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([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38a8e37d0casm12124570f8f.11.2025.01.13.04.26.32 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 13 Jan 2025 04:26:33 -0800 (PST) Message-ID: <6ddbb98b-0819-415b-80b4-6bfe6d343461@redhat.com> Date: Mon, 13 Jan 2025 13:26:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 3/6] mm/migrate: don't call folio_putback_active_hugetlb() on dst hugetlb folio To: Baolin Wang , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Muchun Song , "Matthew Wilcox (Oracle)" References: <20250110182149.746551-1-david@redhat.com> <20250110182149.746551-4-david@redhat.com> <09b71834-157b-4869-91f7-854be47b45e2@redhat.com> <927b8efc-52ea-4f31-add5-62e721c32b90@linux.alibaba.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: <927b8efc-52ea-4f31-add5-62e721c32b90@linux.alibaba.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: pDrh7o8MvruIzSANwIsmoCsVbuCKb346hMlReNAMQho_1736771195 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: 7FC0340011 X-Stat-Signature: tjxyb4mem38x1zz5mttsr5nfy8a4yceo X-Rspam-User: X-Rspamd-Server: rspam11 X-HE-Tag: 1736771198-935483 X-HE-Meta: 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 V0miV8rT 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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 13.01.25 13:21, Baolin Wang wrote: > > > On 2025/1/13 17:50, David Hildenbrand wrote: >> On 13.01.25 08:00, Baolin Wang wrote: >>> >>> >>> On 2025/1/11 02:21, David Hildenbrand wrote: >>>> We replaced a simple put_page() by a putback_active_hugepage() call in >>>> commit 3aaa76e125c1 ("mm: migrate: hugetlb: putback destination hugepage >>>> to active list"), to set the "active" flag on the dst hugetlb folio. >>>> >>>> Nowadays, we decoupled the "active" list from the flag, by calling the >>>> flag "migratable". >>>> >>>> Calling "putback" on something that wasn't allocated is weird and not >>>> future proof, especially if we might reach that path when migration >>>> failed >>>> and we just want to free the freshly allocated hugetlb folio. >>>> >>>> Let's simply set the "migratable" flag in move_hugetlb_state(), where we >>>> know that allocation succeeded, and use simple folio_put() to return >>>> our reference. >>>> >>>> Do we need the hugetlb_lock for setting that flag? Staring at other >>>> users of folio_set_hugetlb_migratable(), it does not look like it. After >>>> all, the dst folio should already be on the active list, and we are not >>>> modifying that list. >>>> >>>> Signed-off-by: David Hildenbrand >>>> --- >>>>    mm/hugetlb.c | 5 +++++ >>>>    mm/migrate.c | 8 ++++---- >>>>    2 files changed, 9 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >>>> index da98d671088d0..b24ccf8ecbf38 100644 >>>> --- a/mm/hugetlb.c >>>> +++ b/mm/hugetlb.c >>>> @@ -7529,6 +7529,11 @@ void move_hugetlb_state(struct folio >>>> *old_folio, struct folio *new_folio, int re >>>>            } >>>>            spin_unlock_irq(&hugetlb_lock); >>>>        } >>>> +    /* >>>> +     * Our old folio is isolated and has "migratable" cleared until it >>>> +     * is putback. As migration succeeded, set the new folio >>>> "migratable". >>>> +     */ >>>> +    folio_set_hugetlb_migratable(new_folio); >>>>    } >>>>    static void hugetlb_unshare_pmds(struct vm_area_struct *vma, >>>> diff --git a/mm/migrate.c b/mm/migrate.c >>>> index 80887cadb2774..7e23e78f1e57b 100644 >>>> --- a/mm/migrate.c >>>> +++ b/mm/migrate.c >>>> @@ -1542,14 +1542,14 @@ static int >>>> unmap_and_move_huge_page(new_folio_t get_new_folio, >>>>            list_move_tail(&src->lru, ret); >>>>        /* >>>> -     * If migration was not successful and there's a freeing >>>> callback, use >>>> -     * it.  Otherwise, put_page() will drop the reference grabbed >>>> during >>>> -     * isolation. >>>> +     * If migration was not successful and there's a freeing callback, >>>> +     * return the folio to that special allocator. Otherwise, simply >>>> drop >>>> +     * our additional reference. >>>>         */ >>>>        if (put_new_folio) >>>>            put_new_folio(dst, private); >>>>        else >>>> -        folio_putback_active_hugetlb(dst); >>>> +        folio_put(dst); >>> >> >> Hi Baolin, >> >> thanks for the review! >> >>> IIUC, after the changes, so the 'dst' folio might not be added into the >>> 'h->hugepage_activelist' list (if the 'dst' i:s temporarily allocated), >>> Could this cause any side effects? >> >> Good point, so far I was under the assumption that the dst folio would >> already be in the active list. >> >> alloc_migration_target() and friends call alloc_hugetlb_folio_nodemask(). >> >> >> There are two cases: >> >> 1) We call dequeue_hugetlb_folio_nodemask() -> >> dequeue_hugetlb_folio_node_exact() >> where we add the folio to the hugepage_activelist. >> >> 2) We call alloc_migrate_hugetlb_folio() >> >> It indeed looks like we don't add them to the active list. So likely we >> should do: >> >> >> diff --git a/mm/hugetlb.c b/mm/hugetlb.c >> index dca4f310617a2..c6463dd7a1fc8 100644 >> --- a/mm/hugetlb.c >> +++ b/mm/hugetlb.c >> @@ -7546,7 +7546,10 @@ void move_hugetlb_state(struct folio *old_folio, >> struct folio *new_folio, int re >>          * Our old folio is isolated and has "migratable" cleared until it >>          * is putback. As migration succeeded, set the new folio >> "migratable". >>          */ >> +       spin_lock_irq(&hugetlb_lock); >>         folio_set_hugetlb_migratable(new_folio); >> +       list_move_tail(&new_folio->lru, >> &(folio_hstate(new_folio))->hugepage_activelist); >> +       spin_unlock_irq(&hugetlb_lock); >>  } >> >>  static void hugetlb_unshare_pmds(struct vm_area_struct *vma, >> >> >> move_hugetlb_state() also takes care of that "temporary" handling. > > LGTM. With the changes: > Reviewed-by: Baolin Wang > Thanks! > >> (I wonder if in case 1) it was a problem that the folio was already on the >> active list) > > Seems harmless, and putback_active_hugepage() did the same before. Yes, I think as we free it, we'll put it automatically back to the freelist using enqueue_hugetlb_folio(). I suspect the temporary-active-although-not-active is no real problem. -- Cheers, David / dhildenb