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Tue, 18 Feb 2025 10:31:48 -0800 (PST) Received: from localhost ([2a03:2880:25ff:74::]) by smtp.gmail.com with ESMTPSA id 00721157ae682-6fb58fa41f3sm18564877b3.120.2025.02.18.10.31.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Feb 2025 10:31:48 -0800 (PST) From: Joshua Hahn To: Dan Carpenter Cc: linux-mm@kvack.org Subject: Re: [bug report] mm/mempolicy: Weighted Interleave Auto-tuning Date: Tue, 18 Feb 2025 10:31:45 -0800 Message-ID: <20250218183146.2297168-1-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.43.5 In-Reply-To: <547331c1-5332-432b-83f0-911b96a79d72@stanley.mountain> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: 414E81A0011 X-Rspamd-Server: rspam12 X-Stat-Signature: fiqq99qgpp17njy37pta8iuy83mk7ysh X-HE-Tag: 1739903509-192593 X-HE-Meta: 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 5u2Pwo3h 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000358, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hello Dan, On Mon, 17 Feb 2025 10:35:20 +0300 Dan Carpenter wrote: > Hello Joshua Hahn, > > Commit aab5f6eb05fd ("mm/mempolicy: Weighted Interleave Auto-tuning") > from Feb 7, 2025 (linux-next), leads to the following Smatch static > checker warning: > > mm/mempolicy.c:220 mempolicy_set_node_perf() > warn: assigned value is less than '1844674407370955161' > > mm/mempolicy.c > 209 int mempolicy_set_node_perf(unsigned int node, struct access_coordinate *coords) > 210 { > 211 uint64_t *old_bw, *new_bw; > 212 uint64_t bw_val; > 213 u8 *old_iw, *new_iw; > 214 > 215 /* > 216 * Bandwidths above this limit cause rounding errors when reducing > 217 * weights. This value is ~16 exabytes, which is unreasonable anyways. > > I see this comment about exabytes > > 218 */ > 219 bw_val = min(coords->read_bandwidth, coords->write_bandwidth); > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ > but these values are u32s > > --> 220 if (bw_val > (U64_MAX / 10)) > ^^^^^^^^^^^^ > There is no way they're going to be more than U64_MAX / 10. Thank you for bringing this to my attention. Ying Huang also brought this up in a patch review [1], and this bug report confirms that it is indeed problematic. I am not entirely sure why I thought the access coordinates were 64 bits, but if I am to imagine what my thought process was at that time, I was probably overthinking the overflow problem and casting all the values into a large data type. I will change all bandwidth-related fields into unsigned int and any aggregate field (sum) to u64. > regards, > dan carpenter Thank you again for your report and your work with Smatch! Have a great day : -) Joshua [1] https://lore.kernel.org/all/87a5ar3mir.fsf@DESKTOP-5N7EMDA/ Sent using hkml (https://github.com/sjp38/hackermail)