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(p200300d82f4e3200c99da38b3f3ad4b3.dip0.t-ipconnect.de. [2003:d8:2f4e:3200:c99d:a38b:3f3a:d4b3]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-429898eb549sm144198f8f.41.2025.10.22.13.09.25 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Oct 2025 13:09:26 -0700 (PDT) Message-ID: Date: Wed, 22 Oct 2025 22:09:24 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 1/4] mm/huge_memory: preserve PG_has_hwpoisoned if a folio is split to >0 order To: Zi Yan , linmiaohe@huawei.com, jane.chu@oracle.com Cc: kernel@pankajraghav.com, akpm@linux-foundation.org, mcgrof@kernel.org, nao.horiguchi@gmail.com, Lorenzo Stoakes , Baolin Wang , "Liam R. Howlett" , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , "Matthew Wilcox (Oracle)" , Wei Yang , Yang Shi , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20251022033531.389351-1-ziy@nvidia.com> <20251022033531.389351-2-ziy@nvidia.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 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: <20251022033531.389351-2-ziy@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 22.10.25 05:35, Zi Yan wrote: > folio split clears PG_has_hwpoisoned, but the flag should be preserved in > after-split folios containing pages with PG_hwpoisoned flag if the folio is > split to >0 order folios. Scan all pages in a to-be-split folio to > determine which after-split folios need the flag. > > An alternatives is to change PG_has_hwpoisoned to PG_maybe_hwpoisoned to > avoid the scan and set it on all after-split folios, but resulting false > positive has undesirable negative impact. To remove false positive, caller > of folio_test_has_hwpoisoned() and folio_contain_hwpoisoned_page() needs to > do the scan. That might be causing a hassle for current and future callers > and more costly than doing the scan in the split code. More details are > discussed in [1]. > > It is OK that current implementation does not do this, because memory > failure code always tries to split to order-0 folios and if a folio cannot > be split to order-0, memory failure code either gives warnings or the split > is not performed. > We're losing PG_has_hwpoisoned for large folios, so likely this should be a stable fix for splitting anything to an order > 0 ? > Link: https://lore.kernel.org/all/CAHbLzkoOZm0PXxE9qwtF4gKR=cpRXrSrJ9V9Pm2DJexs985q4g@mail.gmail.com/ [1] > Signed-off-by: Zi Yan > --- > mm/huge_memory.c | 28 +++++++++++++++++++++++++--- > 1 file changed, 25 insertions(+), 3 deletions(-) > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > index fc65ec3393d2..f3896c1f130f 100644 > --- a/mm/huge_memory.c > +++ b/mm/huge_memory.c > @@ -3455,6 +3455,17 @@ bool can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins) > caller_pins; > } > > +static bool page_range_has_hwpoisoned(struct page *first_page, long nr_pages) > +{ > + long i; > + > + for (i = 0; i < nr_pages; i++) > + if (PageHWPoison(first_page + i)) > + return true; > + > + return false; Nit: I'd just do static bool page_range_has_hwpoisoned(struct page *page, unsigned long nr_pages) { for (; nr_pages; page++, nr_pages--) if (PageHWPoison(page)) return true; } return false; } > +} > + > /* > * It splits @folio into @new_order folios and copies the @folio metadata to > * all the resulting folios. > @@ -3462,22 +3473,32 @@ bool can_split_folio(struct folio *folio, int caller_pins, int *pextra_pins) > static void __split_folio_to_order(struct folio *folio, int old_order, > int new_order) > { > + /* Scan poisoned pages when split a poisoned folio to large folios */ > + bool check_poisoned_pages = folio_test_has_hwpoisoned(folio) && > + new_order != 0; I'd shorten this to "handle_hwpoison" or sth like that. Maybe we can make it const and fit it into a single line. Comparison with 0 is not required. const bool handle_hwpoison = folio_test_has_hwpoisoned(folio) && new_order; > long new_nr_pages = 1 << new_order; > long nr_pages = 1 << old_order; > long i; > > + folio_clear_has_hwpoisoned(folio); > + > + /* Check first new_nr_pages since the loop below skips them */ > + if (check_poisoned_pages && > + page_range_has_hwpoisoned(folio_page(folio, 0), new_nr_pages)) > + folio_set_has_hwpoisoned(folio); > /* > * Skip the first new_nr_pages, since the new folio from them have all > * the flags from the original folio. > */ > for (i = new_nr_pages; i < nr_pages; i += new_nr_pages) { > struct page *new_head = &folio->page + i; > - > /* > * Careful: new_folio is not a "real" folio before we cleared PageTail. > * Don't pass it around before clear_compound_head(). > */ > struct folio *new_folio = (struct folio *)new_head; > + bool poisoned_new_folio = check_poisoned_pages && > + page_range_has_hwpoisoned(new_head, new_nr_pages); Is the temp variable really required? I'm afraid it is a bit ugly either way :) I'd just move it into the if() below. if (handle_hwpoison && page_range_has_hwpoisoned(new_head, new_nr_pages) folio_set_has_hwpoisoned(new_folio); -- Cheers David / dhildenb