[pnfs] [PATCH 06/10] nfs41: New backchannel_rqst.c file.

[Ricardo Labiaga]

This file contains the code to setup the callback xprt on the client side.
It allocates/ destroys the preallocated memory structures used to process
backchannel requests.  Since callbacks are not expected to cause significant
latency, only one callback is handled at a time.

Signed-off-by: Ricardo Labiaga <ricardo.labiaga at netapp.com>
---
 net/sunrpc/backchannel_rqst.c |  133 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 133 insertions(+), 0 deletions(-)
 create mode 100644 net/sunrpc/backchannel_rqst.c

diff --git a/net/sunrpc/backchannel_rqst.c b/net/sunrpc/backchannel_rqst.c
new file mode 100644
index 0000000..5eff7a2
--- /dev/null
+++ b/net/sunrpc/backchannel_rqst.c
@@ -0,0 +1,133 @@
+/*
+ * This file is distributed under GPL. Please see Documentation/COPYING for
+ * details.
+ *
+ * Author: Rahul Iyer <iyer at netapp.com>
+ * 	   Ricardo Labiaga <ricardo.labiaga at netapp.com>
+ */
+
+#include <linux/tcp.h>
+#include <linux/sunrpc/xprt.h>
+
+#ifdef RPC_DEBUG
+# undef  RPC_DEBUG_DATA
+# define RPCDBG_FACILITY	RPCDBG_TRANS
+#endif
+
+#if defined(CONFIG_NFS_V4_1)
+
+int xprt_setup_backchannel(struct rpc_xprt *xprt, unsigned int min_reqs)
+{
+	struct page *page_priv = NULL, *page_snd = NULL;
+	struct xdr_buf *xbufp = NULL;
+
+	BUG_ON(min_reqs > 1);	/* We only prealloate buffers for one slot */
+	dprintk("RPC:        setup backchannel transport\n");
+
+	/* Pre-allocate one backchannel rpc_rqst */
+	xprt->bc_rpc_rqst = kmalloc(sizeof(struct rpc_rqst), GFP_KERNEL);
+	if (xprt->bc_rpc_rqst == NULL) {
+		printk(KERN_ERR "Failed to create backchannel rpc_rqst\n");
+		goto out_free;
+	}
+	xprt->bc_rpc_rqst->rq_xprt = xprt;
+
+	/* Preallocate one XDR private buffer */
+	page_priv = alloc_page(GFP_KERNEL);
+	if (page_priv == NULL) {
+		printk(KERN_ERR "Failed to create backchannel priv xbuf\n");
+		goto out_free;
+	}
+	xbufp = &xprt->bc_rpc_rqst->rq_private_buf;
+	xbufp->head[0].iov_base = page_address(page_priv);
+	xbufp->head[0].iov_len = PAGE_SIZE;
+	xbufp->tail[0].iov_len = 0;
+	xbufp->page_len = 0;
+	xbufp->len = PAGE_SIZE;
+	xbufp->buflen = PAGE_SIZE;
+
+	/* Preallocate one XDR send buffer */
+	page_snd = alloc_page(GFP_KERNEL);
+	if (page_snd == NULL) {
+		printk(KERN_ERR "Failed to create backchannel snd xbuf\n");
+		goto out_free;
+	}
+
+	xbufp = &xprt->bc_rpc_rqst->rq_snd_buf;
+	xbufp->head[0].iov_base = page_address(page_snd);
+	xbufp->head[0].iov_len = 0;
+	xbufp->tail[0].iov_len = 0;
+	xbufp->page_len = 0;
+	xbufp->len = 0;
+	xbufp->buflen = PAGE_SIZE;
+
+	dprintk("RPC:        setup backchannel transport done\n");
+	return 0;
+
+out_free:
+	kfree(page_snd);
+	kfree(page_priv);
+	kfree(xprt->bc_rpc_rqst);
+
+	dprintk("RPC:        setup backchannel transport failed\n");
+	return -1;
+}
+EXPORT_SYMBOL(xprt_setup_backchannel);
+
+void xprt_destroy_backchannel(struct rpc_xprt *xprt)
+{
+	struct rpc_rqst *req = xprt->bc_rpc_rqst;
+	struct xdr_buf *xbufp;
+
+	dprintk("RPC:        destroy backchannel transport\n");
+	/*
+	 * Any of these can be NULL if the user hit ^C
+	 */
+	if (req == NULL)
+		return;		/* Nothing to do */
+	xbufp = &req->rq_private_buf;
+	if (xbufp)
+		kfree(xbufp->head[0].iov_base);
+	xbufp = &req->rq_snd_buf;
+	if (xbufp)
+		kfree(xbufp->head[0].iov_base);
+	kfree(xprt->bc_rpc_rqst);
+}
+EXPORT_SYMBOL(xprt_destroy_backchannel);
+
+/*
+ * A single rpc_rqst structure has been preallocated during the backchannel
+ * setup.  Buffer space for the send and private XDR buffers has been
+ * preallocated as well.  Use xprt_alloc_bc_request to allocate this
+ * space for this request.  Use xprt_free_bc_request to return it.
+ *
+ * Returns the rpc_rqst if it's not in use, otherwise NULL.
+ */
+struct rpc_rqst *xprt_alloc_bc_request(struct rpc_xprt *xprt)
+{
+	struct rpc_rqst *req;
+
+	dprintk("RPC:        allocate a backchannel request\n");
+	req = test_and_set_bit(RPC_BC_PREALLOC_IN_USE, &xprt->bc_flags) ?
+		NULL : xprt->bc_rpc_rqst;
+
+	dprintk("RPC:        backchannel req=%p\n", req);
+	return req;
+}
+
+/*
+ * Return the preallocated rpc_rqst structure and XDR buffers
+ */
+void xprt_free_bc_request(struct rpc_rqst *req)
+{
+	struct rpc_xprt *xprt = req->rq_xprt;
+	dprintk("RPC:        free backchannel req=%p\n", req);
+
+	smp_mb__before_clear_bit();
+	clear_bit(RPC_BC_PREALLOC_IN_USE, &xprt->bc_flags);
+	smp_mb__after_clear_bit();
+
+}
+EXPORT_SYMBOL(xprt_free_bc_request);
+
+#endif /* CONFIG_NFS_V4_1 */
-- 
1.5.3.3