When we don't have a connection and blocking is false, we return NULL
but don't set errp. That's wrong.

We have two paths for calling nbd_co_establish_connection():

1. nbd_open() -> nbd_do_establish_connection() -> ...
  but that will never set blocking=false

2. nbd_reconnect_attempt() -> nbd_co_do_establish_connection() -> ...
  but that uses errp=NULL

So, we are safe with our wrong errp policy in
nbd_co_establish_connection(). Still let's fix it.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
---
 nbd/client-connection.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/nbd/client-connection.c b/nbd/client-connection.c
index 7123b1e189..695f855754 100644
--- a/nbd/client-connection.c
+++ b/nbd/client-connection.c
@@ -318,6 +318,7 @@ nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
         }
 
         if (!blocking) {
+            error_setg(errp, "No connection at the moment");
             return NULL;
         }
 
-- 
2.29.2

On Mon, Sep 06, 2021 at 10:06:46PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> When we don't have a connection and blocking is false, we return NULL
> but don't set errp. That's wrong.

Oops...

> 
> We have two paths for calling nbd_co_establish_connection():
> 
> 1. nbd_open() -> nbd_do_establish_connection() -> ...
>   but that will never set blocking=false
> 
> 2. nbd_reconnect_attempt() -> nbd_co_do_establish_connection() -> ...
>   but that uses errp=NULL
> 
> So, we are safe with our wrong errp policy in
> nbd_co_establish_connection(). Still let's fix it.

...phew!  Thus, it's not critical to backport.

Reviewed-by: Eric Blake <eblake@redhat.com>

> 
> Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
> ---
>  nbd/client-connection.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/nbd/client-connection.c b/nbd/client-connection.c
> index 7123b1e189..695f855754 100644
> --- a/nbd/client-connection.c
> +++ b/nbd/client-connection.c
> @@ -318,6 +318,7 @@ nbd_co_establish_connection(NBDClientConnection *conn, NBDExportInfo *info,
>          }
>  
>          if (!blocking) {
> +            error_setg(errp, "No connection at the moment");
>              return NULL;
>          }
>  
> -- 
> 2.29.2
> 

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org

On Tue, Sep 07, 2021 at 12:44:53PM -0500, Eric Blake wrote:
> On Mon, Sep 06, 2021 at 10:06:46PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> > When we don't have a connection and blocking is false, we return NULL
> > but don't set errp. That's wrong.
> 
> Oops...
> 
> > 
> > We have two paths for calling nbd_co_establish_connection():
> > 
> > 1. nbd_open() -> nbd_do_establish_connection() -> ...
> >   but that will never set blocking=false
> > 
> > 2. nbd_reconnect_attempt() -> nbd_co_do_establish_connection() -> ...
> >   but that uses errp=NULL
> > 
> > So, we are safe with our wrong errp policy in
> > nbd_co_establish_connection(). Still let's fix it.
> 
> ...phew!  Thus, it's not critical to backport.
> 
> Reviewed-by: Eric Blake <eblake@redhat.com>

Queuing this one through my NBD tree.  Given the discussion on 2/9,
I'll leave the rest of the series for later.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org