Drivers: hv: ring_buffer: eliminate hv_ringbuffer_peek()
Currently, there is only one user for hv_ringbuffer_read()/
hv_ringbuffer_peak() functions and the usage of these functions is:
- insecure as we drop ring_lock between them, someone else (in theory
only) can acquire it in between;
- non-optimal as we do a number of things (acquire/release the above
mentioned lock, calculate available space on the ring, ...) twice and
this path is performance-critical.
Remove hv_ringbuffer_peek() moving the logic from __vmbus_recvpacket() to
hv_ringbuffer_read().
Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
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 07f9408..b53702c 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -380,30 +380,59 @@
return 0;
}
-static inline int __hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
- void *buffer, u32 buflen, u32 offset,
- bool *signal, bool advance)
+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;
unsigned long flags;
+ struct vmpacket_descriptor desc;
+ u32 offset;
+ u32 packetlen;
+ int ret = 0;
if (buflen <= 0)
return -EINVAL;
spin_lock_irqsave(&inring_info->ring_lock, flags);
+ *buffer_actual_len = 0;
+ *requestid = 0;
+
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);
+ if (bytes_avail_toread < sizeof(desc)) {
+ /*
+ * No error is set when there is even no header, drivers are
+ * supposed to analyze buffer_actual_len.
+ */
+ goto out_unlock;
+ }
- return -EAGAIN;
+ next_read_location = hv_get_next_read_location(inring_info);
+ next_read_location = hv_copyfrom_ringbuffer(inring_info, &desc,
+ sizeof(desc),
+ next_read_location);
+
+ offset = raw ? 0 : (desc.offset8 << 3);
+ packetlen = (desc.len8 << 3) - offset;
+ *buffer_actual_len = packetlen;
+ *requestid = desc.trans_id;
+
+ if (bytes_avail_toread < packetlen + offset) {
+ ret = -EAGAIN;
+ goto out_unlock;
+ }
+
+ if (packetlen > buflen) {
+ ret = -ENOBUFS;
+ goto out_unlock;
}
next_read_location =
@@ -411,12 +440,9 @@
next_read_location = hv_copyfrom_ringbuffer(inring_info,
buffer,
- buflen,
+ packetlen,
next_read_location);
- if (!advance)
- goto out_unlock;
-
next_read_location = hv_copyfrom_ringbuffer(inring_info,
&prev_indices,
sizeof(u64),
@@ -436,22 +462,5 @@
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);
+ return ret;
}