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bh=bVqXna5WxCsAHx/u/2x8IFda69mGhWNfyQf/4SSeqFo=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=aLwUUOWzunX5b0iNH/5uYpBQudZqjaFb+2mf1Ru3dqDsNAz0NOHpCMRBsw6S9TK8E itS0ih2Yvy91YSkgtOlKPXaxPrHbIljz7H1tYZdFb5UTS8cChG4zr7knEDmrv4gTDh Yeq9YTSaxes/J1zV3nub/Q5DNnbbisNF0JcfJLtQ2dgNAsI1okA6QEcxLm9CYcqJZt ncm3oCg9LhYogbUz1kmm5kr2t2Ze9d+EOyGNtAowSM7nGS0wYFeLnr2cUcrz/aQuoU aZLr7TNlJRop61r8G9swwqUhHsXjoNSy06mmFMbIEp0L4jbkjMfsZunsSPxAaZbZj/ 6tZPpBFVa5NTg== Date: Tue, 31 Jan 2023 15:47:05 +0200 From: Mike Rapoport To: Hyunmin Lee Cc: Andrew Morton , Uladzislau Rezki , Christoph Hellwig , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Gwan-gyeong Mun , Jeungwoo Yoo , Sangyun Kim , Hyeonggon Yoo <42.hyeyoo@gmail.com> Subject: Re: [PATCH] replace BUG_ON to WARN_ON Message-ID: References: <20230127115844.GA1124261@min-iamroot> <20230131105629.GA1195431@min-iamroot> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230131105629.GA1195431@min-iamroot> X-Rspamd-Queue-Id: F1A55C000B X-Rspamd-Server: rspam09 X-Rspam-User: X-Stat-Signature: argn3zbmtd7pgapmes1j6k3c3afym6ir X-HE-Tag: 1675172839-26990 X-HE-Meta: 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 SwawgUwH XhK2kdDZ6CZoCYUufRLUPLomAHR2GKvfrrQgANVSc1Qce1LL5ZEr7XHC9sgpSoBUWviag0kX/SVkG93yghM5B1v8XOnmW28VWM87W3lRZ/zfliwdWWl/R8cvGUVpHr1NJZVV9OKj4ww9Z4FZYjLuH94QH2z3h9igzlVEOhSMZdU7kP+Uao5FtaZdeEycC9WzgNf2HOp/EUJVl5CUkEHCFQrSEYLP+iQqZaFrcNBc9/uwCnjuUnMKK75u7cZEphJ47hnyGrqCeD0fUncKU9lDEY/bJJyM8Cb/wR3Q6AFQmIIu7cjj2L1R0ZZJX4JqySi2vb6ag4a9ay3BZvVG6gctBQfUPj0gEygLdBhwCvqSU8vfkA+rGItVIt/rHaYs4OGou7wntNCsuhbOPZRPirlQ1km74PQSxDgDULJtlcSMS7zLXADY= 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: On Tue, Jan 31, 2023 at 07:56:29PM +0900, Hyunmin Lee wrote: > On Mon, Jan 30, 2023 at 12:14:04PM +0200, Mike Rapoport wrote: > > Hi, > > > > On Fri, Jan 27, 2023 at 08:58:44PM +0900, Hyunmin Lee wrote: > > > Replace unnacessary BUG_ON to WARN_ON. These BUG_ONs verify aruguments of a function. Thus, the WARN_ONs return an EINVAL error when their condition is true. > > > > Some users enable panic_on_warn, so for them WARN_ON will still crash a > > machine. > > > > I think a simple if() will be sufficient. > > > Hi Mike, > > Thank you for your advice. > Would you please give feedback about the below opinion? > - Printing warning messages is helpful to inform what happened in the system to the users. > - When a simple if() is used instead of WARN_ON, the if() should print a warning message. > - The condition of the simple if() should also have unlikely() for optimization of system performance. > - WARN_ON is a macro doing like thoes easily. It has a notifying function and unlikely optimization. > - Eventhough WARN_ON will still crash like BUG_ON by some users who enable panic_on_warn, it is their intention. They should accept the crash by WARN_ON. > - Therefore, using WARN_ON looks like natural and efficient. As this is a validation of the function parameters, there is no need in warning messages and if(unlikely()) will do. There is really no point in WARN_ON() for something that's totally recoverable and very unlikely to happen. > Best, > Hyunmin -- Sincerely yours, Mike.