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 01/18] mm: allow for detecting underflows with page_mapcount() again
Date: Wed, 24 Apr 2024 11:38:51 +0200 [thread overview]
Message-ID: <1af4fd61-7926-47c8-be45-833c0dbec08b@redhat.com> (raw)
In-Reply-To: <20240409192301.907377-2-david@redhat.com>
On 09.04.24 21:22, David Hildenbrand wrote:
> Commit 53277bcf126d ("mm: support page_mapcount() on page_has_type()
> pages") made it impossible to detect mapcount underflows by treating
> any negative raw mapcount value as a mapcount of 0.
>
> We perform such underflow checks in zap_present_folio_ptes() and
> zap_huge_pmd(), which would currently no longer trigger.
>
> Let's check against PAGE_MAPCOUNT_RESERVE instead by using
> page_type_has_type(), like page_has_type() would, so we can still catch
> some underflows.
>
> Fixes: 53277bcf126d ("mm: support page_mapcount() on page_has_type() pages")
> Signed-off-by: David Hildenbrand <david@redhat.com>
> ---
> include/linux/mm.h | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index ef34cf54c14f..0fb8a40f82dd 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1229,11 +1229,10 @@ static inline void page_mapcount_reset(struct page *page)
> */
> static inline int page_mapcount(struct page *page)
> {
> - int mapcount = atomic_read(&page->_mapcount) + 1;
> + int mapcount = atomic_read(&page->_mapcount);
>
> /* Handle page_has_type() pages */
> - if (mapcount < 0)
> - mapcount = 0;
> + mapcount = page_type_has_type(mapcount) ? 0 : mapcount + 1;
> if (unlikely(PageCompound(page)))
> mapcount += folio_entire_mapcount(page_folio(page));
>
From b49849001f3d2aad0af93cf2098065d7cbd9a959 Mon Sep 17 00:00:00 2001
From: David Hildenbrand <david@redhat.com>
Date: Wed, 24 Apr 2024 10:50:09 +0200
Subject: [PATCH] !fixup: mm: allow for detecting underflows with
page_mapcount() again
Let's make page_mapcount() slighly more efficient by inlining the
page_type_has_type() check.
Signed-off-by: David Hildenbrand <david@redhat.com>
---
include/linux/mm.h | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index dc33f8269fb52..cf700c5cdd58b 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1229,10 +1229,11 @@ static inline void page_mapcount_reset(struct page *page)
*/
static inline int page_mapcount(struct page *page)
{
- int mapcount = atomic_read(&page->_mapcount);
+ int mapcount = atomic_read(&page->_mapcount) + 1;
/* Handle page_has_type() pages */
- mapcount = page_type_has_type(mapcount) ? 0 : mapcount + 1;
+ if (mapcount < PAGE_MAPCOUNT_RESERVE + 1)
+ mapcount = 0;
if (unlikely(PageCompound(page)))
mapcount += folio_entire_mapcount(page_folio(page));
--
2.44.0
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2024-04-24 9:39 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 [this message]
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
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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