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[2003:d8:2f28:4900:2c24:4e20:1f21:9fbd]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3b5f32ed100sm12218643f8f.0.2025.07.15.06.36.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 15 Jul 2025 06:36:14 -0700 (PDT) Message-ID: Date: Tue, 15 Jul 2025 15:36:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 mm-new] fs/proc/page: avoid anon folio checks on typed pages except hugetlb To: Harry Yoo Cc: Andrew Morton , Matthew Wilcox , David Rientjes , Christoph Lameter , Roman Gushchin , linux-mm@kvack.org, Vlastimil Babka References: <20250715120748.9290-1-harry.yoo@oracle.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 0bA5RSm5pMFl2eWIUbNPiqoYw7xgI52ImgvN2CmRaQ4_1752586576 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A526D2000B X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: 7f8ffpqee447rd9xq6tbrmawj8za3hx8 X-HE-Tag: 1752586579-291837 X-HE-Meta: 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 rvWlglU6 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 15.07.25 15:30, Harry Yoo wrote: > On Tue, Jul 15, 2025 at 02:31:45PM +0200, David Hildenbrand wrote: >> On 15.07.25 14:07, Harry Yoo wrote: >>> folio_test_anon() and folio_test_ksm() may return false positives when >>> invoked on typed pages (except hugetlb folios), because lower bits of >>> folio->mapping may be set even when they do not indicate >>> FOLIO_MAPPING_* flags. >>> >>> This leads to tools/mm/page-types reporting pages with >>> KPF_SLAB, KPF_ANON and KPF_KSM (with flags, page-counts, MB omitted): >>> $ sudo ./page-types | grep slab >>> _______S___________________________________ slab >>> _______S____a________x_____________________ slab,anonymous,ksm >>> >>> Currently, and going forward (The New York interpretation), >>> typed pages except hugetlb do not have FOLIO_MAPPING_* flags. >>> In the future, they won't even cast to folios. >>> >>> For now, avoid checking FOLIO_MAPPING_* flags on pages if they are >>> typed pages that are not hugetlb folios. >>> >>> Update the comment in FOLIO_MAPPING_* flags accordingly. >>> >>> Fixes: 130d4df57390 ("mm/sl[au]b: rearrange struct slab fields to allow larger rcu_head") >>> Suggested-by: Vlastimil Babka >>> Signed-off-by: Harry Yoo >>> --- >>> >>> v2->v3: Did not introduce folio_has_mapcount() per David's suggestion >>> v2: https://lore.kernel.org/linux-mm/20250707120740.4413-1-harry.yoo@oracle.com >>> >>> fs/proc/page.c | 19 +++++++++++-------- >>> include/linux/page-flags.h | 15 +++++++++------ >>> 2 files changed, 20 insertions(+), 14 deletions(-) >>> >>> diff --git a/fs/proc/page.c b/fs/proc/page.c >>> index 0cdc78c0d23f..07582dbdef45 100644 >>> --- a/fs/proc/page.c >>> +++ b/fs/proc/page.c >>> @@ -148,18 +148,21 @@ u64 stable_page_flags(const struct page *page) >>> folio = page_folio(page); >>> k = folio->flags; >>> - mapping = (unsigned long)folio->mapping; >>> - is_anon = mapping & FOLIO_MAPPING_ANON; >>> /* >>> * pseudo flags for the well known (anonymous) memory mapped pages >>> */ >>> - if (page_mapped(page)) >>> - u |= 1 << KPF_MMAP; >>> - if (is_anon) { >>> - u |= 1 << KPF_ANON; >>> - if (mapping & FOLIO_MAPPING_KSM) >>> - u |= 1 << KPF_KSM; >>> + if (!page_has_type(&folio->page) || folio_test_hugetlb(folio)) { >>> + mapping = (unsigned long)folio->mapping; >>> + is_anon = mapping & FOLIO_MAPPING_ANON; >>> + >>> + if (page_mapped(page)) >>> + u |= 1 << KPF_MMAP; >> >> Note: Luiz switches to folio_mapped() in his patch that is in mm-new. > > Right, but in mm-new Luiz's patch already depends on my v2 patch, > which still leaves me confused about what I should do... :) Haha, right. Yes, just send it as a replacement to you current patch then. The conflict should be easy to resolve. -- Cheers, David / dhildenb