Messages in this thread | | | Subject | Re: [PATCH net] tuntap: raise EPOLLOUT on device up | From | Jason Wang <> | Date | Fri, 18 May 2018 21:26:23 +0800 |
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On 2018年05月18日 21:13, Michael S. Tsirkin wrote: > On Fri, May 18, 2018 at 09:00:43PM +0800, Jason Wang wrote: >> We return -EIO on device down but can not raise EPOLLOUT after it was >> up. This may confuse user like vhost which expects tuntap to raise >> EPOLLOUT to re-enable its TX routine after tuntap is down. This could >> be easily reproduced by transmitting packets from VM while down and up >> the tap device. Fixing this by set SOCKWQ_ASYNC_NOSPACE on -EIO. >> >> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org> >> Cc: Eric Dumazet <edumazet@google.com> >> Fixes: 1bd4978a88ac2 ("tun: honor IFF_UP in tun_get_user()") >> Signed-off-by: Jason Wang <jasowang@redhat.com> >> --- >> drivers/net/tun.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/net/tun.c b/drivers/net/tun.c >> index d45ac37..1b29761 100644 >> --- a/drivers/net/tun.c >> +++ b/drivers/net/tun.c >> @@ -1734,8 +1734,10 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile, >> int skb_xdp = 1; >> bool frags = tun_napi_frags_enabled(tun); >> >> - if (!(tun->dev->flags & IFF_UP)) >> + if (!(tun->dev->flags & IFF_UP)) { > Isn't this racy? What if flag is cleared at this point?
I think you mean "set at this point"? Then yes, so we probably need to set the bit during tun_net_close().
Thanks
>> + set_bit(SOCKWQ_ASYNC_NOSPACE, &tfile->socket.flags); >> return -EIO; >> + } >> >> if (!(tun->flags & IFF_NO_PI)) { >> if (len < sizeof(pi)) >> -- >> 2.7.4
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