[PATCH 0/2] virtio: add gfp_t parameter to add_buf

[PATCH 0/2] virtio: add gfp_t parameter to add_buf

[Michael S. Tsirkin]

We need to allocate memory to post indirect buffers,
and sometimes drivers do this from a thread context,
so it helps to pass in a gfp_t parameter.

To avoid churn changing all drivers, add a new API
with a _gfp prefix, and make the old call lacking
gfp_t an inline wrapper.


-- 
MST


Michael S. Tsirkin (2):
  virtio: add_buf_gfp
  virtio-net: pass gfp to add_buf

 drivers/net/virtio_net.c     |    8 ++++----
 drivers/virtio/virtio_ring.c |   20 +++++++++++---------
 include/linux/virtio.h       |   22 +++++++++++++++++-----
 3 files changed, 32 insertions(+), 18 deletions(-)

[PATCH 1/2] virtio: add_buf_gfp

[Michael S. Tsirkin]

Add an add_buf variant that gets gfp parameter. Use that
to allocate indirect buffers.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/virtio/virtio_ring.c |   20 +++++++++++---------
 include/linux/virtio.h       |   22 +++++++++++++++++-----
 2 files changed, 28 insertions(+), 14 deletions(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 0717b5b..1ca8890 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -110,13 +110,14 @@ struct vring_virtqueue
 static int vring_add_indirect(struct vring_virtqueue *vq,
 			      struct scatterlist sg[],
 			      unsigned int out,
-			      unsigned int in)
+			      unsigned int in,
+			      gfp_t gfp)
 {
 	struct vring_desc *desc;
 	unsigned head;
 	int i;
 
-	desc = kmalloc((out + in) * sizeof(struct vring_desc), GFP_ATOMIC);
+	desc = kmalloc((out + in) * sizeof(struct vring_desc), gfp);
 	if (!desc)
 		return vq->vring.num;
 
@@ -155,11 +156,12 @@ static int vring_add_indirect(struct vring_virtqueue *vq,
 	return head;
 }
 
-int virtqueue_add_buf(struct virtqueue *_vq,
-		  struct scatterlist sg[],
-		  unsigned int out,
-		  unsigned int in,
-		  void *data)
+int virtqueue_add_buf_gfp(struct virtqueue *_vq,
+			  struct scatterlist sg[],
+			  unsigned int out,
+			  unsigned int in,
+			  void *data,
+			  gfp_t gfp)
 {
 	struct vring_virtqueue *vq = to_vvq(_vq);
 	unsigned int i, avail, head, uninitialized_var(prev);
@@ -171,7 +173,7 @@ int virtqueue_add_buf(struct virtqueue *_vq,
 	/* If the host supports indirect descriptor tables, and we have multiple
 	 * buffers, then go indirect. FIXME: tune this threshold */
 	if (vq->indirect && (out + in) > 1 && vq->num_free) {
-		head = vring_add_indirect(vq, sg, out, in);
+		head = vring_add_indirect(vq, sg, out, in, gfp);
 		if (head != vq->vring.num)
 			goto add_head;
 	}
@@ -232,7 +234,7 @@ add_head:
 		return vq->num_free ? vq->vring.num : 0;
 	return vq->num_free;
 }
-EXPORT_SYMBOL_GPL(virtqueue_add_buf);
+EXPORT_SYMBOL_GPL(virtqueue_add_buf_gfp);
 
 void virtqueue_kick(struct virtqueue *_vq)
 {
diff --git a/include/linux/virtio.h b/include/linux/virtio.h
index 5b0fce0..aff5b4f 100644
--- a/include/linux/virtio.h
+++ b/include/linux/virtio.h
@@ -7,6 +7,7 @@
 #include <linux/spinlock.h>
 #include <linux/device.h>
 #include <linux/mod_devicetable.h>
+#include <linux/gfp.h>
 
 /**
  * virtqueue - a queue to register buffers for sending or receiving.
@@ -32,6 +33,7 @@ struct virtqueue {
  *	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).
  *      Returns remaining capacity of queue (sg segments) or a negative error.
  * virtqueue_kick: update after add_buf
  *	vq: the struct virtqueue
@@ -60,11 +62,21 @@ struct virtqueue {
  * All operations can be called in any context.
  */
 
-int virtqueue_add_buf(struct virtqueue *vq,
-		      struct scatterlist sg[],
-		      unsigned int out_num,
-		      unsigned int in_num,
-		      void *data);
+int virtqueue_add_buf_gfp(struct virtqueue *vq,
+			  struct scatterlist sg[],
+			  unsigned int out_num,
+			  unsigned int in_num,
+			  void *data,
+			  gfp_t gfp);
+
+static inline int virtqueue_add_buf(struct virtqueue *vq,
+				    struct scatterlist sg[],
+				    unsigned int out_num,
+				    unsigned int in_num,
+				    void *data)
+{
+	return virtqueue_add_buf_gfp(vq, sg, out_num, in_num, data, GFP_ATOMIC);
+}
 
 void virtqueue_kick(struct virtqueue *vq);
 
-- 
1.7.1.rc1.22.g3163

[PATCH 2/2] virtio-net: pass gfp to add_buf

[Michael S. Tsirkin]

virtio-net bounces buffer allocations off to
a thread if it can't allocate buffers from the atomic
pool. However, if posting buffers still requires atomic
buffers, this is unlikely to succeed.
Fix by passing in the proper gfp_t parameter.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 drivers/net/virtio_net.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 91738d8..fca44b2 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -339,7 +339,7 @@ static int add_recvbuf_small(struct virtnet_info *vi, gfp_t gfp)
 
 	skb_to_sgvec(skb, sg + 1, 0, skb->len);
 
-	err = virtqueue_add_buf(vi->rvq, sg, 0, 2, skb);
+	err = virtqueue_add_buf_gfp(vi->rvq, sg, 0, 2, skb, gfp);
 	if (err < 0)
 		dev_kfree_skb(skb);
 
@@ -386,8 +386,8 @@ static int add_recvbuf_big(struct virtnet_info *vi, gfp_t gfp)
 
 	/* chain first in list head */
 	first->private = (unsigned long)list;
-	err = virtqueue_add_buf(vi->rvq, sg, 0, MAX_SKB_FRAGS + 2,
-				       first);
+	err = virtqueue_add_buf_gfp(vi->rvq, sg, 0, MAX_SKB_FRAGS + 2,
+				    first, gfp);
 	if (err < 0)
 		give_pages(vi, first);
 
@@ -406,7 +406,7 @@ static int add_recvbuf_mergeable(struct virtnet_info *vi, gfp_t gfp)
 
 	sg_init_one(&sg, page_address(page), PAGE_SIZE);
 
-	err = virtqueue_add_buf(vi->rvq, &sg, 0, 1, page);
+	err = virtqueue_add_buf_gfp(vi->rvq, &sg, 0, 1, page, gfp);
 	if (err < 0)
 		give_pages(vi, page);
 
-- 
1.7.1.rc1.22.g3163

Re: [PATCH 2/2] virtio-net: pass gfp to add_buf

[Rusty Russell]

On Thu, 29 Apr 2010 11:56:42 pm Michael S. Tsirkin wrote:
> virtio-net bounces buffer allocations off to
> a thread if it can't allocate buffers from the atomic
> pool. However, if posting buffers still requires atomic
> buffers, this is unlikely to succeed.
> Fix by passing in the proper gfp_t parameter.

Thanks, applied with the predecessor.

Cheers,
Rusty.