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[2003:d8:2f16:1800:a9b4:1776:c5d9:1d9a]) by smtp.gmail.com with ESMTPSA id r8-20020adfda48000000b002be25db0b7bsm4403700wrl.10.2023.01.27.08.23.39 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 27 Jan 2023 08:23:40 -0800 (PST) Message-ID: <4ad5163f-5368-0bd8-de9b-1400a7a653ed@redhat.com> Date: Fri, 27 Jan 2023 17:23:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH 1/2] mm: hugetlb: proc: check for hugetlb shared PMD in /proc/PID/smaps Content-Language: en-US To: Mike Kravetz , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Naoya Horiguchi , James Houghton , Peter Xu , Michal Hocko , Yang Shi , Vishal Moola , Matthew Wilcox , Muchun Song , Andrew Morton , stable@vger.kernel.org References: <20230126222721.222195-1-mike.kravetz@oracle.com> <20230126222721.222195-2-mike.kravetz@oracle.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230126222721.222195-2-mike.kravetz@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org On 26.01.23 23:27, Mike Kravetz wrote: > A hugetlb page will have a mapcount of 1 if mapped by multiple processes > via a shared PMD. This is because only the first process increases the > map count, and subsequent processes just add the shared PMD page to > their page table. > > page_mapcount is being used to decide if a hugetlb page is shared or > private in /proc/PID/smaps. Pages referenced via a shared PMD were > incorrectly being counted as private. > > To fix, check for a shared PMD if mapcount is 1. If a shared PMD is > found count the hugetlb page as shared. A new helper to check for a > shared PMD is added. > > Fixes: 25ee01a2fca0 ("mm: hugetlb: proc: add hugetlb-related fields to /proc/PID/smaps") > Cc: stable@vger.kernel.org > Signed-off-by: Mike Kravetz > --- > fs/proc/task_mmu.c | 10 ++++++++-- > include/linux/hugetlb.h | 12 ++++++++++++ > 2 files changed, 20 insertions(+), 2 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index e35a0398db63..cb9539879402 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -749,8 +749,14 @@ static int smaps_hugetlb_range(pte_t *pte, unsigned long hmask, > > if (mapcount >= 2) > mss->shared_hugetlb += huge_page_size(hstate_vma(vma)); > - else > - mss->private_hugetlb += huge_page_size(hstate_vma(vma)); > + else { Better: if (mapcount >= 2 || hugetlb_pmd_shared(pte)) mss->shared_hugetlb += huge_page_size(hstate_vma(vma)); else mss->private_hugetlb += huge_page_size(hstate_vma(vma)); -- Thanks, David / dhildenb