[PATCH 9/9] Drivers: hv: ring_buffer: eliminate hv_ringbuffer_peek()
From: K. Y. Srinivasan
Date: Mon Dec 14 2015 - 20:29:03 EST
From: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
---
drivers/hv/channel.c | 30 +-------------------
drivers/hv/hyperv_vmbus.h | 11 ++-----
drivers/hv/ring_buffer.c | 65 +++++++++++++++++++++++++-------------------
3 files changed, 42 insertions(+), 64 deletions(-)
diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index dd6de7f..1161d68 100644
--- 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
--- 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
--- 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;
}
--
1.7.4.1
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