Re: [PATCH v1 13/14] xprtrdma: Stack relief in fmr_op_map()

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On 5/4/2015 8:58 PM, Chuck Lever wrote:
fmr_op_map() declares a 64 element array of u64 in automatic
storage. This is 512 bytes (8 * 64) on the stack.

Instead, when FMR memory registration is in use, pre-allocate a
physaddr array for each rpcrdma_mw.

This is a pre-requisite for increasing the r/wsize maximum for
FMR on platforms with 4KB pages.

Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
---
  net/sunrpc/xprtrdma/fmr_ops.c   |   32 ++++++++++++++++++++++----------
  net/sunrpc/xprtrdma/xprt_rdma.h |    7 ++++++-
  2 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/net/sunrpc/xprtrdma/fmr_ops.c b/net/sunrpc/xprtrdma/fmr_ops.c
index 52f9ad5..4a53ad5 100644
--- a/net/sunrpc/xprtrdma/fmr_ops.c
+++ b/net/sunrpc/xprtrdma/fmr_ops.c
@@ -72,13 +72,19 @@ fmr_op_init(struct rpcrdma_xprt *r_xprt)
  	i = (buf->rb_max_requests + 1) * RPCRDMA_MAX_SEGS;
  	dprintk("RPC:       %s: initializing %d FMRs\n", __func__, i);

+	rc = -ENOMEM;
  	while (i--) {
  		r = kzalloc(sizeof(*r), GFP_KERNEL);
  		if (!r)
-			return -ENOMEM;
+			goto out;
+
+		r->r.fmr.physaddrs = kmalloc(RPCRDMA_MAX_FMR_SGES *
+					     sizeof(u64), GFP_KERNEL);
+		if (!r->r.fmr.physaddrs)
+			goto out_free;

-		r->r.fmr = ib_alloc_fmr(pd, mr_access_flags, &fmr_attr);
-		if (IS_ERR(r->r.fmr))
+		r->r.fmr.fmr = ib_alloc_fmr(pd, mr_access_flags, &fmr_attr);
+		if (IS_ERR(r->r.fmr.fmr))
  			goto out_fmr_err;

  		list_add(&r->mw_list, &buf->rb_mws);
@@ -87,9 +93,12 @@ fmr_op_init(struct rpcrdma_xprt *r_xprt)
  	return 0;

  out_fmr_err:
-	rc = PTR_ERR(r->r.fmr);
+	rc = PTR_ERR(r->r.fmr.fmr);
  	dprintk("RPC:       %s: ib_alloc_fmr status %i\n", __func__, rc);
+	kfree(r->r.fmr.physaddrs);
+out_free:
  	kfree(r);
+out:
  	return rc;
  }

@@ -98,7 +107,7 @@ __fmr_unmap(struct rpcrdma_mw *r)
  {
  	LIST_HEAD(l);

-	list_add(&r->r.fmr->list, &l);
+	list_add(&r->r.fmr.fmr->list, &l);
  	return ib_unmap_fmr(&l);
  }

@@ -113,7 +122,6 @@ fmr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
  	struct ib_device *device = ia->ri_device;
  	enum dma_data_direction direction = rpcrdma_data_dir(writing);
  	struct rpcrdma_mr_seg *seg1 = seg;
-	u64 physaddrs[RPCRDMA_MAX_DATA_SEGS];
  	int len, pageoff, i, rc;
  	struct rpcrdma_mw *mw;

@@ -138,7 +146,7 @@ fmr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
  		nsegs = RPCRDMA_MAX_FMR_SGES;
  	for (i = 0; i < nsegs;) {
  		rpcrdma_map_one(device, seg, direction);
-		physaddrs[i] = seg->mr_dma;
+		mw->r.fmr.physaddrs[i] = seg->mr_dma;
  		len += seg->mr_len;
  		++seg;
  		++i;
@@ -148,12 +156,13 @@ fmr_op_map(struct rpcrdma_xprt *r_xprt, struct rpcrdma_mr_seg *seg,
  			break;
  	}

-	rc = ib_map_phys_fmr(mw->r.fmr, physaddrs, i, seg1->mr_dma);
+	rc = ib_map_phys_fmr(mw->r.fmr.fmr, mw->r.fmr.physaddrs,
+			     i, seg1->mr_dma);
  	if (rc)
  		goto out_maperr;

  	seg1->rl_mw = mw;
-	seg1->mr_rkey = mw->r.fmr->rkey;
+	seg1->mr_rkey = mw->r.fmr.fmr->rkey;
  	seg1->mr_base = seg1->mr_dma + pageoff;
  	seg1->mr_nsegs = i;
  	seg1->mr_len = len;
@@ -207,10 +216,13 @@ fmr_op_destroy(struct rpcrdma_buffer *buf)
  	while (!list_empty(&buf->rb_all)) {
  		r = list_entry(buf->rb_all.next, struct rpcrdma_mw, mw_all);
  		list_del(&r->mw_all);
-		rc = ib_dealloc_fmr(r->r.fmr);
+		kfree(r->r.fmr.physaddrs);
+
+		rc = ib_dealloc_fmr(r->r.fmr.fmr);
  		if (rc)
  			dprintk("RPC:       %s: ib_dealloc_fmr failed %i\n",
  				__func__, rc);
+
  		kfree(r);
  	}
  }
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index ae31fc7..e176bae 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -207,9 +207,14 @@ struct rpcrdma_frmr {
  	struct rpcrdma_xprt		*fr_xprt;
  };

+struct rpcrdma_fmr {
+	struct ib_fmr		*fmr;
+	u64			*physaddrs;
+};
+
  struct rpcrdma_mw {
  	union {
-		struct ib_fmr		*fmr;
+		struct rpcrdma_fmr	fmr;
  		struct rpcrdma_frmr	frmr;
  	} r;
  	void			(*mw_sendcompletion)(struct ib_wc *);


Looks good

Reviewed-by: Sagi Grimberg <sagig@xxxxxxxxxxxx>
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