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[2003:d8:2f0c:c200:fa4a:c4ff:1b32:21ce]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4711442932esm46204595e9.6.2025.10.16.13.53.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Oct 2025 13:53:19 -0700 (PDT) Message-ID: Date: Thu, 16 Oct 2025 22:53:18 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 3/6] mm: page_alloc: add alloc_contig_{range_frozen,frozen_pages}() To: Kefeng Wang , Andrew Morton , Oscar Salvador , Muchun Song Cc: sidhartha.kumar@oracle.com, jane.chu@oracle.com, Zi Yan , Vlastimil Babka , Brendan Jackman , Johannes Weiner , linux-mm@kvack.org References: <20251013133854.2466530-1-wangkefeng.wang@huawei.com> <20251013133854.2466530-4-wangkefeng.wang@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: <20251013133854.2466530-4-wangkefeng.wang@huawei.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: l6t1gFnm_-BJA69mrejjw2_NKS8GsKacOkXoITOfIOk_1760648000 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: D4DB580006 X-Rspamd-Server: rspam11 X-Rspam-User: X-Stat-Signature: u91rr6xtq4jgx7q65f85f6kfjd51ewo6 X-HE-Tag: 1760648003-471599 X-HE-Meta: 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 bGxza81a 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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 13.10.25 15:38, Kefeng Wang wrote: > In order to allocate given range of pages or allocate compound > pages without incrementing their refcount, adding two new helper > alloc_contig_{range_frozen,frozen_pages}() which may be beneficial > to some users (eg hugetlb), also free_contig_range_frozen() is > provided to match alloc_contig_range_frozen(), but it is better to > use free_frozen_pages() to free frozen compound pages. > > Signed-off-by: Kefeng Wang > --- > include/linux/gfp.h | 29 +++++-- > mm/page_alloc.c | 183 +++++++++++++++++++++++++++++--------------- > 2 files changed, 143 insertions(+), 69 deletions(-) > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > index 1fefb63e0480..fbbdd8c88483 100644 > --- a/include/linux/gfp.h > +++ b/include/linux/gfp.h > @@ -429,14 +429,27 @@ typedef unsigned int __bitwise acr_flags_t; > #define ACR_FLAGS_CMA ((__force acr_flags_t)BIT(0)) // allocate for CMA > > /* The below functions must be run on a range from a single zone. */ > -extern int alloc_contig_range_noprof(unsigned long start, unsigned long end, > - acr_flags_t alloc_flags, gfp_t gfp_mask); > -#define alloc_contig_range(...) alloc_hooks(alloc_contig_range_noprof(__VA_ARGS__)) > - > -extern struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask, > - int nid, nodemask_t *nodemask); > -#define alloc_contig_pages(...) alloc_hooks(alloc_contig_pages_noprof(__VA_ARGS__)) > - > +int alloc_contig_range_frozen_noprof(unsigned long start, unsigned long end, > + acr_flags_t alloc_flags, gfp_t gfp_mask); Just wondering: given alloc_contig_pages() vs. alloc_contig_frozen_pages_() Shouldn't it be alloc_contig_range() vs. alloc_contig_frozen_range() And then free_contig_frozen_range()? Do we want kerneldoc here as well? > +int alloc_contig_range_frozen_noprof(unsigned long start, unsigned long end, > + acr_flags_t alloc_flags, gfp_t gfp_mask) > { > const unsigned int order = ilog2(end - start); > unsigned long outer_start, outer_end; > @@ -7003,19 +6982,18 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end, > } > > if (!(gfp_mask & __GFP_COMP)) { > - split_free_pages(cc.freepages, gfp_mask); > + split_free_frozen_pages(cc.freepages, gfp_mask); > > /* Free head and tail (if any) */ > if (start != outer_start) > - free_contig_range(outer_start, start - outer_start); > + free_contig_range_frozen(outer_start, start - outer_start); > if (end != outer_end) > - free_contig_range(end, outer_end - end); > + free_contig_range_frozen(end, outer_end - end); > } else if (start == outer_start && end == outer_end && is_power_of_2(end - start)) { > struct page *head = pfn_to_page(start); > > check_new_pages(head, order); > prep_new_page(head, order, gfp_mask, 