Re: [PATCH 2/3] uapi: get rid of STATX_ALL

On Thu, Oct 18, 2018 at 4:32 PM, Miklos Szeredi [off-list ref] wrote:

On Thu, Oct 18, 2018 at 3:15 PM, Florian Weimer [off-list ref] wrote:

quoted

* Miklos Szeredi:

quoted

 #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.

In other words, if STATX_ALL was defined as 0x7fffffff, then that
would mean the same thing, and I wouldn't complain about it.

Thanks,
Miklos