aio_error.3: Wording improvements in RETURN VALUE

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>

man3/aio_error.3

@@ -41,25 +41,27 @@ for a description of the
 .I aiocb
 structure.)
 .SH "RETURN VALUE"
-This function returns
-.B EINPROGRESS
+This function returns one of the following:
+.IP * 3
+.BR EINPROGRESS ,
 if the request has not been
 completed yet.
-It returns
-.B ECANCELED
+.IP *
+.BR ECANCELED ,
 if the request was canceled.
-It returns 0 if the request completed successfully.
-Otherwise an error value is returned, the same value that would have
-been stored in the
+.IP *
+0, if the request completed successfully.
+.IP *
+A positive error, if the asynchronous I/O operation failed.
+This is the same value that would have been stored in the
 .I errno
-variable in case of a synchronous
-.IR read ,
-.IR write ,
-.IR fsync ,
+variable in the case of a synchronous
+.BR read (2),
+.BR write (2),
+.BR fsync (2),
 or
-.I fdatasync
-request.
-On error, the error value is returned.
+.BR fdatasync (2)
+call.
 .SH ERRORS
 .TP
 .B EINVAL