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b=AMqKHFdbqByiISt7gdsCumYhawhuE9fwriGzjlE0yAjkYNrIZC6K2R0bMvHm3GizW sAr5XUXUJNX8HBY/ybbp/jOIg5RlwlZKFKKpi5901ZDK5p+2Byo8TRKA4yC3LKS2AC NMmzxJr3YefLqAEhLts6DW3A9bvzrJ0UHWcmRm61qYPXoYzyiql1+PgeDYnUE5I3Zi 04R5if/6KKbW7kzm4nr3AFj4kE5m+Zt+IJqrCIfYFnWdPEwTGOm4X+SxA9NtAXRumJ 6x6AyjgE9ddCd5dqS73hvfvQXHxdXlryLFx1ySNZZO8tgDnkT29Z9RyK9zzdD/muFf 3G2B2xqGCKexw== From: SJ Park To: Daemyung Kang Cc: SJ Park , damon@lists.linux.dev, linux-mm@kvack.org, akpm@linux-foundation.org, bijantabatab@micron.com, ravis.opensrc@micron.com Subject: Re: [PATCH] mm/damon/vaddr: preserve migration weights above UINT_MAX Date: Tue, 27 Oct 2026 06:53:54 -0700 Message-ID: <20261027135354.149948-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261027035431.1007584-1-charsyam@gmail.com> References: X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: C6C2380006 X-Stat-Signature: m6b7b9ithdp416bpdideu34dhkx31fuh X-Spam-Status: No, score=-9.1 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1793109243-302360 X-HE-Meta: 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 aXPXwkuu 3fqyzE1D7yxkx0XHqaok6/eJw8HzlixqG4AserP34kbq+zloCRsaTp1lFyPcEJpvSL98f/04xZCZqmOch1xvY7jVH58x52Atm7190tmoHFADM7rx5OZtQ4Po9ZK8dHnw0uHjAZspMER4e0zrIvzQd+fSXkzpdYo9xa7oybhS8ZtvfrO2Q//z8fvgvUPrEFYZYoMOpDy3dBl0UauPaeSXRRjCVXEZ2nhFBGRAF8gPEV9qJE7/JA4JuPqLN8QC+iKS0ubUSgHztMpy9FWiHZp9xX8yg5g== 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 Hello Daemyung, On Tue, 27 Oct 2026 12:54:31 +0900 Daemyung Kang wrote: > DAMOS migration accepts an unsigned int weight for each destination, > but sums the weights into an unsigned int. If the total wraps to zero, > no folio is migrated. Other wrapped totals select the wrong node. Thank you for finding the issue. But, is it realistic to have the weight_total overflow? Have you found the issue on real usage? Or, theoretical? > > Sum weights into a u64 once per migration walk. Keep the existing > 32-bit divisor path for totals up to UINT_MAX and use a 64-bit remainder > for larger totals. Add KUnit coverage for the actual summing path and > for destination selection at the overflow boundary. Do we really need to support that user inputs? Unless we have a very real use case that require such huge weight values, I'd prefer not. How about just clearly notify users those are invalid parameters? We could do so by adding weight_total overflow check to the central parameters validation path: damos_commit_dests(). > > Fixes: 19c1dc15c859 ("mm/damon/vaddr: use damos->migrate_dests in migrate_{hot,cold}") Should we Cc: stable? Thanks, SJ [...]