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Tue, 31 Jan 2023 02:56:33 -0800 (PST) Date: Tue, 31 Jan 2023 19:56:29 +0900 From: Hyunmin Lee To: Mike Rapoport 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: <20230131105629.GA1195431@min-iamroot> References: <20230127115844.GA1124261@min-iamroot> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 619F31C0002 X-Stat-Signature: hcx7gjw47h945b7iqi65oyaiyr1ddhms X-Rspam-User: X-HE-Tag: 1675162595-891660 X-HE-Meta: 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 WHGzjBtk 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 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 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. > > > Co-Developed-by: Gwan-gyeong Mun > > Co-Developed-by: Jeungwoo Yoo > > Co-Developed-by: Sangyun Kim > > Signed-off-by: Hyunmin Lee > > Signed-off-by: Gwan-gyeong Mun > > Signed-off-by: Jeungwoo Yoo > > Signed-off-by: Sangyun Kim > > Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com> > > --- > > mm/vmalloc.c | 11 ++++++++--- > > 1 file changed, 8 insertions(+), 3 deletions(-) > > > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > > index 74afa2208558..9f9dba3132c5 100644 > > --- a/mm/vmalloc.c > > +++ b/mm/vmalloc.c > > @@ -1587,9 +1587,14 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > > int purged = 0; > > int ret; > > > > - BUG_ON(!size); > > - BUG_ON(offset_in_page(size)); > > - BUG_ON(!is_power_of_2(align)); > > + if (WARN_ON(!size)) > > + return ERR_PTR(-EINVAL); > > + > > + if (WARN_ON(offset_in_page(size))) > > + return ERR_PTR(-EINVAL); > > + > > + if (WARN_ON(!is_power_of_2(align))) > > + return ERR_PTR(-EINVAL); > > > > if (unlikely(!vmap_initialized)) > > return ERR_PTR(-EBUSY); > > -- > > 2.25.1 > > > > > > -- > Sincerely yours, > Mike. 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. Best, Hyunmin