[PATCH v1 04/18] xprtrdma: Prevent inline overflow

Chuck Lever
2016-04-11T20:10:42Z

When deciding whether to send a Call inline, rpcrdma_marshal_req
doesn't take into account header bytes consumed by chunk lists.
This results in Call messages on the wire that are sometimes larger
than the inline threshold.

Likewise, when a Write list or Reply chunk is in play, the server's
reply has to emit an RDMA Send that includes a larger-than-minimal
RPC-over-RDMA header.

The actual size of a Call message cannot be estimated until after
the chunk lists have been registered. Thus the size of each
RPC-over-RDMA header can be estimated only after chunks are
registered; but the decision to register chunks is based on the size
of that header. Chicken, meet egg.

The best a client can do is estimate header size based on the
largest header that might occur, and then ensure that inline content
is always smaller than that.

Signed-off-by: Chuck Lever <chuck.lever-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>
---
net/sunrpc/xprtrdma/fmr_ops.c | 3 +
net/sunrpc/xprtrdma/frwr_ops.c | 3 +
net/sunrpc/xprtrdma/physical_ops.c | 5 ++
net/sunrpc/xprtrdma/rpc_rdma.c | 85 ++++++++++++++++++++++++++++++++----
net/sunrpc/xprtrdma/xprt_rdma.h | 5 ++
5 files changed, 90 insertions(+), 11 deletions(-)

diff --git a/net/sunrpc/xprtrdma/fmr_ops.c b/net/sunrpc/xprtrdma/fmr_ops.c
index 4aeb104..009694b 100644
--- a/net/sunrpc/xprtrdma/fmr_ops.c
+++ b/net/sunrpc/xprtrdma/fmr_ops.c
@@ -39,6 +39,9 @@ static int
fmr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
struct rpcrdma_create_data_internal *cdata)
{
+ rpcrdma_set_max_header_sizes(ia, cdata, max_t(unsigned int, 1,
+ RPCRDMA_MAX_DATA_SEGS /
+ RPCRDMA_MAX_FMR_SGES));
return 0;
}

diff --git a/net/sunrpc/xprtrdma/frwr_ops.c b/net/sunrpc/xprtrdma/frwr_ops.c
index 2f37598..41e02e7 100644
--- a/net/sunrpc/xprtrdma/frwr_ops.c
+++ b/net/sunrpc/xprtrdma/frwr_ops.c
@@ -231,6 +231,9 @@ frwr_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
depth;
}

+ rpcrdma_set_max_header_sizes(ia, cdata, max_t(unsigned int, 1,
+ RPCRDMA_MAX_DATA_SEGS /
+ ia->ri_max_frmr_depth));
return 0;
}

diff --git a/net/sunrpc/xprtrdma/physical_ops.c b/net/sunrpc/xprtrdma/physical_ops.c
index e16ed54..2dc6ec2 100644
--- a/net/sunrpc/xprtrdma/physical_ops.c
+++ b/net/sunrpc/xprtrdma/physical_ops.c
@@ -36,8 +36,11 @@ physical_op_open(struct rpcrdma_ia *ia, struct rpcrdma_ep *ep,
__func__, PTR_ERR(mr));
return -ENOMEM;
}
-
ia->ri_dma_mr = mr;
+
+ rpcrdma_set_max_header_sizes(ia, cdata, min_t(unsigned int,
+ RPCRDMA_MAX_DATA_SEGS,
+ RPCRDMA_MAX_HDR_SEGS));
return 0;
}

diff --git a/net/sunrpc/xprtrdma/rpc_rdma.c b/net/sunrpc/xprtrdma/rpc_rdma.c
index 888823b..205b81b 100644
--- a/net/sunrpc/xprtrdma/rpc_rdma.c
+++ b/net/sunrpc/xprtrdma/rpc_rdma.c
@@ -61,7 +61,6 @@ enum rpcrdma_chunktype {
rpcrdma_replych
};

-#if IS_ENABLED(CONFIG_SUNRPC_DEBUG)
static const char transfertypes[][12] = {
"pure inline", /* no chunks */
" read chunk", /* some argument via rdma read */
@@ -69,18 +68,72 @@ static const char transfertypes[][12] = {
"write chunk", /* some result via rdma write */
"reply chunk" /* entire reply via rdma write */
};
-#endif
+
+/* Returns size of largest RPC-over-RDMA header in a Call message
+ *
+ * The client marshals only one chunk list per Call message.
+ * The largest list is the Read list.
+ */
+static unsigned int rpcrdma_max_call_header_size(unsigned int maxsegs)
+{
+ unsigned int size;
+
+ /* Fixed header fields and list discriminators */
+ size = RPCRDMA_HDRLEN_MIN;
+
+ /* Maximum Read list size */
+ maxsegs += 2; /* segment for head and tail buffers */
+ size = maxsegs * sizeof(struct rpcrdma_read_chunk);
+
+ dprintk("RPC: %s: max call header size = %u\n",
+ __func__, size);
+ return size;
+}
+
+/* Returns size of largest RPC-over-RDMA header in a Reply message
+ *
+ * There is only one Write list or one Reply chunk per Reply
+ * message. The larger list is the Write list.
+ */
+static unsigned int rpcrdma_max_reply_header_size(unsigned int maxsegs)
+{
+ unsigned int size;
+
+ /* Fixed header fields and list discriminators */
+ size = RPCRDMA_HDRLEN_MIN;
+
+ /* Maximum Write list size */
+ maxsegs += 2; /* segment for head and tail buffers */
+ size = sizeof(__be32); /* segment count */
+ size += maxsegs * sizeof(struct rpcrdma_segment);
+ size += sizeof(__be32); /* list discriminator */
+
+ dprintk("RPC: %s: max reply header size = %u\n",
+ __func__, size);
+ return size;
+}
+
+void rpcrdma_set_max_header_sizes(struct rpcrdma_ia *ia,
+ struct rpcrdma_create_data_internal *cdata,
+ unsigned int maxsegs)
+{
+ ia->ri_max_inline_write = cdata->inline_wsize -
+ rpcrdma_max_call_header_size(maxsegs);
+ ia->ri_max_inline_read = cdata->inline_rsize -
+ rpcrdma_max_reply_header_size(maxsegs);
+}

