On Fri, Jun 14, 2019 at 10:57:42AM +0530, Anshuman Khandual wrote: > > > On 06/13/2019 09:01 PM, Matthew Wilcox wrote: > > On Thu, Jun 13, 2019 at 08:51:17PM +0530, Anshuman Khandual wrote: > >> acceptable ? What we have currently is wrong where vmap_pmd_range() could > >> just wrap EBUSY as ENOMEM and send up the call chain. > > > > It's not wrong. We do it in lots of places. Unless there's a caller > > which really needs to know the difference, it's often better than > > returning the "real error". > > I can understand the fact that because there are no active users of this > return code, the current situation has been alright. But then I fail to > understand how can EBUSY be made ENOMEM and let the caller to think that > vmap_page_rage() failed because of lack of memory when it is clearly not > the case. It is really surprising how it can be acceptable inside kernel > (init_mm) page table functions which need to be thorough enough.
It's a corollary of Steinbach's Guideline for Systems Programming. There is no possible way to handle this error because this error is never supposed to happen. So we may as well return a different error that will still lead to the caller doing the right thing.
