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Tue, 14 Oct 2025 09:41:23 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 4KBmNMMa7miRWgAAD6G6ig (envelope-from ); Tue, 14 Oct 2025 09:41:23 +0000 Date: Tue, 14 Oct 2025 10:41:18 +0100 From: Pedro Falcato To: Lorenzo Stoakes Cc: Andrew Morton , "Liam R . Howlett" , Vlastimil Babka , Jann Horn , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm/mremap: correctly account old mapping after MREMAP_DONTUNMAP remap Message-ID: References: <20251013165836.273113-1-lorenzo.stoakes@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251013165836.273113-1-lorenzo.stoakes@oracle.com> X-Rspamd-Action: no action X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 11FD0140008 X-Stat-Signature: zmgx7xjtho3an3mxpnxfgb4yhpmnnudw X-Rspam-User: X-HE-Tag: 1760434885-762855 X-HE-Meta: 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 7MBN9WxA USUVmQlhfaPm6OUWnPqESRF0OvvsxFtopkn42XrJG/tC72/A9iTpj821NYTpyBLt8rWgmJKkNVKDDGbmhS3RAdXQ+N2pAiFL3rGUYeUfntquKCDchT37nN2bjXCIkV/o4xGPDRz/pbFwjwd89IO+GOI6QL9HD3M1/Cp9P8jmPP9WrJ2Y8lQpJ++LEPaNV8TZwBDr96prNxLL8IY/opAuzj+gjFE73XqGNNpRX8YYBVgEk5sBkLaAPjvVDPmblNswYBVcC7BaUVvvuDWcyaqx6lJoL8PCDiAG7SMecNcIBRCuMLVrxD9GJPBAwnPAXawts/Ej3VEQ6MDZPmiWsu2AOomiFCetBSHAehjOxr6T3VVYHOfWP+FoOX1qDIbkrjw93LwEFWHQF7njK6D4= 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 Mon, Oct 13, 2025 at 05:58:36PM +0100, Lorenzo Stoakes wrote: > Commit b714ccb02a76 ("mm/mremap: complete refactor of move_vma()") > mistakenly introduced a new behaviour - clearing the VM_ACCOUNT flag of the > old mapping when a mapping is mremap()'d with the MREMAP_DONTUNMAP flag > set. > > While we always clear the VM_LOCKED and VM_LOCKONFAULT flags for the old > mapping (the page tables have been moved, so there is no data that could > possibly be locked in memor), there is no reason to touch any other VMA memory > flags. > > This is because after the move the old mapping is in a state as if it were > freshly mapped. This implies that the attributes of the mapping ought to > remain the same, including whether or not the mapping is accounted. > > Signed-off-by: Lorenzo Stoakes Reviewed-by: Pedro Falcato Looks good, thanks! Should we add a test for it? -- Pedro