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(p200300d82f1424000afc9797137ca25b.dip0.t-ipconnect.de. [2003:d8:2f14:2400:afc:9797:137c:a25b]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-46e2b610cf3sm11459255e9.1.2025.09.24.03.55.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Sep 2025 03:55:33 -0700 (PDT) Message-ID: <9c263334-c0f3-4af0-88a8-8ed19ef6b83d@redhat.com> Date: Wed, 24 Sep 2025 12:55:32 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [v6 01/15] mm/zone_device: support large zone device private folios To: Zi Yan , Balbir Singh , Alistair Popple Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, damon@lists.linux.dev, dri-devel@lists.freedesktop.org, Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , 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: <20250916122128.2098535-1-balbirs@nvidia.com> <20250916122128.2098535-2-balbirs@nvidia.com> <882D81FA-DA40-4FF9-8192-166DBE1709AF@nvidia.com> From: David Hildenbrand 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: <882D81FA-DA40-4FF9-8192-166DBE1709AF@nvidia.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: gP6BnPsJ0Zc7HuZf0INv5YtSAPsQCnkmltvCBrSI8C0_1758711335 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 8F6EC18000C X-Stat-Signature: 96mxoh3s9yffxagq1fzfabe36ksu4ekb X-HE-Tag: 1758711338-44683 X-HE-Meta: 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 2A9B1S+P 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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 18.09.25 04:49, Zi Yan wrote: > On 16 Sep 2025, at 8:21, 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. >> >> Signed-off-by: Balbir Singh >> Cc: David Hildenbrand >> Cc: Zi Yan >> Cc: Joshua Hahn >> Cc: Rakie Kim >> Cc: Byungchul Park >> Cc: Gregory Price >> Cc: Ying Huang >> Cc: Alistair Popple >> Cc: Oscar Salvador >> Cc: Lorenzo Stoakes >> Cc: Baolin Wang >> Cc: "Liam R. Howlett" >> Cc: Nico Pache >> Cc: Ryan Roberts >> Cc: Dev Jain >> Cc: Barry Song >> Cc: Lyude Paul >> Cc: Danilo Krummrich >> Cc: David Airlie >> Cc: Simona Vetter >> Cc: Ralph Campbell >> Cc: Mika Penttilä >> Cc: Matthew Brost >> Cc: Francois Dugast >> --- >> include/linux/memremap.h | 10 +++++++++- >> mm/memremap.c | 34 +++++++++++++++++++++------------- >> mm/rmap.c | 6 +++++- >> 3 files changed, 35 insertions(+), 15 deletions(-) >> >> diff --git a/include/linux/memremap.h b/include/linux/memremap.h >> index e5951ba12a28..9c20327c2be5 100644 >> --- a/include/linux/memremap.h >> +++ b/include/linux/memremap.h >> @@ -206,7 +206,7 @@ static inline bool is_fsdax_page(const struct page *page) >> } >> >> #ifdef CONFIG_ZONE_DEVICE >> -void zone_device_page_init(struct page *page); >> +void zone_device_folio_init(struct folio *folio, unsigned int order); >> void *memremap_pages(struct dev_pagemap *pgmap, int nid); >> void memunmap_pages(struct dev_pagemap *pgmap); >> void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap); >> @@ -215,6 +215,14 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn); >> bool pgmap_pfn_valid(struct dev_pagemap *pgmap, unsigned long pfn); >> >> unsigned long memremap_compat_align(void); >> + >> +static inline void zone_device_page_init(struct page *page) >> +{ >> + struct folio *folio = page_folio(page); >> + >> + zone_device_folio_init(folio, 0); > > I assume it is for legacy code, where only non-compound page exists? > > It seems that you assume @page is always order-0, but there is no check > for it. Adding VM_WARN_ON_ONCE_FOLIO(folio_order(folio) != 0, folio) > above it would be useful to detect misuse. > >> +} >> + >> #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 46cb1b0b6f72..a8481ebf94cc 100644 >> --- a/mm/memremap.c >> +++ b/mm/memremap.c >> @@ -416,20 +416,19 @@ 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; >> >> 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)); >> } >> >> /* >> @@ -456,8 +455,8 @@ void free_zone_device_folio(struct folio *folio) >> 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_many(&folio->pgmap->ref, nr); >> break; >> >> case MEMORY_DEVICE_GENERIC: >> @@ -480,14 +479,23 @@ 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); > > It is strange to see a folio is converted back to page in > a function called zone_device_folio_init(). > >> + >> + VM_WARN_ON_ONCE(order > MAX_ORDER_NR_PAGES); >> + >> /* >> * 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); >> + } > > OK, so basically, @folio is not a compound page yet when zone_device_folio_init() > is called. > > I feel that your zone_device_page_init() and zone_device_folio_init() > implementations are inverse. They should follow the same pattern > as __alloc_pages_noprof() and __folio_alloc_noprof(), where > zone_device_page_init() does the actual initialization and > zone_device_folio_init() just convert a page to folio. > > Something like: > > void zone_device_page_init(struct page *page, unsigned int order) > { > VM_WARN_ON_ONCE(order > MAX_ORDER_NR_PAGES); > > /* > * Drivers shouldn't be allocating pages after calling > * memunmap_pages(). > */ > > WARN_ON_ONCE(!percpu_ref_tryget_many(&page_pgmap(page)->ref, 1 << order)); > > /* > * anonymous folio does not support order-1, high order file-backed folio > * is not supported at all. > */ > VM_WARN_ON_ONCE(order == 1); > > if (order > 1) > prep_compound_page(page, order); > > /* page has to be compound head here */ > set_page_count(page, 1); > lock_page(page); > } > > void zone_device_folio_init(struct folio *folio, unsigned int order) > { > struct page *page = folio_page(folio, 0); > > zone_device_page_init(page, order); > page_rmappable_folio(page); > } > > Or > > struct folio *zone_device_folio_init(struct page *page, unsigned int order) > { > zone_device_page_init(page, order); > return page_rmappable_folio(page); > } I think the problem is that it will all be weird once we dynamically allocate "struct folio". I have not yet a clear understanding on how that would really work. For example, should it be pgmap->ops->page_folio() ? Who allocates the folio? Do we allocate all order-0 folios initially, to then merge them when constructing large folios? How do we manage the "struct folio" during such merging splitting? With that in mind, I don't really know what the proper interface should be today. zone_device_folio_init(struct page *page, unsigned int order) looks cleaner, agreed. > > > Then, it comes to free_zone_device_folio() above, > I feel that pgmap->ops->page_free() should take an additional order > parameter to free a compound page like free_frozen_pages(). > IIRC free_frozen_pages() does not operate on compound pages. If we know that we are operating on a compound page (or single page) then passing in the page (or better the folio) should work. -- Cheers David / dhildenb