On Tue, Oct 26, 2010 at 10:23:38AM +1100, Neil Brown wrote:
> On Mon, 25 Oct 2010 11:03:08 -0400
> "J. Bruce Fields" <bfields@xxxxxxxxxxxx> wrote:
>
> > On Mon, Oct 25, 2010 at 01:10:24PM +1100, Neil Brown wrote:
> > > On Sun, 24 Oct 2010 21:21:33 -0400
> > > "J. Bruce Fields" <bfields@xxxxxxxxxx> wrote:
> > >
> > > > The only caller (svc_send) has already checked XPT_DEAD.
> > > >
> > > > Signed-off-by: J. Bruce Fields <bfields@xxxxxxxxxx>
> > > > ---
> > > > net/sunrpc/svcsock.c | 3 ---
> > > > 1 files changed, 0 insertions(+), 3 deletions(-)
> > > >
> > > > diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> > > > index 1454739..07919e1 100644
> > > > --- a/net/sunrpc/svcsock.c
> > > > +++ b/net/sunrpc/svcsock.c
> > > > @@ -1135,9 +1135,6 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp)
> > > > reclen = htonl(0x80000000|((xbufp->len ) - 4));
> > > > memcpy(xbufp->head[0].iov_base, &reclen, 4);
> > > >
> > > > - if (test_bit(XPT_DEAD, &rqstp->rq_xprt->xpt_flags))
> > > > - return -ENOTCONN;
> > > > -
> > > > sent = svc_sendto(rqstp, &rqstp->rq_res);
> > > > if (sent != xbufp->len) {
> > > > printk(KERN_NOTICE
> > >
> > >
> > > So after removing all these references to XPT_DEAD, do we need XPT_DEAD at
> > > all???
> > >
> > > I think it is only used in two other places.
> > >
> > > 1/ In svc_revisit we don't queue the deferred request to an XPT_DEAD
> > > transport.
> > > We could avoid that but changing the 'owner' of a deferred request from the
> > > service to the xprt, and call cache_clean_deferred in svc_delete_xprt
> >
> > That use does seem a bit of a hack to me, so I'd be happy to get rid of
> > it.
> >
> > > 2/ in svc_send(). I wonder if we need this at all. There doesn't seem to be
> > > any locking to ensure that XPT_DEAD doesn't get set immediately after the
> > > test, and the underlying sendto (whether tcp or udp or whatever) should fail
> > > if the socket is closed, and if it doesn't it shouldn't really matter??
> >
> > Does it make a difference in the case of a half-close? If the client
> > follows a request immediately by a FIN, and if that results in our
> > setting DEAD (I think it does, assuming svc_tcp_state_change() is called
> > in that case), then the current code may have the effect of preventing
> > us from sending the reply.
> >
> > I don't know if that's good or bad.
> >
> > > So can we get rid of XPT_DEAL altogether?
> >
> > OK, I also had another use in mind: for the purposes of 4.1 (which needs
> > to know when a connection goes down, e.g. to know that it's no longer
> > available for callbacks), I added a list of callbacks to the xprt,
> > called on svc_delete_xprt().
> >
> > I just noticed that I think my current code allows the 4.1 code to
> > register an xprt after svc_delete_xprt() is called. I could fix that
> > race by checking for DEAD after trying to register.
> >
> > (That callback code already seems messier than it should be, so maybe
> > someone else could suggest a better scheme. I'm stuck.
> >
> > In any case, it wouldn't be so bad if that were the one remaining use of
> > DEAD.)
>
> Could you use XPT_CLOSE for that??
Good idea, yes, I think so.
--b.
--
To unsubscribe from this list: send the line "unsubscribe linux-nfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
