[PATCH 0/3] Drivers: hv: ring_buffer: do some code cleanup

[PATCH 0/3] Drivers: hv: ring_buffer: do some code cleanup

[Vitaly Kuznetsov]

1) Fix comment style in ring_buffer.c
2) Remove unneeded smp_read_barrier_depends() from hyperv.h
3) Unify hv_ringbuffer_peek/read() functions.

Vitaly Kuznetsov (3):
  Drivers: hv: ring_buffer.c: fix comment style
  Drivers: hv: ring_buffer: remove stray smp_read_barrier_depends()
  Drivers: hv: ring_buffer: remove code duplication from
    hv_ringbuffer_peek/read()

 drivers/hv/ring_buffer.c | 199 ++++++++++++-----------------------------------
 include/linux/hyperv.h   |   2 -
 2 files changed, 49 insertions(+), 152 deletions(-)

-- 
2.4.3

[PATCH 1/3] Drivers: hv: ring_buffer.c: fix comment style

[Vitaly Kuznetsov]

Convert 6+-string comments repeating function names to normal kernel-style
comments and fix a couple of other comment style issues. No textual or
functional changes intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/hv/ring_buffer.c | 135 +++++++++--------------------------------------
 1 file changed, 26 insertions(+), 109 deletions(-)

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 70a1a9a..7bca513 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -112,9 +112,7 @@ static bool hv_need_to_signal_on_read(u32 prev_write_sz,
 	u32 read_loc = rbi->ring_buffer->read_index;
 	u32 pending_sz = rbi->ring_buffer->pending_send_sz;
 
-	/*
-	 * If the other end is not blocked on write don't bother.
-	 */
+	/* If the other end is not blocked on write don't bother. */
 	if (pending_sz == 0)
 		return false;
 
@@ -128,12 +126,7 @@ static bool hv_need_to_signal_on_read(u32 prev_write_sz,
 	return false;
 }
 
-/*
- * hv_get_next_write_location()
- *
- * Get the next write location for the specified ring buffer
- *
- */
+/* Get the next write location for the specified ring buffer. */
 static inline u32
 hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
 {
@@ -142,12 +135,7 @@ hv_get_next_write_location(struct hv_ring_buffer_info *ring_info)
 	return next;
 }
 
-/*
- * hv_set_next_write_location()
- *
- * Set the next write location for the specified ring buffer
- *
- */
+/* Set the next write location for the specified ring buffer. */
 static inline void
 hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
 		     u32 next_write_location)
@@ -155,11 +143,7 @@ hv_set_next_write_location(struct hv_ring_buffer_info *ring_info,
 	ring_info->ring_buffer->write_index = next_write_location;
 }
 
-/*
- * hv_get_next_read_location()
- *
- * Get the next read location for the specified ring buffer
- */
+/* Get the next read location for the specified ring buffer. */
 static inline u32
 hv_get_next_read_location(struct hv_ring_buffer_info *ring_info)
 {
@@ -169,10 +153,8 @@ hv_get_next_read_location(struct hv_ring_buffer_info *ring_info)
 }
 
 /*
- * hv_get_next_readlocation_withoffset()
- *
  * Get the next read location + offset for the specified ring buffer.
- * This allows the caller to skip
+ * This allows the caller to skip.
  */
 static inline u32
 hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info,
@@ -186,13 +168,7 @@ hv_get_next_readlocation_withoffset(struct hv_ring_buffer_info *ring_info,
 	return next;
 }
 
-/*
- *
- * hv_set_next_read_location()
- *
- * Set the next read location for the specified ring buffer
- *
- */
+/* Set the next read location for the specified ring buffer. */
 static inline void
 hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
 		    u32 next_read_location)
@@ -201,12 +177,7 @@ hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
 }
 
 
-/*
- *
- * hv_get_ring_buffer()
- *
- * Get the start of the ring buffer
- */
+/* Get the start of the ring buffer. */
 static inline void *
 hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info)
 {
@@ -214,25 +185,14 @@ hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info)
 }
 
 
-/*
- *
- * hv_get_ring_buffersize()
- *
- * Get the size of the ring buffer
- */
+/* Get the size of the ring buffer. */
 static inline u32
 hv_get_ring_buffersize(struct hv_ring_buffer_info *ring_info)
 {
 	return ring_info->ring_datasize;
 }
 
