diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index b0f189815512..d811b24db65b 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1023,7 +1023,7 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask,
 
 	if (folio) {
 		/* We treat non-present entries as "maybe shared". */
-		if (!present || folio_likely_mapped_shared(folio) ||
+		if (!present || folio_maybe_mapped_shared(folio) ||
 		    hugetlb_pmd_shared(pte))
 			mss->shared_hugetlb += huge_page_size(hstate_vma(vma));
 		else
@@ -1882,7 +1882,7 @@ static int pagemap_hugetlb_range(pte_t *ptep, unsigned long hmask,
 		if (!folio_test_anon(folio))
 			flags |= PM_FILE;
 
-		if (!folio_likely_mapped_shared(folio) &&
+		if (!folio_maybe_mapped_shared(folio) &&
 		    !hugetlb_pmd_shared(ptep))
 			flags |= PM_MMAP_EXCLUSIVE;
 
diff --git a/include/linux/mm.h b/include/linux/mm.h
index f366c180f2b6..82776b409391 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2251,23 +2251,18 @@ static inline size_t folio_size(const struct folio *folio)
 }
 
 /**
- * folio_likely_mapped_shared - Estimate if the folio is mapped into the page
- *				tables of more than one MM
+ * folio_maybe_mapped_shared - Whether the folio is mapped into the page
+ *			       tables of more than one MM
  * @folio: The folio.
  *
- * This function checks if the folio is currently mapped into more than one
- * MM ("mapped shared"), or if the folio is only mapped into a single MM
- * ("mapped exclusively").
+ * This function checks if the folio maybe currently mapped into more than one
+ * MM ("maybe mapped shared"), or if the folio is certainly mapped into a single
+ * MM ("mapped exclusively").
  *
  * For KSM folios, this function also returns "mapped shared" when a folio is
  * mapped multiple times into the same MM, because the individual page mappings
  * are independent.
  *
- * As precise information is not easily available for all folios, this function
- * estimates the number of MMs ("sharers") that are currently mapping a folio
- * using the number of times the first page of the folio is currently mapped
- * into page tables.
- *
  * For small anonymous folios and anonymous hugetlb folios, the return
  * value will be exactly correct: non-KSM folios can only be mapped at most once
  * into an MM, and they cannot be partially mapped. KSM folios are
@@ -2275,8 +2270,8 @@ static inline size_t folio_size(const struct folio *folio)
  *
  * For other folios, the result can be fuzzy:
  *    #. For partially-mappable large folios (THP), the return value can wrongly
- *       indicate "mapped exclusively" (false negative) when the folio is
- *       only partially mapped into at least one MM.
+ *       indicate "mapped shared" (false positive) if a folio was mapped by
+ *       more than two MMs at one point in time.
  *    #. For pagecache folios (including hugetlb), the return value can wrongly
  *       indicate "mapped shared" (false positive) when two VMAs in the same MM
  *       cover the same file range.
@@ -2293,7 +2288,7 @@ static inline size_t folio_size(const struct folio *folio)
  *
  * Return: Whether the folio is estimated to be mapped into more than one MM.
  */
-static inline bool folio_likely_mapped_shared(struct folio *folio)
+static inline bool folio_maybe_mapped_shared(struct folio *folio)
 {
 	int mapcount = folio_mapcount(folio);
 
@@ -2301,16 +2296,22 @@ static inline bool folio_likely_mapped_shared(struct folio *folio)
 	if (!folio_test_large(folio) || unlikely(folio_test_hugetlb(folio)))
 		return mapcount > 1;
 
-	/* A single mapping implies "mapped exclusively". */
-	if (mapcount <= 1)
-		return false;
-
-	/* If any page is mapped more than once we treat it "mapped shared". */
-	if (folio_entire_mapcount(folio) || mapcount > folio_nr_pages(folio))
+	/*
+	 * vm_insert_page() without CONFIG_TRANSPARENT_HUGEPAGE ...
+	 * simply assume "mapped shared", nobody should really care
+	 * about this for arbitrary kernel allocations.
+	 */
+	if (!IS_ENABLED(CONFIG_MM_ID))
 		return true;
 
