Re: [Qemu-devel] [PATCH v4] tap: setting error appropriately when calling net_init_tap_one()

[Zhoujian (jay)]

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> -----Original Message-----
> From: Zhoujian (jay)
> Sent: Tuesday, February 06, 2018 8:54 PM
> To: address@hidden
> Cc: address@hidden; address@hidden; address@hidden; Huangweidong (C)
> <address@hidden>; wangxin (U) <address@hidden>; Gonglei
> (Arei) <address@hidden>; Zhoujian (jay) <address@hidden>
> Subject: [PATCH v4] tap: setting error appropriately when calling
> net_init_tap_one()
> 
> If netdev_add tap,id=net0,...,vhost=on failed in net_init_tap_one(), the
> followed up device_add virtio-net-pci,netdev=net0 will fail too, prints:
> 
>    TUNSETOFFLOAD ioctl() failed: Bad file descriptor TUNSETOFFLOAD
>    ioctl() failed: Bad file descriptor
> 
> The reason is that the fd of tap is closed when error occured after calling
> net_init_tap_one().
> 
> The fd should be closed when calling net_init_tap_one failed:
>    - if tap_set_sndbuf() failed
>    - if tap_set_sndbuf() succeeded but vhost failed to open or
>      initialize with vhostforce flag on
> The fd should not be closed just because vhost failed to open or initialize
> but without vhostforce flag. So the followed up device_add can fall back to
> userspace virtio successfully.
> 
> Suggested-by: Michael S. Tsirkin <address@hidden>
> Suggested-by: Igor Mammedov <address@hidden>
> Suggested-by: Jason Wang <address@hidden>
> Signed-off-by: Jay Zhou <address@hidden>
> ---
> v4: - reduce duplication
>     - close the fd by caller
>     - tweak the title
> 
> v3: - set errp appropriately
> ---
>  include/net/vhost_net.h |  3 +++
>  net/tap.c               | 24 ++++++++++++++++++------
>  2 files changed, 21 insertions(+), 6 deletions(-)
> 
> diff --git a/include/net/vhost_net.h b/include/net/vhost_net.h index
> afc1499..77e4739 100644
> --- a/include/net/vhost_net.h
> +++ b/include/net/vhost_net.h
> @@ -4,6 +4,9 @@
>  #include "net/net.h"
>  #include "hw/virtio/vhost-backend.h"
> 
> +#define VHOST_NET_INIT_FAILED \
> +    "vhost-net requested but could not be initialized"
> +
>  struct vhost_net;
>  typedef struct vhost_net VHostNetState;
> 
> diff --git a/net/tap.c b/net/tap.c
> index 979e622..14d230f 100644
> --- a/net/tap.c
> +++ b/net/tap.c
> @@ -686,14 +686,23 @@ static void net_init_tap_one(const NetdevTapOptions
> *tap, NetClientState *peer,
>          if (vhostfdname) {
>              vhostfd = monitor_fd_param(cur_mon, vhostfdname, &err);
>              if (vhostfd == -1) {
> -                error_propagate(errp, err);
> +                if (tap->has_vhostforce && tap->vhostforce) {
> +                    error_propagate(errp, err);
> +                } else {
> +                    warn_report_err(err);
> +                }
>                  return;
>              }
>          } else {
>              vhostfd = open("/dev/vhost-net", O_RDWR);
>              if (vhostfd < 0) {
> -                error_setg_errno(errp, errno,
> -                                 "tap: open vhost char device failed");
> +                if (tap->has_vhostforce && tap->vhostforce) {
> +                    error_setg_errno(errp, errno,
> +                                     "tap: open vhost char device failed");
> +                } else {
> +                    warn_report("tap: open vhost char device failed: %s",
> +                                strerror(errno));
> +                }
>                  return;
>              }
>              fcntl(vhostfd, F_SETFL, O_NONBLOCK); @@ -702,12 +711,15 @@
> static void net_init_tap_one(const NetdevTapOptions *tap, NetClientState
> *peer,
> 
>          s->vhost_net = vhost_net_init(&options);
>          if (!s->vhost_net) {
> -            error_setg(errp,
> -                       "vhost-net requested but could not be initialized");
> +            if (tap->has_vhostforce && tap->vhostforce) {
> +                error_setg(errp, VHOST_NET_INIT_FAILED);
> +            } else {
> +                warn_report(VHOST_NET_INIT_FAILED);
> +            }
>              return;
>          }
>      } else if (vhostfdname) {
> -        error_setg(errp, "vhostfd(s)= is not valid without vhost");
> +        warn_report("vhostfd(s)= is not valid without vhost");
>      }
>  }
> 
> --
> 1.8.3.1
>