svcrdma: Add a "parsed chunk list" data structure

This simple data structure binds the location of each data payload
inside of an RPC message to the chunk that will be used to push it
to or pull it from the client.

There are several benefits to this small additional overhead:

 * It enables support for more than one chunk in incoming Read and
   Write lists.

 * It translates the version-specific on-the-wire format into a
   generic in-memory structure, enabling support for multiple
   versions of the RPC/RDMA transport protocol.

 * It enables the server to re-organize a chunk list if it needs to
   adjust where Read chunk data lands in server memory without
   altering the contents of the XDR-encoded Receive buffer.

Construction of these lists is done while sanity checking each
incoming RPC/RDMA header. Subsequent patches will make use of the
generated data structures.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

1 files changed, 115 insertions, 81 deletions

diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
index c6ea2903c21a..ec9d259b149c 100644
--- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
+++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
@@ -93,6 +93,7 @@
  * (see rdma_read_complete() below).
  */
 
+#include <linux/slab.h>
 #include <linux/spinlock.h>
 #include <asm/unaligned.h>
 #include <rdma/ib_verbs.h>
@@ -143,6 +144,10 @@ svc_rdma_recv_ctxt_alloc(struct svcxprt_rdma *rdma)
 		goto fail2;
 
 	svc_rdma_recv_cid_init(rdma, &ctxt->rc_cid);
+	pcl_init(&ctxt->rc_call_pcl);
+	pcl_init(&ctxt->rc_read_pcl);
+	pcl_init(&ctxt->rc_write_pcl);
+	pcl_init(&ctxt->rc_reply_pcl);
 
 	ctxt->rc_recv_wr.next = NULL;
 	ctxt->rc_recv_wr.wr_cqe = &ctxt->rc_cqe;
@@ -226,6 +231,11 @@ void svc_rdma_recv_ctxt_put(struct svcxprt_rdma *rdma,
 	for (i = 0; i < ctxt->rc_page_count; i++)
 		put_page(ctxt->rc_pages[i]);
 
+	pcl_free(&ctxt->rc_call_pcl);
+	pcl_free(&ctxt->rc_read_pcl);
+	pcl_free(&ctxt->rc_write_pcl);
+	pcl_free(&ctxt->rc_reply_pcl);
+
 	if (!ctxt->rc_temp)
 		llist_add(&ctxt->rc_node, &rdma->sc_recv_ctxts);
 	else
@@ -385,100 +395,123 @@ static void svc_rdma_build_arg_xdr(struct svc_rqst *rqstp,
 	arg->len = ctxt->rc_byte_len;
 }
 
-/* This accommodates the largest possible Write chunk.
- */
-#define MAX_BYTES_WRITE_CHUNK ((u32)(RPCSVC_MAXPAGES << PAGE_SHIFT))
-
-/* This accommodates the largest possible Position-Zero
- * Read chunk or Reply chunk.
- */
-#define MAX_BYTES_SPECIAL_CHUNK ((u32)((RPCSVC_MAXPAGES + 2) << PAGE_SHIFT))
-
-/* Sanity check the Read list.
+/**
+ * xdr_count_read_segments - Count number of Read segments in Read list
+ * @rctxt: Ingress receive context
+ * @p: Start of an un-decoded Read list
  *
- * Implementation limits:
- * - This implementation supports only one Read chunk.
+ * Before allocating anything, ensure the ingress Read list is safe
+ * to use.
  *
- * Sanity checks:
- * - Read list does not overflow Receive buffer.
- * - Segment size limited by largest NFS data payload.
- *
- * The segment count is limited to how many segments can
- * fit in the transport header without overflowing the
- * buffer. That's about 40 Read segments for a 1KB inline
- * threshold.
+ * The segment count is limited to how many segments can fit in the
+ * transport header without overflowing the buffer. That's about 40
+ * Read segments for a 1KB inline threshold.
  *
  * Return values:
- *       %true: Read list is valid. @rctxt's xdr_stream is updated
- *		to point to the first byte past the Read list.
- *      %false: Read list is corrupt. @rctxt's xdr_stream is left
- *		in an unknown state.
+ *   %true: Read list is valid. @rctxt's xdr_stream is updated to point
+ *	    to the first byte past the Read list. rc_read_pcl and
+ *	    rc_call_pcl cl_count fields are set to the number of
+ *	    Read segments in the list.
+ *  %false: Read list is corrupt. @rctxt's xdr_stream is left in an
+ *	    unknown state.
  */
-static bool xdr_check_read_list(struct svc_rdma_recv_ctxt *rctxt)
+static bool xdr_count_read_segments(struct svc_rdma_recv_ctxt *rctxt, __be32 *p)
 {
-	u32 position, len;
-	bool first;
-	__be32 *p;
-
-	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
-	if (!p)
-		return false;
-
-	len = 0;
-	first = true;
+	rctxt->rc_call_pcl.cl_count = 0;
+	rctxt->rc_read_pcl.cl_count = 0;
 	while (xdr_item_is_present(p)) {
+		u32 position, handle, length;
+		u64 offset;
+
 		p = xdr_inline_decode(&rctxt->rc_stream,
 				      rpcrdma_readseg_maxsz * sizeof(*p));
 		if (!p)
 			return false;
 
-		if (first) {
-			position = be32_to_cpup(p);
-			first = false;
-		} else if (be32_to_cpup(p) != position) {
-			return false;
+		xdr_decode_read_segment(p, &position, &handle,
+					    &length, &offset);
+		if (position) {
+			if (position & 3)
+				return false;
+			++rctxt->rc_read_pcl.cl_count;
+		} else {
+			++rctxt->rc_call_pcl.cl_count;
 		}
-		p += 2;
-		len += be32_to_cpup(p);
 
 		p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 		if (!p)
 			return false;
 	}
-	return len <= MAX_BYTES_SPECIAL_CHUNK;
+	return true;
 }
 
