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Fri, 21 Mar 2025 04:26:53 -0700 (PDT) X-Google-Smtp-Source: AGHT+IE/Qqfyr6B8bsLxXxeQh/Wo7JYQY4tOPbEFYCnCV92lF5CSImpeVqV3WqCvsyiNvSwQwA8gIQ== X-Received: by 2002:a05:6a00:4fd1:b0:736:9e40:13b1 with SMTP id d2e1a72fcca58-73905a253aamr5091461b3a.23.1742556412745; Fri, 21 Mar 2025 04:26:52 -0700 (PDT) Received: from [192.168.68.55] ([180.233.125.167]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-739061592c4sm1582987b3a.154.2025.03.21.04.26.48 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 21 Mar 2025 04:26:52 -0700 (PDT) Message-ID: <908c37d2-2da7-4892-bd07-4ec7ffb8fc3f@redhat.com> Date: Fri, 21 Mar 2025 21:26:47 +1000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm: Fix parameter passed to page_mapcount_is_type() To: David Hildenbrand , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org, willy@infradead.org, vbabka@suse.cz, osalvador@suse.de, gehao@kylinos.cn, shan.gavin@gmail.com References: <20250321053148.1434076-1-gshan@redhat.com> <20250321053148.1434076-2-gshan@redhat.com> Content-Language: en-US From: Gavin Shan In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 3/21/25 8:13 PM, David Hildenbrand wrote: > On 21.03.25 06:31, Gavin Shan wrote: >> As the comments of page_mapcount_is_type() indicate, the parameter >> passed to the function should be one more than page->__mapcount. >> However, page->__mapcount (equivalent to page->page_type) is passed to >> the function by commit 4ffca5a96678 ("mm: support only one page_type per >> page") where page_type_has_type() is replaced by page_mapcount_is_type(), >> but the parameter isn't adjusted. >> >> Fix the parameter passed to page_mapcount_is_type() to be (page->__mapcount >> + 1). >> >> Fixes: 4ffca5a96678 ("mm: support only one page_type per page") >> Cc: stable@vger.kernel.org # v6.12+ >> Signed-off-by: Gavin Shan >> --- >>   include/linux/page-flags.h | 2 +- >>   1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h >> index 36d283552f80..ad87b4cf1f9a 100644 >> --- a/include/linux/page-flags.h >> +++ b/include/linux/page-flags.h >> @@ -950,7 +950,7 @@ static inline bool page_mapcount_is_type(unsigned int mapcount) >>   static inline bool page_has_type(const struct page *page) >>   { >> -    return page_mapcount_is_type(data_race(page->page_type)); >> +    return page_mapcount_is_type(data_race(page->page_type) + 1); > > Probably we should just call page_type_has_type() instead? > Yes, page_type_has_type() is better. It will be used in v2. Thanks, Gavin