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Tue, 27 Jan 2026 09:51:48 -0500 (EST) Date: Tue, 27 Jan 2026 14:51:43 +0000 From: Kiryl Shutsemau To: Muchun Song Cc: Oscar Salvador , Mike Rapoport , Vlastimil Babka , Lorenzo Stoakes , Zi Yan , Baoquan He , Michal Hocko , Johannes Weiner , Jonathan Corbet , kernel-team@meta.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, Andrew Morton , David Hildenbrand , Matthew Wilcox , Usama Arif , Frank van der Linden Subject: Re: [PATCHv4 09/14] mm/hugetlb: Remove fake head pages Message-ID: References: <20260121162253.2216580-1-kas@kernel.org> <20260121162253.2216580-10-kas@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: EDC7D40006 X-Stat-Signature: krhf55txmq5sgp6ka61xtmd4xincnasw X-Rspam-User: X-HE-Tag: 1769525513-872833 X-HE-Meta: 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 v9l7IEgC 2L3z8yq7C+ADdygiLXzzAt+wIGfOys5Ysw894mGAmEKg1PKOo5FIhwqo8qkFf6lenJuhtVz3lhtTWdXAGei8+b5NLBuvAvY1gTWN5a2OrJ1+8n6qmorZao6GSfl6Rg0YFkssHvOk2HwgY7i3X1cs8tQRGAjsfe6GiOYB8RrRouJ3K1IozCKwHznWEKAROtYMguUR0s/4mBZ5S2unuSwFY7b6XkazShf6NK87hQkEOBNvVATYPPYSb1EnaAh9cNTcdzC1B1vPRrgy6mjbfMN2qnoYswg== 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 Thu, Jan 22, 2026 at 03:00:03PM +0800, Muchun Song wrote: > > + if (pfn) > > + return pfn_to_page(pfn); > > + > > + tail = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0); > > + if (!tail) > > + return NULL; > > + > > + p = page_to_virt(tail); > > + for (int i = 0; i < PAGE_SIZE / sizeof(struct page); i++) > > + prep_compound_tail(p + i, NULL, order); > > + > > + spin_lock(&hugetlb_lock); > > hugetlb_lock is considered a contended lock, better not to abuse it. > cmpxchg() is enought in this case. We hit the lock once per node (excluding races). Its contribution to the lock contention is negligible. spin_lock() is easier to follow. I will keep it. Ack for the rest of your comments. -- Kiryl Shutsemau / Kirill A. Shutemov