0); > - set_page_refcounted(head); > } else { > ret = -EINVAL; > WARN(true, "PFN range: requested [%lu, %lu), allocated [%lu, %lu)\n", > @@ -7025,16 +7003,48 @@ int alloc_contig_range_noprof(unsigned long start, unsigned long end, > undo_isolate_page_range(start, end); > return ret; > } > -EXPORT_SYMBOL(alloc_contig_range_noprof); > > -static int __alloc_contig_pages(unsigned long start_pfn, > - unsigned long nr_pages, gfp_t gfp_mask) > +/** > + * alloc_contig_range() -- tries to allocate given range of pages > + * @start: start PFN to allocate > + * @end: one-past-the-last PFN to allocate > + * @alloc_flags: allocation information > + * @gfp_mask: GFP mask. Node/zone/placement hints are ignored; only some > + * action and reclaim modifiers are supported. Reclaim modifiers > + * control allocation behavior during compaction/migration/reclaim. > + * > + * The PFN range does not have to be pageblock aligned. The PFN range must > + * belong to a single zone. > + * > + * The first thing this routine does is attempt to MIGRATE_ISOLATE all > + * pageblocks in the range. Once isolated, the pageblocks should not > + * be modified by others. > + * > + * Return: zero on success or negative error code. On success all > + * pages which PFN is in [start, end) are allocated for the caller and > + * need to be freed with free_contig_range(). > + */ > +int alloc_contig_range_noprof(unsigned long start, unsigned long end, > + acr_flags_t alloc_flags, gfp_t gfp_mask) > { > - unsigned long end_pfn = start_pfn + nr_pages; > + int ret; > + > + ret = alloc_contig_range_frozen_noprof(start, end, alloc_flags, gfp_mask); > + if (ret) > + return ret; > + > + if (gfp_mask & __GFP_COMP) { > + set_page_refcounted(pfn_to_page(start)); > + } else { > + unsigned long pfn; > + > + for (pfn = start; pfn < end; pfn++) > + set_page_refcounted(pfn_to_page(pfn)); > + } Might read better as unsigned long pfn; ... if (gfp_mask & __GFP_COMP) { set_page_refcounted(pfn_to_page(start)); return 0; } for (pfn = start; pfn < end; pfn++) set_page_refcounted(pfn_to_page(pfn)); return 0; One could also do something fancy like unsigned long pfn; ... for (pfn = start; pfn < end; pfn++) { set_page_refcounted(pfn_to_page(pfn)); if (gfp_mask & __GFP_COMP) break; } return 0: > > - return alloc_contig_range_noprof(start_pfn, end_pfn, ACR_FLAGS_NONE, > - gfp_mask); > + return 0; > } > +EXPORT_SYMBOL(alloc_contig_range_noprof); > > static bool pfn_range_valid_contig(struct zone *z, unsigned long start_pfn, > unsigned long nr_pages) > @@ -7067,31 +7077,8 @@ static bool zone_spans_last_pfn(const struct zone *zone, > return zone_spans_pfn(zone, last_pfn); > } ... kerneldoc? :) > +struct page *alloc_contig_frozen_pages_noprof(unsigned long nr_pages, > + gfp_t gfp_mask, int nid, nodemask_t *nodemask) > { > unsigned long ret, pfn, flags; > struct zonelist *zonelist; > @@ -7114,7 +7101,9 @@ struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask, > * and cause alloc_contig_range() to fail... > */ > spin_unlock_irqrestore(&zone->lock, flags); > - ret = __alloc_contig_pages(pfn, nr_pages, > + ret = alloc_contig_range_frozen_noprof(pfn, > + pfn + nr_pages, > + ACR_FLAGS_NONE, > gfp_mask); > if (!ret) > return pfn_to_page(pfn); > @@ -7126,6 +7115,78 @@ struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask, > } > return NULL; > } > +EXPORT_SYMBOL(alloc_contig_range_frozen_noprof); > + kerneldoc? :) > +void free_contig_range_frozen(unsigned long pfn, unsigned long nr_pages) > +{ > + struct folio *folio = pfn_folio(pfn); > + > + if (folio_test_large(folio)) { > + int expected = folio_nr_pages(folio); > + > + WARN_ON(folio_ref_count(folio)); > + > + if (nr_pages == expected) > + free_frozen_pages(&folio->page, folio_order(folio)); > + else > + WARN(true, "PFN %lu: nr_pages %lu != expected %d\n", > + pfn, nr_pages, expected); > + return; > + } > + > + for (; nr_pages--; pfn++) { > + struct page *page = pfn_to_page(pfn); > + > + WARN_ON(page_ref_count(page)); > + free_frozen_pages(page, 0); > + } That's mostly a copy-and-paste of free_contig_range(). I wonder if there is some way to avoid duplicating a lot of free_contig_range() here. Hmmm. Also, the folio stuff in there looks a bit weird I'm afraid. Can't we just refuse to free compound pages throught this interface and free_contig_range() ? IIRC only hugetlb uses it and uses folio_put() either way? Then we can just document that compound allocations are to be freed differently. And do something like diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 600d9e981c23d..776b4addc3685 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -7123,29 +7123,25 @@ struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask, } #endif /* CONFIG_CONTIG_ALLOC */ -void free_contig_range(unsigned long pfn, unsigned long nr_pages) +static inline void __free_contig_range(unsigned long pfn, unsigned long nr_pages, bool put_ref) { - unsigned long count = 0; - struct folio *folio = pfn_folio(pfn); - - if (folio_test_large(folio)) { - int expected = folio_nr_pages(folio); - - if (nr_pages == expected) - folio_put(folio); - else - WARN(true, "PFN %lu: nr_pages %lu != expected %d\n", - pfn, nr_pages, expected); - return; - } + if (WARN_ON_ONCE(PageHead(pfn_to_page(pfn)))) + break; for (; nr_pages--; pfn++) { struct page *page = pfn_to_page(pfn); - count += page_count(page) != 1; - __free_page(page); + if (put_ref) + page_ref_dec(page); + if (WARN_ON_ONCE(page_count(page))) + continue; + free_frozen_pages(page, 0); } - WARN(count != 0, "%lu pages are still in use!\n", count); +} + +void free_contig_range(unsigned long pfn, unsigned long nr_pages) +{ + return __free_contig_range(pfn, nr_pages, /* put_ref= */ true); } EXPORT_SYMBOL(free_contig_range); Just a thought, I dislike current free_contig_range() and the duplicated variant. > +} > +EXPORT_SYMBOL(free_contig_range_frozen); > + > +/** > + * alloc_contig_pages() -- tries to find and allocate contiguous range of pages > + * @nr_pages: Number of contiguous pages to allocate > + * @gfp_mask: GFP mask. Node/zone/placement hints limit the search; only some > + * action and reclaim modifiers are supported. Reclaim modifiers > + * control allocation behavior during compaction/migration/reclaim. > + * @nid: Target node > + * @nodemask: Mask for other possible nodes > + * > + * This routine is a wrapper around alloc_contig_range(). It scans over zones > + * on an applicable zonelist to find a contiguous pfn range which can then be > + * tried for allocation with alloc_contig_range(). This routine is intended > + * for allocation requests which can not be fulfilled with the buddy allocator. > + * > + * The allocated memory is always aligned to a page boundary. If nr_pages is a > + * power of two, then allocated range is also guaranteed to be aligned to same > + * nr_pages (e.g. 1GB request would be aligned to 1GB). > + * > + * Allocated pages can be freed with free_contig_range() or by manually calling > + * __free_page() on each allocated page. > + * > + * Return: pointer to contiguous pages on success, or NULL if not successful. > + */ > +struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask, > + int nid, nodemask_t *nodemask) > +{ > + struct page *page; > + > + page = alloc_contig_frozen_pages_noprof(nr_pages, gfp_mask, nid, > + nodemask); > + if (!page) > + return NULL; > + > + if (gfp_mask & __GFP_COMP) { > + set_page_refcounted(page); > + } else { > + unsigned long pfn = page_to_pfn(page); > + > + for (; nr_pages--; pfn++) > + set_page_refcounted(pfn_to_page(pfn)); > + } > + > + return page; Same here, might be able to make it easier to read like I suggested for the alloc_contig_range_noprof(). Or that part can just be factored out? void set_pages_refcounted(struct page *page, unsigned long nr_pages, gfp_t gfp_mask) or better void set_pages_refcounted(struct page *page, unsigned long nr_pages) And deriving __GFP_COMP from PageHead(). -- Cheers David / dhildenb