Commit 32cf5a4e authored by Chuck Lever's avatar Chuck Lever
Browse files

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

Performance regression reported with NFS/RDMA using Omnipath,
bisected to commit e084ee67 ("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: e084ee67 ("svcrdma: Add Write chunk WRs to the RPC's Send WR chain")
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
parent f488138b

include/linux/sunrpc/svc_rdma.h

+3 −10
Original line number Diff line number Diff line
@@ -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;
@@ -274,13 +270,10 @@ 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,

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,

net/sunrpc/xprtrdma/svc_rdma_rw.c

+22 −64
Original line number Diff line number Diff line
@@ -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_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,

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 @@ static int svc_rdma_prepare_write_chunk(struct svcxprt_rdma *rdma, 
}



/**

 * 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,

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;

	}

net/sunrpc/xprtrdma/svc_rdma_sendto.c

+1 −4
Original line number Diff line number Diff line
@@ -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;