-	/* Let's guess based on the first subpage. */
-	return atomic_read(&folio->_mapcount) > 0;
+	/*
+	 * A single mapping implies "mapped exclusively", even if the
+	 * folio flag says something different: it's easier to handle this
+	 * case here instead of on the RMAP hot path.
+	 */
+	if (mapcount <= 1)
+		return false;
+	return folio_test_large_maybe_mapped_shared(folio);
 }
 
 #ifndef HAVE_ARCH_MAKE_FOLIO_ACCESSIBLE
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 22e4e1194e9e..7433369d5d1f 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2155,7 +2155,7 @@ bool madvise_free_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
 	 * If other processes are mapping this folio, we couldn't discard
 	 * the folio unless they all do MADV_FREE so let's skip the folio.
 	 */
-	if (folio_likely_mapped_shared(folio))
+	if (folio_maybe_mapped_shared(folio))
 		goto out;
 
 	if (!folio_trylock(folio))
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 5f0be134141e..cc945c6ab3bd 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -607,7 +607,7 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma,
 		VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio);
 
 		/* See hpage_collapse_scan_pmd(). */
-		if (folio_likely_mapped_shared(folio)) {
+		if (folio_maybe_mapped_shared(folio)) {
 			++shared;
 			if (cc->is_khugepaged &&
 			    shared > khugepaged_max_ptes_shared) {
@@ -1359,11 +1359,9 @@ static int hpage_collapse_scan_pmd(struct mm_struct *mm,
 
 		/*
 		 * We treat a single page as shared if any part of the THP
-		 * is shared. "False negatives" from
-		 * folio_likely_mapped_shared() are not expected to matter
-		 * much in practice.
+		 * is shared.
 		 */
-		if (folio_likely_mapped_shared(folio)) {
+		if (folio_maybe_mapped_shared(folio)) {
 			++shared;
 			if (cc->is_khugepaged &&
 			    shared > khugepaged_max_ptes_shared) {
diff --git a/mm/madvise.c b/mm/madvise.c
index e01e93e179a8..388dc289b5d1 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -387,7 +387,7 @@ static int madvise_cold_or_pageout_pte_range(pmd_t *pmd,
 		folio = pmd_folio(orig_pmd);
 
 		/* Do not interfere with other mappings of this folio */
-		if (folio_likely_mapped_shared(folio))
+		if (folio_maybe_mapped_shared(folio))
 			goto huge_unlock;
 
 		if (pageout_anon_only_filter && !folio_test_anon(folio))
@@ -486,7 +486,7 @@ restart:
 			if (nr < folio_nr_pages(folio)) {
 				int err;
 
-				if (folio_likely_mapped_shared(folio))
+				if (folio_maybe_mapped_shared(folio))
 					continue;
 				if (pageout_anon_only_filter && !folio_test_anon(folio))
 					continue;
@@ -721,7 +721,7 @@ static int madvise_free_pte_range(pmd_t *pmd, unsigned long addr,
 			if (nr < folio_nr_pages(folio)) {
 				int err;
 
