On Fri, Jun 04, 2021 at 12:43:22AM -0700, Ming Lin wrote: > Adds new flag MAP_NOSIGBUS of mmap() to specify the behavior of > "don't SIGBUS on fault". Right now, this flag is only allowed > for private mapping. That's not what your use case asks for. SIGBUS can be generated for a number of reasons, not only on fault beyond end-of-file. vmf_error() would convert any errno, except ENOMEM to VM_FAULT_SIGBUS. Do you want to ignore -EIO or -ENOSPC? I don't think so. > For MAP_NOSIGBUS mapping, map in the zero page on read fault > or fill a freshly allocated page with zeroes on write fault. I don't like the resulting semantics: if you had a read fault beyond EOF and got zero page, you will still see zero page even if the file grows. Yes, it's allowed by POSIX for MAP_PRIVATE to get out-of-sync with the file, but it's not what users used to. It might be enough for the use case, but I would rather avoid one-user features. -- Kirill A. Shutemov
