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Miller" , "Andreas Larsson" , "Alexander Viro" , "Christian Brauner" , "Matthew Brost" , "Joshua Hahn" , "Rakie Kim" , "Byungchul Park" , "Gregory Price" , "Ying Huang" , "Alistair Popple" , "Chris Li" , "Kairui Song" , "Kemeng Shi" , "Nhat Pham" , "Baoquan He" , "Youngjun Park" , "Johannes Weiner" , "Qi Zheng" , "Shakeel Butt" , "Axel Rasmussen" , "Yuanchu Xie" , "Wei Xu" , "Chengming Zhou" , "Michal Hocko" , "Miklos Szeredi" , "Xu Xin" From: "Zi Yan" X-Mailer: aerc 0.22.0 References: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-0-4583d8a23bca@kernel.org> <20260917-b4-mmap-prepare-vma-flag-sanify-v3-31-4583d8a23bca@kernel.org> In-Reply-To: <20260917-b4-mmap-prepare-vma-flag-sanify-v3-31-4583d8a23bca@kernel.org> X-ClientProxiedBy: BN0PR03CA0057.namprd03.prod.outlook.com (2603:10b6:408:e7::32) To IA0PR12MB8374.namprd12.prod.outlook.com (2603:10b6:208:40e::7) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 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12:22 PM EDT, Lorenzo Stoakes (ARM) wrote: > Introduce vma[_flags]_is_persistent() for the purposes of identifying > mappings that are persistent in the sense that bytes to the mapping stay > there, and bytes read from the mapping are the same unless changed by > actions taken by userland. > > Kernel-owned mappings do not fall into this category, as their owner may > change the contents without the user having initiated it, and nor of cour= se > does memory-mapped I/O. > > We exclude fixed mappings as these are singled out as being unmergeable a= nd > so cannot be guaranteed to persist user data. > > hugetlb mappings are fixed mappings, but their contents are entirely the > user's, so they are explicitly carved out as persistent, as the MADV_DODU= MP > check already does. > > It excludes droppable mappings, which by their nature are ephemeral. > > Use this functionality to update the madvise MADV_DODUMP check to test fo= r > persistence rather than open-coding this. > > This replaces the VM_SPECIAL check which means it no longer checks for > VMA_IO_BIT, however this is safe as we have established the invariant tha= t > only kernel-owned mappings may set VMA_IO_BIT, so we implicitly include > these. > > No functional change intended. > > Signed-off-by: Lorenzo Stoakes (ARM) > --- > include/linux/mm.h | 44 ++++++++++++++++++++++++++++++++++++++++++++ > mm/madvise.c | 4 ++-- > 2 files changed, 46 insertions(+), 2 deletions(-) > LGTM. Acked-by: Zi Yan --=20 Best Regards, Yan, Zi