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[2003:cb:c72e:2200:7ed7:c239:d423:3b31]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3675a1030dfsm9238745f8f.100.2024.07.01.00.44.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Jul 2024 00:44:57 -0700 (PDT) Message-ID: <0d7158fb-2e75-4358-936d-eb7d4ffc8a53@redhat.com> Date: Mon, 1 Jul 2024 09:44:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 1/2] mm/migrate: make migrate_misplaced_folio() return 0 on success To: "Huang, Ying" Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Andrew Morton References: <20240620212935.656243-1-david@redhat.com> <20240620212935.656243-2-david@redhat.com> <87plrxo96w.fsf@yhuang6-desk2.ccr.corp.intel.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 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: <87plrxo96w.fsf@yhuang6-desk2.ccr.corp.intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 52882A0005 X-Stat-Signature: jrhdo78widi6y51rfbnpwcgphn8abfpm X-Rspam-User: X-HE-Tag: 1719819901-462566 X-HE-Meta: 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 cBHXn9H7 7bpCRzC7oRraAKmWBFkcGdK+yHpW/6lOicTiWr7vGsIP2T155QbjluaQjrk5ALVyXmMjPzWULIZWOHhAUoPeZrEzVMdlm5eTNPnTh4zz4FBQoU6rgw4pUHshLsA42S4EzPGuh2XIwQyUQn0rVLGjhPxHqJFH5pmIbbMgfhbIIugQD82VH3Clbr/S61frhNab1N8WyIbjycQsfOUDhxoS4uqlSKdEPdMV4Hn/vc2Tx4DgtD5XhUxV7HB4oJJNOn6VMK8jvKPxpmSYlgqh4NRrNapVcDWdESp58bvPaFGb2Jo52YvfUJAipvus0EPRJHA4LlSSO/jMeoM6jmOimEchN7dfa3AzSbsYZVXdvGIz06JAszAS9oADcGPLoynuwsGInUw372gGYwVIYv8ojm9tyb0pozMCJhNS5Wv/dI1W5zL0NI7L6oCiI2WSEvAbHdR6PC//N 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 01.07.24 09:36, Huang, Ying wrote: > David Hildenbrand writes: > >> Let's just return 0 on success, which is less confusing. >> >> ... especially because we got it wrong in the migrate.h stub where we >> have "return -EAGAIN; /* can't migrate now */" instead of "return 0;". >> Likely this wrong return value doesn't currently matter, but it >> certainly adds confusion. >> >> We'll add migrate_misplaced_folio_prepare() next, where we want to use >> the same "return 0 on success" approach, so let's just clean this up. >> >> Signed-off-by: David Hildenbrand >> --- >> mm/huge_memory.c | 5 ++--- >> mm/memory.c | 2 +- >> mm/migrate.c | 4 ++-- >> 3 files changed, 5 insertions(+), 6 deletions(-) >> >> diff --git a/mm/huge_memory.c b/mm/huge_memory.c >> index 0fffaa58a47a..fc27dabcd8e3 100644 >> --- a/mm/huge_memory.c >> +++ b/mm/huge_memory.c >> @@ -1652,7 +1652,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf) >> unsigned long haddr = vmf->address & HPAGE_PMD_MASK; >> int nid = NUMA_NO_NODE; >> int target_nid, last_cpupid = (-1 & LAST_CPUPID_MASK); >> - bool migrated = false, writable = false; >> + bool writable = false; >> int flags = 0; >> >> vmf->ptl = pmd_lock(vma->vm_mm, vmf->pmd); >> @@ -1696,8 +1696,7 @@ vm_fault_t do_huge_pmd_numa_page(struct vm_fault *vmf) >> spin_unlock(vmf->ptl); >> writable = false; >> >> - migrated = migrate_misplaced_folio(folio, vma, target_nid); >> - if (migrated) { >> + if (!migrate_misplaced_folio(folio, vma, target_nid)) { >> flags |= TNF_MIGRATED; >> nid = target_nid; >> } else { >> diff --git a/mm/memory.c b/mm/memory.c >> index 00728ea95583..118660de5bcc 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -5354,7 +5354,7 @@ static vm_fault_t do_numa_page(struct vm_fault *vmf) >> ignore_writable = true; >> >> /* Migrate to the requested node */ >> - if (migrate_misplaced_folio(folio, vma, target_nid)) { >> + if (!migrate_misplaced_folio(folio, vma, target_nid)) { >> nid = target_nid; >> flags |= TNF_MIGRATED; >> } else { >> diff --git a/mm/migrate.c b/mm/migrate.c >> index 781979567f64..0307b54879a0 100644 >> --- a/mm/migrate.c >> +++ b/mm/migrate.c >> @@ -2629,11 +2629,11 @@ int migrate_misplaced_folio(struct folio *folio, struct vm_area_struct *vma, >> nr_succeeded); >> } >> BUG_ON(!list_empty(&migratepages)); >> - return isolated; >> + return isolated ? 0 : -EAGAIN; > > Is it good to use -EAGAIN as error code always? At least if > nr_remaining < 0, we can use that? Thanks for the review. I kept it simple for now, because the migrate_misplaced_folio_prepare() stub has: return -EAGAIN; /* can't migrate now */ and it doesn't really make a difference right now which exact return value we use. (maybe some cases, like the stub, should return -EINVAL or -EOPNOTSUPP once we start caring about the exact value) -- Cheers, David / dhildenb