-/* The segment count is limited to how many segments can
- * fit in the transport header without overflowing the
- * buffer. That's about 60 Write segments for a 1KB inline
- * threshold.
+/* Sanity check the Read list.
+ *
+ * Sanity checks:
+ * - Read list does not overflow Receive buffer.
+ * - Chunk size limited by largest NFS data payload.
+ *
+ * Return values:
+ *   %true: Read list is valid. @rctxt's xdr_stream is updated
+ *	    to point to the first byte past the Read list.
+ *  %false: Read list is corrupt. @rctxt's xdr_stream is left
+ *	    in an unknown state.
  */
-static bool xdr_check_write_chunk(struct svc_rdma_recv_ctxt *rctxt, u32 maxlen)
+static bool xdr_check_read_list(struct svc_rdma_recv_ctxt *rctxt)
 {
-	u32 i, segcount, total;
 	__be32 *p;
 
 	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 	if (!p)
 		return false;
-	segcount = be32_to_cpup(p);
+	if (!xdr_count_read_segments(rctxt, p))
+		return false;
+	if (!pcl_alloc_call(rctxt, p))
+		return false;
+	return pcl_alloc_read(rctxt, p);
+}
 
-	total = 0;
-	for (i = 0; i < segcount; i++) {
-		u32 handle, length;
-		u64 offset;
+static bool xdr_check_write_chunk(struct svc_rdma_recv_ctxt *rctxt)
+{
+	u32 segcount;
+	__be32 *p;
 
-		p = xdr_inline_decode(&rctxt->rc_stream,
-				      rpcrdma_segment_maxsz * sizeof(*p));
-		if (!p)
-			return false;
+	if (xdr_stream_decode_u32(&rctxt->rc_stream, &segcount))
+		return false;
 
-		xdr_decode_rdma_segment(p, &handle, &length, &offset);
-		trace_svcrdma_decode_wseg(handle, length, offset);
+	/* A bogus segcount causes this buffer overflow check to fail. */
+	p = xdr_inline_decode(&rctxt->rc_stream,
+			      segcount * rpcrdma_segment_maxsz * sizeof(*p));
+	return p != NULL;
+}
 
-		total += length;
+/**
+ * xdr_count_write_chunks - Count number of Write chunks in Write list
+ * @rctxt: Received header and decoding state
+ * @p: start of an un-decoded Write list
+ *
+ * Before allocating anything, ensure the ingress Write list is
+ * safe to use.
+ *
+ * Return values:
+ *       %true: Write list is valid. @rctxt's xdr_stream is updated
+ *		to point to the first byte past the Write list, and
+ *		the number of Write chunks is in rc_write_pcl.cl_count.
+ *      %false: Write list is corrupt. @rctxt's xdr_stream is left
+ *		in an indeterminate state.
+ */
+static bool xdr_count_write_chunks(struct svc_rdma_recv_ctxt *rctxt, __be32 *p)
+{
+	rctxt->rc_write_pcl.cl_count = 0;
+	while (xdr_item_is_present(p)) {
+		if (!xdr_check_write_chunk(rctxt))
+			return false;
+		++rctxt->rc_write_pcl.cl_count;
+		p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
+		if (!p)
+			return false;
 	}
-	return total <= maxlen;
+	return true;
 }
 
 /* Sanity check the Write list.
@@ -498,24 +531,22 @@ static bool xdr_check_write_chunk(struct svc_rdma_recv_ctxt *rctxt, u32 maxlen)
  */
 static bool xdr_check_write_list(struct svc_rdma_recv_ctxt *rctxt)
 {
-	u32 chcount = 0;
 	__be32 *p;
 
 	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 	if (!p)
 		return false;
-	rctxt->rc_write_list = p;
-	while (xdr_item_is_present(p)) {
-		if (!xdr_check_write_chunk(rctxt, MAX_BYTES_WRITE_CHUNK))
-			return false;
-		++chcount;
-		p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
-		if (!p)
-			return false;
-	}
-	if (!chcount)
-		rctxt->rc_write_list = NULL;
-	return chcount < 2;
+
+	rctxt->rc_write_list = NULL;
+	if (!xdr_count_write_chunks(rctxt, p))
+		return false;
+	if (!pcl_alloc_write(rctxt, &rctxt->rc_write_pcl, p))
+		return false;
+
+	if (!pcl_is_empty(&rctxt->rc_write_pcl))
+		rctxt->rc_write_list = p;
+	rctxt->rc_cur_result_payload = pcl_first_chunk(&rctxt->rc_write_pcl);
+	return rctxt->rc_write_pcl.cl_count < 2;
 }
 
 /* Sanity check the Reply chunk.
@@ -537,13 +568,16 @@ static bool xdr_check_reply_chunk(struct svc_rdma_recv_ctxt *rctxt)
 	p = xdr_inline_decode(&rctxt->rc_stream, sizeof(*p));
 	if (!p)
 		return false;
+
 	rctxt->rc_reply_chunk = NULL;
-	if (xdr_item_is_present(p)) {
-		if (!xdr_check_write_chunk(rctxt, MAX_BYTES_SPECIAL_CHUNK))
-			return false;
-		rctxt->rc_reply_chunk = p;
-	}
-	return true;
+	if (!xdr_item_is_present(p))
+		return true;
+	if (!xdr_check_write_chunk(rctxt))
+		return false;
+
+	rctxt->rc_reply_chunk = p;
+	rctxt->rc_reply_pcl.cl_count = 1;
+	return pcl_alloc_write(rctxt, &rctxt->rc_reply_pcl, p);
 }
 
 /* RPC-over-RDMA Version One private extension: Remote Invalidation.