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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-442cd33103dsm12361095e9.10.2025.05.07.13.46.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 07 May 2025 13:46:17 -0700 (PDT) Date: Wed, 7 May 2025 21:46:16 +0100 From: David Laight To: WangYuli Cc: Matthew Wilcox , akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yuzhao@google.com, stevensd@chromium.org, kaleshsingh@google.com, zhanjun@uniontech.com, niecheng1@uniontech.com, guanwentao@uniontech.com Subject: Re: [PATCH] mm: vmscan: Avoid signedness error for GCC 5.4 Message-ID: <20250507214616.4d91620e@pumpkin> In-Reply-To: References: <85050791B887DC13+20250506160238.799984-1-wangyuli@uniontech.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 6AEC7180007 X-Stat-Signature: dqz6ijrnfqz34e6r7w7xbf94kdq5gyza X-HE-Tag: 1746650779-358609 X-HE-Meta: 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 zFFIpr3k zEE6+Ht0PgyzclKwNB/z18GVytcsG1WCZgrNr7+TpQxhsJvzQ6RglY/tGopTBmdPDg0MfXO1ANQgYt8ZKSPnUokY7+RO0YCnFijFrx3tEq7hAEqVtwRr6r2C73nqSfChUDkWm8k9xYS7FjmBfntghi2LsByrOLau5PeNzVn/EfkvUAXtl6vE8si1Yb4krEgMbQ/N+t+IprTxnMgSbFMAr65FylVlRhrv/OJ9N1zFMhYsMqbBAqxugegtA9H6h7u3LVq/cuR7tFtRMKfNiaoE0L0tbfUIFBXXgEkVz5Ps9yRQInMxNCQe4t/JInDI8tuHa2+WTnHO8zwda6KpsbLhTFer2xeQFBwOXVe0cTZ8N8J1CK26VGoPGm/gNoWuOySJNuMzEnpTUN5p11RDuiXgMuNyUd+Wq0QIyOcx2UdYCEb3uJficRNPxzWd84HNn/NGFrBM6Ow1XG0uXtDPpZMOOrTJtDqoh8KxI/sh3 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 Wed, 7 May 2025 10:55:31 +0800 WangYuli wrote: > Hi Matthew Wilcox and Andrew Morton, > > On 2025/5/7 00:22, Matthew Wilcox wrote: > > 1. This has nothing to do with the compiler version; the type-checking > > is built into min(). > > Thank you for pointing that out! My previous statement was incorrect. > > The error is actually from the __types_ok check within the > __careful_cmp_once macro failing, which triggered BUILD_BUG_ON. > > But then, why do newer compilers compile this without error? Is it > perhaps because they consider 4U - 1 to be signed? No, statically_true(tier >= 0) is true even though 'tier' is signed because the compiler has inlined the function and followed the domain of 'tier' from the assignments and loops. David