+.. option:: nowait : [pvsync2] [libaio] [io_uring]
+
+ By default if a request cannot be executed immediately (e.g. resource starvation,
+ waiting on locks) it is queued and the initiating process will be blocked until
+ the required resource becomes free.
+
+ This option sets the RWF_NOWAIT flag (supported from the 4.14 Linux kernel) and
+ the call will return instantly with EAGAIN or a partial result rather than waiting.
+
+ It is useful to also use ignore_error=EAGAIN when using this option.
+
+ Note: glibc 2.27, 2.28 have a bug in syscall wrappers preadv2, pwritev2.
+ They return EOPNOTSUP instead of EAGAIN.
+
+ For cached I/O, using this option usually means a request operates only with
+ cached data. Currently the RWF_NOWAIT flag does not supported for cached write.
+
+ For direct I/O, requests will only succeed if cache invalidation isn't required,
+ file blocks are fully allocated and the disk request could be issued immediately.
+