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Commit 940b68e2 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Greg Kroah-Hartman
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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: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarK. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 667d3740

drivers/hv/channel.c

+2 −28
Original line number Original line Diff line number Diff line
@@ -927,37 +927,11 @@ __vmbus_recvpacket(struct vmbus_channel *channel, void *buffer, 
		   u32 bufferlen, u32 *buffer_actual_len, u64 *requestid,

		   u32 bufferlen, u32 *buffer_actual_len, u64 *requestid,

		   bool raw)

		   bool raw)

{

{

	struct vmpacket_descriptor desc;

	u32 packetlen;

	u32 userlen;

	int ret;

	int ret;

	bool signal = false;

	bool signal = false;





	*buffer_actual_len = 0;

	ret = hv_ringbuffer_read(&channel->inbound, buffer, bufferlen,

	*requestid = 0;

				 buffer_actual_len, requestid, &signal, raw);





	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);





	if (signal)

	if (signal)

		vmbus_setevent(channel);

		vmbus_setevent(channel);

drivers/hv/hyperv_vmbus.h

+3 −8
Original line number Original line Diff line number Diff line
@@ -619,14 +619,9 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *ring_info, 
		    struct kvec *kv_list,

		    struct kvec *kv_list,

		    u32 kv_count, bool *signal);

		    u32 kv_count, bool *signal);





int hv_ringbuffer_peek(struct hv_ring_buffer_info *ring_info, void *buffer,

int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,

		   u32 buflen);

		       void *buffer, u32 buflen, u32 *buffer_actual_len,



		       u64 *requestid, bool *signal, bool raw);

int hv_ringbuffer_read(struct hv_ring_buffer_info *ring_info,

		   void *buffer,

		   u32 buflen,

		   u32 offset, bool *signal);







void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,

void hv_ringbuffer_get_debuginfo(struct hv_ring_buffer_info *ring_info,

			    struct hv_ring_buffer_debug_info *debug_info);

			    struct hv_ring_buffer_debug_info *debug_info);

drivers/hv/ring_buffer.c

+37 −28
Original line number Original line Diff line number Diff line
@@ -380,30 +380,59 @@ int hv_ringbuffer_write(struct hv_ring_buffer_info *outring_info, 
	return 0;

	return 0;

}

}





static inline int __hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,

int hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info,

				       void *buffer, u32 buflen, u32 offset,

		       void *buffer, u32 buflen, u32 *buffer_actual_len,

				       bool *signal, bool advance)

		       u64 *requestid, bool *signal, bool raw)

{

{

	u32 bytes_avail_towrite;

	u32 bytes_avail_towrite;

	u32 bytes_avail_toread;

	u32 bytes_avail_toread;

	u32 next_read_location = 0;

	u32 next_read_location = 0;

	u64 prev_indices = 0;

	u64 prev_indices = 0;

	unsigned long flags;

	unsigned long flags;

	struct vmpacket_descriptor desc;

	u32 offset;

	u32 packetlen;

	int ret = 0;





	if (buflen <= 0)

	if (buflen <= 0)

		return -EINVAL;

		return -EINVAL;





	spin_lock_irqsave(&inring_info->ring_lock, flags);

	spin_lock_irqsave(&inring_info->ring_lock, flags);





	*buffer_actual_len = 0;

	*requestid = 0;



	hv_get_ringbuffer_availbytes(inring_info,

	hv_get_ringbuffer_availbytes(inring_info,

				&bytes_avail_toread,

				&bytes_avail_toread,

				&bytes_avail_towrite);

				&bytes_avail_towrite);





	/* Make sure there is something to read */

	/* Make sure there is something to read */

	if (bytes_avail_toread < buflen) {

	if (bytes_avail_toread < sizeof(desc)) {

		spin_unlock_irqrestore(&inring_info->ring_lock, flags);

		/*

		 * 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 =

	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,

	next_read_location = hv_copyfrom_ringbuffer(inring_info,

						buffer,

						buffer,

						buflen,

						packetlen,

						next_read_location);

						next_read_location);





	if (!advance)

		goto out_unlock;



	next_read_location = hv_copyfrom_ringbuffer(inring_info,

	next_read_location = hv_copyfrom_ringbuffer(inring_info,

						&prev_indices,

						&prev_indices,

						sizeof(u64),

						sizeof(u64),
@@ -436,22 +462,5 @@ static inline int __hv_ringbuffer_read(struct hv_ring_buffer_info *inring_info, 




out_unlock:

out_unlock:

	spin_unlock_irqrestore(&inring_info->ring_lock, flags);

	spin_unlock_irqrestore(&inring_info->ring_lock, flags);

	return 0;

	return ret;

}



/* 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);

}
 
}