On Wed, Mar 20, 2019 at 05:22:43AM -0700, Matthew Wilcox wrote: > On Wed, Mar 20, 2019 at 01:20:15PM +0100, Oscar Salvador wrote: > > On Wed, Mar 20, 2019 at 04:19:59AM -0700, Matthew Wilcox wrote: > > > On Wed, Mar 20, 2019 at 03:35:38PM +0800, Baoquan He wrote: > > > > /* > > > > - * returns the number of sections whose mem_maps were properly > > > > - * set. If this is <=0, then that means that the passed-in > > > > - * map was not consumed and must be freed. > > > > + * sparse_add_one_section - add a memory section > > > > + * @nid: The node to add section on > > > > + * @start_pfn: start pfn of the memory range > > > > + * @altmap: device page map > > > > + * > > > > + * Return 0 on success and an appropriate error code otherwise. > > > > */ > > > > > > I think it's worth documenting what those error codes are. Seems to be > > > just -ENOMEM and -EEXIST, but it'd be nice for users to know what they > > > can expect under which circumstances. > > > > > > Also, -EEXIST is a bad errno to return here: > > > > > > $ errno EEXIST > > > EEXIST 17 File exists > > > > > > What file? I think we should be using -EBUSY instead in case this errno > > > makes it back to userspace: > > > > > > $ errno EBUSY > > > EBUSY 16 Device or resource busy > > > > We return -EEXIST in case the section we are trying to add is already > > there, and that error is being caught by __add_pages(), which ignores the > > error in case is -EXIST and keeps going with further sections. > > > > Sure we can change that for -EBUSY, but I think -EEXIST makes more sense, > > plus that kind of error is never handed back to userspace. > > Not returned to userspace today. It's also bad precedent for other parts > of the kernel where errnos do get returned to userspace. Yes, I get your point, but I do not really see -EBUSY fitting here. Actually, we do have the same kind of situation when dealing with resources. We return -EEXIST in register_memory_resource() in case the resource we are trying to add conflicts with another one. I think that -EEXIST is more intuitive in that code path, but I am not going to insist. -- Oscar Salvador SUSE L3
