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From: Muchun Song In-Reply-To: <20251218150949.721480-12-kas@kernel.org> Date: Mon, 22 Dec 2025 14:00:09 +0800 Cc: Andrew Morton , David Hildenbrand , Matthew Wilcox , Usama Arif , Frank van der Linden , 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 Content-Transfer-Encoding: 7bit Message-Id: <48BA4DA6-DE9D-4F07-B347-19D2F68B357A@linux.dev> References: <20251218150949.721480-1-kas@kernel.org> <20251218150949.721480-12-kas@kernel.org> To: Kiryl Shutsemau X-Migadu-Flow: FLOW_OUT X-Stat-Signature: d7iff5cufibmor5qbujd6h99xps4y4am X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 8E64540016 X-Rspam-User: X-HE-Tag: 1766383255-927578 X-HE-Meta: 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 hIMmhV6h JGjIP6bY/SDwJe48sPXf9WhwJjETUVCBw3TbO5Gpy3y6eaZ6V+WA0Z66fW4ATLlfNhDowKv7kwAX1DdEVx5bMPmQimkY0dRt0IraiRccXOrQMGGk1hIDKQN1ea5D5ktu8UymPSDEAQZ1396o9vMW3eXuFIGLqxCkeXl/wvt97mh+igxjDsk7CFWjcUF/nyNdrpzmbZOSMBZs55XptOvJHZTrKhesK1sFgjuiUAIPFynTZV+9MohzSCH+Mn8kbTUEap+DaEJd3E9BevCl//4h+/9JXLr5KvvBVrtBdHJ6XCngM21wTnVbWtu6ZRQ== 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 Dec 18, 2025, at 23:09, Kiryl Shutsemau wrote: > > The VMEMMAP_SYNCHRONIZE_RCU flag triggered synchronize_rcu() calls to > prevent a race between HVO remapping and page_ref_add_unless(). The > race could occur when a speculative PFN walker tried to modify the > refcount on a struct page that was in the process of being remapped > to a fake head. > > With fake heads eliminated, page_ref_add_unless() no longer needs RCU > protection. > > Remove the flag and synchronize_rcu() calls. > > Signed-off-by: Kiryl Shutsemau Reviewed-by: Muchun Song Thanks.