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Date: Tue, 19 Feb 2013 18:26:25 +1030
From: Rusty Russell <rusty@...tcorp.com.au>
To: Paolo Bonzini <pbonzini@...hat.com>
Cc: Rusty Russell <rusty@...tcorp.com.au>, Asias He <asias@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org
Subject: [PATCH 07/16] virtio_ring: don't count elements twice for add_buf path.
Extract the post-counting code into virtqueue_add(), make both callers
use it.
Signed-off-by: Rusty Russell <rusty@...tcorp.com.au>
---
drivers/virtio/virtio_ring.c | 147 +++++++++++++++++++++++-------------------
1 file changed, 80 insertions(+), 67 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 27e31d3..c537385 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -163,69 +163,17 @@ static int vring_add_indirect(struct vring_virtqueue *vq,
return head;
}
-/**
- * virtqueue_add_buf - expose buffer to other end
- * @vq: the struct virtqueue we're talking about.
- * @sg: the description of the buffer(s).
- * @out_num: the number of sg readable by other side
- * @in_num: the number of sg which are writable (after readable ones)
- * @data: the token identifying the buffer.
- * @gfp: how to do memory allocations (if necessary).
- *
- * Caller must ensure we don't call this with other virtqueue operations
- * at the same time (except where noted).
- *
- * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
- */
-int virtqueue_add_buf(struct virtqueue *_vq,
- struct scatterlist sg[],
- unsigned int out,
- unsigned int in,
- void *data,
- gfp_t gfp)
-{
- struct scatterlist *sgs[2];
- unsigned int i;
-
- sgs[0] = sg;
- sgs[1] = sg + out;
-
- /* Workaround until callers pass well-formed sgs. */
- for (i = 0; i < out + in; i++)
- sg_unmark_end(sg + i);
-
- sg_mark_end(sg + out + in - 1);
- if (out && in)
- sg_mark_end(sg + out - 1);
-
- return virtqueue_add_sgs(_vq, sgs, out ? 1 : 0, in ? 1 : 0, data, gfp);
-}
-EXPORT_SYMBOL_GPL(virtqueue_add_buf);
-
-/**
- * virtqueue_add_sgs - expose buffers to other end
- * @vq: the struct virtqueue we're talking about.
- * @sgs: array of terminated scatterlists.
- * @out_num: the number of scatterlists readable by other side
- * @in_num: the number of scatterlists which are writable (after readable ones)
- * @data: the token identifying the buffer.
- * @gfp: how to do memory allocations (if necessary).
- *
- * Caller must ensure we don't call this with other virtqueue operations
- * at the same time (except where noted).
- *
- * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
- */
-int virtqueue_add_sgs(struct virtqueue *_vq,
- struct scatterlist *sgs[],
- unsigned int out_sgs,
- unsigned int in_sgs,
- void *data,
- gfp_t gfp)
+static int virtqueue_add(struct virtqueue *_vq,
+ struct scatterlist *sgs[],
+ unsigned int total_sg,
+ unsigned int out_sgs,
+ unsigned int in_sgs,
+ void *data,
+ gfp_t gfp)
{
struct vring_virtqueue *vq = to_vvq(_vq);
struct scatterlist *sg;
- unsigned int i, n, avail, uninitialized_var(prev), total_sg;
+ unsigned int i, n, avail, uninitialized_var(prev);
int head;
START_USE(vq);
@@ -245,13 +193,6 @@ int virtqueue_add_sgs(struct virtqueue *_vq,
}
#endif
- /* Count them first. */
- for (i = total_sg = 0; i < out_sgs + in_sgs; i++) {
- struct scatterlist *sg;
- for (sg = sgs[i]; sg; sg = sg_next(sg))
- total_sg++;
- }
-
/* If the host supports indirect descriptor tables, and we have multiple
* buffers, then go indirect. FIXME: tune this threshold */
if (vq->indirect && total_sg > 1 && vq->vq.num_free) {
@@ -329,6 +270,78 @@ add_head:
return 0;
}
+
+/**
+ * virtqueue_add_buf - expose buffer to other end
+ * @vq: the struct virtqueue we're talking about.
+ * @sg: the description of the buffer(s).
+ * @out_num: the number of sg readable by other side
+ * @in_num: the number of sg which are writable (after readable ones)
+ * @data: the token identifying the buffer.
+ * @gfp: how to do memory allocations (if necessary).
+ *
+ * Caller must ensure we don't call this with other virtqueue operations
+ * at the same time (except where noted).
+ *
+ * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
+ */
+int virtqueue_add_buf(struct virtqueue *_vq,
+ struct scatterlist sg[],
+ unsigned int out,
+ unsigned int in,
+ void *data,
+ gfp_t gfp)
+{
+ struct scatterlist *sgs[2];
+ unsigned int i;
+
+ sgs[0] = sg;
+ sgs[1] = sg + out;
+
+ /* Workaround until callers pass well-formed sgs. */
+ for (i = 0; i < out + in; i++)
+ sg_unmark_end(sg + i);
+
+ sg_mark_end(sg + out + in - 1);
+ if (out && in)
+ sg_mark_end(sg + out - 1);
+
+ return virtqueue_add(_vq, sgs, out+in, out ? 1 : 0, in ? 1 : 0,
+ data, gfp);
+}
+EXPORT_SYMBOL_GPL(virtqueue_add_buf);
+
+/**
+ * virtqueue_add_sgs - expose buffers to other end
+ * @vq: the struct virtqueue we're talking about.
+ * @sgs: array of terminated scatterlists.
+ * @out_num: the number of scatterlists readable by other side
+ * @in_num: the number of scatterlists which are writable (after readable ones)
+ * @data: the token identifying the buffer.
+ * @gfp: how to do memory allocations (if necessary).
+ *
+ * Caller must ensure we don't call this with other virtqueue operations
+ * at the same time (except where noted).
+ *
+ * Returns zero or a negative error (ie. ENOSPC, ENOMEM).
+ */
+int virtqueue_add_sgs(struct virtqueue *_vq,
+ struct scatterlist *sgs[],
+ unsigned int out_sgs,
+ unsigned int in_sgs,
+ void *data,
+ gfp_t gfp)
+{
+ unsigned int i, total_sg;
+
+ /* Count them first. */
+ for (i = total_sg = 0; i < out_sgs + in_sgs; i++) {
+ struct scatterlist *sg;
+ for (sg = sgs[i]; sg; sg = sg_next(sg))
+ total_sg++;
+ }
+ return virtqueue_add(_vq, sgs, total_sg, out_sgs, in_sgs, data, gfp);
+}
EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
/**
--
1.7.10.4
--
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