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/channel.c b/drivers/hv/channel.c
index dd6de7f..1161d68 100644 (file)
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -927,37 +927,11 @@ __vmbus_recvpacket(struct vmbus_channel *channel, void *buffer,
                   u32 bufferlen, u32 *buffer_actual_len, u64 *requestid,
                   bool raw)
 {
-       struct vmpacket_descriptor desc;
-       u32 packetlen;
-       u32 userlen;
        int ret;
        bool signal = false;
 
-       *buffer_actual_len = 0;
-       *requestid = 0;
-
-
-       ret = hv_ringbuffer_peek(&channel->inbound, &desc,
-                            sizeof(struct vmpacket_descriptor));
-       if (ret != 0)
-               return 0;
-
-       packetlen = desc.len8 << 3;
-       if (!raw)
-               userlen = packetlen - (desc.offset8 << 3);
-       else
-               userlen = packetlen;
-
-       *buffer_actual_len = userlen;
-
-       if (userlen > bufferlen)
-               return -ENOBUFS;
-
-       *requestid = desc.trans_id;
-
-       /* Copy over the packet to the user buffer */
-       ret = hv_ringbuffer_read(&channel->inbound, buffer, userlen,
-                                raw ? 0 : desc.offset8 << 3, &signal);
+       ret = hv_ringbuffer_read(&channel->inbound, buffer, bufferlen,
+                                buffer_actual_len, requestid, &signal, raw);
 
        if (signal)
                vmbus_setevent(channel);

diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
index 4d67e98..0411b7b 100644 (file)
--- a/drivers/hv/hyperv_vmbus.h
+++ b/drivers/hv/hyperv_vmbus.h
@@ -619,14 +619,9 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *ring_info,
                    struct kvec *kv_list,
                    u32 kv_count, bool *signal);
 
-int hv_ringbuffer_peek(struct hv_ring_buffer_info *ring_info, void *buffer,
-                  u32 buflen);
-
-int hv_ringbuffer_read(struct hv_ring_buffer_info *ring_info,
-                  void *buffer,
-                  u32 buflen,
-                  u32 offset, bool *signal);
-
+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);
 
 void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,
                            struct hv_ring_buffer_debug_info *debug_info);

diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index 07f9408..b53702c 100644 (file)
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -380,30 +380,59 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info,
        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 @@ static inline int __hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,
 
        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 @@ static inline int __hv_ringbuffer_read(struct hv_ring_buffer_info *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);
+       return ret;
 }