On Wed, Jul 18, 2018 at 10:15 PM, Joseph Myers [off-list ref] wrote:

On Tue, 17 Jul 2018, Arnd Bergmann wrote:

quoted

That would definitely help. See below for the stat implementation
I did in my musl libc prototype based on statx(). It passes the
LTP syscall tests, but that doesn't mean all the corner cases
are correct.

Well, you definitely need explicit timestamp conversions on the result of
statx to be usable in struct stat when userspace "long" is 64-bit, for BE
because otherwise the integer nanoseconds will be in the wrong place for
struct timespec, and for LE if the "__reserved is held in case we need a
yet finer resolution." might start being returned as nonzero (for integer
attoseconds, I suppose) in future.

Right. The musl implementation I sent did that by simply copying each
field we care about from the statx structure into the stat structure
individually. This is the more or less the same thing that the kernel
does to implement stat() as well.

     Arnd