On Wed, Nov 12, 2014 at 09:41:28PM -0500, Jeff Layton wrote:
> On Wed, 12 Nov 2014 18:04:04 -0500
> Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> wrote:
>
> > Both xprt_lookup_rqst() and xprt_complete_rqst() require that you
> > take the transport lock in order to avoid races with xprt_transmit().
Thanks, looks right.
Have you seen this in practice? (I'm just wondering whether it's worth
a stable cc:.)
--b.
> > Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
> > Cc: Bruce Fields <bfields@xxxxxxxxxxxx>
> > ---
> > net/sunrpc/svcsock.c | 27 ++++++++++++++++-----------
> > 1 file changed, 16 insertions(+), 11 deletions(-)
> >
> > diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> > index 3f959c681885..f9c052d508f0 100644
> > --- a/net/sunrpc/svcsock.c
> > +++ b/net/sunrpc/svcsock.c
> > @@ -1019,17 +1019,12 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
> > xid = *p++;
> > calldir = *p;
> >
> > - if (bc_xprt)
> > - req = xprt_lookup_rqst(bc_xprt, xid);
> > -
> > - if (!req) {
> > - printk(KERN_NOTICE
> > - "%s: Got unrecognized reply: "
> > - "calldir 0x%x xpt_bc_xprt %p xid %08x\n",
> > - __func__, ntohl(calldir),
> > - bc_xprt, ntohl(xid));
> > + if (!bc_xprt)
> > return -EAGAIN;
> > - }
> > + spin_lock_bh(&bc_xprt->transport_lock);
> > + req = xprt_lookup_rqst(bc_xprt, xid);
> > + if (!req)
> > + goto unlock_notfound;
> >
> > memcpy(&req->rq_private_buf, &req->rq_rcv_buf, sizeof(struct xdr_buf));
> > /*
> > @@ -1040,11 +1035,21 @@ static int receive_cb_reply(struct svc_sock *svsk, struct svc_rqst *rqstp)
> > dst = &req->rq_private_buf.head[0];
> > src = &rqstp->rq_arg.head[0];
> > if (dst->iov_len < src->iov_len)
> > - return -EAGAIN; /* whatever; just giving up. */
> > + goto unlock_eagain; /* whatever; just giving up. */
> > memcpy(dst->iov_base, src->iov_base, src->iov_len);
> > xprt_complete_rqst(req->rq_task, rqstp->rq_arg.len);
> > rqstp->rq_arg.len = 0;
> > + spin_unlock_bh(&bc_xprt->transport_lock);
> > return 0;
> > +unlock_notfound:
> > + printk(KERN_NOTICE
> > + "%s: Got unrecognized reply: "
> > + "calldir 0x%x xpt_bc_xprt %p xid %08x\n",
> > + __func__, ntohl(calldir),
> > + bc_xprt, ntohl(xid));
> > +unlock_eagain:
> > + spin_unlock_bh(&bc_xprt->transport_lock);
> > + return -EAGAIN;
> > }
> >
> > static int copy_pages_to_kvecs(struct kvec *vec, struct page **pages, int len)
>
> Nice catch. It would also be good to pair this with a
> lockdep_assert_held() call in xprt_lookup_rqst, but that could be added
> in a separate patch.
>
> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
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