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-rw-r--r--fs/proc/task_mmu.c4
-rw-r--r--include/linux/mm.h43
-rw-r--r--mm/huge_memory.c2
-rw-r--r--mm/khugepaged.c8
-rw-r--r--mm/madvise.c6
-rw-r--r--mm/memory.c2
-rw-r--r--mm/mempolicy.c8
-rw-r--r--mm/migrate.c7
-rw-r--r--mm/mprotect.c2
-rw-r--r--mm/rmap.c2
10 files changed, 41 insertions, 43 deletions
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;
generated by cgit (git 2.34.1) at 2025-08-05 22:59:15 +0000