-/*
- *
- * hv_get_ring_bufferindices()
- *
- * Get the read and write indices as u64 of the specified ring buffer
- *
- */
+/* Get the read and write indices as u64 of the specified ring buffer. */
 static inline u64
 hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
 {
@@ -240,12 +200,8 @@ hv_get_ring_bufferindices(struct hv_ring_buffer_info *ring_info)
 }
 
 /*
- *
- * hv_copyfrom_ringbuffer()
- *
  * Helper routine to copy to source from ring buffer.
  * Assume there is enough room. Handles wrap-around in src case only!!
- *
  */
 static u32 hv_copyfrom_ringbuffer(
 	struct hv_ring_buffer_info	*ring_info,
@@ -277,12 +233,8 @@ static u32 hv_copyfrom_ringbuffer(
 
 
 /*
- *
- * hv_copyto_ringbuffer()
- *
  * Helper routine to copy from source to ring buffer.
  * Assume there is enough room. Handles wrap-around in dest case only!!
- *
  */
 static u32 hv_copyto_ringbuffer(
 	struct hv_ring_buffer_info	*ring_info,
@@ -308,13 +260,7 @@ static u32 hv_copyto_ringbuffer(
 	return start_write_offset;
 }
 
-/*
- *
- * hv_ringbuffer_get_debuginfo()
- *
- * Get various debug metrics for the specified ring buffer
- *
- */
+/* Get various debug metrics for the specified ring buffer. */
 void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
 			    struct hv_ring_buffer_debug_info *debug_info)
 {
@@ -337,13 +283,7 @@ void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
 	}
 }
 
-/*
- *
- * hv_ringbuffer_init()
- *
- *Initialize the ring buffer
- *
- */
+/* Initialize the ring buffer. */
 int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 		   void *buffer, u32 buflen)
 {
@@ -356,9 +296,7 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 	ring_info->ring_buffer->read_index =
 		ring_info->ring_buffer->write_index = 0;
 
-	/*
-	 * Set the feature bit for enabling flow control.
-	 */
+	/* Set the feature bit for enabling flow control. */
 	ring_info->ring_buffer->feature_bits.value = 1;
 
 	ring_info->ring_size = buflen;
@@ -369,24 +307,12 @@ int hv_ringbuffer_init(struct hv_ring_buffer_info *ring_info,
 	return 0;
 }
 
-/*
- *
- * hv_ringbuffer_cleanup()
- *
- * Cleanup the ring buffer
- *
- */
+/* Cleanup the ring buffer. */
 void hv_ringbuffer_cleanup(struct hv_ring_buffer_info *ring_info)
 {
 }
 
-/*
- *
- * hv_ringbuffer_write()
- *
- * Write to the ring buffer
- *
- */
+/* Write to the ring buffer. */
 int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 		    struct kvec *kv_list, u32 kv_count, bool *signal)
 {
@@ -411,10 +337,11 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 				&bytes_avail_toread,
 				&bytes_avail_towrite);
 
-
-	/* If there is only room for the packet, assume it is full. */
-	/* Otherwise, the next time around, we think the ring buffer */
-	/* is empty since the read index == write index */
+	/*
+	 * If there is only room for the packet, assume it is full.
+	 * Otherwise, the next time around, we think the ring buffer
+	 * is empty since the read index == write index.
+	 */
 	if (bytes_avail_towrite <= totalbytes_towrite) {
 		spin_unlock_irqrestore(&outring_info->ring_lock, flags);
 		return -EAGAIN;
@@ -454,13 +381,7 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 }
 
 
-/*
- *
- * hv_ringbuffer_peek()
- *
- * Read without advancing the read index
- *
- */
+/* Read without advancing the read index. */
 int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info,
 		   void *Buffer, u32 buflen)
 {
@@ -497,13 +418,7 @@ int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info,
 }
 
 
-/*
- *
- * hv_ringbuffer_read()
- *
- * Read and advance the read index
- *
- */
+/* Read and advance the read index. */
 int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
 		   u32 buflen, u32 offset, bool *signal)
 {
@@ -542,9 +457,11 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
 						sizeof(u64),
 						next_read_location);
 
-	/* Make sure all reads are done before we update the read index since */
-	/* the writer may start writing to the read area once the read index */
-	/*is updated */
+	/*
+	 * Make sure all reads are done before we update the read index since
+	 * the writer may start writing to the read area once the read index
+	 * is updated.
+	 */
 	mb();
 
