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Groups > linux.kernel > #1363779

[PATCH 1/7] Drivers: hv: vmbus: Introduce functions for estimating room in the ring buffer

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Introduce separate functions for estimating how much can be read from
and written to the ring buffer.

Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
---
 drivers/hv/ring_buffer.c |   24 ++++--------------------
 include/linux/hyperv.h   |   27 +++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 20 deletions(-)

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 085003a..902375b 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -38,8 +38,6 @@ void hv_begin_read(struct hv_ring_buffer_info *rbi)
 
 u32 hv_end_read(struct hv_ring_buffer_info *rbi)
 {
-	u32 read;
-	u32 write;
 
 	rbi->ring_buffer->interrupt_mask = 0;
 	mb();
@@ -49,9 +47,7 @@ u32 hv_end_read(struct hv_ring_buffer_info *rbi)
 	 * If it is not, we raced and we need to process new
 	 * incoming messages.
 	 */
-	hv_get_ringbuffer_availbytes(rbi, &read, &write);
-
-	return read;
+	return hv_get_bytes_to_read(rbi);
 }
 
 /*
@@ -106,18 +102,13 @@ static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi)
 static bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
 {
 	u32 cur_write_sz;
-	u32 r_size;
-	u32 write_loc = rbi->ring_buffer->write_index;
-	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 (pending_sz == 0)
 		return false;
 
-	r_size = rbi->ring_datasize;
-	cur_write_sz = write_loc >= read_loc ? r_size - (write_loc - read_loc) :
-			read_loc - write_loc;
+	cur_write_sz = hv_get_bytes_to_write(rbi);
 
 	if (cur_write_sz >= pending_sz)
 		return true;
@@ -317,7 +308,6 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 {
 	int i = 0;
 	u32 bytes_avail_towrite;
-	u32 bytes_avail_toread;
 	u32 totalbytes_towrite = 0;
 
 	u32 next_write_location;
@@ -333,9 +323,7 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
 	if (lock)
 		spin_lock_irqsave(&outring_info->ring_lock, flags);
 
-	hv_get_ringbuffer_availbytes(outring_info,
-				&bytes_avail_toread,
-				&bytes_avail_towrite);
+	bytes_avail_towrite = hv_get_bytes_to_write(outring_info);
 
 	/*
 	 * If there is only room for the packet, assume it is full.
@@ -386,7 +374,6 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 		       void *buffer, u32 buflen, u32 *buffer_actual_len,
 		       u64 *requestid, bool *signal, bool raw)
 {
-	u32 bytes_avail_towrite;
 	u32 bytes_avail_toread;
 	u32 next_read_location = 0;
 	u64 prev_indices = 0;
@@ -402,10 +389,7 @@ int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 	*buffer_actual_len = 0;
 	*requestid = 0;
 
-	hv_get_ringbuffer_availbytes(inring_info,
-				&bytes_avail_toread,
-				&bytes_avail_towrite);
-
+	bytes_avail_toread = hv_get_bytes_to_read(inring_info);
 	/* Make sure there is something to read */
 	if (bytes_avail_toread < sizeof(desc)) {
 		/*
diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h
index ecd81c3..a6b053c 100644
--- a/include/linux/hyperv.h
+++ b/include/linux/hyperv.h
@@ -151,6 +151,33 @@ hv_get_ringbuffer_availbytes(struct hv_ring_buffer_info *rbi,
 	*read = dsize - *write;
 }
 
+static inline u32 hv_get_bytes_to_read(struct hv_ring_buffer_info *rbi)
+{
+	u32 read_loc, write_loc, dsize, read;
+
+	dsize = rbi->ring_datasize;
+	read_loc = rbi->ring_buffer->read_index;
+	write_loc = READ_ONCE(rbi->ring_buffer->write_index);
+
+	read = write_loc >= read_loc ? (write_loc - read_loc) :
+		(dsize - read_loc) + write_loc;
+
+	return read;
+}
+
+static inline u32 hv_get_bytes_to_write(struct hv_ring_buffer_info *rbi)
+{
+	u32 read_loc, write_loc, dsize, write;
+
+	dsize = rbi->ring_datasize;
+	read_loc = READ_ONCE(rbi->ring_buffer->read_index);
+	write_loc = rbi->ring_buffer->write_index;
+
+	write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
+		read_loc - write_loc;
+	return write;
+}
+
 /*
  * VMBUS version is 32 bit entity broken up into
  * two 16 bit quantities: major_number. minor_number.
-- 
1.7.4.1

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[PATCH 1/7] Drivers: hv: vmbus: Introduce functions for estimating room in the ring buffer "K. Y. Srinivasan" <kys@microsoft.com> - 2016-03-24 00:20 +0100
  [PATCH 5/7] Drivers: hv: vmbus: Export the vmbus_set_event() API "K. Y. Srinivasan" <kys@microsoft.com> - 2016-03-24 00:20 +0100
  [PATCH 6/7] Drivers: hv: vmbus: Move some ring buffer functions to hyperv.h "K. Y. Srinivasan" <kys@microsoft.com> - 2016-03-24 00:20 +0100
  [PATCH 3/7] Drivers: hv: vmbus: Fix a bug in hv_need_to_signal_on_read() "K. Y. Srinivasan" <kys@microsoft.com> - 2016-03-24 00:20 +0100
    Re: [PATCH 3/7] Drivers: hv: vmbus: Fix a bug in  hv_need_to_signal_on_read() Greg KH <gregkh@linuxfoundation.org> - 2016-04-01 02:00 +0200
      RE: [PATCH 3/7] Drivers: hv: vmbus: Fix a bug in  hv_need_to_signal_on_read() KY Srinivasan <kys@microsoft.com> - 2016-04-01 23:10 +0200
    Re: [PATCH 3/7] Drivers: hv: vmbus: Fix a bug in  hv_need_to_signal_on_read() Greg KH <gregkh@linuxfoundation.org> - 2016-04-01 02:10 +0200
      RE: [PATCH 3/7] Drivers: hv: vmbus: Fix a bug in  hv_need_to_signal_on_read() KY Srinivasan <kys@microsoft.com> - 2016-04-02 00:00 +0200
  [PATCH 7/7] Drivers: hv: vmbus: Implement APIs to support "in place" consumption of vmbus packets "K. Y. Srinivasan" <kys@microsoft.com> - 2016-03-24 00:20 +0100

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