Revert "svcrdma: Add Write chunk WRs to the RPC's Send WR chain"

Performance regression reported with NFS/RDMA using Omnipath,
bisected to commit e084ee673c77 ("svcrdma: Add Write chunk WRs to
the RPC's Send WR chain").

Tracing on the server reports:

  nfsd-7771  [060]  1758.891809: svcrdma_sq_post_err:
	cq.id=205 cid=226 sc_sq_avail=13643/851 status=-12

sq_post_err reports ENOMEM, and the rdma->sc_sq_avail (13643) is
larger than rdma->sc_sq_depth (851). The number of available Send
Queue entries is always supposed to be smaller than the Send Queue
depth. That seems like a Send Queue accounting bug in svcrdma.

As it's getting to be late in the 6.9-rc cycle, revert this commit.
It can be revisited in a subsequent kernel release.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=218743
Fixes: e084ee673c77 ("svcrdma: Add Write chunk WRs to the RPC's Send WR chain")
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/include/linux/sunrpc/svc_rdma.h b/include/linux/sunrpc/svc_rdma.h
index 24cd199dd6f3a972f44344eb3994334201145e63..d33bab33099ab0fe4db1a889117307510e1035fa 100644 (file)
--- a/include/linux/sunrpc/svc_rdma.h
+++ b/include/linux/sunrpc/svc_rdma.h
@@ -210,7 +210,6 @@ struct svc_rdma_recv_ctxt {
  */
 struct svc_rdma_write_info {
        struct svcxprt_rdma     *wi_rdma;
-       struct list_head        wi_list;
 
        const struct svc_rdma_chunk     *wi_chunk;
 
@@ -239,10 +238,7 @@ struct svc_rdma_send_ctxt {
        struct ib_cqe           sc_cqe;
        struct xdr_buf          sc_hdrbuf;
        struct xdr_stream       sc_stream;
-
-       struct list_head        sc_write_info_list;
        struct svc_rdma_write_info sc_reply_info;
-
        void                    *sc_xprt_buf;
        int                     sc_page_count;
        int                     sc_cur_sge_no;
@@ -274,14 +270,11 @@ extern void svc_rdma_cc_init(struct svcxprt_rdma *rdma,
 extern void svc_rdma_cc_release(struct svcxprt_rdma *rdma,
                                struct svc_rdma_chunk_ctxt *cc,
                                enum dma_data_direction dir);
-extern void svc_rdma_write_chunk_release(struct svcxprt_rdma *rdma,
-                                        struct svc_rdma_send_ctxt *ctxt);
 extern void svc_rdma_reply_chunk_release(struct svcxprt_rdma *rdma,
                                         struct svc_rdma_send_ctxt *ctxt);
-extern int svc_rdma_prepare_write_list(struct svcxprt_rdma *rdma,
-                                      const struct svc_rdma_pcl *write_pcl,
-                                      struct svc_rdma_send_ctxt *sctxt,
-                                      const struct xdr_buf *xdr);
+extern int svc_rdma_send_write_list(struct svcxprt_rdma *rdma,
+                                   const struct svc_rdma_recv_ctxt *rctxt,
+                                   const struct xdr_buf *xdr);
 extern int svc_rdma_prepare_reply_chunk(struct svcxprt_rdma *rdma,
                                        const struct svc_rdma_pcl *write_pcl,
                                        const struct svc_rdma_pcl *reply_pcl,

diff --git a/net/sunrpc/xprtrdma/svc_rdma_rw.c b/net/sunrpc/xprtrdma/svc_rdma_rw.c
index f2a100c4c81f12e8ed91d0400938b53e3dd0dc46..40797114d50a49a4e10cb30c182f094fc8e7313d 100644 (file)
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c
@@ -230,28 +230,6 @@ static void svc_rdma_write_info_free(struct svc_rdma_write_info *info)
        queue_work(svcrdma_wq, &info->wi_work);
 }
 
