[PATCH v2 08/21] xprtrdma: Back off rkey when FAST_REG_MR fails

[Chuck Lever <chuck.lever@oracle.com>]

If posting a FAST_REG_MR Work Reqeust fails, revert the rkey update
to avoid subsequent IB_WC_MW_BIND_ERR completions.

Suggested-by: Steve Wise <swise@opengridcomputing.com>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 net/sunrpc/xprtrdma/verbs.c |   27 ++++++++++++++++++++-------
 1 file changed, 20 insertions(+), 7 deletions(-)

diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index ce847d2..14d24ec 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1487,6 +1487,24 @@ rpcrdma_unmap_one(struct rpcrdma_ia *ia, struct rpcrdma_mr_seg *seg)
 				seg->mr_dma, seg->mr_dmalen, seg->mr_dir);
 }
 
+static void
+rpcrdma_increment_frmr_rkey(struct rpcrdma_mw *mw)
+{
+	struct ib_mr *mr = mw->r.frmr.fr_mr;
+	u8 key = mr->rkey & 0x000000FF;
+
+	ib_update_fast_reg_key(mr, ++key);
+}
+
+static void
+rpcrdma_decrement_frmr_rkey(struct rpcrdma_mw *mw)
+{
+	struct ib_mr *mr = mw->r.frmr.fr_mr;
+	u8 key = mr->rkey & 0x000000FF;
+
+	ib_update_fast_reg_key(mr, --key);
+}
+
 static int
 rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
 			int *nsegs, int writing, struct rpcrdma_ia *ia,
@@ -1496,8 +1514,6 @@ rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
 	struct rpcrdma_mw *mw = seg1->mr_chunk.rl_mw;
 	struct rpcrdma_frmr *frmr = &mw->r.frmr;
 	struct ib_send_wr invalidate_wr, frmr_wr, *bad_wr, *post_wr;
-
-	u8 key;
 	int len, pageoff;
 	int i, rc;
 	int seg_len;
@@ -1557,14 +1573,10 @@ rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
 		rc = -EIO;
 		goto out_err;
 	}
-
-	/* Bump the key */
-	key = (u8)(frmr->fr_mr->rkey & 0x000000FF);
-	ib_update_fast_reg_key(frmr->fr_mr, ++key);
-
 	frmr_wr.wr.fast_reg.access_flags = (writing ?
 				IB_ACCESS_REMOTE_WRITE | IB_ACCESS_LOCAL_WRITE :
 				IB_ACCESS_REMOTE_READ);
+	rpcrdma_increment_frmr_rkey(mw);
 	frmr_wr.wr.fast_reg.rkey = frmr->fr_mr->rkey;
 	DECR_CQCOUNT(&r_xprt->rx_ep);
 
@@ -1573,6 +1585,7 @@ rpcrdma_register_frmr_external(struct rpcrdma_mr_seg *seg,
 	if (rc) {
 		dprintk("RPC:       %s: failed ib_post_send for register,"
 			" status %i\n", __func__, rc);
+		rpcrdma_decrement_frmr_rkey(seg1->mr_chunk.rl_mw);
 		goto out_err;
 	} else {
 		seg1->mr_rkey = frmr->fr_mr->rkey;