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Commit 16f906d6 authored by Chuck Lever's avatar Chuck Lever Committed by Anna Schumaker
Browse files

xprtrdma: Reduce required number of send SGEs 



The MAX_SEND_SGES check introduced in commit 655fec69
("xprtrdma: Use gathered Send for large inline messages") fails
for devices that have a small max_sge.

Instead of checking for a large fixed maximum number of SGEs,
check for a minimum small number. RPC-over-RDMA will switch to
using a Read chunk if an xdr_buf has more pages than can fit in
the device's max_sge limit. This is considerably better than
failing all together to mount the server.

This fix supports devices that have as few as three send SGEs
available.

Reported-by: default avatarSelvin Xavier <selvin.xavier@broadcom.com>
Reported-by: default avatarDevesh Sharma <devesh.sharma@broadcom.com>
Reported-by: default avatarHonggang Li <honli@redhat.com>
Reported-by: default avatarRam Amrani <Ram.Amrani@cavium.com>
Fixes: 655fec69 ("xprtrdma: Use gathered Send for large ...")
Cc: stable@vger.kernel.org # v4.9+
Tested-by: default avatarHonggang Li <honli@redhat.com>
Tested-by: default avatarRam Amrani <Ram.Amrani@cavium.com>
Tested-by: default avatarSteve Wise <swise@opengridcomputing.com>
Reviewed-by: default avatarParav Pandit <parav@mellanox.com>
Signed-off-by: default avatarChuck Lever <chuck.lever@oracle.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent c95a3c6b

net/sunrpc/xprtrdma/rpc_rdma.c

+23 −3
Original line number Diff line number Diff line
@@ -125,14 +125,34 @@ void rpcrdma_set_max_header_sizes(struct rpcrdma_xprt *r_xprt) 
/* The client can send a request inline as long as the RPCRDMA header

 * plus the RPC call fit under the transport's inline limit. If the

 * combined call message size exceeds that limit, the client must use

 * the read chunk list for this operation.

 * a Read chunk for this operation.

 *

 * A Read chunk is also required if sending the RPC call inline would

 * exceed this device's max_sge limit.

 */

static bool rpcrdma_args_inline(struct rpcrdma_xprt *r_xprt,

				struct rpc_rqst *rqst)

{

	struct rpcrdma_ia *ia = &r_xprt->rx_ia;

	struct xdr_buf *xdr = &rqst->rq_snd_buf;

	unsigned int count, remaining, offset;



	if (xdr->len > r_xprt->rx_ia.ri_max_inline_write)

		return false;



	if (xdr->page_len) {

		remaining = xdr->page_len;

		offset = xdr->page_base & ~PAGE_MASK;

		count = 0;

		while (remaining) {

			remaining -= min_t(unsigned int,

					   PAGE_SIZE - offset, remaining);

			offset = 0;

			if (++count > r_xprt->rx_ia.ri_max_send_sges)

				return false;

		}

	}



	return rqst->rq_snd_buf.len <= ia->ri_max_inline_write;

	return true;

}



/* The client can't know how large the actual reply will be. Thus it

net/sunrpc/xprtrdma/verbs.c

+7 −6
Original line number Diff line number Diff line
@@ -491,15 +491,16 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia, 
		  struct rpcrdma_create_data_internal *cdata)

{

	struct rpcrdma_connect_private *pmsg = &ep->rep_cm_private;

	unsigned int max_qp_wr, max_sge;

	struct ib_cq *sendcq, *recvcq;

	unsigned int max_qp_wr;

	int rc;



	if (ia->ri_device->attrs.max_sge < RPCRDMA_MAX_SEND_SGES) {

		dprintk("RPC:       %s: insufficient sge's available\n",

			__func__);

	max_sge = min(ia->ri_device->attrs.max_sge, RPCRDMA_MAX_SEND_SGES);

	if (max_sge < RPCRDMA_MIN_SEND_SGES) {

		pr_warn("rpcrdma: HCA provides only %d send SGEs\n", max_sge);

		return -ENOMEM;

	}

	ia->ri_max_send_sges = max_sge - RPCRDMA_MIN_SEND_SGES;



	if (ia->ri_device->attrs.max_qp_wr <= RPCRDMA_BACKWARD_WRS) {

		dprintk("RPC:       %s: insufficient wqe's available\n",
@@ -524,7 +525,7 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, struct rpcrdma_ia *ia, 
	ep->rep_attr.cap.max_recv_wr = cdata->max_requests;

	ep->rep_attr.cap.max_recv_wr += RPCRDMA_BACKWARD_WRS;

	ep->rep_attr.cap.max_recv_wr += 1;	/* drain cqe */

	ep->rep_attr.cap.max_send_sge = RPCRDMA_MAX_SEND_SGES;

	ep->rep_attr.cap.max_send_sge = max_sge;

	ep->rep_attr.cap.max_recv_sge = 1;

	ep->rep_attr.cap.max_inline_data = 0;

	ep->rep_attr.sq_sig_type = IB_SIGNAL_REQ_WR;

net/sunrpc/xprtrdma/xprt_rdma.h

+2 −0
Original line number Diff line number Diff line
@@ -74,6 +74,7 @@ struct rpcrdma_ia { 
	unsigned int		ri_max_frmr_depth;

	unsigned int		ri_max_inline_write;

	unsigned int		ri_max_inline_read;

	unsigned int		ri_max_send_sges;

	bool			ri_reminv_expected;

	bool			ri_implicit_roundup;

	enum ib_mr_type		ri_mrtype;
@@ -311,6 +312,7 @@ struct rpcrdma_mr_seg { /* chunk descriptors */ 
 * - xdr_buf tail iovec

 */

enum {

	RPCRDMA_MIN_SEND_SGES = 3,

	RPCRDMA_MAX_SEND_PAGES = PAGE_SIZE + RPCRDMA_MAX_INLINE - 1,

	RPCRDMA_MAX_PAGE_SGES = (RPCRDMA_MAX_SEND_PAGES >> PAGE_SHIFT) + 1,

	RPCRDMA_MAX_SEND_SGES = 1 + 1 + RPCRDMA_MAX_PAGE_SGES + 1,