/* The client can send a request inline as long as the RPCRDMA header
* plus the RPC call fit under the transport's inline limit. If the
* combined call message size exceeds that limit, the client must use
* the read chunk list for this operation.
*/
-static bool rpcrdma_args_inline(struct rpc_rqst *rqst)
+static bool rpcrdma_args_inline(struct rpcrdma_xprt *r_xprt,
+ struct rpc_rqst *rqst)
{
- unsigned int callsize = RPCRDMA_HDRLEN_MIN + rqst->rq_snd_buf.len;
+ struct rpcrdma_ia *ia = &r_xprt->rx_ia;

- return callsize <= RPCRDMA_INLINE_WRITE_THRESHOLD(rqst);
+ return rqst->rq_snd_buf.len <= ia->ri_max_inline_write;
}

/* The client can't know how large the actual reply will be. Thus it
@@ -89,11 +142,12 @@ static bool rpcrdma_args_inline(struct rpc_rqst *rqst)
* limit, the client must provide a write list or a reply chunk for
* this request.
*/
-static bool rpcrdma_results_inline(struct rpc_rqst *rqst)
+static bool rpcrdma_results_inline(struct rpcrdma_xprt *r_xprt,
+ struct rpc_rqst *rqst)
{
- unsigned int repsize = RPCRDMA_HDRLEN_MIN + rqst->rq_rcv_buf.buflen;
+ struct rpcrdma_ia *ia = &r_xprt->rx_ia;

- return repsize <= RPCRDMA_INLINE_READ_THRESHOLD(rqst);
+ return rqst->rq_rcv_buf.buflen <= ia->ri_max_inline_read;
}

static int
@@ -492,7 +546,7 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
*/
if (rqst->rq_rcv_buf.flags & XDRBUF_READ)
wtype = rpcrdma_writech;
- else if (rpcrdma_results_inline(rqst))
+ else if (rpcrdma_results_inline(r_xprt, rqst))
wtype = rpcrdma_noch;
else
wtype = rpcrdma_replych;
@@ -511,7 +565,7 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
* that both has a data payload, and whose non-data arguments
* by themselves are larger than the inline threshold.
*/
- if (rpcrdma_args_inline(rqst)) {
+ if (rpcrdma_args_inline(r_xprt, rqst)) {
rtype = rpcrdma_noch;
} else if (rqst->rq_snd_buf.flags & XDRBUF_WRITE) {
rtype = rpcrdma_readch;
@@ -561,6 +615,9 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)
if (hdrlen < 0)
return hdrlen;

+ if (hdrlen + rpclen > RPCRDMA_INLINE_WRITE_THRESHOLD(rqst))
+ goto out_overflow;
+
dprintk("RPC: %s: %s: hdrlen %zd rpclen %zd"
" headerp 0x%p base 0x%p lkey 0x%x\n",
__func__, transfertypes[wtype], hdrlen, rpclen,
@@ -587,6 +644,14 @@ rpcrdma_marshal_req(struct rpc_rqst *rqst)

req->rl_niovs = 2;
return 0;
+
+out_overflow:
+ pr_err("rpcrdma: send overflow: hdrlen %zd rpclen %zu %s\n",
+ hdrlen, rpclen, transfertypes[wtype]);
+ /* Terminate this RPC. Chunks registered above will be
+ * released by xprt_release -> xprt_rmda_free .
+ */
+ return -EIO;
}

/*
diff --git a/net/sunrpc/xprtrdma/xprt_rdma.h b/net/sunrpc/xprtrdma/xprt_rdma.h
index 0028748..4349e03 100644
--- a/net/sunrpc/xprtrdma/xprt_rdma.h
+++ b/net/sunrpc/xprtrdma/xprt_rdma.h
@@ -73,6 +73,8 @@ struct rpcrdma_ia {
struct completion ri_done;
int ri_async_rc;
unsigned int ri_max_frmr_depth;
+ unsigned int ri_max_inline_write;
+ unsigned int ri_max_inline_read;
struct ib_qp_attr ri_qp_attr;
struct ib_qp_init_attr ri_qp_init_attr;
};
@@ -538,6 +540,9 @@ void rpcrdma_reply_handler(struct rpcrdma_rep *);
* RPC/RDMA protocol calls - xprtrdma/rpc_rdma.c
*/
int rpcrdma_marshal_req(struct rpc_rqst *);
+void rpcrdma_set_max_header_sizes(struct rpcrdma_ia *,
+ struct rpcrdma_create_data_internal *,
+ unsigned int);

/* RPC/RDMA module init - xprtrdma/transport.c
*/