-/**
- * svc_rdma_write_chunk_release - Release Write chunk I/O resources
- * @rdma: controlling transport
- * @ctxt: Send context that is being released
- */
-void svc_rdma_write_chunk_release(struct svcxprt_rdma *rdma,
-                                 struct svc_rdma_send_ctxt *ctxt)
-{
-       struct svc_rdma_write_info *info;
-       struct svc_rdma_chunk_ctxt *cc;
-
-       while (!list_empty(&ctxt->sc_write_info_list)) {
-               info = list_first_entry(&ctxt->sc_write_info_list,
-                                       struct svc_rdma_write_info, wi_list);
-               list_del(&info->wi_list);
-
-               cc = &info->wi_cc;
-               svc_rdma_wake_send_waiters(rdma, cc->cc_sqecount);
-               svc_rdma_write_info_free(info);
-       }
-}
-
 /**
  * svc_rdma_reply_chunk_release - Release Reply chunk I/O resources
  * @rdma: controlling transport
@@ -308,11 +286,13 @@ static void svc_rdma_write_done(struct ib_cq *cq, struct ib_wc *wc)
        struct ib_cqe *cqe = wc->wr_cqe;
        struct svc_rdma_chunk_ctxt *cc =
                        container_of(cqe, struct svc_rdma_chunk_ctxt, cc_cqe);
+       struct svc_rdma_write_info *info =
+                       container_of(cc, struct svc_rdma_write_info, wi_cc);
 
        switch (wc->status) {
        case IB_WC_SUCCESS:
                trace_svcrdma_wc_write(&cc->cc_cid);
-               return;
+               break;
        case IB_WC_WR_FLUSH_ERR:
                trace_svcrdma_wc_write_flush(wc, &cc->cc_cid);
                break;
@@ -320,11 +300,12 @@ static void svc_rdma_write_done(struct ib_cq *cq, struct ib_wc *wc)
                trace_svcrdma_wc_write_err(wc, &cc->cc_cid);
        }
 
-       /* The RDMA Write has flushed, so the client won't get
-        * some of the outgoing RPC message. Signal the loss
-        * to the client by closing the connection.
-        */
-       svc_xprt_deferred_close(&rdma->sc_xprt);
+       svc_rdma_wake_send_waiters(rdma, cc->cc_sqecount);
+
+       if (unlikely(wc->status != IB_WC_SUCCESS))
+               svc_xprt_deferred_close(&rdma->sc_xprt);
+
+       svc_rdma_write_info_free(info);
 }
 
 /**
@@ -620,19 +601,13 @@ static int svc_rdma_xb_write(const struct xdr_buf *xdr, void *data)
        return xdr->len;
 }
 
-/* Link Write WRs for @chunk onto @sctxt's WR chain.
- */
-static int svc_rdma_prepare_write_chunk(struct svcxprt_rdma *rdma,
-                                       struct svc_rdma_send_ctxt *sctxt,
-                                       const struct svc_rdma_chunk *chunk,
-                                       const struct xdr_buf *xdr)
+static int svc_rdma_send_write_chunk(struct svcxprt_rdma *rdma,
+                                    const struct svc_rdma_chunk *chunk,
+                                    const struct xdr_buf *xdr)
 {
        struct svc_rdma_write_info *info;
        struct svc_rdma_chunk_ctxt *cc;
-       struct ib_send_wr *first_wr;
        struct xdr_buf payload;
-       struct list_head *pos;
-       struct ib_cqe *cqe;
        int ret;
 
        if (xdr_buf_subsegment(xdr, &payload, chunk->ch_position,
@@ -648,25 +623,10 @@ static int svc_rdma_prepare_write_chunk(struct svcxprt_rdma *rdma,
        if (ret != payload.len)
                goto out_err;
 
