linux-kernel - [PATCH 3/4] Drivers: hv: ring_buffer: use wrap around mappings in hv_copy{from,to}

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Date:	Fri, 10 Jun 2016 11:47:11 +0200
From:	Vitaly Kuznetsov <vkuznets@...hat.com>
To:	devel@...uxdriverproject.org
Cc:	linux-kernel@...r.kernel.org,
	"K. Y. Srinivasan" <kys@...rosoft.com>,
	Haiyang Zhang <haiyangz@...rosoft.com>
Subject: [PATCH 3/4] Drivers: hv: ring_buffer: use wrap around mappings in hv_copy{from,to}_ringbuffer()

With wrap around mappings for ring buffers we can always use a single
memcpy() to do the job.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 drivers/hv/ring_buffer.c | 24 +++---------------------
 1 file changed, 3 insertions(+), 21 deletions(-)

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index a84c45a..53e912a 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -164,18 +164,7 @@ static u32 hv_copyfrom_ringbuffer(
 	void *ring_buffer = hv_get_ring_buffer(ring_info);
 	u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
 
-	u32 frag_len;
-
-	/* wrap-around detected at the src */
-	if (destlen > ring_buffer_size - start_read_offset) {
-		frag_len = ring_buffer_size - start_read_offset;
-
-		memcpy(dest, ring_buffer + start_read_offset, frag_len);
-		memcpy(dest + frag_len, ring_buffer, destlen - frag_len);
-	} else
-
-		memcpy(dest, ring_buffer + start_read_offset, destlen);
-
+	memcpy(dest, ring_buffer + start_read_offset, destlen);
 
 	start_read_offset += destlen;
 	start_read_offset %= ring_buffer_size;
@@ -196,15 +185,8 @@ static u32 hv_copyto_ringbuffer(
 {
 	void *ring_buffer = hv_get_ring_buffer(ring_info);
 	u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
-	u32 frag_len;
-
-	/* wrap-around detected! */
-	if (srclen > ring_buffer_size - start_write_offset) {
-		frag_len = ring_buffer_size - start_write_offset;
-		memcpy(ring_buffer + start_write_offset, src, frag_len);
-		memcpy(ring_buffer, src + frag_len, srclen - frag_len);
-	} else
-		memcpy(ring_buffer + start_write_offset, src, srclen);
+
+	memcpy(ring_buffer + start_write_offset, src, srclen);
 
 	start_write_offset += srclen;
 	start_write_offset %= ring_buffer_size;
-- 
2.5.5