[$] Making O_TMPFILE atomic (and statx() additions)

Right on the heels of his previous filesystem
session at the
2022 Linux Storage,
Filesystem, Memory-management and BPF Summit (LSFMM), Steve French led
a session on temporary files and their interaction with network
filesystems.
The problem is that creating temporary files is not always atomic, so he was
proposing changing that, which would eliminate a possible race condition
and be more efficient for network filesystems.
Since the temporary-file discussion did not fill the 30-minute slot, however, French took
the opportunity to discuss some attributes he would like to see get added for the
statx()
system call.