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Wed, 10 Sep 2025 10:05:28 +0800 Message-ID: Date: Wed, 10 Sep 2025 10:05:27 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 6/9] mm: page_alloc: add alloc_contig_frozen_pages() To: Zi Yan , Matthew Wilcox CC: Andrew Morton , David Hildenbrand , Oscar Salvador , Muchun Song , , , Vlastimil Babka , Brendan Jackman , Johannes Weiner , References: <20250902124820.3081488-1-wangkefeng.wang@huawei.com> <20250902124820.3081488-7-wangkefeng.wang@huawei.com> Content-Language: en-US From: Kefeng Wang In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.243] X-ClientProxiedBy: kwepems200002.china.huawei.com (7.221.188.68) To dggpemf100008.china.huawei.com (7.185.36.138) X-Rspamd-Queue-Id: E26D3A0008 X-Rspamd-Server: rspam05 X-Stat-Signature: 3zhqkdijp1nufww4arj65ufishtrs1k6 X-Rspam-User: X-HE-Tag: 1757469953-773567 X-HE-Meta: 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 WqC3fVv5 7KOHb8KsR6lgWmSCYmJQiXfW5t5KGKaBhkG+BqoQFh76Pv5+ICiomUSVM2r6kpNjmaCjSN1+NWDKKw9H09hUpM77fNuhGNhaRFvM5lhprXyvsITIdzNznTSB8WW0zz8LtRWd3EtYFYj3r1KU9qESZZOzLVcL72JfE5vLOMqbhrTa5D7RrESG3Pl/q+JsoCetRHDR2GB2BxEJGRkAwyhbZgAbrmG9a5GE8sqGUKRndBC02YDBygwgKiVzOaWHndVm9mnAs6BCVnAvCbrkrn9UD+ft5lCd0bI9NPNMsU9kz7jYePag0LwCAlV80wQ== 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 2025/9/10 3:08, Zi Yan wrote: > On 9 Sep 2025, at 14:55, Matthew Wilcox wrote: > >> On Tue, Sep 02, 2025 at 08:48:17PM +0800, Kefeng Wang wrote: >>> Introduce a ACR_FLAGS_FROZEN flags to indicate that we want to >>> allocate a frozen compound pages by alloc_contig_range(), also >>> provide alloc_contig_frozen_pages() to allocate pages without >>> incrementing their refcount, which may be beneficial to some >>> users (eg hugetlb). >> >> No, this is not the way to do it. We're moving towards a future where >> pages don't have refcounts (their owning structs eg folios may have a >> refcount, but struct page does not have a refcount). So work towards >> that; if you need to keep compatibility with some users, then by all >> means keep alloc_contig_range_noprof() as a wrapper that calls >> alloc_contig_range_frozen_noprof() and then calls set_page_refcounted() >> if alloc_contig_range_frozen_noprof() does not return NULL. But I'd >> be looking to see if alloc_contig_range_noprof() can always return a >> non-refcounted page. > Yes, Zi has been comment this shown below, alloc_contig_pages_noprof() is called by may driver(directly or indirectly), I originally only hoped to minimize the changes, if we follow your plan, we can do a bit more, let me try the new way. Also I will separate this patchset to let the cleanup patch could be merged first. > Something like: > > struct page *alloc_contig_pages_noprof(unsigned long nr_pages, gfp_t gfp_mask, > int nid, nodemask_t *nodemask) > { > struct page *page = __alloc_frozen_contig_pages_noprof(...); > > // just added page == NULL check > if (!page) > return NULL; > > if (gfp_mask & __GFP_COMP) > set_page_refcounted(page); > else { > unsigned long i; > > for (i = 0; i < nr_pages; i++) > set_page_refcounted(page + i); > } > return page; > } > > as I suggested in another email[1] (of course I forgot to check page == NULL). > > And other TODOs: > > 1. remove set_page_refcounted() in split_free_pages(); > 2. a new split_frozen_page() to do split_page() work without > set_page_refcounted() and split_page() can just call it; > 3. a new free_frozen_contig_range() and free_contig_range() > calls it. > Thanks Matthew/Zi. > > [1] https://lore.kernel.org/linux-mm/298B40E0-8EA5-4667-86EF-22F88B832839@nvidia.com/ > > Best Regards, > Yan, Zi