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[2003:cb:c73b:5600:c716:d8e0:609d:ae92]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-388c8060905sm12357212f8f.99.2024.12.17.14.27.14 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 17 Dec 2024 14:27:15 -0800 (PST) Message-ID: <4b5768b7-96e0-4864-9dbe-88fd1f0e87b8@redhat.com> Date: Tue, 17 Dec 2024 23:27:13 +0100 Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 14/25] rmap: Add support for PUD sized mappings to rmap To: Alistair Popple , akpm@linux-foundation.org, 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: <7f739c9e9f0a25cafb76a482e31e632c8f72102e.1734407924.git-series.apopple@nvidia.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <7f739c9e9f0a25cafb76a482e31e632c8f72102e.1734407924.git-series.apopple@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 17.12.24 06:12, Alistair Popple wrote: > The rmap doesn't currently support adding a PUD mapping of a > folio. This patch adds support for entire PUD mappings of folios, > primarily to allow for more standard refcounting of device DAX > folios. Currently DAX is the only user of this and it doesn't require > support for partially mapped PUD-sized folios so we don't support for > that for now. > > Signed-off-by: Alistair Popple > > --- > > David - Thanks for your previous comments, I'm less familiar with the > rmap code so I would appreciate you taking another look. In particular > I haven't added a stat for PUD mapped folios as it seemed like > overkill for just the device DAX case but let me know if you think > otherwise. > > Changes for v4: > > - New for v4, split out rmap changes as suggested by David. > --- > include/linux/rmap.h | 15 ++++++++++++- > mm/rmap.c | 56 +++++++++++++++++++++++++++++++++++++++++++++- > 2 files changed, 71 insertions(+) > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index 683a040..7043914 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -192,6 +192,7 @@ typedef int __bitwise rmap_t; > enum rmap_level { > RMAP_LEVEL_PTE = 0, > RMAP_LEVEL_PMD, > + RMAP_LEVEL_PUD, > }; > > static inline void __folio_rmap_sanity_checks(const struct folio *folio, > @@ -228,6 +229,14 @@ static inline void __folio_rmap_sanity_checks(const struct folio *folio, > VM_WARN_ON_FOLIO(folio_nr_pages(folio) != HPAGE_PMD_NR, folio); > VM_WARN_ON_FOLIO(nr_pages != HPAGE_PMD_NR, folio); > break; > + case RMAP_LEVEL_PUD: > + /* > + * Assume that we are creating * a single "entire" mapping of the > + * folio. > + */ > + VM_WARN_ON_FOLIO(folio_nr_pages(folio) != HPAGE_PUD_NR, folio); > + VM_WARN_ON_FOLIO(nr_pages != HPAGE_PUD_NR, folio); > + break; > default: > VM_WARN_ON_ONCE(true); > } > @@ -251,12 +260,16 @@ void folio_add_file_rmap_ptes(struct folio *, struct page *, int nr_pages, > folio_add_file_rmap_ptes(folio, page, 1, vma) > void folio_add_file_rmap_pmd(struct folio *, struct page *, > struct vm_area_struct *); > +void folio_add_file_rmap_pud(struct folio *, struct page *, > + struct vm_area_struct *); > void folio_remove_rmap_ptes(struct folio *, struct page *, int nr_pages, > struct vm_area_struct *); > #define folio_remove_rmap_pte(folio, page, vma) \ > folio_remove_rmap_ptes(folio, page, 1, vma) > void folio_remove_rmap_pmd(struct folio *, struct page *, > struct vm_area_struct *); > +void folio_remove_rmap_pud(struct folio *, struct page *, > + struct vm_area_struct *); > > void hugetlb_add_anon_rmap(struct folio *, struct vm_area_struct *, > unsigned long address, rmap_t flags); > @@ -341,6 +354,7 @@ static __always_inline void __folio_dup_file_rmap(struct folio *folio, > atomic_add(orig_nr_pages, &folio->_large_mapcount); > break; > case RMAP_LEVEL_PMD: > + case RMAP_LEVEL_PUD: > atomic_inc(&folio->_entire_mapcount); > atomic_inc(&folio->_large_mapcount); > break; > @@ -437,6 +451,7 @@ static __always_inline int __folio_try_dup_anon_rmap(struct folio *folio, > atomic_add(orig_nr_pages, &folio->_large_mapcount); > break; > case RMAP_LEVEL_PMD: > + case RMAP_LEVEL_PUD: > if (PageAnonExclusive(page)) { > if (unlikely(maybe_pinned)) > return -EBUSY; > diff --git a/mm/rmap.c b/mm/rmap.c > index c6c4d4e..39d0439 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1203,6 +1203,11 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio, > } > atomic_inc(&folio->_large_mapcount); > break; > + case RMAP_LEVEL_PUD: > + /* We only support entire mappings of PUD sized folios in rmap */ > + atomic_inc(&folio->_entire_mapcount); > + atomic_inc(&folio->_large_mapcount); > + break; This way you don't account the pages at all as mapped, whereby PTE-mapping it would? And IIRC, these PUD-sized pages can be either mapped using PTEs or using a single PUD. I suspect what you want is to diff --git a/mm/rmap.c b/mm/rmap.c index c6c4d4ea29a7e..1477028d3a176 100644 --- a/mm/rmap.c +++ b/mm/rmap.c @@ -1187,12 +1187,19 @@ static __always_inline unsigned int __folio_add_rmap(struct folio *folio, atomic_add(orig_nr_pages, &folio->_large_mapcount); break; case RMAP_LEVEL_PMD: + case RMAP_LEVEL_PUD: first = atomic_inc_and_test(&folio->_entire_mapcount); if (first) { nr = atomic_add_return_relaxed(ENTIRELY_MAPPED, mapped); if (likely(nr < ENTIRELY_MAPPED + ENTIRELY_MAPPED)) { - *nr_pmdmapped = folio_nr_pages(folio); - nr = *nr_pmdmapped - (nr & FOLIO_PAGES_MAPPED); + nr_pages = folio_nr_pages(folio); + /* + * We only track PMD mappings of PMD-sized + * folios separately. + */ + if (level == RMAP_LEVEL_PMD) + *nr_pmdmapped = nr_pages; + nr = nr_pages - (nr & FOLIO_PAGES_MAPPED); /* Raced ahead of a remove and another add? */ if (unlikely(nr < 0)) nr = 0; Similar on the removal path. -- Cheers, David / dhildenb