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

From: Miklos Szeredi
Date: Thu Oct 18 2018 - 10:34:34 EST

On Thu, Oct 18, 2018 at 4:32 PM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> 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.

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