

[Andrew Morton]

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The patch titled
     Subject: mm: extend rmap flags arguments for folio_add_new_anon_rmap
has been added to the -mm mm-unstable branch.  Its filename is
     mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Barry Song <v-songbaohua@oppo.com>
Subject: mm: extend rmap flags arguments for folio_add_new_anon_rmap
Date: Tue, 18 Jun 2024 11:11:35 +1200

Patch series "mm: clarify folio_add_new_anon_rmap() and
__folio_add_anon_rmap()", v2.

This patchset is preparatory work for mTHP swapin.

folio_add_new_anon_rmap() assumes that new anon rmaps are always
exclusive.  However, this assumption doesn’t hold true for cases like
do_swap_page(), where a new anon might be added to the swapcache and is
not necessarily exclusive.

The patchset extends the rmap flags to allow folio_add_new_anon_rmap() to
handle both exclusive and non-exclusive new anon folios.  The
do_swap_page() function is updated to use this extended API with rmap
flags.  Consequently, all new anon folios now consistently use
folio_add_new_anon_rmap().  The special case for !folio_test_anon() in
__folio_add_anon_rmap() can be safely removed.

In conclusion, new anon folios always use folio_add_new_anon_rmap(),
regardless of exclusivity.  Old anon folios continue to use
__folio_add_anon_rmap() via folio_add_anon_rmap_pmd() and
folio_add_anon_rmap_ptes().


This patch (of 3):

In the case of a swap-in, a new anonymous folio is not necessarily
exclusive.  This patch updates the rmap flags to allow a new anonymous
folio to be treated as either exclusive or non-exclusive.  To maintain the
existing behavior, we always use EXCLUSIVE as the default setting.

Link: https://lkml.kernel.org/r/20240617231137.80726-1-21cnbao@gmail.com
Link: https://lkml.kernel.org/r/20240617231137.80726-2-21cnbao@gmail.com
Signed-off-by: Barry Song <v-songbaohua@oppo.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Tested-by: Shuai Yuan <yuanshuai@oppo.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: "Huang, Ying" <ying.huang@intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: Yosry Ahmed <yosryahmed@google.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/rmap.h    |    2 +-
 kernel/events/uprobes.c |    2 +-
 mm/huge_memory.c        |    2 +-
 mm/khugepaged.c         |    2 +-
 mm/memory.c             |   10 +++++-----
 mm/migrate_device.c     |    2 +-
 mm/rmap.c               |   17 ++++++++++-------
 mm/swapfile.c           |    2 +-
 mm/userfaultfd.c        |    2 +-
 9 files changed, 22 insertions(+), 19 deletions(-)

--- a/include/linux/rmap.h~mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap
+++ a/include/linux/rmap.h
@@ -244,7 +244,7 @@ void folio_add_anon_rmap_ptes(struct fol
 void folio_add_anon_rmap_pmd(struct folio *, struct page *,
 		struct vm_area_struct *, unsigned long address, rmap_t flags);
 void folio_add_new_anon_rmap(struct folio *, struct vm_area_struct *,
-		unsigned long address);
+		unsigned long address, rmap_t flags);
 void folio_add_file_rmap_ptes(struct folio *, struct page *, int nr_pages,
 		struct vm_area_struct *);
 #define folio_add_file_rmap_pte(folio, page, vma) \
--- a/kernel/events/uprobes.c~mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap
+++ a/kernel/events/uprobes.c
@@ -181,7 +181,7 @@ static int __replace_page(struct vm_area
 
 	if (new_page) {
 		folio_get(new_folio);
-		folio_add_new_anon_rmap(new_folio, vma, addr);
+		folio_add_new_anon_rmap(new_folio, vma, addr, RMAP_EXCLUSIVE);
 		folio_add_lru_vma(new_folio, vma);
 	} else
 		/* no new page, just dec_mm_counter for old_page */
--- a/mm/huge_memory.c~mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap
+++ a/mm/huge_memory.c
@@ -973,7 +973,7 @@ static vm_fault_t __do_huge_pmd_anonymou
 
