On Apr 9, 2014, at 7:56 PM, Devesh Sharma <Devesh.Sharma@xxxxxxxxxx> wrote:
> Hi Chuk and Trond
>
> I will resend a v2 for this.
> What if ib_post_send() fails with immidate error, I that case also DECR_CQCOUNT() will be called but no completion will be reported. Will that not cause any problems?
We should investigate whether an error return from ib_post_{send,recv} means there will be no completion. But I’ve never seen these verbs fail in practice, so I’m not in a hurry to make work for anyone! ;-)
However it seems to me the new (!ia->ri_id->qp) checks outside the connect logic are unnecessary.
Clearly, as you noticed, the ib_post_{send,recv} verbs do not check that their “qp" argument is NULL before dereferencing it.
But I don’t understand how xprtrdma can post any operation if the transport isn’t connected. In other words, how would it be possible to call rpcrdma_ep_post_recv() if the connect had failed and there was no QP?
If disconnect wipes ia->ri_id->qp while there are still operations in progress, that would be the real bug.
> Also in rpcrdma_register_frmr_external() I am seeing DECT_CQCOUNT is called twice
> First at line 1538 (unlikely however) and second at line 1562. Shouldn't it be only at 1562?
if (seg1->mr_chunk.rl_mw->r.frmr.state == FRMR_IS_VALID) then rpcrdma_register_frmr_external() posts two Work Requests (LOCAL_INV then FAST_REG_MR) with one ib_post_send(). Thus it is correct to DECR_CQCOUNT twice in that case because each WR will trigger a separate completion event.
> -----Original Message-----
> From: Chuck Lever [mailto:chuck.lever@xxxxxxxxxx]
> Sent: Thursday, April 10, 2014 1:57 AM
> To: Devesh Sharma
> Cc: Linux NFS Mailing List; linux-rdma@xxxxxxxxxxxxxxx; Trond Myklebust
> Subject: Re: [PATCH V1] NFS-RDMA: fix qp pointer validation checks
>
>
> On Apr 9, 2014, at 4:22 PM, Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx> wrote:
>
>> Hi Devesh,
>>
>> This looks a lot better. I still have a couple of small suggestions, though.
>>
>> On Apr 9, 2014, at 14:40, Devesh Sharma <devesh.sharma@xxxxxxxxxx> wrote:
>>
>>> If the rdma_create_qp fails to create qp due to device firmware being
>>> in invalid state xprtrdma still tries to destroy the non-existant qp
>>> and ends up in a NULL pointer reference crash.
>>> Adding proper checks for vaidating QP pointer avoids this to happen.
>>>
>>> Signed-off-by: Devesh Sharma <devesh.sharma@xxxxxxxxxx>
>>> ---
>>> net/sunrpc/xprtrdma/verbs.c | 29 +++++++++++++++++++++++++----
>>> 1 files changed, 25 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/net/sunrpc/xprtrdma/verbs.c
>>> b/net/sunrpc/xprtrdma/verbs.c index 9372656..902ac78 100644
>>> --- a/net/sunrpc/xprtrdma/verbs.c
>>> +++ b/net/sunrpc/xprtrdma/verbs.c
>>> @@ -831,10 +831,12 @@ rpcrdma_ep_connect(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia)
>>> if (ep->rep_connected != 0) {
>>> struct rpcrdma_xprt *xprt;
>>> retry:
>>> - rc = rpcrdma_ep_disconnect(ep, ia);
>>> - if (rc && rc != -ENOTCONN)
>>> - dprintk("RPC: %s: rpcrdma_ep_disconnect"
>>> + if (ia->ri_id->qp) {
>>> + rc = rpcrdma_ep_disconnect(ep, ia);
>>> + if (rc && rc != -ENOTCONN)
>>> + dprintk("RPC: %s: rpcrdma_ep_disconnect"
>>> " status %i\n", __func__, rc);
>>> + }
>>> rpcrdma_clean_cq(ep->rep_cq);
>>>
>>> xprt = container_of(ia, struct rpcrdma_xprt, rx_ia); @@ -859,7
>>> +861,9 @@ retry:
>>> goto out;
>>> }
>>> /* END TEMP */
>>> - rdma_destroy_qp(ia->ri_id);
>>> + if (ia->ri_id->qp) {
>>> + rdma_destroy_qp(ia->ri_id);
>>> + }
>>
>> Nit: No need for braces here.
