Next issue:  seems like file slot reuse is not working correctly.
Attached program compares reads using io_uring with plain reads of
proc files.

In the below example it is using two slots alternately but the number
of slots does not seem to matter, read is apparently always using a
stale file (the prior one to the most recent open on that slot).  See
how the sizes of the files lag by two lines:

root@kvm:~# ./procreads
procreads: /proc/1/stat: ok (313)
procreads: /proc/2/stat: ok (149)
procreads: /proc/3/stat: read size mismatch 313/150
procreads: /proc/4/stat: read size mismatch 149/154
procreads: /proc/5/stat: read size mismatch 150/161
procreads: /proc/6/stat: read size mismatch 154/171
...

Any ideas?

Thanks,
Miklos