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Thu, 9 Sep 2021 09:07:25 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap1.suse-dmz.suse.de with ESMTPSA id SP/pMM3OOWGsHwAAGKfGzw (envelope-from ); Thu, 09 Sep 2021 09:07:25 +0000 Message-ID: Date: Thu, 9 Sep 2021 11:07:25 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.0.3 Subject: Re: [PATCH] mm/page_isolation: don't putback unisolated page Content-Language: en-US To: David Hildenbrand , John Hubbard , Miaohe Lin , akpm@linux-foundation.org Cc: iamjoonsoo.kim@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20210904091839.20270-1-linmiaohe@huawei.com> <3b36529f-ab97-ddfe-0407-66f0cd1fd38d@redhat.com> <2d06db75-5c26-8fe2-6883-ac99056a9894@redhat.com> <80cfffdc-227e-c045-be74-1c08fb62c1e3@redhat.com> From: Vlastimil Babka In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=mXqPO+Ei; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=R0VZbYPF; spf=pass (imf02.hostedemail.com: domain of vbabka@suse.cz designates 195.135.220.28 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none X-Stat-Signature: fxy6ecgbfzu5qctu3z4i8oxcizx4axa6 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 7681D700178D X-HE-Tag: 1631178447-185176 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 9/9/21 10:56, David Hildenbrand wrote: > On 09.09.21 00:42, John Hubbard wrote: >> On 9/7/21 2:56 AM, David Hildenbrand wrote: >> ... >>>> If this can be handled gracefully, then I'd rather go with VM_WARN_ON. >>>> Maybe even WARN_ON_ONCE? >>>> >>> >>> I think either VM_BUG_ON() or VM_WARN_ON() -- compiling the runtime >>> checks out -- should be good >>> enough. >>> >>> I'd just go with VM_BUG_ON(), because anybody messing with >>> __isolate_free_page() should clearly spot >>> that we expect the current handling. But no strong opinion. >>> >> >> If in doubt, WARN*() should be preferred over BUG*(). There's a pretty long >> history of "don't kill the machine unless you have to" emails about this, let >> me dig up one...OK, maybe not the best example, but the tip of the iceberg: > > Please note the subtle difference between BUG_ON and VM_BUG_ON. We expect > VM_BUG_ON to be compiled out on any production system. So it's really only a > mean to identify things that really shouldn't be like that during > debugging/testing. IIRC Fedora used to have CONFIG_DEBUG_VM enabled, did it change? > Using WARN... instead of VM_BUG_ON is even worse for production systems. > There are distros that set panic_on_warn, essentially converting WARN... > into BUG... Uh, does any distro really do that?