>>
>>> rdma_destroy_id(ia->ri_id);
>>> ia->ri_id = id;
>>> }
>>> @@ -1557,6 +1561,13 @@ rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
>>> frmr_wr.wr.fast_reg.rkey = seg1->mr_chunk.rl_mw->r.frmr.fr_mr->rkey;
>>> DECR_CQCOUNT(&r_xprt->rx_ep);
>
> I don't think you can DECR_CQCOUNT, then exit without posting the send. That will screw up the completion counter and result in a transport hang, won't it?
>
>>>
>>> + if (!ia->ri_is->qp) {
>>> + rc = -EINVAL;
>>> + while (i--)
>>> + rpcrdma_unmap_one(ia, --seg);
>>> + goto out;
>>> + }
>>
>> Instead of duplicating the rpcrdma_unmap_one() cleanup here, why not
>> just do
>>
>> if (ia->ri_is->qp)
>> rc = ib_post_send(...)
>> else
>> rc = -EINVAL;
>>
>> BTW: can we not simply test for ia->ri_is->qp before we even call rpcrdma_map_one() and hence bail out before we have to do any cleanup?
>>
>>> +
>>> rc = ib_post_send(ia->ri_id->qp, post_wr, &bad_wr);
>>>
>>> if (rc) {
>>> @@ -1571,6 +1582,7 @@ rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
>>> seg1->mr_len = len;
>>> }
>>> *nsegs = i;
>>> +out:
>>> return rc;
>>> }
>>>
>>> @@ -1592,6 +1604,9 @@ rpcrdma_deregister_frmr_external(struct rpcrdma_mr_seg *seg,
>>> invalidate_wr.ex.invalidate_rkey = seg1->mr_chunk.rl_mw->r.frmr.fr_mr->rkey;
>>> DECR_CQCOUNT(&r_xprt->rx_ep);
>
> Ditto.
>
>>>
>>> + if (!ia->ri_id->qp)
>>> + return -EINVAL;
>>> +
>>> rc = ib_post_send(ia->ri_id->qp, &invalidate_wr, &bad_wr);
>>> if (rc)
>>> dprintk("RPC: %s: failed ib_post_send for invalidate,"
>>> @@ -1923,6 +1938,9 @@ rpcrdma_ep_post(struct rpcrdma_ia *ia,
>>> send_wr.send_flags = IB_SEND_SIGNALED;
>>> }
>
> Ditto.
>
>>>
>>> + if (!ia->ri_id->qp)
>>> + return -EINVAL;
>>> +
>>> rc = ib_post_send(ia->ri_id->qp, &send_wr, &send_wr_fail);
>>> if (rc)
>>> dprintk("RPC: %s: ib_post_send returned %i\n", __func__,
>>> @@ -1951,6 +1969,9 @@ rpcrdma_ep_post_recv(struct rpcrdma_ia *ia,
>>> rep->rr_iov.addr, rep->rr_iov.length, DMA_BIDIRECTIONAL);
>>>
>>> DECR_CQCOUNT(ep);
>
> And here.
>
>>> +
>>> + if (!ia->ri_id->qp)
>>> + return -EINVAL;
>>> rc = ib_post_recv(ia->ri_id->qp, &recv_wr, &recv_wr_fail);
>>>
>>> if (rc)
>>> --
>>> 1.7.1
>>>
>>
>> _________________________________
>> Trond Myklebust
>> Linux NFS client maintainer, PrimaryData
>> trond.myklebust@xxxxxxxxxxxxxxx
>>
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>
> --
> Chuck Lever
> chuck[dot]lever[at]oracle[dot]com
>
>
>
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--
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