On 06/13/2019 03:03 PM, Roman Penyaev wrote: > On 2019-06-13 10:12, Anshuman Khandual wrote: >> vmap_pte_range() returns an -EBUSY when it encounters a non-empty PTE. But >> currently vmap_pmd_range() unifies both -EBUSY and -ENOMEM return code as >> -ENOMEM and send it up the call chain which is wrong. Interestingly enough >> vmap_page_range_noflush() tests for the absolute error return value from >> vmap_p4d_range() but it does not help because -EBUSY has been merged with >> -ENOMEM. So all it can return is -ENOMEM. Fix this by testing for absolute >> error return from vmap_pmd_range() all the way up to vmap_p4d_range(). > > I could not find any real external caller of vmap API who really cares > about the errno, and frankly why they should? This is allocation path, map_vm_area() which is an exported symbol suppose to provide the right error code regardless whether it's current users care for it or not. > allocation failed - game over. When you step on -EBUSY case something > has gone completely wrong in your kernel, you get a big warning in > your dmesg and it is already does not matter what errno you get. Its true that vmap_pte_range() does warn during error conditions. But if we really dont care about error return code then we should just remove specific error details (ENOMEM/EBUSY) and instead replace them with simple boolean false/true or (0/1/-1) return values at each level. Will that be acceptable ? What we have currently is wrong where vmap_pmd_range() could just wrap EBUSY as ENOMEM and send up the call chain.
