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 NjvgPu7Z 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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: > > > [...] > > > > > Turning them into VM_WARN_ON > > > > > should be reasonably safe as they are not enabled in production > > > > > environment anyway so we cannot really rely on those. Having them in > > > > > WARN form would be still useful for debugging and those that really need > > > > > a crash dump while debugging can achieve the same result. > > > > > > > > One question is if we should be VM_WARN_ON vs. VM_WARN_ON_ONCE ... > > > > > > *WARN_ONCE ha a very limited use from code paths which are generally > > > shared by many callers. You just see one and then nothing. Some time ago > > > we have discussed an option to have _ONCE per call trace but I haven't > > > see any follow up. > > > > > > Anyway starting without _ONCE seems like safer option because we are not > > > losing potentially useful debugging information. Afterall this is > > > debugging only thing. But no strong position on my side. > > > > > > > VM_BUG_ON is essentially a "once" thing so far, but then, we don't continue > > > > ... so probably most should be _ONCE. > > > > > > > > > > > > > > So while I agree that many of them could be dropped or made more clear > > > > > those could be dealt with after a mass move. An advantage of this would > > > > > be that we can drop VM_BUG_ON* and stop new instances from being added. > > > > > > > > As a first step we could probably just #define them to go to the > > > > VM_WARN_ON_* variants and see what happens. > > > > > > You meand VM_BUG_ON expand to VM_WARN_ON by default? > > > > Sorry to interject in the conversation, but to boldly throw my two English pence > > into the mix: > > > > As the "king of churn" (TM) you'll not be surprised to hear that I'm in favour > > of us just doing a big patch and convert all VM_BUG_ON() -> VM_WARN_ON_ONCE() > > and remove VM_BUG_ON*(). > > > > Pull the band-aid off... I think better than a #define if this indeed what you > > meant David. > > > > But of course, you'd expect me to have this opinion ;) > > See my reply to Michal regarding keeping VM_BUG_ON() until we actually > decided what the right cleanup is. Sure, but to me the concept of VM_BUG_ON() is surely fundamentally broken - if BUG_ON() means 'stop everything we're going to corrupt' then it makes no sense to add a '...but only if CONFIG_DEBUG_VM is set' in there. 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. I think this being debug code gives us a lot of leeway here. After the big change, we can always revisit individual cases and see if the warning is valid at all. > > I don't have a very strong opinion on any of this ... as long as VM_BUG_ON() > goes away one way or the other. Am happy to come up with the churn-meister version of this patch and take the heat :P > > -- > Cheers, > > David / dhildenb > Cheers, Lorenzo