On Thu, Mar 31, 2022, Shivam Kumar wrote: > > > + if (!dirty_quota || (pages_dirtied < dirty_quota)) > > > + return 1; > > I don't love returning 0/1 from a function that suggests it returns a bool, but > > I do agree it's better than actually returning a bool. I also don't have a better > > name, so I'm just whining in the hope that Paolo or someone else has an idea :-) > I've seen plenty of check functions returning 0/1 but please do let me know > if there's a convention to use a bool in such scenarios. The preferred style for KVM is to return a bool for helpers that are obviously testing something, e.g. functions with names is "is_valid", "check_request", etc... But we also very strongly prefer not returning bools from functions that have side effects or can fail, i.e. don't use a bool to indicate success. KVM has a third, gross use case of 0/1, where 0 means "exit to userspace" and 1 means "re-enter the guest". Unfortunately, it's so ubiquitous that replacing it with a proper enum is all but guaranteed to introduce bugs, and the 0/1 behavior allows KVM to do things liek "if (!some_function())". This helper falls into this last category of KVM's special 0/1 handling. The reason I don't love the name is the "check" part, which also puts it into "this is a check helper". But returning a bool would be even worse because the helper does more than just check the quota, it also fills in the exit reason.
