The patch titled
Subject: kpageflags: detect isolated KPF_THP folios
has been added to the -mm mm-unstable branch. Its filename is
kpageflags-detect-isolated-kpf_thp-folios.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kpageflags-detect-isolated-kpf_thp-folios.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: Ran Xiaokai <ran.xiaokai@xxxxxxxxxx>
Subject: kpageflags: detect isolated KPF_THP folios
Date: Fri, 5 Jul 2024 10:43:43 +0000
When folio is isolated, the PG_lru bit is cleared. So the PG_lru check in
stable_page_flags() will miss this kind of isolated folios. Use
folio_test_large_rmappable() instead to also include isolated folios.
Since pagecache supports large folios and the introduction of mTHP, the
semantics of KPF_THP have been expanded, now it indicates not only
PMD-sized THP. Update related documentation to clearly state that KPF_THP
indicates multiple order THPs.
Link: https://lkml.kernel.org/r/20240705104343.112680-1-ranxiaokai627@xxxxxxx
Signed-off-by: Ran Xiaokai <ran.xiaokai@xxxxxxxxxx>
Acked-by: David Hildenbrand <david@xxxxxxxxxx>
Cc: Andrei Vagin <avagin@xxxxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Muhammad Usama Anjum <usama.anjum@xxxxxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: Svetly Todorov <svetly.todorov@xxxxxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Zi Yan <ziy@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/admin-guide/mm/pagemap.rst | 4 ++--
fs/proc/page.c | 21 +++++++++------------
2 files changed, 11 insertions(+), 14 deletions(-)
--- a/Documentation/admin-guide/mm/pagemap.rst~kpageflags-detect-isolated-kpf_thp-folios
+++ a/Documentation/admin-guide/mm/pagemap.rst
@@ -118,7 +118,7 @@ Short descriptions to the page flags
21 - KSM
Identical memory pages dynamically shared between one or more processes.
22 - THP
- Contiguous pages which construct transparent hugepages.
+ Contiguous pages which construct THP of any size and mapped by any granularity.
23 - OFFLINE
The page is logically offline.
24 - ZERO_PAGE
@@ -231,7 +231,7 @@ Following flags about pages are currentl
- ``PAGE_IS_PRESENT`` - Page is present in the memory
- ``PAGE_IS_SWAPPED`` - Page is in swapped
- ``PAGE_IS_PFNZERO`` - Page has zero PFN
-- ``PAGE_IS_HUGE`` - Page is THP or Hugetlb backed
+- ``PAGE_IS_HUGE`` - Page is PMD-mapped THP or Hugetlb backed
- ``PAGE_IS_SOFT_DIRTY`` - Page is soft-dirty
The ``struct pm_scan_arg`` is used as the argument of the IOCTL.
--- a/fs/proc/page.c~kpageflags-detect-isolated-kpf_thp-folios
+++ a/fs/proc/page.c
@@ -147,19 +147,16 @@ u64 stable_page_flags(const struct page
u |= 1 << KPF_COMPOUND_TAIL;
if (folio_test_hugetlb(folio))
u |= 1 << KPF_HUGE;
- /*
- * We need to check PageLRU/PageAnon
- * to make sure a given page is a thp, not a non-huge compound page.
- */
- else if (folio_test_large(folio)) {
- if ((k & (1 << PG_lru)) || is_anon)
- u |= 1 << KPF_THP;
- else if (is_huge_zero_folio(folio)) {
- u |= 1 << KPF_ZERO_PAGE;
- u |= 1 << KPF_THP;
- }
- } else if (is_zero_pfn(page_to_pfn(page)))
+ else if (folio_test_large(folio) &&
+ folio_test_large_rmappable(folio)) {
+ /* Note: we indicate any THPs here, not just PMD-sized ones */
+ u |= 1 << KPF_THP;
+ } else if (is_huge_zero_folio(folio)) {
+ u |= 1 << KPF_ZERO_PAGE;
+ u |= 1 << KPF_THP;
+ } else if (is_zero_pfn(page_to_pfn(page))) {
u |= 1 << KPF_ZERO_PAGE;
+ }
/*
* Caveats on high order pages: PG_buddy and PG_slab will only be set
_
Patches currently in -mm which might be from ran.xiaokai@xxxxxxxxxx are
kpageflags-detect-isolated-kpf_thp-folios.patch
