[Libguestfs] [libnbd PATCH v3 18/29] CONNECT_COMMAND.START: fix small comment thinko about socket pair usage

[Richard W.M. Jones]

On Wed, Feb 15, 2023 at 03:11:47PM +0100, Laszlo Ersek wrote:
> A comment currently states that "*the* socket must be set to non-blocking
> only in the parent" (emphasis mine). This is a thinko: it implies that we
> have just one file descriptor, and that the underlying file description
> (which is manipulated by fcntl()'s F_GETFL and F_SETFL) is shared by the
> parent and the child processes. That's not the case: we have *two* sockets
> here (a socket pair), one of which is used by the parent exclusively, and
> the other is used by the child exclusively.
> 
> Clarify the comment: say that we set the parent-side end of the socket
> pair to non-blocking.
> 
> This clarification will play a role in a subsequent patch.
> 
> Signed-off-by: Laszlo Ersek <lersek at redhat.com>
> ---
> 
> Notes:
>     context:-U5
> 
>  generator/states-connect.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/generator/states-connect.c b/generator/states-connect.c
> index 8a286e6630ff..95a96b9114c6 100644
> --- a/generator/states-connect.c
> +++ b/generator/states-connect.c
> @@ -281,11 +281,11 @@  CONNECT_COMMAND.START:
>    /* Parent. */
>    close (sv[1]);
>  
>    h->pid = pid;
>  
> -  /* The socket must be set to non-blocking only in the parent,
> +  /* Only the parent-side end of the socket pair must be set to non-blocking,
>     * because the child may not be expecting a non-blocking socket.
>     */
>    flags = fcntl (sv[0], F_GETFL, 0);
>    if (flags == -1 ||
>        fcntl (sv[0], F_SETFL, flags|O_NONBLOCK) == -1) {

Reviewed-by: Richard W.M. Jones <rjones at redhat.com>


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