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[2003:cb:c711:6400:d1b9:21c5:b517:5f4e]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-388c801211dsm2844150f8f.17.2024.12.14.07.32.01 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 14 Dec 2024 07:32:03 -0800 (PST) Message-ID: Date: Sat, 14 Dec 2024 16:32:00 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 14/25] huge_memory: Allow mappings of PUD sized pages To: Alistair Popple , dan.j.williams@intel.com, linux-mm@kvack.org Cc: lina@asahilina.net, zhang.lyra@gmail.com, gerald.schaefer@linux.ibm.com, vishal.l.verma@intel.com, dave.jiang@intel.com, logang@deltatee.com, bhelgaas@google.com, jack@suse.cz, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, mpe@ellerman.id.au, npiggin@gmail.com, dave.hansen@linux.intel.com, ira.weiny@intel.com, willy@infradead.org, djwong@kernel.org, tytso@mit.edu, linmiaohe@huawei.com, peterx@redhat.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-xfs@vger.kernel.org, jhubbard@nvidia.com, hch@lst.de, david@fromorbit.com References: From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20241214_073208_203374_03F6BBCB X-CRM114-Status: GOOD ( 21.12 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 22.11.24 02:40, Alistair Popple wrote: > Currently DAX folio/page reference counts are managed differently to > normal pages. To allow these to be managed the same as normal pages > introduce vmf_insert_folio_pud. This will map the entire PUD-sized folio > and take references as it would for a normally mapped page. > > This is distinct from the current mechanism, vmf_insert_pfn_pud, which > simply inserts a special devmap PUD entry into the page table without > holding a reference to the page for the mapping. > > Signed-off-by: Alistair Popple > --- Hi, The patch subject of this (and especially the next patch) is misleading. Likely you meant to have it as: "mm/huge_memory: add vmf_insert_folio_pud() for mapping PUD sized pages" > for (i = 0; i < nr_pages; i++) { > @@ -1523,6 +1531,26 @@ void folio_add_file_rmap_pmd(struct folio *folio, struct page *page, > #endif > } > > +/** > + * folio_add_file_rmap_pud - add a PUD mapping to a page range of a folio > + * @folio: The folio to add the mapping to > + * @page: The first page to add > + * @vma: The vm area in which the mapping is added > + * > + * The page range of the folio is defined by [page, page + HPAGE_PUD_NR) > + * > + * The caller needs to hold the page table lock. > + */ > +void folio_add_file_rmap_pud(struct folio *folio, struct page *page, > + struct vm_area_struct *vma) > +{ > +#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD > + __folio_add_file_rmap(folio, page, HPAGE_PUD_NR, vma, RMAP_LEVEL_PUD); > +#else > + WARN_ON_ONCE(true); > +#endif > +} > + > static __always_inline void __folio_remove_rmap(struct folio *folio, > struct page *page, int nr_pages, struct vm_area_struct *vma, > enum rmap_level level) > @@ -1552,6 +1580,7 @@ static __always_inline void __folio_remove_rmap(struct folio *folio, > partially_mapped = nr && atomic_read(mapped); > break; > case RMAP_LEVEL_PMD: > + case RMAP_LEVEL_PUD: > atomic_dec(&folio->_large_mapcount); > last = atomic_add_negative(-1, &folio->_entire_mapcount); > if (last) { If you simply reuse that code (here and on the adding path), you will end up effectively setting nr_pmdmapped to a very large value and passing that into __folio_mod_stat(). There, we will adjust NR_SHMEM_PMDMAPPED/NR_FILE_PMDMAPPED, which is wrong (it's PUD mapped ;) ). It's probably best to split out the rmap changes from the other things in this patch. -- Cheers, David / dhildenb