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Wed, 19 Mar 2025 17:09:07 +0800 Message-ID: <64a43d16-606c-4255-8a8b-96d6e4e44729@linux.alibaba.com> Date: Wed, 19 Mar 2025 17:09:06 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/vmalloc: fix mischeck pfn valid in vmap_pfns To: Christoph Hellwig Cc: akpm@linux-foundation.org, bingbu.cao@linux.intel.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, lorenzo.stoakes@oracle.com, opensource.kernel@vivo.com, rppt@kernel.org, ryan.roberts@arm.com, urezki@gmail.com, ziy@nvidia.com, vivek.kasireddy@intel.com, Huan Yang References: <20250317055304.GB26662@lst.de> <5a12454c-16a1-4400-a764-f49293d8dece@vivo.com> <20250318064805.GA16121@lst.de> <5229b24f-1984-4225-ae03-8b952de56e3b@vivo.com> <20250318083330.GB18902@lst.de> <20250318084453.GB19274@lst.de> From: Gao Xiang In-Reply-To: <20250318084453.GB19274@lst.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 9C9D1A0009 X-Stat-Signature: 5rgkn4wq6199acc9nqrsnux9whk8akam X-HE-Tag: 1742375353-656348 X-HE-Meta: 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 S+1WoOqo ik2Jzs0c4egpx/iVX25tw87WBdDZvdJJ2H5jeI0Ar4JKgnvZvg5o2usZJqxavEeagrwoKb4MtoryD4PL5g80a4J7uH8DwE8sJnDmynzoowo7RR9vglCZyxfmw8tLyKoACjit/k6D2V846zg9ZvyrzHBuqkFlb+xkva6hhsemDRRbRUge1G8Y0kaITKg5tA7AxDtALjM9AbltixFVoKCvFlgRzdrjGUpN8IIOztvZefZC+Iwaa7rBE2Boh6pXmo2CQtkKq+X7Wtz/fBg+BFO79QX/wN8dvF4oj4IlZxHcRLm91tBQ= X-Bogosity: Ham, tests=bogofilter, spamicity=0.120415, 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 2025/3/18 16:44, Christoph Hellwig wrote: > On Tue, Mar 18, 2025 at 04:39:40PM +0800, Huan Yang wrote: >> A folio may be 2MB or more large 1GB, what if we only need a little, 1M or 512MB, can vmap based on folio can solve it? > > Then you only map part of it by passing a length argument. Note that > in general when you have these large folios you also don't have highmem, > so if you only map one of them, or part of one of them you don't actually > need vmap at all and can just use folio-address.. > >> Normally, can offer 4k-page based array map it. But consider HVO, can't. That's why wanto base on pfn. > > Well, for any large folio using this 4k based page interface is > actually highly inefficient. So let's fix that. And my loop in > willy as Mr. Folio while you're at it. The minimum map unit is page size instead of variable-size folio. For many cases, vmap (to combine many partial folios) is useful (instead of split all folios to order-0 folios in advance) but I agree page array may be inefficient. So I don't think another folio vmap() version is better overall anyway. Thanks, Gao Xiang