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    SubjectRe: [PATCH v2] xen-netfront: Improve error handling during initialization
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    On 02/07/2017 11:33 PM, Boris Ostrovsky wrote:
    > On 02/07/2017 09:55 AM, Ross Lagerwall wrote:
    >> This fixes a crash when running out of grant refs when creating many
    >> queues across many netdevs.
    >>
    >> * If creating queues fails (i.e. there are no grant refs available),
    >> call xenbus_dev_fatal() to ensure that the xenbus device is set to the
    >> closed state.
    >> * If no queues are created, don't call xennet_disconnect_backend as
    >> netdev->real_num_tx_queues will not have been set correctly.
    >> * If setup_netfront() fails, ensure that all the queues created are
    >> cleaned up, not just those that have been set up.
    >> * If any queues were set up and an error occurs, call
    >> xennet_destroy_queues() to clean up the napi context.
    >> * If any fatal error occurs, unregister and destroy the netdev to avoid
    >> leaving around a half setup network device.
    >>
    >> Signed-off-by: Ross Lagerwall <ross.lagerwall@citrix.com>
    >> ---
    >>
    >> Changed in V2:
    >> * Retested on top of v4.10-rc7 + "xen-netfront: Delete rx_refill_timer
    >> in xennet_disconnect_backend()".
    >> * Don't move setup_timer as it is not necessary.
    >>
    >> drivers/net/xen-netfront.c | 33 +++++++++++++++------------------
    >> 1 file changed, 15 insertions(+), 18 deletions(-)
    >>
    >> diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c
    >> index 722fe9f..5399a86 100644
    >> --- a/drivers/net/xen-netfront.c
    >> +++ b/drivers/net/xen-netfront.c
    >> @@ -1823,27 +1823,23 @@ static int talk_to_netback(struct xenbus_device *dev,
    >> xennet_destroy_queues(info);
    >>
    >> err = xennet_create_queues(info, &num_queues);
    >> - if (err < 0)
    >> - goto destroy_ring;
    >> + if (err < 0) {
    >> + xenbus_dev_fatal(dev, err, "creating queues");
    >> + if (num_queues > 0) {
    >> + goto destroy_ring;
    >
    > The only way for us to have (err<0) && (num_queues>0) is when we get a
    > -ENOMEM right at the top, isn't it? So there is nothing to disconnect or
    > destroy, it seems to me. And if that's true you can directly 'goto out'.
    >

    You're right, although that might make it a bit more fragile if
    something in xennet_create_queues() changes in the future. Nevertheless,
    I'll update the patch.

    --
    Ross Lagerwall

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