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Message-Id: <20171019131700.562299892@linuxfoundation.org>
Date: Thu, 19 Oct 2017 15:39:03 +0200
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-kernel@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
stable@...r.kernel.org, Stephen Hemminger <sthemmin@...rosoft.com>,
"K. Y. Srinivasan" <kys@...rosoft.com>
Subject: [PATCH 4.13 08/11] vmbus: simplify hv_ringbuffer_read
4.13-stable review patch. If anyone has any objections, please let me know.
------------------
From: Stephen Hemminger <stephen@...workplumber.org>
commit 4226ff69a3dff78bead7d9a270423cd21f8d40b8 upstream.
With new iterator functions (and the double mapping) the ring buffer
read function can be greatly simplified.
Signed-off-by: Stephen Hemminger <sthemmin@...rosoft.com>
Signed-off-by: K. Y. Srinivasan <kys@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
drivers/hv/ring_buffer.c | 116 ++++++-----------------------------------------
1 file changed, 16 insertions(+), 100 deletions(-)
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -94,30 +94,6 @@ hv_set_next_write_location(struct hv_rin
ring_info->ring_buffer->write_index = next_write_location;
}
-/* Get the next read location for the specified ring buffer. */
-static inline u32
-hv_get_next_read_location(const struct hv_ring_buffer_info *ring_info)
-{
- return ring_info->ring_buffer->read_index;
-}
-
-/*
- * Get the next read location + offset for the specified ring buffer.
- * This allows the caller to skip.
- */
-static inline u32
-hv_get_next_readlocation_withoffset(const struct hv_ring_buffer_info *ring_info,
- u32 offset)
-{
- u32 next = ring_info->ring_buffer->read_index;
-
- next += offset;
- if (next >= ring_info->ring_datasize)
- next -= ring_info->ring_datasize;
-
- return next;
-}
-
/* Set the next read location for the specified ring buffer. */
static inline void
hv_set_next_read_location(struct hv_ring_buffer_info *ring_info,
@@ -142,29 +118,6 @@ hv_get_ring_bufferindices(struct hv_ring
}
/*
- * Helper routine to copy to source from ring buffer.
- * Assume there is enough room. Handles wrap-around in src case only!!
- */
-static u32 hv_copyfrom_ringbuffer(
- const struct hv_ring_buffer_info *ring_info,
- void *dest,
- u32 destlen,
- u32 start_read_offset)
-{
- void *ring_buffer = hv_get_ring_buffer(ring_info);
- u32 ring_buffer_size = hv_get_ring_buffersize(ring_info);
-
- memcpy(dest, ring_buffer + start_read_offset, destlen);
-
- start_read_offset += destlen;
- if (start_read_offset >= ring_buffer_size)
- start_read_offset -= ring_buffer_size;
-
- return start_read_offset;
-}
-
-
-/*
* Helper routine to copy from source to ring buffer.
* Assume there is enough room. Handles wrap-around in dest case only!!
*/
@@ -334,33 +287,22 @@ int hv_ringbuffer_write(struct vmbus_cha
return 0;
}
-static inline void
-init_cached_read_index(struct hv_ring_buffer_info *rbi)
-{
- rbi->cached_read_index = rbi->ring_buffer->read_index;
-}
-
int hv_ringbuffer_read(struct vmbus_channel *channel,
void *buffer, u32 buflen, u32 *buffer_actual_len,
u64 *requestid, bool raw)
{
- u32 bytes_avail_toread;
- u32 next_read_location;
- u64 prev_indices = 0;
- struct vmpacket_descriptor desc;
- u32 offset;
- u32 packetlen;
- struct hv_ring_buffer_info *inring_info = &channel->inbound;
+ struct vmpacket_descriptor *desc;
+ u32 packetlen, offset;
- if (buflen <= 0)
+ if (unlikely(buflen == 0))
return -EINVAL;
*buffer_actual_len = 0;
*requestid = 0;
- bytes_avail_toread = hv_get_bytes_to_read(inring_info);
/* Make sure there is something to read */
- if (bytes_avail_toread < sizeof(desc)) {
+ desc = hv_pkt_iter_first(channel);
+ if (desc == NULL) {
/*
* No error is set when there is even no header, drivers are
* supposed to analyze buffer_actual_len.
@@ -368,48 +310,22 @@ int hv_ringbuffer_read(struct vmbus_chan
return 0;
}
- init_cached_read_index(inring_info);
-
- 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;
+ 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)
- return -EAGAIN;
+ *requestid = desc->trans_id;
- if (packetlen > buflen)
+ if (unlikely(packetlen > buflen))
return -ENOBUFS;
- next_read_location =
- hv_get_next_readlocation_withoffset(inring_info, offset);
+ /* since ring is double mapped, only one copy is necessary */
+ memcpy(buffer, (const char *)desc + offset, packetlen);
- next_read_location = hv_copyfrom_ringbuffer(inring_info,
- buffer,
- packetlen,
- next_read_location);
-
- next_read_location = hv_copyfrom_ringbuffer(inring_info,
- &prev_indices,
- sizeof(u64),
- next_read_location);
+ /* Advance ring index to next packet descriptor */
+ __hv_pkt_iter_next(channel, desc);
- /*
- * Make sure all reads are done before we update the read index since
- * the writer may start writing to the read area once the read index
- * is updated.
- */
- virt_mb();
-
- /* Update the read index */
- hv_set_next_read_location(inring_info, next_read_location);
-
- hv_signal_on_read(channel);
+ /* Notify host of update */
+ hv_pkt_iter_close(channel);
return 0;
}
@@ -442,7 +358,7 @@ struct vmpacket_descriptor *hv_pkt_iter_
struct hv_ring_buffer_info *rbi = &channel->inbound;
/* set state for later hv_signal_on_read() */
- init_cached_read_index(rbi);
+ rbi->cached_read_index = rbi->ring_buffer->read_index;
if (hv_pkt_iter_avail(rbi) < sizeof(struct vmpacket_descriptor))
return NULL;
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