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Thu, 26 Mar 2026 22:50:54 -0700 (PDT) From: Liew Rui Yan To: sj@kernel.org Cc: aethernet65535@gmail.com, damon@lists.linux.dev, linux-mm@kvack.org Subject: Re: (sashiko review) [RFC v5] mm/damon: add synchronous commit for commit_inputs Date: Fri, 27 Mar 2026 13:50:51 +0800 Message-ID: <20260327055051.61731-1-aethernet65535@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260327050823.43382-1-sj@kernel.org> References: <20260327050823.43382-1-sj@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 82422160006 X-Stat-Signature: nnm531ak7hnbmhd8inadzz7fxtnsibxk X-HE-Tag: 1774590656-372125 X-HE-Meta: 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 kyMXw/kS Fa1vzpF0T7iQsjCB4lV+u9aI3EmURLXcnra+FvzJgTmKmm97gR401eXjNFUKjdaV7LI4hg3myGLVBQjPcdMEpwqq239D0uBcBa/oaRkeicstsKVYn4Y803BjF1VBVNdxWKoTxTCI8e7g/jUH7zESuQH341bcxpvXn8CIvgxsfdOGMgBJi9Au19I8yX7D94TziBeYMctVoHLvgXpbIgl5SOZ+TujfUX1CHDqLSUN9UqnALHOxp7GxaPsTnK2BrSZytSHq50YfAhjRD25Kr5Tczzdl70quWtv4jRsatTAo2HX/yzjnn8smSH1TVENMNuZyluXGilMme1rP1824efkXJXU7U/r9tnoebsdbmZCl6HGCFRCzVX39g18cpj564fxAedratReHdOjHKjSMBn1jeD+VePaNbmrZNxzbmkkpaXJOt0Lg8LHiFGVd1jUuTDENH6InO7jPuJ/IsDtQ0ByI/vFXPrEQbXLbdmCjNNC/+Aba2rt9gzlJFnwLRwQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi SeongJae, On Thu, 26 Mar 2026 22:08:22 -0700 SeongJae Park wrote: > [...] > > > > I will add a patch in v6 to validate 'addr_unit' in addr_unit_store() to > > > > reject non-power-of-2 inputs immediately. > > > > > > That's because kdamond_fn() has recently changed to exit the loop if > > > damon_commit_ctx() fails in the loop for any reason. Refer to commit > > > 26f775a054c3 ("mm/damon/core: avoid use of half-online-committed context") for > > > more details. > > > > > > Adding the validation in addr_unit_store() would work, but it could be a kind > > > of whack-a-mole game. I'd prefer doing the validation of all inputs in one > > > place, just before the last damon_commit_ctx() call. DAMON_SYSFS is doing so, > > > by making a test context and try committing user input to the test context > > > before doing that to the running context. How about doing so here, too? > > > > Thank you for the suggestion. I have now added the check > > '!src->addr_unit || ! is_power_of_2(src->addr_unit)' to > > damon_commit_ctx(). > > No, what I'm suggesting is not adding more checks, but reusing the existing > checks in damon_commit_ctx(). I just realized my previous reply might have caused a small misunderstanding. My intention was not to _add_ a new check, but to _move_ the validation to damon_commit_ctx(). So that patch will only modify damon_commit_ctx(). > > And, now I think bit differently. Given the purpose of this patch is making > commit_inputs synchronous, I think making more complete validation check is > somewhat that can be done separately. So my suggestion now is just keeping > this part just as is. Understood. I will keep this series focused on making 'commit_inputs' synchronous, and prepare the validation for 'addr_unit' as a separate patch later. Thanks for helping me scope this properly. > [...] > > > So the issue already exists. But let's ensure the fix is merged before this > > > patch, since this patch adds another exploitable path that can consequence in > > > whole param_lock deadlock. > > > > Should I wait for your fix to be merged into damon/next before I post > > the next version? > > As long as you agree about the mainline merge order, I think you don't need to > wait for my fix. Please feel free to post next version. > > FYI, the latest version of my fix is available [1] on the mailing list. > > [1] https://lore.kernel.org/20260327004952.58266-1-sj@kernel.org Thank you for your confirmation, and your fix. :> Best regards, Rui Yan [...]