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kpageflags: detect isolated KPF_THP folios

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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.

[ran.xiaokai@zte.com.cn: directly use is_zero_folio(), per David]
  Link: https://lkml.kernel.org/r/20240708062601.165215-1-ranxiaokai627@163.com
Link: https://lkml.kernel.org/r/20240705104343.112680-1-ranxiaokai627@163.com
Signed-off-by: Ran Xiaokai <ran.xiaokai@zte.com.cn>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: Andrei Vagin <avagin@google.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Svetly Todorov <svetly.todorov@memverge.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Ran Xiaokai 2024-07-05 10:43:43 +00:00 committed by Andrew Morton
parent 00f5810420
commit 4c8763e84a
2 changed files with 11 additions and 14 deletions
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4
Documentation/admin-guide/mm/pagemap.rst
View File

@ -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 currently supported:
- ``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.

21
fs/proc/page.c
View File

@ -147,19 +147,16 @@ u64 stable_page_flags(const struct page *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_folio(folio)) {
u |= 1 << KPF_ZERO_PAGE;
}
/*
* Caveats on high order pages: PG_buddy and PG_slab will only be set