The patch titled
Subject: fs/proc/task_mmu: properly detect PM_MMAP_EXCLUSIVE per page of PMD-mapped THPs
has been added to the -mm mm-unstable branch. Its filename is
fs-proc-task_mmu-properly-detect-pm_mmap_exclusive-per-page-of-pmd-mapped-thps.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-properly-detect-pm_mmap_exclusive-per-page-of-pmd-mapped-thps.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: properly detect PM_MMAP_EXCLUSIVE per page of PMD-mapped THPs
Date: Fri, 7 Jun 2024 14:23:54 +0200
We added PM_MMAP_EXCLUSIVE in 2015 via commit 77bb499bb60f ("pagemap: add
mmap-exclusive bit for marking pages mapped only here"), when THPs could
not be partially mapped and page_mapcount() returned something that was
true for all pages of the THP.
In 2016, we added support for partially mapping THPs via commit
53f9263baba6 ("mm: rework mapcount accounting to enable 4k mapping of
THPs") but missed to determine PM_MMAP_EXCLUSIVE as well per page.
Checking page_mapcount() on the head page does not tell the whole story.
We should check each individual page. In a future without per-page
mapcounts it will be different, but we'll change that to be consistent
with PTE-mapped THPs once we deal with that.
Link: https://lkml.kernel.org/r/20240607122357.115423-4-david@xxxxxxxxxx
Fixes: 53f9263baba6 ("mm: rework mapcount accounting to enable 4k mapping of THPs")
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Lance Yang <ioworker0@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 22 ++++++++++++----------
1 file changed, 12 insertions(+), 10 deletions(-)
--- a/fs/proc/task_mmu.c~fs-proc-task_mmu-properly-detect-pm_mmap_exclusive-per-page-of-pmd-mapped-thps
+++ a/fs/proc/task_mmu.c
@@ -1474,6 +1474,7 @@ static int pagemap_pmd_range(pmd_t *pmdp
ptl = pmd_trans_huge_lock(pmdp, vma);
if (ptl) {
+ unsigned int idx = (addr & ~PMD_MASK) >> PAGE_SHIFT;
u64 flags = 0, frame = 0;
pmd_t pmd = *pmdp;
struct page *page = NULL;
@@ -1490,8 +1491,7 @@ static int pagemap_pmd_range(pmd_t *pmdp
if (pmd_uffd_wp(pmd))
flags |= PM_UFFD_WP;
if (pm->show_pfn)
- frame = pmd_pfn(pmd) +
- ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+ frame = pmd_pfn(pmd) + idx;
}
#ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
else if (is_swap_pmd(pmd)) {
@@ -1500,11 +1500,9 @@ static int pagemap_pmd_range(pmd_t *pmdp
if (pm->show_pfn) {
if (is_pfn_swap_entry(entry))
- offset = swp_offset_pfn(entry);
+ offset = swp_offset_pfn(entry) + idx;
else
- offset = swp_offset(entry);
- offset = offset +
- ((addr & ~PMD_MASK) >> PAGE_SHIFT);
+ offset = swp_offset(entry) + idx;
frame = swp_type(entry) |
(offset << MAX_SWAPFILES_SHIFT);
}
@@ -1520,12 +1518,16 @@ static int pagemap_pmd_range(pmd_t *pmdp
if (page && !PageAnon(page))
flags |= PM_FILE;
- if (page && (flags & PM_PRESENT) && page_mapcount(page) == 1)
- flags |= PM_MMAP_EXCLUSIVE;
- for (; addr != end; addr += PAGE_SIZE) {
- pagemap_entry_t pme = make_pme(frame, flags);
+ for (; addr != end; addr += PAGE_SIZE, idx++) {
+ unsigned long cur_flags = flags;
+ pagemap_entry_t pme;
+
+ if (page && (flags & PM_PRESENT) &&
+ page_mapcount(page + idx) == 1)
+ cur_flags |= PM_MMAP_EXCLUSIVE;
+ pme = make_pme(frame, cur_flags);
err = add_to_pagemap(&pme, pm);
if (err)
break;
_
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
