[PATCH linux-next v2] SUNRPC: rpcrdma_register_default_external: Dynamically allocate ib_phys_buf

[Tim Gardner]

rpcrdma_register_default_external() is several frames into the call stack which
goes deeper yet. You run the risk of stack corruption by declaring such a large
automatic variable, so move the array of 'struct ib_phys_buf' objects into the
requestor structure 'struct rpcrdma_req' (which is dynamically allocated) in
order to silence the frame-larger-than warning.

net/sunrpc/xprtrdma/verbs.c: In function 'rpcrdma_register_default_external':
net/sunrpc/xprtrdma/verbs.c:1774:1: warning: the frame size of 1056 bytes is larger than 1024 bytes [-Wframe-larger-than=]

gcc version 4.6.3

Cc: Trond Myklebust <Trond.Myklebust@xxxxxxxxxx>
Cc: "J. Bruce Fields" <bfields@xxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Tom Tucker <tom@xxxxxx>
Cc: Haggai Eran <haggaie@xxxxxxxxxxxx>
Cc: Or Gerlitz <ogerlitz@xxxxxxxxxxxx>
Cc: Shani Michaeli <shanim@xxxxxxxxxxxx>
Cc: linux-nfs@xxxxxxxxxxxxxxx
Cc: netdev@xxxxxxxxxxxxxxx

Signed-off-by: Tim Gardner <tim.gardner@xxxxxxxxxxxxx>
---

v1 - Use kmalloc() to dynamically allocate and free the array of 'struct
ib_phys_buf' objects

v2 - Move the array of 'struct ib_phys_buf' objects into struct rpcrdma_req
and pass this request down through rpcrdma_register_external() and
rpcrdma_register_default_external(). This is less overhead then using
kmalloc() and requires no extra error checking as the allocation burden is
shifted to the transport client.

 net/sunrpc/xprtrdma/rpc_rdma.c  |    2 +-
 net/sunrpc/xprtrdma/verbs.c     |   11 ++++++-----
 net/sunrpc/xprtrdma/xprt_rdma.h |    3 ++-
 3 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index e03725b..c89448b 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -203,7 +203,7 @@ rpcrdma_create_chunks(struct rpc_rqst *rqst, struct xdr_buf *target,
 
 	do {
 		/* bind/register the memory, then build chunk from result. */
-		int n = rpcrdma_register_external(seg, nsegs,
+		int n = rpcrdma_register_external(req, seg, nsegs,
 						cur_wchunk != NULL, r_xprt);
 		if (n <= 0)
 			goto out;
diff --git a/net/sunrpc/xprtrdma/verbs.c b/net/sunrpc/xprtrdma/verbs.c
index 93726560..5b439ed 100644
--- a/net/sunrpc/xprtrdma/verbs.c
+++ b/net/sunrpc/xprtrdma/verbs.c
@@ -1730,13 +1730,14 @@ rpcrdma_deregister_memwin_external(struct rpcrdma_mr_seg *seg,
 }
 
 static int
-rpcrdma_register_default_external(struct rpcrdma_mr_seg *seg,
-			int *nsegs, int writing, struct rpcrdma_ia *ia)
+rpcrdma_register_default_external(struct rpcrdma_req *req,
+			struct rpcrdma_mr_seg *seg, int *nsegs, int writing,
+			struct rpcrdma_ia *ia)
 {
 	int mem_priv = (writing ? IB_ACCESS_REMOTE_WRITE :
 				  IB_ACCESS_REMOTE_READ);
 	struct rpcrdma_mr_seg *seg1 = seg;
-	struct ib_phys_buf ipb[RPCRDMA_MAX_DATA_SEGS];
+	struct ib_phys_buf *ipb = req->rl_ipb;
 	int len, i, rc = 0;
 
 	if (*nsegs > RPCRDMA_MAX_DATA_SEGS)
@@ -1791,7 +1792,7 @@ rpcrdma_deregister_default_external(struct rpcrdma_mr_seg *seg,
 }
 
 int
-rpcrdma_register_external(struct rpcrdma_mr_seg *seg,
+rpcrdma_register_external(struct rpcrdma_req *req, struct rpcrdma_mr_seg *seg,
 			int nsegs, int writing, struct rpcrdma_xprt *r_xprt)
 {
 	struct rpcrdma_ia *ia = &r_xprt->rx_ia;
@@ -1827,7 +1828,7 @@ rpcrdma_register_external(struct rpcrdma_mr_seg *seg,
 
 	/* Default registration each time */
 	default:
-		rc = rpcrdma_register_default_external(seg, &nsegs, writing, ia);
+		rc = rpcrdma_register_default_external(req, seg, &nsegs, writing, ia);
 		break;
 	}
 	if (rc)
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index cc1445d..b10ed34 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -192,6 +192,7 @@ struct rpcrdma_req {
 	struct ib_sge	rl_send_iov[4];	/* for active requests */
 	struct ib_sge	rl_iov;		/* for posting */
 	struct ib_mr	*rl_handle;	/* handle for mem in rl_iov */
+	struct ib_phys_buf rl_ipb[RPCRDMA_MAX_DATA_SEGS]; /* temp work array */
 	char		rl_base[MAX_RPCRDMAHDR]; /* start of actual buffer */
 	__u32 		rl_xdr_buf[0];	/* start of returned rpc rq_buffer */
 };
@@ -327,7 +328,7 @@ int rpcrdma_register_internal(struct rpcrdma_ia *, void *, int,
 int rpcrdma_deregister_internal(struct rpcrdma_ia *,
 				struct ib_mr *, struct ib_sge *);
 
-int rpcrdma_register_external(struct rpcrdma_mr_seg *,
+int rpcrdma_register_external(struct rpcrdma_req *, struct rpcrdma_mr_seg *,
 				int, int, struct rpcrdma_xprt *);
 int rpcrdma_deregister_external(struct rpcrdma_mr_seg *,
 				struct rpcrdma_xprt *, void *);
-- 
1.7.9.5

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