 	/* Update the read index */
-- 
2.4.3

[PATCH 2/3] Drivers: hv: ring_buffer: remove stray smp_read_barrier_depends()

[Vitaly Kuznetsov]

smp_read_barrier_depends() does nothing on almost all arcitectures
including x86 and having it in the beginning of
hv_get_ringbuffer_availbytes() does not provide any guarantees anyway.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 include/linux/hyperv.h | 2 --
 1 file changed, 2 deletions(-)

diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index 8fdc17b..1777dc8 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -141,8 +141,6 @@ hv_get_ringbuffer_availbytes(struct hv_ring_buffer_info *rbi,
 {
 	u32 read_loc, write_loc, dsize;
 
-	smp_read_barrier_depends();
-
 	/* Capture the read/write indices before they changed */
 	read_loc = rbi->ring_buffer->read_index;
 	write_loc = rbi->ring_buffer->write_index;
-- 
2.4.3

[PATCH 3/3] Drivers: hv: ring_buffer: remove code duplication from hv_ringbuffer_peek/read()

[Vitaly Kuznetsov]

hv_ringbuffer_peek() does the same as hv_ringbuffer_read() without
advancing the read index. The only functional change this patch brings
is moving hv_need_to_signal_on_read() call under the ring_lock but this
function is just a couple of comparisons.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 drivers/hv/ring_buffer.c | 68 ++++++++++++++++++------------------------------
 1 file changed, 25 insertions(+), 43 deletions(-)

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 7bca513..07f9408 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -380,47 +380,9 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 	return 0;
 }
 
-
-/* Read without advancing the read index. */
-int hv_ringbuffer_peek(struct hv_ring_buffer_info *Inring_info,
-		   void *Buffer, u32 buflen)
-{
-	u32 bytes_avail_towrite;
-	u32 bytes_avail_toread;
-	u32 next_read_location = 0;
-	unsigned long flags;
-
-	spin_lock_irqsave(&Inring_info->ring_lock, flags);
-
-	hv_get_ringbuffer_availbytes(Inring_info,
-				&bytes_avail_toread,
-				&bytes_avail_towrite);
-
-	/* Make sure there is something to read */
-	if (bytes_avail_toread < buflen) {
-
-		spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
-
-		return -EAGAIN;
-	}
-
-	/* Convert to byte offset */
-	next_read_location = hv_get_next_read_location(Inring_info);
-
-	next_read_location = hv_copyfrom_ringbuffer(Inring_info,
-						Buffer,
-						buflen,
-						next_read_location);
-
-	spin_unlock_irqrestore(&Inring_info->ring_lock, flags);
-
-	return 0;
-}
-
-
-/* Read and advance the read index. */
-int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
-		   u32 buflen, u32 offset, bool *signal)
+static inline int __hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
+				       void *buffer, u32 buflen, u32 offset,
+				       bool *signal, bool advance)
 {
 	u32 bytes_avail_towrite;
 	u32 bytes_avail_toread;
@@ -452,6 +414,9 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
 						buflen,
 						next_read_location);
 
+	if (!advance)
+		goto out_unlock;
+
 	next_read_location = hv_copyfrom_ringbuffer(inring_info,
 						&prev_indices,
 						sizeof(u64),
@@ -467,9 +432,26 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, void *buffer,
 	/* Update the read index */
 	hv_set_next_read_location(inring_info, next_read_location);
 
-	spin_unlock_irqrestore(&inring_info->ring_lock, flags);
-
 	*signal = hv_need_to_signal_on_read(bytes_avail_towrite, inring_info);
 
+out_unlock:
+	spin_unlock_irqrestore(&inring_info->ring_lock, flags);
 	return 0;
 }
+
+/* Read from ring buffer without advancing the read index. */
+int hv_ringbuffer_peek(struct hv_ring_buffer_info *inring_info,
+		       void *buffer, u32 buflen)
+{
+	return __hv_ringbuffer_read(inring_info, buffer, buflen,
+				    0, NULL, false);
+}
+
+/* Read from ring buffer and advance the read index. */
+int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
+		       void *buffer, u32 buflen, u32 offset,
+		       bool *signal)
+{
+	return __hv_ringbuffer_read(inring_info, buffer, buflen,
+				    offset, signal, true);
+}
-- 
2.4.3