io_uring_enter(2): Clarify how to read from and write to non-seekable files
IORING_OP_READ* and IORING_OP_WRITE* all take a file offset. These
operations can still be used with non-seekable files, as long as the
offset is set to zero.
@@ -195,6 +195,9 @@ Vectored read and write operations, similar to
.BR preadv2 (2)
and
.BR pwritev2 (2).
+If the file is not seekable,
+.I off
+must be set to zero.
.TP
.B IORING_OP_READ_FIXED
@@ -588,6 +591,10 @@ contains the buffer in question,
contains the length of the IO operation, and
.I offs
contains the read or write offset. If
+.I fd
+does not refer to a seekable file,
+.I off
+must be set to zero. If
.I offs
is set to -1, the offset will use (and advance) the file position, like the
.BR read(2)
