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Howlett" , Vlastimil Babka , Jann Horn , Pedro Falcato Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Nickolai Zeldovich Subject: Re: [PATCH] mm/mremap: populate calculated fields in vrm state correctly Message-ID: References: <20261019-mremap-fix-shrink-charge-v1-1-a3ce209e5360@kernel.org> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261019-mremap-fix-shrink-charge-v1-1-a3ce209e5360@kernel.org> X-Rspam-User: X-Rspamd-Queue-Id: A8B71100005 X-Stat-Signature: jjhmhtjggj7wqt3oegysuni4a5m9iqfa X-Rspamd-Server: rspam01 X-Spam-Status: No, score=-6.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_BLOCKED,RCVD_IN_ZEN_BLOCKED_OPENDNS, SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-HE-Tag: 1792421971-534667 X-HE-Meta: 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 vsBh34u4 Iknu4SjsEbzNF9+qhRpp2KR5rExnX8P0b42THy7ddgYWWLAgtHRQ/SfuSe81iQF/CEbeTne6IEtOgD4yx1eaii914AJzfTJC3QSsRA49BTD2z1G1zfu7CcJU2X6b33Hsm659ceeN8fKkNGrGVQFynqBoIp2jKc8RKOfKRblIzIVesdrB/Y8r1MNUkDRYH0kHPI8BBvUEXY7EYtshQHVV1JWB1nRxVXuwTujmxDWuaAKyHDw1NxJoW4LENHg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Mon, Oct 19, 2026 at 03:28:27PM +0100, Lorenzo Stoakes (ARM) wrote: > Commit d5c8aec0542e ("mm/mremap: initial refactor of move_vma()") > introduced the vma_remap_struct helper to pass state sanely through > mremap() logic. > > Part of this state is vrm->delta - equal to the absolute difference between > vrm->old_len and vrm->new_len (the old and new lengths of the VMA, > respectively). > > This value is used to correctly charge accounted VMAs. > > When shrinking a VMA, mremap_to() sets vrm->old_len equal to vrm->new_len > having performed the shrink of the VMA first, prior to any potential > move (e.g. MREMAP_FIXED | MREMAP_MAYMOVE specified). > > However it does not recalculate vrm->delta, which results in incorrectly > overcharging the VMA. Andrew - could you update this to: >> However it does not recalculate vrm->delta, which results in incorrectly overcharging the VMA when both moving and shrinking a VMA. << To make it clear that only when you do this (rather unusual) action do you encounter the issue. -- Cheers, Lorenzo