 		entry = mk_huge_pmd(page, vma->vm_page_prot);
 		entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma);
-		folio_add_new_anon_rmap(folio, vma, haddr);
+		folio_add_new_anon_rmap(folio, vma, haddr, RMAP_EXCLUSIVE);
 		folio_add_lru_vma(folio, vma);
 		pgtable_trans_huge_deposit(vma->vm_mm, vmf->pmd, pgtable);
 		set_pmd_at(vma->vm_mm, haddr, vmf->pmd, entry);
--- a/mm/khugepaged.c~mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap
+++ a/mm/khugepaged.c
@@ -1210,7 +1210,7 @@ static int collapse_huge_page(struct mm_
 
 	spin_lock(pmd_ptl);
 	BUG_ON(!pmd_none(*pmd));
-	folio_add_new_anon_rmap(folio, vma, address);
+	folio_add_new_anon_rmap(folio, vma, address, RMAP_EXCLUSIVE);
 	folio_add_lru_vma(folio, vma);
 	pgtable_trans_huge_deposit(mm, pmd, pgtable);
 	set_pmd_at(mm, address, pmd, _pmd);
--- a/mm/memory.c~mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap
+++ a/mm/memory.c
@@ -930,7 +930,7 @@ copy_present_page(struct vm_area_struct
 	*prealloc = NULL;
 	copy_user_highpage(&new_folio->page, page, addr, src_vma);
 	__folio_mark_uptodate(new_folio);
-	folio_add_new_anon_rmap(new_folio, dst_vma, addr);
+	folio_add_new_anon_rmap(new_folio, dst_vma, addr, RMAP_EXCLUSIVE);
 	folio_add_lru_vma(new_folio, dst_vma);
 	rss[MM_ANONPAGES]++;
 
@@ -3400,7 +3400,7 @@ static vm_fault_t wp_page_copy(struct vm
 		 * some TLBs while the old PTE remains in others.
 		 */
 		ptep_clear_flush(vma, vmf->address, vmf->pte);
-		folio_add_new_anon_rmap(new_folio, vma, vmf->address);
+		folio_add_new_anon_rmap(new_folio, vma, vmf->address, RMAP_EXCLUSIVE);
 		folio_add_lru_vma(new_folio, vma);
 		BUG_ON(unshare && pte_write(entry));
 		set_pte_at(mm, vmf->address, vmf->pte, entry);
@@ -4337,7 +4337,7 @@ check_folio:
 
 	/* ksm created a completely new copy */
 	if (unlikely(folio != swapcache && swapcache)) {
-		folio_add_new_anon_rmap(folio, vma, address);
+		folio_add_new_anon_rmap(folio, vma, address, RMAP_EXCLUSIVE);
 		folio_add_lru_vma(folio, vma);
 	} else {
 		folio_add_anon_rmap_ptes(folio, page, nr_pages, vma, address,
@@ -4592,7 +4592,7 @@ static vm_fault_t do_anonymous_page(stru
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 	count_mthp_stat(folio_order(folio), MTHP_STAT_ANON_FAULT_ALLOC);
 #endif
-	folio_add_new_anon_rmap(folio, vma, addr);
+	folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE);
 	folio_add_lru_vma(folio, vma);
 setpte:
 	if (vmf_orig_pte_uffd_wp(vmf))
@@ -4790,7 +4790,7 @@ void set_pte_range(struct vm_fault *vmf,
 	/* copy-on-write page */
 	if (write && !(vma->vm_flags & VM_SHARED)) {
 		VM_BUG_ON_FOLIO(nr != 1, folio);
-		folio_add_new_anon_rmap(folio, vma, addr);
+		folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE);
 		folio_add_lru_vma(folio, vma);
 	} else {
 		folio_add_file_rmap_ptes(folio, page, nr, vma);
--- a/mm/migrate_device.c~mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap
+++ a/mm/migrate_device.c
@@ -658,7 +658,7 @@ static void migrate_vma_insert_page(stru
 		goto unlock_abort;
 
 	inc_mm_counter(mm, MM_ANONPAGES);
-	folio_add_new_anon_rmap(folio, vma, addr);
+	folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE);
 	if (!folio_is_zone_device(folio))
 		folio_add_lru_vma(folio, vma);
 	folio_get(folio);
--- a/mm/rmap.c~mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap
+++ a/mm/rmap.c
@@ -1406,25 +1406,26 @@ void folio_add_anon_rmap_pmd(struct foli
  * This means the inc-and-test can be bypassed.
  * The folio does not have to be locked.
  *
- * If the folio is pmd-mappable, it is accounted as a THP.  As the folio
- * is new, it's assumed to be mapped exclusively by a single process.
+ * If the folio is pmd-mappable, it is accounted as a THP.
  */
 void folio_add_new_anon_rmap(struct folio *folio, struct vm_area_struct *vma,
-		unsigned long address)
+		unsigned long address, rmap_t flags)
 {
 	int nr = folio_nr_pages(folio);
 	int nr_pmdmapped = 0;
+	bool exclusive = flags & RMAP_EXCLUSIVE;
 
