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Thu, 22 Jan 2026 08:02:10 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id j+18DoLZcWncTAAAD6G6ig (envelope-from ); Thu, 22 Jan 2026 08:02:10 +0000 Message-ID: Date: Thu, 22 Jan 2026 09:02:09 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v6 1/5] mm/zone_device: Reinitialize large zone device private folios Content-Language: en-US From: Vlastimil Babka To: Francois Dugast , intel-xe@lists.freedesktop.org Cc: dri-devel@lists.freedesktop.org, Matthew Brost , Zi Yan , Alistair Popple , adhavan Srinivasan , Nicholas Piggin , Michael Ellerman , "Christophe Leroy (CS GROUP)" , Felix Kuehling , Alex Deucher , =?UTF-8?Q?Christian_K=C3=B6nig?= , David Airlie , Simona Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Lyude Paul , Danilo Krummrich , David Hildenbrand , Oscar Salvador , Andrew Morton , Jason Gunthorpe , Leon Romanovsky , Lorenzo Stoakes , "Liam R . Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Balbir Singh , linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-mm@kvack.org, linux-cxl@vger.kernel.org References: <20260116111325.1736137-1-francois.dugast@intel.com> <20260116111325.1736137-2-francois.dugast@intel.com> Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 8D871180002 X-Stat-Signature: cgpu99isumymsjpho4nnr6wdr9k1scj3 X-Rspam-User: X-HE-Tag: 1769068933-130546 X-HE-Meta: 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 frC7lECY JMLjRiDyi67ZR6f6YJy+W54pWoe8fXublyudMwMLVhyEbiThHZ5+weAzVMneW7U4798KZyLvZPpRHxTZsD93UQLxUQY9I0cvn1X37NSz3Njzg9POLEIwncbEaKZfmlhV4vAfu6Vm0zBUNoTVMEfPicSmC2H7w/uKA6SkihBcO0SSkQutZ2RJjRuveAaht+tSQ5O3TuLzms7zWjgqvtKkvgLa8R9NrifmI8IeY9h14qdzNXyZN5M3rxZXB0fPhLnThtRRCZ+FqTYdbfIvJXuLYfzRfmTtDvGx+gbOY73aOGTUlTKYgHXclT7wC261A4Aur1WafetBFe6VzU0DZ8SXP7ZkEHuXZtQnYuCZ5pIPuGynYwsg= 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 1/16/26 17:07, Vlastimil Babka wrote: > On 1/16/26 12:10, Francois Dugast wrote: >> From: Matthew Brost >> diff --git a/mm/memremap.c b/mm/memremap.c >> index 63c6ab4fdf08..ac7be07e3361 100644 >> --- a/mm/memremap.c >> +++ b/mm/memremap.c >> @@ -477,10 +477,43 @@ void free_zone_device_folio(struct folio *folio) >> } >> } >> >> -void zone_device_page_init(struct page *page, unsigned int order) >> +void zone_device_page_init(struct page *page, struct dev_pagemap *pgmap, >> + unsigned int order) >> { >> + struct page *new_page = page; >> + unsigned int i; >> + >> VM_WARN_ON_ONCE(order > MAX_ORDER_NR_PAGES); >> >> + for (i = 0; i < (1UL << order); ++i, ++new_page) { >> + struct folio *new_folio = (struct folio *)new_page; >> + >> + /* >> + * new_page could have been part of previous higher order folio >> + * which encodes the order, in page + 1, in the flags bits. We >> + * blindly clear bits which could have set my order field here, >> + * including page head. >> + */ >> + new_page->flags.f &= ~0xffUL; /* Clear possible order, page head */ >> + >> +#ifdef NR_PAGES_IN_LARGE_FOLIO >> + /* >> + * This pointer math looks odd, but new_page could have been >> + * part of a previous higher order folio, which sets _nr_pages >> + * in page + 1 (new_page). Therefore, we use pointer casting to >> + * correctly locate the _nr_pages bits within new_page which >> + * could have modified by previous higher order folio. >> + */ >> + ((struct folio *)(new_page - 1))->_nr_pages = 0; >> +#endif >> + >> + new_folio->mapping = NULL; >> + new_folio->pgmap = pgmap; /* Also clear compound head */ >> + new_folio->share = 0; /* fsdax only, unused for device private */ >> + VM_WARN_ON_FOLIO(folio_ref_count(new_folio), new_folio); >> + VM_WARN_ON_FOLIO(!folio_is_zone_device(new_folio), new_folio); >> + } >> + >> /* >> * Drivers shouldn't be allocating pages after calling >> * memunmap_pages(). > > Can't say I'm a fan of this. It probably works now (so I'm not nacking) but > seems rather fragile. It seems likely to me somebody will try to change some > implementation detail in the page allocator and not notice it breaks this, > for example. I hope we can eventually get to something more robust. For doing this as a hotfix for 6.19, assuming we'll refactor later: Acked-by: Vlastimil Babka