commit 011a7c3cc3aa60c7ea6bb49d847e80a299ba7b36
author K. Y. Srinivasan <kys@microsoft.com> Sat Feb 01 19:02:20 2014 -0800
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> Fri Feb 07 15:22:40 2014 -0800
tree 97dc47f7d4d372b76ccefc50582e2abcf9489d21
parent 90f3453585479d5beb75058da46eb573ced0e6ac

Drivers: hv: vmbus: Cleanup the packet send path

The current channel code is using scatterlist abstraction to pass data to the
ringbuffer API on the send path. This causes unnecessary translations
between virtual and physical addresses. Fix this.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/hv/channel.c

diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 69ea36f..602ca86 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -27,6 +27,7 @@
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/hyperv.h>
+#include <linux/uio.h>
 
 #include "hyperv_vmbus.h"
 
@@ -554,14 +555,14 @@
  *
  * Mainly used by Hyper-V drivers.
  */
-int vmbus_sendpacket(struct vmbus_channel *channel, const void *buffer,
+int vmbus_sendpacket(struct vmbus_channel *channel, void *buffer,
 			   u32 bufferlen, u64 requestid,
 			   enum vmbus_packet_type type, u32 flags)
 {
 	struct vmpacket_descriptor desc;
 	u32 packetlen = sizeof(struct vmpacket_descriptor) + bufferlen;
 	u32 packetlen_aligned = ALIGN(packetlen, sizeof(u64));
-	struct scatterlist bufferlist[3];
+	struct kvec bufferlist[3];
 	u64 aligned_data = 0;
 	int ret;
 	bool signal = false;
@@ -575,11 +576,12 @@
 	desc.len8 = (u16)(packetlen_aligned >> 3);
 	desc.trans_id = requestid;
 
-	sg_init_table(bufferlist, 3);
-	sg_set_buf(&bufferlist[0], &desc, sizeof(struct vmpacket_descriptor));
-	sg_set_buf(&bufferlist[1], buffer, bufferlen);
-	sg_set_buf(&bufferlist[2], &aligned_data,
-		   packetlen_aligned - packetlen);
+	bufferlist[0].iov_base = &desc;
+	bufferlist[0].iov_len = sizeof(struct vmpacket_descriptor);
+	bufferlist[1].iov_base = buffer;
+	bufferlist[1].iov_len = bufferlen;
+	bufferlist[2].iov_base = &aligned_data;
+	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
 	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);
 
@@ -605,7 +607,7 @@
 	u32 descsize;
 	u32 packetlen;
 	u32 packetlen_aligned;
-	struct scatterlist bufferlist[3];
+	struct kvec bufferlist[3];
 	u64 aligned_data = 0;
 	bool signal = false;
 
@@ -637,11 +639,12 @@
 		desc.range[i].pfn	 = pagebuffers[i].pfn;
 	}
 
-	sg_init_table(bufferlist, 3);
-	sg_set_buf(&bufferlist[0], &desc, descsize);
-	sg_set_buf(&bufferlist[1], buffer, bufferlen);
-	sg_set_buf(&bufferlist[2], &aligned_data,
-		packetlen_aligned - packetlen);
+	bufferlist[0].iov_base = &desc;
+	bufferlist[0].iov_len = descsize;
+	bufferlist[1].iov_base = buffer;
+	bufferlist[1].iov_len = bufferlen;
+	bufferlist[2].iov_base = &aligned_data;
+	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
 	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);
 
@@ -665,7 +668,7 @@
 	u32 descsize;
 	u32 packetlen;
 	u32 packetlen_aligned;
-	struct scatterlist bufferlist[3];
+	struct kvec bufferlist[3];
 	u64 aligned_data = 0;
 	bool signal = false;
 	u32 pfncount = NUM_PAGES_SPANNED(multi_pagebuffer->offset,
@@ -700,11 +703,12 @@
 	memcpy(desc.range.pfn_array, multi_pagebuffer->pfn_array,
 	       pfncount * sizeof(u64));
 
-	sg_init_table(bufferlist, 3);
-	sg_set_buf(&bufferlist[0], &desc, descsize);
-	sg_set_buf(&bufferlist[1], buffer, bufferlen);
-	sg_set_buf(&bufferlist[2], &aligned_data,
-		packetlen_aligned - packetlen);
+	bufferlist[0].iov_base = &desc;
+	bufferlist[0].iov_len = descsize;
+	bufferlist[1].iov_base = buffer;
+	bufferlist[1].iov_len = bufferlen;
+	bufferlist[2].iov_base = &aligned_data;
+	bufferlist[2].iov_len = (packetlen_aligned - packetlen);
 
 	ret = hv_ringbuffer_write(&channel->outbound, bufferlist, 3, &signal);