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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3c711d9f3a8sm16439115f8f.62.2025.08.26.07.22.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 26 Aug 2025 07:22:41 -0700 (PDT) Message-ID: <54bfb6c0-eb35-4e53-ab45-04139623abb0@redhat.com> Date: Tue, 26 Aug 2025 16:22:39 +0200 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: [v3 01/11] mm/zone_device: support large zone device private folios To: Balbir Singh , dri-devel@lists.freedesktop.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Andrew Morton , Zi Yan , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Oscar Salvador , Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lyude Paul , Danilo Krummrich , David Airlie , Simona Vetter , Ralph Campbell , =?UTF-8?Q?Mika_Penttil=C3=A4?= , Matthew Brost , Francois Dugast References: <20250812024036.690064-1-balbirs@nvidia.com> <20250812024036.690064-2-balbirs@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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20250812024036.690064-2-balbirs@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 12.08.25 04:40, Balbir Singh wrote: > Add routines to support allocation of large order zone device folios > and helper functions for zone device folios, to check if a folio is > device private and helpers for setting zone device data. > > When large folios are used, the existing page_free() callback in > pgmap is called when the folio is freed, this is true for both > PAGE_SIZE and higher order pages. > > Zone device private large folios do not support deferred split and > scan like normal THP folios. [...] > #else > static inline void *devm_memremap_pages(struct device *dev, > struct dev_pagemap *pgmap) > diff --git a/mm/memremap.c b/mm/memremap.c > index b0ce0d8254bd..13e87dd743ad 100644 > --- a/mm/memremap.c > +++ b/mm/memremap.c > @@ -427,20 +427,19 @@ EXPORT_SYMBOL_GPL(get_dev_pagemap); > void free_zone_device_folio(struct folio *folio) > { > struct dev_pagemap *pgmap = folio->pgmap; > + unsigned long nr = folio_nr_pages(folio); > + int i; Not that it will currently matter much but unsigned long i, nr = folio_nr_pages(folio); might be more consistent > > if (WARN_ON_ONCE(!pgmap)) > return; > > mem_cgroup_uncharge(folio); > > - /* > - * Note: we don't expect anonymous compound pages yet. Once supported > - * and we could PTE-map them similar to THP, we'd have to clear > - * PG_anon_exclusive on all tail pages. > - */ > if (folio_test_anon(folio)) { > - VM_BUG_ON_FOLIO(folio_test_large(folio), folio); > - __ClearPageAnonExclusive(folio_page(folio, 0)); > + for (i = 0; i < nr; i++) > + __ClearPageAnonExclusive(folio_page(folio, i)); > + } else { > + VM_WARN_ON_ONCE(folio_test_large(folio)); > } > > /* > @@ -464,11 +463,15 @@ void free_zone_device_folio(struct folio *folio) > > switch (pgmap->type) { > case MEMORY_DEVICE_PRIVATE: Why are you effectively dropping the if (WARN_ON_ONCE(!pgmap->ops || !pgmap->ops->page_free)) > + percpu_ref_put_many(&folio->pgmap->ref, nr); > + pgmap->ops->page_free(&folio->page); > + folio->page.mapping = NULL; Why are we adding this here? Does not seem large-folio specific. > + break; > case MEMORY_DEVICE_COHERENT: > if (WARN_ON_ONCE(!pgmap->ops || !pgmap->ops->page_free)) > break; > - pgmap->ops->page_free(folio_page(folio, 0)); > - put_dev_pagemap(pgmap); > + pgmap->ops->page_free(&folio->page); > + percpu_ref_put(&folio->pgmap->ref); This looks like an independent change that does not belong in this patch. Can't you just leave the code as is and simply convert percpu_ref_put to percpu_ref_put_many()? What am I missing? > break; > > case MEMORY_DEVICE_GENERIC: > @@ -491,14 +494,23 @@ void free_zone_device_folio(struct folio *folio) > } > } > > -void zone_device_page_init(struct page *page) > +void zone_device_folio_init(struct folio *folio, unsigned int order) > { > + struct page *page = folio_page(folio, 0); > + > + VM_WARN_ON_ONCE(order > MAX_ORDER_NR_PAGES); order vs. pages is wrong. In context of [1] this should probably be VM_WARN_ON_ONCE(order > MAX_FOLIO_ORDER); And before that is in VM_WARN_ON_ONCE((1u << order) > MAX_FOLIO_NR_PAGES); because we don't involve the buddy, so likely buddy limits do not apply. [1] https://lore.kernel.org/all/20250821200701.1329277-1-david@redhat.com/ > + > /* > * Drivers shouldn't be allocating pages after calling > * memunmap_pages(). > */ > - WARN_ON_ONCE(!percpu_ref_tryget_live(&page_pgmap(page)->ref)); > - set_page_count(page, 1); > + WARN_ON_ONCE(!percpu_ref_tryget_many(&page_pgmap(page)->ref, 1 << order)); > + folio_set_count(folio, 1); > lock_page(page); > + > + if (order > 1) { > + prep_compound_page(page, order); > + folio_set_large_rmappable(folio); > + } > } > -EXPORT_SYMBOL_GPL(zone_device_page_init); > +EXPORT_SYMBOL_GPL(zone_device_folio_init); > diff --git a/mm/rmap.c b/mm/rmap.c > index 568198e9efc2..b5837075b6e0 100644 > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -1769,9 +1769,13 @@ static __always_inline void __folio_remove_rmap(struct folio *folio, > * the folio is unmapped and at least one page is still mapped. > * > * Check partially_mapped first to ensure it is a large folio. > + * > + * Device private folios do not support deferred splitting and > + * shrinker based scanning of the folios to free. > */ > if (partially_mapped && folio_test_anon(folio) && > - !folio_test_partially_mapped(folio)) > + !folio_test_partially_mapped(folio) && > + !folio_is_device_private(folio)) Please indent like the previous line. if (partially_mapped && folio_test_anon(folio) && !folio_test_partially_mapped(folio) && !folio_is_device_private(folio)) > deferred_split_folio(folio, true); > > __folio_mod_stat(folio, -nr, -nr_pmdmapped); -- Cheers David / dhildenb