-       ret = -EINVAL;
-       if (unlikely(cc->cc_sqecount > rdma->sc_sq_depth))
-               goto out_err;
-
-       first_wr = sctxt->sc_wr_chain;
-       cqe = &cc->cc_cqe;
-       list_for_each(pos, &cc->cc_rwctxts) {
-               struct svc_rdma_rw_ctxt *rwc;
-
-               rwc = list_entry(pos, struct svc_rdma_rw_ctxt, rw_list);
-               first_wr = rdma_rw_ctx_wrs(&rwc->rw_ctx, rdma->sc_qp,
-                                          rdma->sc_port_num, cqe, first_wr);
-               cqe = NULL;
-       }
-       sctxt->sc_wr_chain = first_wr;
-       sctxt->sc_sqecount += cc->cc_sqecount;
-       list_add(&info->wi_list, &sctxt->sc_write_info_list);
-
        trace_svcrdma_post_write_chunk(&cc->cc_cid, cc->cc_sqecount);
+       ret = svc_rdma_post_chunk_ctxt(rdma, cc);
+       if (ret < 0)
+               goto out_err;
        return 0;
 
 out_err:
@@ -675,27 +635,25 @@ out_err:
 }
 
 /**
- * svc_rdma_prepare_write_list - Construct WR chain for sending Write list
+ * svc_rdma_send_write_list - Send all chunks on the Write list
  * @rdma: controlling RDMA transport
- * @write_pcl: Write list provisioned by the client
- * @sctxt: Send WR resources
+ * @rctxt: Write list provisioned by the client
  * @xdr: xdr_buf containing an RPC Reply message
  *
  * Returns zero on success, or a negative errno if one or more
  * Write chunks could not be sent.
  */
-int svc_rdma_prepare_write_list(struct svcxprt_rdma *rdma,
-                               const struct svc_rdma_pcl *write_pcl,
-                               struct svc_rdma_send_ctxt *sctxt,
-                               const struct xdr_buf *xdr)
+int svc_rdma_send_write_list(struct svcxprt_rdma *rdma,
+                            const struct svc_rdma_recv_ctxt *rctxt,
+                            const struct xdr_buf *xdr)
 {
        struct svc_rdma_chunk *chunk;
        int ret;
 
-       pcl_for_each_chunk(chunk, write_pcl) {
+       pcl_for_each_chunk(chunk, &rctxt->rc_write_pcl) {
                if (!chunk->ch_payload_length)
                        break;
-               ret = svc_rdma_prepare_write_chunk(rdma, sctxt, chunk, xdr);
+               ret = svc_rdma_send_write_chunk(rdma, chunk, xdr);
                if (ret < 0)
                        return ret;
        }

diff --git a/net/sunrpc/xprtrdma/svc_rdma_sendto.c b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
index dfca39abd16c8860ade9a8f3fc0be4bc023361cd..bb5436b719e05126e250596b61b39230204620c3 100644 (file)
--- a/net/sunrpc/xprtrdma/svc_rdma_sendto.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_sendto.c
@@ -142,7 +142,6 @@ svc_rdma_send_ctxt_alloc(struct svcxprt_rdma *rdma)
        ctxt->sc_send_wr.sg_list = ctxt->sc_sges;
        ctxt->sc_send_wr.send_flags = IB_SEND_SIGNALED;
        ctxt->sc_cqe.done = svc_rdma_wc_send;
-       INIT_LIST_HEAD(&ctxt->sc_write_info_list);
        ctxt->sc_xprt_buf = buffer;
        xdr_buf_init(&ctxt->sc_hdrbuf, ctxt->sc_xprt_buf,
                     rdma->sc_max_req_size);
@@ -228,7 +227,6 @@ static void svc_rdma_send_ctxt_release(struct svcxprt_rdma *rdma,
        struct ib_device *device = rdma->sc_cm_id->device;
        unsigned int i;
 
-       svc_rdma_write_chunk_release(rdma, ctxt);
        svc_rdma_reply_chunk_release(rdma, ctxt);
 
        if (ctxt->sc_page_count)
@@ -1015,8 +1013,7 @@ int svc_rdma_sendto(struct svc_rqst *rqstp)
        if (!p)
                goto put_ctxt;
 
-       ret = svc_rdma_prepare_write_list(rdma, &rctxt->rc_write_pcl, sctxt,
-                                         &rqstp->rq_res);
+       ret = svc_rdma_send_write_list(rdma, rctxt, &rqstp->rq_res);
        if (ret < 0)
                goto put_ctxt;