[RFC] [PATCH 1/7] [net/9p] Additional elements to p9_fcall to accomodate zero copy.

["Venkateswararao Jujjuri (JV)" <jvrao@linux.vnet.ibm.com>]

Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
---
 net/9p/Makefile       |    1 +
 net/9p/trans_common.c |   88 +++++++++++++++++++++++++++++++++++++++++++++++++
 net/9p/trans_common.h |   26 ++++++++++++++
 3 files changed, 115 insertions(+), 0 deletions(-)
 create mode 100644 net/9p/trans_common.c
 create mode 100644 net/9p/trans_common.h

diff --git a/net/9p/Makefile b/net/9p/Makefile
index 198a640..a0874cc 100644
--- a/net/9p/Makefile
+++ b/net/9p/Makefile
@@ -9,6 +9,7 @@ obj-$(CONFIG_NET_9P_RDMA) += 9pnet_rdma.o
 	util.o \
 	protocol.o \
 	trans_fd.o \
+	trans_common.o \
 
 9pnet_virtio-objs := \
 	trans_virtio.o \
diff --git a/net/9p/trans_common.c b/net/9p/trans_common.c
new file mode 100644
index 0000000..dad57d2
--- /dev/null
+++ b/net/9p/trans_common.c
@@ -0,0 +1,88 @@
+/*
+ * Copyright IBM Corporation, 2010
+ * Author Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ */
+
+#include <linux/slab.h>
+#include <net/9p/9p.h>
+#include <net/9p/client.h>
+#include <linux/scatterlist.h>
+#include "trans_common.h"
+
+/**
+ *  p9_release_req_pages - Release pages after the transaction.
+ *  @*private: PDU's private page of type virtio_rpage_info_t
+ */
+void
+p9_release_req_pages(void *private)
+{
+	virtio_rpage_info_t *vpinfo = private;
+	int i = 0;
+
+	while (vpinfo->vp_data[i] && vpinfo->vp_nr_pages--) {
+		put_page(vpinfo->vp_data[i]);
+		i++;
+	}
+}
+
+/**
+ * payload_gup - Calculates number of pages that needs to be pinned and
+ * pins them ehter for read/write through get_user_pages_fast().
+ */
+int
+payload_gup(struct p9_req_t *req, size_t *pdata_off, int *pdata_len, u8 rw)
+{
+	int nr_pages;
+	uint32_t first_page_bytes = 0;
+	uint32_t pdata_mapped_pages;
+	virtio_rpage_info_t  *rpinfo;
+
+	nr_pages = req->tc->pbuf_size >> PAGE_SHIFT;
+	*pdata_off = (size_t)req->tc->pbuf & (PAGE_SIZE-1);
+
+	if (*pdata_off)
+		first_page_bytes = min((PAGE_SIZE - *pdata_off),
+				req->tc->pbuf_size);
+
+	if (req->tc->pbuf_size - (first_page_bytes + (nr_pages << PAGE_SHIFT))){
+		/* trailing partial page */
+		nr_pages++;
+	}       
+	if (first_page_bytes) {
+		/* leading partial page */
+		nr_pages++;
+	}
+	/* TODO: Use buffer on PDU instead of allocating */
+	rpinfo = kmalloc(sizeof(virtio_rpage_info_t) +
+			sizeof(struct page *) * nr_pages, GFP_KERNEL);
+	req->tc->private = (void *)rpinfo;
+	pdata_mapped_pages = get_user_pages_fast((unsigned long)req->tc->pbuf,
+			nr_pages, rw, &rpinfo->vp_data[0]);
+
+	if (pdata_mapped_pages < 0) {
+		printk("get_user_pages_fast failed:%d udata:%p" "nr_pages:%d\n",
+				pdata_mapped_pages, req->tc->pbuf, nr_pages);
+		pdata_mapped_pages = 0;
+		kfree(rpinfo);
+		return -EIO;
+	}
+	rpinfo->vp_nr_pages = pdata_mapped_pages;
+	if (*pdata_off) {
+		*pdata_len = first_page_bytes;
+		*pdata_len += min((req->tc->pbuf_size - *pdata_len),
+				((size_t)pdata_mapped_pages - 1) << PAGE_SHIFT);
+	} else {
+		*pdata_len = min (req->tc->pbuf_size,
+				(size_t)pdata_mapped_pages << PAGE_SHIFT);
+	}
+	return 0;
+}
diff --git a/net/9p/trans_common.h b/net/9p/trans_common.h
new file mode 100644
index 0000000..8c85392
--- /dev/null
+++ b/net/9p/trans_common.h
@@ -0,0 +1,26 @@
+/*
+ * Copyright IBM Corporation, 2010
+ * Author Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2.1 of the GNU Lesser General Public License
+ * as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ */
+
+/**
+ * struct virtio_rpage_info - To store mapped page information in PDU.
+ * @vp_nr_pages: Number of mapped pages
+ * @vp_data: Array of page pointers
+ */
+typedef struct virtio_rpage_info {
+       int vp_nr_pages;
+       struct page *vp_data[0];
+} virtio_rpage_info_t;
+
+void p9_release_req_pages(void *);
+int payload_gup(struct p9_req_t *, size_t *, int *, u8);
-- 
1.6.5.2