xprtrdma: Place registered MWs on a per-req list

Instead of placing registered MWs sparsely into the rl_segments
array, place these MWs on a per-req list.

ro_unmap_{sync,safe} can then simply pull those MWs off the list
instead of walking through the array.

This change significantly reduces the size of struct rpcrdma_req
by removing nsegs and rl_mw from every array element.

As an additional clean-up, chunk co-ordinates are returned in the
"*mw" output argument so they are no longer needed in every
array element.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>

net/sunrpc/xprtrdma/frwr_ops.c

@@ -128,6 +128,10 @@ frwr_op_release_mr(struct rpcrdma_mw *r)
 {
 	int rc;
 
+	/* Ensure MW is not on any rl_registered list */
+	if (!list_empty(&r->mw_list))
+		list_del(&r->mw_list);
+
 	rc = ib_dereg_mr(r->frmr.fr_mr);
 	if (rc)
 		pr_err("rpcrdma: final ib_dereg_mr for %p returned %i\n",
@@ -333,10 +337,9 @@ frwr_wc_localinv_wake(struct ib_cq *cq, struct ib_wc *wc)
  */
 static int
 frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
-	    int nsegs, bool writing)
+	    int nsegs, bool writing, struct rpcrdma_mw **out)
 {
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
-	struct rpcrdma_mr_seg *seg1 = seg;
 	struct rpcrdma_mw *mw;
 	struct rpcrdma_frmr *frmr;
 	struct ib_mr *mr;
@@ -345,8 +348,7 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 	int rc, i, n, dma_nents;
 	u8 key;
 
-	mw = seg1->rl_mw;
-	seg1->rl_mw = NULL;
+	mw = NULL;
 	do {
 		if (mw)
 			rpcrdma_defer_mr_recovery(mw);
@@ -416,12 +418,11 @@ frwr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
 	if (rc)
 		goto out_senderr;
 
-	seg1->rl_mw = mw;
-	seg1->mr_rkey = mr->rkey;
-	seg1->mr_base = mr->iova;
-	seg1->mr_nsegs = mw->mw_nents;
-	seg1->mr_len = mr->length;
+	mw->mw_handle = mr->rkey;
+	mw->mw_length = mr->length;
+	mw->mw_offset = mr->iova;
 
+	*out = mw;
 	return mw->mw_nents;
 
 out_dmamap_err:
@@ -443,9 +444,8 @@ out_senderr:
 }
 
 static struct ib_send_wr *
-__frwr_prepare_linv_wr(struct rpcrdma_mr_seg *seg)
+__frwr_prepare_linv_wr(struct rpcrdma_mw *mw)
 {
-	struct rpcrdma_mw *mw = seg->rl_mw;
 	struct rpcrdma_frmr *f = &mw->frmr;
 	struct ib_send_wr *invalidate_wr;
 
@@ -465,16 +465,16 @@ __frwr_prepare_linv_wr(struct rpcrdma_mr_seg *seg)
  *
  * Sleeps until it is safe for the host CPU to access the
  * previously mapped memory regions.
+ *
+ * Caller ensures that req->rl_registered is not empty.
  */
 static void
 frwr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 {
 	struct ib_send_wr *invalidate_wrs, *pos, *prev, *bad_wr;
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
-	struct rpcrdma_mr_seg *seg;
-	unsigned int i, nchunks;
+	struct rpcrdma_mw *mw, *tmp;
 	struct rpcrdma_frmr *f;
-	struct rpcrdma_mw *mw;
 	int rc;
 
 	dprintk("RPC:       %s: req %p\n", __func__, req);
@@ -484,22 +484,18 @@ frwr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 	 * Chain the LOCAL_INV Work Requests and post them with
 	 * a single ib_post_send() call.
 	 */
+	f = NULL;
 	invalidate_wrs = pos = prev = NULL;
-	seg = NULL;
-	for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
-		seg = &req->rl_segments[i];
-
-		pos = __frwr_prepare_linv_wr(seg);
+	list_for_each_entry(mw, &req->rl_registered, mw_list) {
+		pos = __frwr_prepare_linv_wr(mw);
 
 		if (!invalidate_wrs)
 			invalidate_wrs = pos;
 		else
 			prev->next = pos;
 		prev = pos;
-
-		i += seg->mr_nsegs;
+		f = &mw->frmr;
 	}
-	f = &seg->rl_mw->frmr;
 
 	/* Strong send queue ordering guarantees that when the
 	 * last WR in the chain completes, all WRs in the chain
@@ -524,20 +520,12 @@ frwr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
 	 * them to the free MW list.
 	 */
 unmap:
-	for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
-		seg = &req->rl_segments[i];
-		mw = seg->rl_mw;
-		seg->rl_mw = NULL;
-
+	list_for_each_entry_safe(mw, tmp, &req->rl_registered, mw_list) {
+		list_del_init(&mw->mw_list);
 		ib_dma_unmap_sg(ia->ri_device,
 				mw->mw_sg, mw->mw_nents, mw->mw_dir);
 		rpcrdma_put_mw(r_xprt, mw);
-
-		i += seg->mr_nsegs;
-		seg->mr_nsegs = 0;
 	}
-
-	req->rl_nchunks = 0;
 	return;
 
 reset_mrs:
@@ -547,17 +535,12 @@ reset_mrs:
 	/* Find and reset the MRs in the LOCAL_INV WRs that did not
 	 * get posted. This is synchronous, and slow.
 	 */
-	for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
-		seg = &req->rl_segments[i];
-		mw = seg->rl_mw;
+	list_for_each_entry(mw, &req->rl_registered, mw_list) {
 		f = &mw->frmr;
-
 		if (mw->frmr.fr_mr->rkey == bad_wr->ex.invalidate_rkey) {
 			__frwr_reset_mr(ia, mw);
 			bad_wr = bad_wr->next;
 		}
-
-		i += seg->mr_nsegs;
 	}
 	goto unmap;
 }
@@ -569,22 +552,17 @@ static void
 frwr_op_unmap_safe(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req,
 		   bool sync)
 {
-	struct rpcrdma_mr_seg *seg;
 	struct rpcrdma_mw *mw;
-	unsigned int i;
 
-	for (i = 0; req->rl_nchunks; req->rl_nchunks--) {
-		seg = &req->rl_segments[i];
-		mw = seg->rl_mw;
+	while (!list_empty(&req->rl_registered)) {
+		mw = list_first_entry(&req->rl_registered,
+				      struct rpcrdma_mw, mw_list);
+		list_del_init(&mw->mw_list);
 
 		if (sync)
 			frwr_op_recover_mr(mw);
 		else
 			rpcrdma_defer_mr_recovery(mw);
-
-		i += seg->mr_nsegs;
-		seg->mr_nsegs = 0;
-		seg->rl_mw = NULL;
 	}
 }