From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org,
cgroups@vger.kernel.org, linux-sh@vger.kernel.org,
linux-trace-kernel@vger.kernel.org,
linux-fsdevel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
"Matthew Wilcox (Oracle)" <willy@infradead.org>,
Peter Xu <peterx@redhat.com>, Ryan Roberts <ryan.roberts@arm.com>,
Yin Fengwei <fengwei.yin@intel.com>,
Yang Shi <shy828301@gmail.com>, Zi Yan <ziy@nvidia.com>,
Jonathan Corbet <corbet@lwn.net>, Hugh Dickins <hughd@google.com>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Rich Felker <dalias@libc.org>,
John Paul Adrian Glaubitz <glaubitz@physik.fu-berlin.de>,
Chris Zankel <chris@zankel.net>,
Max Filippov <jcmvbkbc@gmail.com>,
Muchun Song <muchun.song@linux.dev>,
Miaohe Lin <linmiaohe@huawei.com>,
Naoya Horiguchi <naoya.horiguchi@nec.com>,
Richard Chang <richardycc@google.com>
Subject: Re: [PATCH v1 06/18] mm: make folio_mapcount() return 0 for small typed folios
Date: Wed, 24 Apr 2024 11:40:07 +0200 [thread overview]
Message-ID: <c30fcda1-ed87-46f5-8297-cdedbddac009@redhat.com> (raw)
In-Reply-To: <20240409192301.907377-7-david@redhat.com>
On 09.04.24 21:22, David Hildenbrand wrote:
> We already handle it properly for large folios. Let's also return "0"
> for small typed folios, like page_mapcount() currently would.
>
> Consequently, folio_mapcount() will never return negative values for
> typed folios, but may return negative values for underflows.
>
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> include/linux/mm.h | 11 +++++++++--
> 1 file changed, 9 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index daf687f0e8e5..d453232bba62 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1260,12 +1260,19 @@ static inline int folio_large_mapcount(const struct folio *folio)
> * references the entire folio counts exactly once, even when such special
> * page table entries are comprised of multiple ordinary page table entries.
> *
> + * Will report 0 for pages which cannot be mapped into userspace, such as
> + * slab, page tables and similar.
> + *
> * Return: The number of times this folio is mapped.
> */
> static inline int folio_mapcount(const struct folio *folio)
> {
> - if (likely(!folio_test_large(folio)))
> - return atomic_read(&folio->_mapcount) + 1;
> + int mapcount;
> +
> + if (likely(!folio_test_large(folio))) {
> + mapcount = atomic_read(&folio->_mapcount);
> + return page_type_has_type(mapcount) ? 0 : mapcount + 1;
> + }
> return folio_large_mapcount(folio);
> }
>
From 98acfb7ff35cb65fcfca5e799bf58f8afe84a645 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <david@redhat.com>
Date: Wed, 24 Apr 2024 10:56:17 +0200
Subject: [PATCH] !fixup: mm: make folio_mapcount() return 0 for small typed
folios
Just like page_mapcount(), let's make folio_mapcount() slightly more
efficient.
Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/mm.h | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index cf700c5cdd58b..78e583b50e421 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1271,8 +1271,11 @@ static inline int folio_mapcount(const struct folio *folio)
int mapcount;
if (likely(!folio_test_large(folio))) {
- mapcount = atomic_read(&folio->_mapcount);
- return page_type_has_type(mapcount) ? 0 : mapcount + 1;
+ mapcount = atomic_read(&folio->_mapcount) + 1;
+ /* Handle page_has_type() pages */
+ if (mapcount < PAGE_MAPCOUNT_RESERVE + 1)
+ mapcount = 0;
+ return mapcount;
}
return folio_large_mapcount(folio);
}
--
2.44.0
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2024-04-24 9:40 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-09 19:22 [PATCH v1 00/18] mm: mapcount for large folios + page_mapcount() cleanups David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 01/18] mm: allow for detecting underflows with page_mapcount() again David Hildenbrand
2024-04-09 20:06 ` Zi Yan
2024-04-09 21:42 ` Matthew Wilcox
2024-04-10 8:10 ` David Hildenbrand
2024-04-24 9:38 ` David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 02/18] mm/rmap: always inline anon/file rmap duplication of a single PTE David Hildenbrand
2024-04-19 2:25 ` Yin, Fengwei
2024-04-19 9:14 ` David Hildenbrand
2024-04-19 14:01 ` Yin, Fengwei
2024-04-09 19:22 ` [PATCH v1 03/18] mm/rmap: add fast-path for small folios when adding/removing/duplicating David Hildenbrand
2024-04-19 14:02 ` Yin, Fengwei
2024-04-09 19:22 ` [PATCH v1 04/18] mm: track mapcount of large folios in single value David Hildenbrand
2024-04-09 20:13 ` Zi Yan
2024-04-10 8:20 ` David Hildenbrand
2024-04-18 14:50 ` Lance Yang
2024-04-18 15:09 ` David Hildenbrand
2024-04-19 0:31 ` Lance Yang
2024-04-19 14:02 ` Yin, Fengwei
2024-04-09 19:22 ` [PATCH v1 05/18] mm: improve folio_likely_mapped_shared() using the mapcount of large folios David Hildenbrand
2024-04-16 10:40 ` Lance Yang
2024-04-16 10:47 ` David Hildenbrand
2024-04-16 10:52 ` Lance Yang
2024-04-16 10:53 ` David Hildenbrand
2024-04-19 2:29 ` Yin, Fengwei
2024-04-19 9:19 ` David Hildenbrand
2024-04-19 13:47 ` Yin, Fengwei
2024-04-19 13:48 ` David Hildenbrand
2024-04-19 14:03 ` Yin, Fengwei
2024-04-09 19:22 ` [PATCH v1 06/18] mm: make folio_mapcount() return 0 for small typed folios David Hildenbrand
2024-04-24 9:40 ` David Hildenbrand [this message]
2024-04-09 19:22 ` [PATCH v1 07/18] mm/memory: use folio_mapcount() in zap_present_folio_ptes() David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 08/18] mm/huge_memory: use folio_mapcount() in zap_huge_pmd() sanity check David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 09/18] mm/memory-failure: use folio_mapcount() in hwpoison_user_mappings() David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 10/18] mm/page_alloc: use folio_mapped() in __alloc_contig_migrate_range() David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 11/18] mm/migrate: use folio_likely_mapped_shared() in add_page_for_migration() David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 12/18] sh/mm/cache: use folio_mapped() in copy_from_user_page() David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 13/18] mm/filemap: use folio_mapcount() in filemap_unaccount_folio() David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 14/18] mm/migrate_device: use folio_mapcount() in migrate_vma_check_page() David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 15/18] trace/events/page_ref: trace the raw page mapcount value David Hildenbrand
2024-04-09 19:22 ` [PATCH v1 16/18] xtensa/mm: convert check_tlb_entry() to sanity check folios David Hildenbrand
2024-04-09 19:23 ` [PATCH v1 17/18] mm/debug: print only page mapcount (excluding folio entire mapcount) in __dump_folio() David Hildenbrand
2024-04-09 19:23 ` [PATCH v1 18/18] Documentation/admin-guide/cgroup-v1/memory.rst: don't reference page_mapcount() David Hildenbrand
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