 	VM_WARN_ON_FOLIO(folio_test_hugetlb(folio), folio);
 	VM_BUG_ON_VMA(address < vma->vm_start ||
 			address + (nr << PAGE_SHIFT) > vma->vm_end, vma);
 	__folio_set_swapbacked(folio);
-	__folio_set_anon(folio, vma, address, true);
+	__folio_set_anon(folio, vma, address, exclusive);
 
 	if (likely(!folio_test_large(folio))) {
 		/* increment count (starts at -1) */
 		atomic_set(&folio->_mapcount, 0);
-		SetPageAnonExclusive(&folio->page);
+		if (exclusive)
+			SetPageAnonExclusive(&folio->page);
 	} else if (!folio_test_pmd_mappable(folio)) {
 		int i;
 
@@ -1433,7 +1434,8 @@ void folio_add_new_anon_rmap(struct foli
 
 			/* increment count (starts at -1) */
 			atomic_set(&page->_mapcount, 0);
-			SetPageAnonExclusive(page);
+			if (exclusive)
+				SetPageAnonExclusive(page);
 		}
 
 		/* increment count (starts at -1) */
@@ -1445,7 +1447,8 @@ void folio_add_new_anon_rmap(struct foli
 		/* increment count (starts at -1) */
 		atomic_set(&folio->_large_mapcount, 0);
 		atomic_set(&folio->_nr_pages_mapped, ENTIRELY_MAPPED);
-		SetPageAnonExclusive(&folio->page);
+		if (exclusive)
+			SetPageAnonExclusive(&folio->page);
 		nr_pmdmapped = nr;
 	}
 
--- a/mm/swapfile.c~mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap
+++ a/mm/swapfile.c
@@ -1919,7 +1919,7 @@ static int unuse_pte(struct vm_area_stru
 
 		folio_add_anon_rmap_pte(folio, page, vma, addr, rmap_flags);
 	} else { /* ksm created a completely new copy */
-		folio_add_new_anon_rmap(folio, vma, addr);
+		folio_add_new_anon_rmap(folio, vma, addr, RMAP_EXCLUSIVE);
 		folio_add_lru_vma(folio, vma);
 	}
 	new_pte = pte_mkold(mk_pte(page, vma->vm_page_prot));
--- a/mm/userfaultfd.c~mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap
+++ a/mm/userfaultfd.c
@@ -216,7 +216,7 @@ int mfill_atomic_install_pte(pmd_t *dst_
 			folio_add_lru(folio);
 		folio_add_file_rmap_pte(folio, page, dst_vma);
 	} else {
-		folio_add_new_anon_rmap(folio, dst_vma, dst_addr);
+		folio_add_new_anon_rmap(folio, dst_vma, dst_addr, RMAP_EXCLUSIVE);
 		folio_add_lru_vma(folio, dst_vma);
 	}
 
_

Patches currently in -mm which might be from v-songbaohua@oppo.com are

cifs-drop-the-incorrect-assertion-in-cifs_swap_rw.patch
mm-remove-the-implementation-of-swap_free-and-always-use-swap_free_nr.patch
mm-introduce-pte_move_swp_offset-helper-which-can-move-offset-bidirectionally.patch
mm-introduce-arch_do_swap_page_nr-which-allows-restore-metadata-for-nr-pages.patch
mm-swap-reuse-exclusive-folio-directly-instead-of-wp-page-faults.patch
mm-introduce-pmdpte_needs_soft_dirty_wp-helpers-for-softdirty-write-protect.patch
mm-set-pte-writable-while-pte_soft_dirty-is-true-in-do_swap_page.patch
mm-extend-rmap-flags-arguments-for-folio_add_new_anon_rmap.patch
mm-use-folio_add_new_anon_rmap-if-folio_test_anonfolio==false.patch
mm-remove-folio_test_anonfolio==false-path-in-__folio_add_anon_rmap.patch