Drivers: hv: vmbus: Introduce functions for estimating room in the ring buffer

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index a40a73a..544362c 100644 (file)
--- 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);
 }
 
 /*
@@ -106,9 +102,6 @@ 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;
-       u32 read_loc = rbi->ring_buffer->read_index;
        u32 pending_sz;
 
        /*
@@ -125,14 +118,11 @@ static bool hv_need_to_signal_on_read(struct hv_ring_buffer_info *rbi)
        mb();
 
        pending_sz = rbi->ring_buffer->pending_send_sz;
-       write_loc = rbi->ring_buffer->write_index;
        /* 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;
@@ -332,7 +322,6 @@ 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;
@@ -348,9 +337,7 @@ 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.
@@ -401,7 +388,6 @@ 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;
@@ -417,10 +403,7 @@ 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 aa0fadc..66226ce 100644 (file)
--- 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.