The patch titled
Subject: fs/proc/task_mmu: don't indicate PM_MMAP_EXCLUSIVE without PM_PRESENT
has been added to the -mm mm-unstable branch. Its filename is
fs-proc-task_mmu-dont-indicate-pm_mmap_exclusive-without-pm_present.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fs-proc-task_mmu-dont-indicate-pm_mmap_exclusive-without-pm_present.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: David Hildenbrand <david@xxxxxxxxxx>
Subject: fs/proc/task_mmu: don't indicate PM_MMAP_EXCLUSIVE without PM_PRESENT
Date: Fri, 7 Jun 2024 14:23:53 +0200
Relying on the mapcount for non-present PTEs that reference pages doesn't
make any sense: they are not accounted in the mapcount, so page_mapcount()
== 1 won't return the result we actually want to know.
While we don't check the mapcount for migration entries already, we could
end up checking it for swap, hwpoison, device exclusive, ... entries,
which we really shouldn't.
There is one exception: device private entries, which we consider
fake-present (e.g., incremented the mapcount). But we won't care about
that for now for PM_MMAP_EXCLUSIVE, because indicating PM_SWAP for them
although they are fake-present already sounds suspiciously wrong.
Let's never indicate PM_MMAP_EXCLUSIVE without PM_PRESENT.
Link: https://lkml.kernel.org/r/20240607122357.115423-3-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Lance Yang <ioworker0@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)
--- a/fs/proc/task_mmu.c~fs-proc-task_mmu-dont-indicate-pm_mmap_exclusive-without-pm_present
+++ a/fs/proc/task_mmu.c
@@ -1415,7 +1415,6 @@ static pagemap_entry_t pte_to_pagemap_en
{
u64 frame = 0, flags = 0;
struct page *page = NULL;
- bool migration = false;
if (pte_present(pte)) {
if (pm->show_pfn)
@@ -1447,7 +1446,6 @@ static pagemap_entry_t pte_to_pagemap_en
(offset << MAX_SWAPFILES_SHIFT);
}
flags |= PM_SWAP;
- migration = is_migration_entry(entry);
if (is_pfn_swap_entry(entry))
page = pfn_swap_entry_to_page(entry);
if (pte_marker_entry_uffd_wp(entry))
@@ -1456,7 +1454,7 @@ static pagemap_entry_t pte_to_pagemap_en
if (page && !PageAnon(page))
flags |= PM_FILE;
- if (page && !migration && page_mapcount(page) == 1)
+ if (page && (flags & PM_PRESENT) && page_mapcount(page) == 1)
flags |= PM_MMAP_EXCLUSIVE;
if (vma->vm_flags & VM_SOFTDIRTY)
flags |= PM_SOFT_DIRTY;
@@ -1473,7 +1471,6 @@ static int pagemap_pmd_range(pmd_t *pmdp
pte_t *pte, *orig_pte;
int err = 0;
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- bool migration = false;
ptl = pmd_trans_huge_lock(pmdp, vma);
if (ptl) {
@@ -1517,14 +1514,13 @@ static int pagemap_pmd_range(pmd_t *pmdp
if (pmd_swp_uffd_wp(pmd))
flags |= PM_UFFD_WP;
VM_BUG_ON(!is_pmd_migration_entry(pmd));
- migration = is_migration_entry(entry);
page = pfn_swap_entry_to_page(entry);
}
#endif
if (page && !PageAnon(page))
flags |= PM_FILE;
- if (page && !migration && page_mapcount(page) == 1)
+ if (page && (flags & PM_PRESENT) && page_mapcount(page) == 1)
flags |= PM_MMAP_EXCLUSIVE;
for (; addr != end; addr += PAGE_SIZE) {
_
Patches currently in -mm which might be from david@xxxxxxxxxx are
revert-mm-init_mlocked_on_free_v3.patch
mm-memory-move-page_count-check-into-validate_page_before_insert.patch
mm-memory-cleanly-support-zeropage-in-vm_insert_page-vm_map_pages-and-vmf_insert_mixed.patch
mm-rmap-sanity-check-that-zeropages-are-not-passed-to-rmap.patch
mm-update-_mapcount-and-page_type-documentation.patch
mm-allow-reuse-of-the-lower-16-bit-of-the-page-type-with-an-actual-type.patch
mm-zsmalloc-use-a-proper-page-type.patch
mm-page_alloc-clear-pagebuddy-using-__clearpagebuddy-for-bad-pages.patch
mm-filemap-reinitialize-folio-_mapcount-directly.patch
mm-mm_init-initialize-page-_mapcount-directly-in-__init_single_page.patch
fs-proc-task_mmu-indicate-pm_file-for-pmd-mapped-file-thp.patch
fs-proc-task_mmu-dont-indicate-pm_mmap_exclusive-without-pm_present.patch
fs-proc-task_mmu-properly-detect-pm_mmap_exclusive-per-page-of-pmd-mapped-thps.patch
fs-proc-task_mmu-account-non-present-entries-as-maybe-shared-but-no-idea-how-often.patch
fs-proc-move-page_mapcount-to-fs-proc-internalh.patch
documentation-admin-guide-mm-pagemaprst-drop-using-pagemap-to-do-something-useful.patch
