[PATCH v2 0/4] fsstress,fsx: add io_uring test and do some fix

[Zorro Lang <zlang@redhat.com>]

This patchset tries to add new IO_URING test into fsstress [1/4] and fsx [4/4].
And then do some changes and bug fix by the way [2/4 and 3/4].

fsstress and fsx are important tools in xfstests to do filesystem I/Os test,
lots of test cases use it. So add IO_URING operation into fsstress and fsx
will help to cover IO_URING test from fs side.

I'm not an IO_URING expert, so cc io-uring@ list, please feel free to
tell me if you find something wrong or have any suggestions to improve
the test.

V2 did below changes:
1) 1/4 change the definition of URING_ENTRIES to 1
2) 2/4 change the difinition of AIO_ENTRIES to 1, undo an unrelated changed line
3) 4/4 turn to use io_uring_prep_readv/io_uring_prep_writev, due to old
       liburing(0.2-2) doesn't support io_uring_prep_read/io_uring_prep_write.

Thanks,
Zorro