FMR's ro_unmap method is already synchronous because ib_unmap_fmr()
is a synchronous verb. However, some improvements can be made here.
1. Gather all the MRs for the RPC request onto a list, and invoke
ib_unmap_fmr() once with that list. This reduces the number of
doorbells when there is more than one MR to invalidate
2. Perform the DMA unmap _after_ the MRs are unmapped, not before.
This is critical after invalidating a Write chunk.
Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
net/sunrpc/xprtrdma/fmr_ops.c | 64 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 64 insertions(+)
diff --git a/net/sunrpc/xprtrdma/fmr_ops.c b/net/sunrpc/xprtrdma/fmr_ops.c
index f1e8daf..c14f3a4 100644
--- a/net/sunrpc/xprtrdma/fmr_ops.c
+++ b/net/sunrpc/xprtrdma/fmr_ops.c
@@ -179,6 +179,69 @@ out_maperr:
return rc;
}
+static void
+__fmr_dma_unmap(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg)
+{
+ struct ib_device *device = r_xprt->rx_ia.ri_device;
+ struct rpcrdma_mw *mw = seg->rl_mw;
+ int nsegs = seg->mr_nsegs;
+
+ seg->rl_mw = NULL;
+
+ while (nsegs--)
+ rpcrdma_unmap_one(device, seg++);
+
+ rpcrdma_put_mw(r_xprt, mw);
+}
+
+/* Invalidate all memory regions that were registered for "req".
+ *
+ * Sleeps until it is safe for the host CPU to access the
+ * previously mapped memory regions.
+ */
+static void
+fmr_op_unmap_sync(struct rpcrdma_xprt *r_xprt, struct rpcrdma_req *req)
+{
+ struct rpcrdma_mr_seg *seg;
+ unsigned int i, nchunks;
+ struct rpcrdma_mw *mw;
+ LIST_HEAD(unmap_list);
+ int rc;
+
+ dprintk("RPC: %s: req %p\n", __func__, req);
+
+ /* ORDER: Invalidate all of the req's MRs first
+ *
+ * ib_unmap_fmr() is slow, so use a single call instead
+ * of one call per mapped MR.
+ */
+ for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
+ seg = &req->rl_segments[i];
+ mw = seg->rl_mw;
+
+ list_add(&mw->r.fmr.fmr->list, &unmap_list);
+
+ i += seg->mr_nsegs;
+ }
+ rc = ib_unmap_fmr(&unmap_list);
+ if (rc)
+ pr_warn("%s: ib_unmap_fmr failed (%i)\n", __func__, rc);
+
+ /* ORDER: Now DMA unmap all of the req's MRs, and return
+ * them to the free MW list.
+ */
+ for (i = 0, nchunks = req->rl_nchunks; nchunks; nchunks--) {
+ seg = &req->rl_segments[i];
+
+ __fmr_dma_unmap(r_xprt, seg);
+
+ i += seg->mr_nsegs;
+ seg->mr_nsegs = 0;
+ }
+
+ req->rl_nchunks = 0;
+}
+
/* Use the ib_unmap_fmr() verb to prevent further remote
* access via RDMA READ or RDMA WRITE.
*/
@@ -231,6 +294,7 @@ fmr_op_destroy(struct rpcrdma_buffer *buf)
const struct rpcrdma_memreg_ops rpcrdma_fmr_memreg_ops = {
.ro_map = fmr_op_map,
+ .ro_unmap_sync = fmr_op_unmap_sync,
.ro_unmap = fmr_op_unmap,
.ro_open = fmr_op_open,
.ro_maxpages = fmr_op_maxpages,
--
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