On Thu, Oct 18, 2018 at 3:15 PM, Florian Weimer <fw@xxxxxxxxxxxxx> wrote: > * Miklos Szeredi: > >> #define STATX__RESERVED 0x80000000U /* Reserved for future struct statx expansion */ > > What about this? Isn't it similar to STATX_ALL in the sense that we > don't know yet what it will mean? Kernel will return -EINVAL if request_mask contains STATX__RESERVED, so it's definitely different from other flag values. Specifying this in the UAPI sort of implies that other flag values will *not* need a struct statx expansion, so it's safe to pass in any random value not containing STATX__RESERVED on any past or future kernel and it will not write beyond the current struct statx boundary. Not sure if that's a useful thing or not, but it's not actively harmful, like the STATX_ALL flag. Thanks, Miklos
