[PATCH v2 0/3] fstests: fix io_uring testing

[Zorro Lang <zlang@kernel.org>]

[PATCH 1/3]
According to the manual of io_uring_queue_init, it doesn't set errno
but return the -errno on failure. So we should check the return value
of io_uring_queue_init, to make sure if the io_uring is supported by
kernel. We've left this problem in xfstests/ltp/fsstress.c long time.

V2 replace "if()...else..." with "switch()..."

[PATCH 2/3]
And besides kernel build without CONFIG_IO_URING, a system can disable
the io_uring supporting manually, by set sysctl kernel.io_uring_disabled=2.
The former cause io_uring_queue_init return ENOSYS, but the latter will
return EPERM. So I let fsstress to deal with both situations.

V2 follows the "switch()..." format of patch 1/3

[PATCH 3/3]
This patch is re-written totally, and no any RVB.
This v2 decides to notrun if sysctl kernel.io_uring_disabled is 2. Then
change README to clarify how to make sure io_uring testing to be run.

Thanks,
Zorro