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Shutemov" , Mahesh J Salgaonkar , Michael Ellerman , Madhavan Srinivasan , "Aneesh Kumar K . V" , Donet Tom , LKML , Sachin P Bappalige Subject: Re: [RFC v3 -next] cma: Enforce non-zero pageblock_order during cma_init_reserved_mem() Message-Id: <20241112225902.f20215e5015f4d7cdf502302@linux-foundation.org> In-Reply-To: <054b416302486c2d3fdd5924b624477929100bf6.1728656994.git.ritesh.list@gmail.com> References: <054b416302486c2d3fdd5924b624477929100bf6.1728656994.git.ritesh.list@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: D80F12000C X-Stat-Signature: kg7dyti4dqezxhu593zfxs1h1pkfnkgw X-HE-Tag: 1731481100-169140 X-HE-Meta: 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 zkPIqU33 65TKCEw2hhK2WDHOQ6myO2TWLfasnXGKYVkcKywXrsAEXZFgF/rLxtizK8eDt2PxF/EX60peTaekmLF2GBG5z1K5+lzZzKma/w92Ls8HDg/wGlmRM1Qx9LSkEexJKDwn8i6QXysEgaqD4LBO9l550MG/nXnfuf8qgzjIrk3vPPa0Da6+1B1aDZ4Hb7faTsbEYh4PklRw9WbnwvJ2u+ujnFnfPa79XwNQHvpaSbDYJpmzEXz5jwC9wm4967xMzi3/iHxtFfmYCpLtNZMyLHoFuSxbury8uQklaeoX6Ry583MRoCz8katmLnWpvnMsO6ttW2EowO0ipMy9+pJRV24HpBtIe5rAscM1q0NHmKYAcu4EeirhrWanBfShpAeKTSVXB80IK09aO7sR7i2Ob8Sdb29X+5EWYVl6/FIeZkG+DguFVcl18mzGsNLPHUzmovlspzfvA 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 Fri, 11 Oct 2024 20:26:09 +0530 "Ritesh Harjani (IBM)" wrote: > cma_init_reserved_mem() checks base and size alignment with > CMA_MIN_ALIGNMENT_BYTES. However, some users might call this during > early boot when pageblock_order is 0. This sounds like "some users" are in error. Please tell us precisely which users we're talking about here. Is there a startup ordering issue here? It feels like a bad idea to work around callers' flaws within the callee. Please also describe the userspace-visible effects of this. Because it might be the case that we will want to backport any fix into earlier kernels, and we shouldn't do that until we know how those kernels will benefit. And to aid all of this, please attempt to identify a Fixes: target, to aid others in identifying which kernel version(s) need patching. Please answer all the above in the next (non-RFC!) version's changelog. Meanwhile, I'll queue up this version for some testing. Thanks.