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(p200300d82f40b30053f7d260aff47256.dip0.t-ipconnect.de. [2003:d8:2f40:b300:53f7:d260:aff4:7256]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-453823c0812sm162261985e9.34.2025.06.30.05.07.46 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 30 Jun 2025 05:07:48 -0700 (PDT) Message-ID: Date: Mon, 30 Jun 2025 14:07:46 +0200 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 RFC 11/29] mm/migrate: move movable_ops page handling out of move_to_new_folio() To: linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, virtualization@lists.linux.dev, linux-fsdevel@vger.kernel.org, Andrew Morton , Jonathan Corbet , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , Christophe Leroy , Jerrin Shaji George , Arnd Bergmann , Greg Kroah-Hartman , "Michael S. Tsirkin" , Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Alexander Viro , Christian Brauner , Jan Kara , Zi Yan , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , "Matthew Wilcox (Oracle)" , Minchan Kim , Sergey Senozhatsky , Brendan Jackman , Johannes Weiner , Jason Gunthorpe , John Hubbard , Peter Xu , Xu Xin , Chengming Zhou , Miaohe Lin , Naoya Horiguchi , Oscar Salvador , Rik van Riel , Harry Yoo , Qi Zheng , Shakeel Butt References: <20250618174014.1168640-1-david@redhat.com> <20250618174014.1168640-12-david@redhat.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: <20250618174014.1168640-12-david@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 18.06.25 19:39, David Hildenbrand wrote: > Let's move that handling directly into migrate_folio_move(), so we can > simplify move_to_new_folio(). While at it, fixup the documentation a > bit. > > Note that unmap_and_move_huge_page() does not care, because it only > deals with actual folios. (we only support migration of > individual movable_ops pages) > > Signed-off-by: David Hildenbrand > --- > mm/migrate.c | 61 ++++++++++++++++++++++++---------------------------- > 1 file changed, 28 insertions(+), 33 deletions(-) > > diff --git a/mm/migrate.c b/mm/migrate.c > index 456e41dad83a2..db807f9bbf975 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -1024,11 +1024,12 @@ static int fallback_migrate_folio(struct address_space *mapping, > } > > /* > - * Move a page to a newly allocated page > - * The page is locked and all ptes have been successfully removed. > + * Move a src folio to a newly allocated dst folio. > * > - * The new page will have replaced the old page if this function > - * is successful. > + * The src and dst folios are locked and the src folios was unmapped from > + * the page tables. > + * > + * On success, the src folio was replaced by the dst folio. > * > * Return value: > * < 0 - error code > @@ -1037,34 +1038,30 @@ static int fallback_migrate_folio(struct address_space *mapping, > static int move_to_new_folio(struct folio *dst, struct folio *src, > enum migrate_mode mode) > { > + struct address_space *mapping = folio_mapping(src); > int rc = -EAGAIN; > - bool is_lru = !__folio_test_movable(src); > > VM_BUG_ON_FOLIO(!folio_test_locked(src), src); > VM_BUG_ON_FOLIO(!folio_test_locked(dst), dst); > > - if (likely(is_lru)) { > - struct address_space *mapping = folio_mapping(src); > - > - if (!mapping) > - rc = migrate_folio(mapping, dst, src, mode); > - else if (mapping_inaccessible(mapping)) > - rc = -EOPNOTSUPP; > - else if (mapping->a_ops->migrate_folio) > - /* > - * Most folios have a mapping and most filesystems > - * provide a migrate_folio callback. Anonymous folios > - * are part of swap space which also has its own > - * migrate_folio callback. This is the most common path > - * for page migration. > - */ > - rc = mapping->a_ops->migrate_folio(mapping, dst, src, > - mode); > - else > - rc = fallback_migrate_folio(mapping, dst, src, mode); > + if (!mapping) > + rc = migrate_folio(mapping, dst, src, mode); > + else if (mapping_inaccessible(mapping)) > + rc = -EOPNOTSUPP; > + else if (mapping->a_ops->migrate_folio) > + /* > + * Most folios have a mapping and most filesystems > + * provide a migrate_folio callback. Anonymous folios > + * are part of swap space which also has its own > + * migrate_folio callback. This is the most common path > + * for page migration. > + */ > + rc = mapping->a_ops->migrate_folio(mapping, dst, src, > + mode); > + else > + rc = fallback_migrate_folio(mapping, dst, src, mode); > > - if (rc != MIGRATEPAGE_SUCCESS) > - goto out; > + if (rc == MIGRATEPAGE_SUCCESS) { > /* > * For pagecache folios, src->mapping must be cleared before src > * is freed. Anonymous folios must stay anonymous until freed. > @@ -1074,10 +1071,7 @@ static int move_to_new_folio(struct folio *dst, struct folio *src, > > if (likely(!folio_is_zone_device(dst))) > flush_dcache_folio(dst); > - } else { > - rc = migrate_movable_ops_page(&dst->page, &src->page, mode); > } > -out: > return rc; > } > > @@ -1328,20 +1322,21 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private, > int rc; > int old_page_state = 0; > struct anon_vma *anon_vma = NULL; > - bool is_lru = !__folio_test_movable(src); > struct list_head *prev; > > __migrate_folio_extract(dst, &old_page_state, &anon_vma); > prev = dst->lru.prev; > list_del(&dst->lru); > > + if (unlikely(__folio_test_movable(src))) { > + rc = migrate_movable_ops_page(&dst->page, &src->page, mode); > + goto out_unlock_both; > + } > + I suspect this was the issue I was chasing: diff --git a/mm/migrate.c b/mm/migrate.c index 9dd327a63abc5..22c115710d0e2 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1330,6 +1330,8 @@ static int migrate_folio_move(free_folio_t put_new_folio, unsigned long private, if (unlikely(__folio_test_movable(src))) { rc = migrate_movable_ops_page(&dst->page, &src->page, mode); + if (rc) + goto out; goto out_unlock_both; } Testing ... -- Cheers, David / dhildenb