-				if (folio_likely_mapped_shared(folio))
+				if (folio_maybe_mapped_shared(folio))
 					continue;
 				if (!folio_trylock(folio))
 					continue;
diff --git a/mm/memory.c b/mm/memory.c
index 5d5a2d81f05a..8873b7a4962c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5698,7 +5698,7 @@ int numa_migrate_check(struct folio *folio, struct vm_fault *vmf,
 	 * Flag if the folio is shared between multiple address spaces. This
 	 * is later used when determining whether to group tasks together
 	 */
-	if (folio_likely_mapped_shared(folio) && (vma->vm_flags & VM_SHARED))
+	if (folio_maybe_mapped_shared(folio) && (vma->vm_flags & VM_SHARED))
 		*flags |= TNF_SHARED;
 	/*
 	 * For memory tiering mode, cpupid of slow memory page is used
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index bbaadbeeb291..530e71fe9147 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -642,11 +642,11 @@ static int queue_folios_hugetlb(pte_t *pte, unsigned long hmask,
 	 * Unless MPOL_MF_MOVE_ALL, we try to avoid migrating a shared folio.
 	 * Choosing not to migrate a shared folio is not counted as a failure.
 	 *
-	 * See folio_likely_mapped_shared() on possible imprecision when we
+	 * See folio_maybe_mapped_shared() on possible imprecision when we
 	 * cannot easily detect if a folio is shared.
 	 */
 	if ((flags & MPOL_MF_MOVE_ALL) ||
-	    (!folio_likely_mapped_shared(folio) && !hugetlb_pmd_shared(pte)))
+	    (!folio_maybe_mapped_shared(folio) && !hugetlb_pmd_shared(pte)))
 		if (!folio_isolate_hugetlb(folio, qp->pagelist))
 			qp->nr_failed++;
 unlock:
@@ -1033,10 +1033,10 @@ static bool migrate_folio_add(struct folio *folio, struct list_head *foliolist,
 	 * Unless MPOL_MF_MOVE_ALL, we try to avoid migrating a shared folio.
 	 * Choosing not to migrate a shared folio is not counted as a failure.
 	 *
-	 * See folio_likely_mapped_shared() on possible imprecision when we
+	 * See folio_maybe_mapped_shared() on possible imprecision when we
 	 * cannot easily detect if a folio is shared.
 	 */
-	if ((flags & MPOL_MF_MOVE_ALL) || !folio_likely_mapped_shared(folio)) {
+	if ((flags & MPOL_MF_MOVE_ALL) || !folio_maybe_mapped_shared(folio)) {
 		if (folio_isolate_lru(folio)) {
 			list_add_tail(&folio->lru, foliolist);
 			node_stat_mod_folio(folio,
diff --git a/mm/migrate.c b/mm/migrate.c
index a991d3691bda..c0adea67cd62 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -2226,7 +2226,7 @@ static int __add_folio_for_migration(struct folio *folio, int node,
 	if (folio_nid(folio) == node)
 		return 0;
 
-	if (folio_likely_mapped_shared(folio) && !migrate_all)
+	if (folio_maybe_mapped_shared(folio) && !migrate_all)
 		return -EACCES;
 
 	if (folio_test_hugetlb(folio)) {
@@ -2651,11 +2651,10 @@ int migrate_misplaced_folio_prepare(struct folio *folio,
 		 * processes with execute permissions as they are probably
 		 * shared libraries.
 		 *
-		 * See folio_likely_mapped_shared() on possible imprecision
+		 * See folio_maybe_mapped_shared() on possible imprecision
 		 * when we cannot easily detect if a folio is shared.
 		 */
-		if ((vma->vm_flags & VM_EXEC) &&
-		    folio_likely_mapped_shared(folio))
+		if ((vma->vm_flags & VM_EXEC) && folio_maybe_mapped_shared(folio))
 			return -EACCES;
 
 		/*
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 1444878f7aeb..62c1f7945741 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -133,7 +133,7 @@ static long change_pte_range(struct mmu_gather *tlb,
 				/* Also skip shared copy-on-write pages */
 				if (is_cow_mapping(vma->vm_flags) &&
 				    (folio_maybe_dma_pinned(folio) ||
-				     folio_likely_mapped_shared(folio)))
+				     folio_maybe_mapped_shared(folio)))
 					continue;
 
 				/*
diff --git a/mm/rmap.c b/mm/rmap.c
index c9922928616e..8de415157bc8 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -889,7 +889,7 @@ static bool folio_referenced_one(struct folio *folio,
 		if ((!atomic_read(&vma->vm_mm->mm_users) ||
 		    check_stable_address_space(vma->vm_mm)) &&
 		    folio_test_anon(folio) && folio_test_swapbacked(folio) &&
-		    !folio_likely_mapped_shared(folio)) {
+		    !folio_maybe_mapped_shared(folio)) {
 			pra->referenced = -1;
 			page_vma_mapped_walk_done(&pvmw);
 			return false;