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 mxucPMgH 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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: List-Subscribe: List-Unsubscribe: On 6/6/25 11:15 AM, David Hildenbrand wrote: > On 06.06.25 20:06, Lorenzo Stoakes wrote: >> On Fri, Jun 06, 2025 at 10:57:44AM -0700, John Hubbard wrote: >>> On 6/6/25 4:04 AM, Lorenzo Stoakes wrote: >>>> On Fri, Jun 06, 2025 at 12:28:28PM +0200, David Hildenbrand wrote: >>>>> On 06.06.25 12:19, Lorenzo Stoakes wrote: >>>>>> On Fri, Jun 06, 2025 at 12:13:27PM +0200, Michal Hocko wrote: >>>>>>> On Fri 06-06-25 11:01:18, David Hildenbrand wrote: >>>>>>>> On 06.06.25 10:31, Michal Hocko wrote: >>>>>>> [...] >>>> So to me the only assessment needed is 'do we want to warn on this or not?'. >>>> >>>> And as you say, really WARN_ON_ONCE() seems appropriate, because nearly always >>>> we will get flooded with useless information. >>>> >>> >>> As yet another victim of such WARN_ON() floods at times, I've followed >>> this thread with great interest. And after reflecting on it a bit, I believe >>> that, surprisingly enough, WARN_ON() is a better replacement for VM_BUG_ON() >>> than WARN_ON_ONCE(), because: >> >> Right, these shouldn't be happening _at all_. > > > I'm easy on this point, I'd say in that case VM_WARN_ON() is the most >> _conservative_ approach, since these are things that must not happen, and >> so it's not unreasonable to fail to repress repetitions of the 'impossible' >> :) >> >> But I get the general point about ...WARN_ON_ONCE() avoiding floods. >> >> David, what do you think? > > Well, in this patch here I deliberately want _ONCE for the unpin sanity > checks. Because if they start happening (IOW, now after 5 years observed > for the first time?) I *absolutely don't* want to get flooded and > *really* figure out what is going on by seeing what else failed. > > And crashing on VM_BUG_ON() and not observing anything else was also not > particularly helpful :) > > Because ... they shouldn't be happening ... > > (well, it goes back to my initial point about requiring individual > decisions etc ...) > > Not sure what's best now in the general case, in the end I don't care > that much. > > Roll a dice? ;) One last data point: I've often logged onto systems that were running long enough that the dmesg had long since rolled over. And this makes the WARN_ON_ONCE() items disappear. > thanks, -- John Hubbard