[PATCH v1 04/14] xprtrdma: Support for SG_GAP devices

[Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>]

Some devices (such as the Mellanox CX-4) can register, under a
single R_key, a set of memory regions that are not contiguous. When
this is done, all the segments in a Reply list, say, can then be
invalidated in a single LocalInv Work Request (or via Remote
Invalidation, which can invalidate exactly one R_key when completing
a Receive).

This means a single FastReg WR is used to register, and one or zero
LocalInv WRs can invalidate, the memory involved with RDMA transfers
on behalf of an RPC.

Signed-off-by: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
---
 net/sunrpc/xprtrdma/frwr_ops.c  |   20 +++++++++++++-------
 net/sunrpc/xprtrdma/xprt_rdma.h |    1 +
 2 files changed, 14 insertions(+), 7 deletions(-)

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index adbf52c..e99bf61 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -101,7 +101,7 @@
 	struct rpcrdma_frmr *f = &r->frmr;
 	int rc;
 
-	f->fr_mr = ib_alloc_mr(ia->ri_pd, IB_MR_TYPE_MEM_REG, depth);
+	f->fr_mr = ib_alloc_mr(ia->ri_pd, ia->ri_mrtype, depth);
 	if (IS_ERR(f->fr_mr))
 		goto out_mr_err;
 
@@ -157,7 +157,7 @@
 		return rc;
 	}
 
-	f->fr_mr = ib_alloc_mr(ia->ri_pd, IB_MR_TYPE_MEM_REG,
+	f->fr_mr = ib_alloc_mr(ia->ri_pd, ia->ri_mrtype,
 			       ia->ri_max_frmr_depth);
 	if (IS_ERR(f->fr_mr)) {
 		pr_warn("rpcrdma: ib_alloc_mr status %ld, frwr %p orphaned\n",
@@ -210,11 +210,16 @@
 frwr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
 	     struct rpcrdma_create_data_internal *cdata)
 {
+	struct ib_device_attr *attrs = &ia->ri_device->attrs;
 	int depth, delta;
 
+	ia->ri_mrtype = IB_MR_TYPE_MEM_REG;
+	if (attrs->device_cap_flags & IB_DEVICE_SG_GAPS_REG)
+		ia->ri_mrtype = IB_MR_TYPE_SG_GAPS;
+
 	ia->ri_max_frmr_depth =
 			min_t(unsigned int, RPCRDMA_MAX_DATA_SEGS,
-			      ia->ri_device->attrs.max_fast_reg_page_list_len);
+			      attrs->max_fast_reg_page_list_len);
 	dprintk("RPC:       %s: device's max FR page list len = %u\n",
 		__func__, ia->ri_max_frmr_depth);
 
@@ -241,8 +246,8 @@
 	}
 
 	ep->rep_attr.cap.max_send_wr *= depth;
-	if (ep->rep_attr.cap.max_send_wr > ia->ri_device->attrs.max_qp_wr) {
-		cdata->max_requests = ia->ri_device->attrs.max_qp_wr / depth;
+	if (ep->rep_attr.cap.max_send_wr > attrs->max_qp_wr) {
+		cdata->max_requests = attrs->max_qp_wr / depth;
 		if (!cdata->max_requests)
 			return -EINVAL;
 		ep->rep_attr.cap.max_send_wr = cdata->max_requests *
@@ -348,6 +353,7 @@
 	    int nsegs, bool writing, struct rpcrdma_mw **out)
 {
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
+	bool holes_ok = ia->ri_mrtype == IB_MR_TYPE_SG_GAPS;
 	struct rpcrdma_mw *mw;
 	struct rpcrdma_frmr *frmr;
 	struct ib_mr *mr;
@@ -383,8 +389,8 @@
 
 		++seg;
 		++i;
-
-		/* Check for holes */
+		if (holes_ok)
+			continue;
 		if ((i < nsegs && offset_in_page(seg->mr_offset)) ||
 		    offset_in_page((seg-1)->mr_offset + (seg-1)->mr_len))
 			break;
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index f6ae1b2..b8424fa 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -75,6 +75,7 @@ struct rpcrdma_ia {
 	unsigned int		ri_max_inline_write;
 	unsigned int		ri_max_inline_read;
 	bool			ri_reminv_expected;
+	enum ib_mr_type		ri_mrtype;
 	struct ib_qp_attr	ri_qp_attr;
 	struct ib_qp_init_attr	ri_qp_init_attr;
 };

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