mm: convert page_try_share_anon_rmap() to folio_try_share_anon_rmap_[pte|pmd]()

Let's convert it like we converted all the other rmap functions.  Don't
introduce folio_try_share_anon_rmap_ptes() for now, as we don't have a
user that wants rmap batching in sight.  Pretty easy to add later.

All users are easy to convert -- only ksm.c doesn't use folios yet but
that is left for future work -- so let's just do it in a single shot.

While at it, turn the BUG_ON into a WARN_ON_ONCE.

Note that page_try_share_anon_rmap() so far didn't care about pte/pmd
mappings (no compound parameter).  We're changing that so we can perform
better sanity checks and make the code actually more readable/consistent. 
For example, __folio_rmap_sanity_checks() will make sure that a PMD range
actually falls completely into the folio.

Link: https://lkml.kernel.org/r/20231220224504.646757-39-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

6 files changed, 18 insertions, 15 deletions

diff --git a/mm/gup.c b/mm/gup.c
index 0a5f0e91bfec..df83182ec72d 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -177,7 +177,7 @@ struct folio *try_grab_folio(struct page *page, int refs, unsigned int flags)
 	/*
 	 * Adjust the pincount before re-checking the PTE for changes.
 	 * This is essentially a smp_mb() and is paired with a memory
-	 * barrier in page_try_share_anon_rmap().
+	 * barrier in folio_try_share_anon_rmap_*().
 	 */
 	smp_mb__after_atomic();
 
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index de623b942b6e..1a588e29d287 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2523,10 +2523,11 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 		 * In case we cannot clear PageAnonExclusive(), split the PMD
 		 * only and let try_to_migrate_one() fail later.
 		 *
-		 * See page_try_share_anon_rmap(): invalidate PMD first.
+		 * See folio_try_share_anon_rmap_pmd(): invalidate PMD first.
 		 */
 		anon_exclusive = PageAnonExclusive(page);
-		if (freeze && anon_exclusive && page_try_share_anon_rmap(page))
+		if (freeze && anon_exclusive &&
+		    folio_try_share_anon_rmap_pmd(folio, page))
 			freeze = false;
 		if (!freeze) {
 			rmap_t rmap_flags = RMAP_NONE;
@@ -3554,9 +3555,9 @@ int set_pmd_migration_entry(struct page_vma_mapped_walk *pvmw,
 	flush_cache_range(vma, address, address + HPAGE_PMD_SIZE);
 	pmdval = pmdp_invalidate(vma, address, pvmw->pmd);
 
-	/* See page_try_share_anon_rmap(): invalidate PMD first. */
+	/* See folio_try_share_anon_rmap_pmd(): invalidate PMD first. */
 	anon_exclusive = folio_test_anon(folio) && PageAnonExclusive(page);
-	if (anon_exclusive && page_try_share_anon_rmap(page)) {
+	if (anon_exclusive && folio_try_share_anon_rmap_pmd(folio, page)) {
 		set_pmd_at(mm, address, pvmw->pmd, pmdval);
 		return -EBUSY;
 	}
diff --git a/mm/internal.h b/mm/internal.h
index a94355e70bd7..29589bc3f046 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -1047,7 +1047,7 @@ enum {
  * * Ordinary GUP: Using the PT lock
  * * GUP-fast and fork(): mm->write_protect_seq
  * * GUP-fast and KSM or temporary unmapping (swap, migration): see
- *    page_try_share_anon_rmap()
+ *    folio_try_share_anon_rmap_*()
  *
  * Must be called with the (sub)page that's actually referenced via the
  * page table entry, which might not necessarily be the head page for a
@@ -1090,7 +1090,7 @@ static inline bool gup_must_unshare(struct vm_area_struct *vma,
 		return is_cow_mapping(vma->vm_flags);
 	}
 
-	/* Paired with a memory barrier in page_try_share_anon_rmap(). */
+	/* Paired with a memory barrier in folio_try_share_anon_rmap_*(). */
 	if (IS_ENABLED(CONFIG_HAVE_FAST_GUP))
 		smp_rmb();
 
diff --git a/mm/ksm.c b/mm/ksm.c
index 716e2f87dd79..8c001819cf10 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -1331,8 +1331,9 @@ static int write_protect_page(struct vm_area_struct *vma, struct page *page,
 			goto out_unlock;
 		}
 
-		/* See page_try_share_anon_rmap(): clear PTE first. */
-		if (anon_exclusive && page_try_share_anon_rmap(page)) {
+		/* See folio_try_share_anon_rmap_pte(): clear PTE first. */
+		if (anon_exclusive &&
+		    folio_try_share_anon_rmap_pte(page_folio(page), page)) {
 			set_pte_at(mm, pvmw.address, pvmw.pte, entry);
 			goto out_unlock;
 		}
diff --git a/mm/migrate_device.c b/mm/migrate_device.c
index 39b7754480c6..b6c27c76e1a0 100644
--- a/mm/migrate_device.c
+++ b/mm/migrate_device.c
@@ -202,7 +202,7 @@ again:
 			if (anon_exclusive) {
 				pte = ptep_clear_flush(vma, addr, ptep);
 
-				if (page_try_share_anon_rmap(page)) {
+				if (folio_try_share_anon_rmap_pte(folio, page)) {
 					set_pte_at(mm, addr, ptep, pte);
 					folio_unlock(folio);
 					folio_put(folio);
diff --git a/mm/rmap.c b/mm/rmap.c
index 3ee254a99622..6209e65985a2 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1866,9 +1866,9 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
 				break;
 			}
 
-			/* See page_try_share_anon_rmap(): clear PTE first. */
+			/* See folio_try_share_anon_rmap(): clear PTE first. */
 			if (anon_exclusive &&
-			    page_try_share_anon_rmap(subpage)) {
+			    folio_try_share_anon_rmap_pte(folio, subpage)) {
 				swap_free(entry);
 				set_pte_at(mm, address, pvmw.pte, pteval);
 				ret = false;
@@ -2142,7 +2142,8 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 			pte_t swp_pte;
 
 			if (anon_exclusive)
-				BUG_ON(page_try_share_anon_rmap(subpage));
+				WARN_ON_ONCE(folio_try_share_anon_rmap_pte(folio,
+									   subpage));
 
 			/*
 			 * Store the pfn of the page in a special migration
@@ -2213,7 +2214,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 			VM_BUG_ON_PAGE(pte_write(pteval) && folio_test_anon(folio) &&
 				       !anon_exclusive, subpage);
 
-			/* See page_try_share_anon_rmap(): clear PTE first. */
+			/* See folio_try_share_anon_rmap_pte(): clear PTE first. */
 			if (folio_test_hugetlb(folio)) {
 				if (anon_exclusive &&
 				    hugetlb_try_share_anon_rmap(folio)) {
@@ -2224,7 +2225,7 @@ static bool try_to_migrate_one(struct folio *folio, struct vm_area_struct *vma,
 					break;
 				}
 			} else if (anon_exclusive &&
-				   page_try_share_anon_rmap(subpage)) {
+				   folio_try_share_anon_rmap_pte(folio, subpage)) {
 				set_pte_at(mm, address, pvmw.pte, pteval);
 				ret = false;
 				page_vma_mapped_walk_done(&pvmw);