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[2003:d8:2f09:9c00:8173:2a94:640d:dd31]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45b7e7d23b7sm230998375e9.1.2025.09.03.02.16.03 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Sep 2025 02:16:04 -0700 (PDT) Message-ID: <3c283054-b14e-4f36-966f-78cf3bc0f3af@redhat.com> Date: Wed, 3 Sep 2025 11:16:03 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] filemap: optimize order0 folio in filemap_map_pages To: Jinjiang Tu , willy@infradead.org, akpm@linux-foundation.org, linux-mm@kvack.org Cc: wangkefeng.wang@huawei.com References: <20250903084223.1653192-1-tujinjiang@huawei.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: <20250903084223.1653192-1-tujinjiang@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: xhQB80j7NGvyDh3nk4YAqiw2aWxWcC-PgtRzDSJyNAA_1756890965 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: 113x1s8p6xg8ae1k1z4apchczb3mw4sn X-Rspam-User: X-Rspamd-Queue-Id: 107D68000E X-Rspamd-Server: rspam01 X-HE-Tag: 1756890967-978456 X-HE-Meta: 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 aBWqxBhU 8+OEHgTFwsf5aH7+7AuLnhb9QKyWuQqNrqeVbGTEEShB2LruHB8PLKFPNIA/lDamP6zF5GQdK5TZ3UvImugu85qPSH+Lu8tYXvsAXWUNxbSMYdTjFZIcj1YgVdkbN7vnejAGooCkmkRZbxCj55LsAtQfCE900k1wS+Wty0Ow18J5/4zsSP+cQxWnvZx4G5DHoy6/yCTZaJPLUuy++/KGEbppq/nw/kDuAalZbdBsbgSROfvV9ndvjIbeHvVXe0K7TOlvxfeN7x3YotvHn/H7s18gsbfU2+Zq1xHXX5iew3+1uA7Spp73dfg/Jlm5ueabz0dvSerbLK4o3mE9qyF9xpeUePjo2xddQxxQjE7nlfJHlJBy8yMzfdO3khaYdmDnLWQ1DUKq9BfXr1rudDQ2+7wPjkirqnsbCXzd5o7TEIZXiTBbQquq8W6C5Tv4WdGCBE0T82rx3et3x4yxk+Qvw/A0nuDptLP+zSp0g 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: > +++ b/mm/filemap.c > @@ -3693,6 +3693,7 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf, > } > > vmf->pte = old_ptep; > + folio_put(folio); > > return ret; > } > @@ -3705,7 +3706,7 @@ static vm_fault_t filemap_map_order0_folio(struct vm_fault *vmf, > struct page *page = &folio->page; > > if (PageHWPoison(page)) > - return ret; > + goto out; > > /* See comment of filemap_map_folio_range() */ > if (!folio_test_workingset(folio)) > @@ -3717,15 +3718,17 @@ static vm_fault_t filemap_map_order0_folio(struct vm_fault *vmf, > * the fault-around logic. > */ > if (!pte_none(ptep_get(vmf->pte))) > - return ret; > + goto out; > > if (vmf->address == addr) > ret = VM_FAULT_NOPAGE; > > set_pte_range(vmf, folio, page, 1, addr); > (*rss)++; > - folio_ref_inc(folio); > + return ret; > > +out: > + folio_put(folio); We can use a folio_ref_dec() here /* Locked folios cannot get truncated. */ folio_ref_dec(folio); > return ret; > } > > @@ -3785,7 +3788,6 @@ vm_fault_t filemap_map_pages(struct vm_fault *vmf, > nr_pages, &rss, &mmap_miss); > > folio_unlock(folio); > - folio_put(folio); > } while ((folio = next_uptodate_folio(&xas, mapping, end_pgoff)) != NULL); > add_mm_counter(vma->vm_mm, folio_type, rss); > pte_unmap_unlock(vmf->pte, vmf->ptl); I think we can optimize filemap_map_folio_range() as well: diff --git a/mm/filemap.c b/mm/filemap.c index b101405b770ae..d1fcddc72c5f6 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3646,6 +3646,7 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf, unsigned long addr, unsigned int nr_pages, unsigned long *rss, unsigned short *mmap_miss) { + bool ref_from_caller = true; vm_fault_t ret = 0; struct page *page = folio_page(folio, start); unsigned int count = 0; @@ -3679,7 +3680,9 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf, if (count) { set_pte_range(vmf, folio, page, count, addr); *rss += count; - folio_ref_add(folio, count); + if (count - ref_from_caller) + folio_ref_add(folio, count - ref_from_caller); + ref_from_caller = false; if (in_range(vmf->address, addr, count * PAGE_SIZE)) ret = VM_FAULT_NOPAGE; } @@ -3694,13 +3697,19 @@ static vm_fault_t filemap_map_folio_range(struct vm_fault *vmf, if (count) { set_pte_range(vmf, folio, page, count, addr); *rss += count; - folio_ref_add(folio, count); + if (count - ref_from_caller) + folio_ref_add(folio, count - ref_from_caller); + ref_from_caller = false; if (in_range(vmf->address, addr, count * PAGE_SIZE)) ret = VM_FAULT_NOPAGE; } vmf->pte = old_ptep; + if (ref_from_caller) + /* Locked folios cannot get truncated. */ + folio_ref_dec(folio); + return ret; } It would save at least a folio_ref_dec(), and in corner cases (only map a single page) also a folio_ref_add(). -- Cheers David / dhildenb