From 4c8763e84aae4d04d94b35aca9f7db6a8930ad77 Mon Sep 17 00:00:00 2001 From: Ran Xiaokai Date: Fri, 5 Jul 2024 10:43:43 +0000 Subject: [PATCH] kpageflags: detect isolated KPF_THP folios 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 Acked-by: David Hildenbrand Cc: Andrei Vagin Cc: Jonathan Corbet Cc: Muhammad Usama Anjum Cc: Ryan Roberts Cc: Svetly Todorov Cc: Vlastimil Babka Cc: Zi Yan Signed-off-by: Andrew Morton --- Documentation/admin-guide/mm/pagemap.rst | 4 ++-- fs/proc/page.c | 21 +++++++++------------ 2 files changed, 11 insertions(+), 14 deletions(-) diff --git a/Documentation/admin-guide/mm/pagemap.rst b/Documentation/admin-guide/mm/pagemap.rst index f2817a801596..caba0f52dd36 100644 --- a/Documentation/admin-guide/mm/pagemap.rst +++ b/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 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. diff --git a/fs/proc/page.c b/fs/proc/page.c index e8440db8cfbf..b7a5c84b5819 100644 --- a/fs/proc/page.c +++ b/fs/proc/page.c @@ -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