Re: [Qemu-devel] [PATCH 11/19] io/channel-socket: qio_channel_socket_writev handle EPIPE

[Vladimir Sementsov-Ogievskiy]

30.05.2017 18:04, Daniel P. Berrange wrote:
> On Tue, May 30, 2017 at 05:30:44PM +0300, Vladimir Sementsov-Ogievskiy wrote:
> > Return QIO_CHANNEL_ERR_EPIPE on EPIPE, we will need it to improve error
> > path in nbd server.
> >
> > Signed-off-by: Vladimir Sementsov-Ogievskiy <address@hidden>
> > ---
> >   include/io/channel.h | 1 +
> >   io/channel-socket.c  | 2 +-
> >   2 files changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/include/io/channel.h b/include/io/channel.h
> > index 5d48906998..5529c2da31 100644
> > --- a/include/io/channel.h
> > +++ b/include/io/channel.h
> > @@ -38,6 +38,7 @@ typedef struct QIOChannel QIOChannel;
> >   typedef struct QIOChannelClass QIOChannelClass;
> >   
> >   #define QIO_CHANNEL_ERR_BLOCK -2
> > +#define QIO_CHANNEL_ERR_EPIPE -3
> >   
> >   typedef enum QIOChannelFeature QIOChannelFeature;
> >   
> > diff --git a/io/channel-socket.c b/io/channel-socket.c
> > index 53386b7ba3..50f9f966c6 100644
> > --- a/io/channel-socket.c
> > +++ b/io/channel-socket.c
> > @@ -542,7 +542,7 @@ static ssize_t qio_channel_socket_writev(QIOChannel *ioc,
> >           }
> >           error_setg_errno(errp, errno,
> >                            "Unable to write to socket");
> > -        return -1;
> > +        return errno == EPIPE ? QIO_CHANNEL_ERR_EPIPE : -1;
> >       }
> >       return ret;
> Ewwww, no. We don't want to go down the road of special casing
> further errno values for every error scenario.

I need to distinguish client socket closed without reading nbd server 
reply from other errors, because this is a valid behavior accordingly to 
the protocol.
Any way to do this? Hmm, I can examine the contents of errp, of course, 
but I'm afraid it would be even less appropriate. This is funny: user 
has this information in errp message, but the code - doesn't..

Alternatively:
1. not report errors on sending reply after OPT_ABORT at all
2. report all errors, (including this EPIPE, which actually is not a 
failure)

Paolo, what do you think?

(current behavior is (1))

> Regards,
> Daniel


--
Best regards,
Vladimir