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Date: Thu, 7 Feb 2013 13:22:27 +0100
From: Paolo Bonzini <pbonzini@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: Wanlong Gao <gaowanlong@...fujitsu.com>, asias@...hat.com,
Rusty Russell <rusty@...tcorp.com.au>, mst@...hat.com,
kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: [RFC PATCH 3/8] virtio-blk: use virtqueue_start_buf on bio path
Move the creation of the request header and response footer to
__virtblk_add_req. vbr->sg only contains the data scatterlist,
the header/footer are added separately using the new piecewise
API for building virtqueue buffers.
With this change, virtio-blk is not relying anymore on the virtio
functions ignoring the end markers in a scatterlist.
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
---
drivers/block/virtio_blk.c | 75 +++++++++++++++++++++++++++-----------------
1 files changed, 46 insertions(+), 29 deletions(-)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index fd8a689..538cc40 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -62,6 +62,7 @@ struct virtblk_req
struct virtio_blk *vblk;
int flags;
u8 status;
+ int sg_count;
struct scatterlist sg[];
};
@@ -100,24 +101,53 @@ static inline struct virtblk_req *virtblk_alloc_req(struct virtio_blk *vblk,
return vbr;
}
-static inline int __virtblk_add_req(struct virtqueue *vq,
- struct virtblk_req *vbr,
- unsigned long out,
- unsigned long in)
+static int __virtblk_add_req(struct virtqueue *vq,
+ struct virtblk_req *vbr)
{
- return virtqueue_add_buf(vq, vbr->sg, out, in, vbr, GFP_ATOMIC);
+ struct virtqueue_buf buf;
+ struct scatterlist sg;
+ enum dma_data_direction dir;
+ int ret;
+
+ unsigned int count = 2;
+ unsigned int count_sg = 2;
+
+ if (vbr->sg_count) {
+ count_sg++;
+ count += vbr->sg_count;
+ }
+
+ ret = virtqueue_start_buf(vq, &buf, vbr, count, count_sg, GFP_ATOMIC);
+ if (ret < 0)
+ return ret;
+
+ dir = DMA_TO_DEVICE;
+ sg_init_one(&sg, &vbr->out_hdr, sizeof(vbr->out_hdr));
+ virtqueue_add_sg_single(&buf, &sg, dir);
+
+ if (vbr->sg_count) {
+ if ((vbr->out_hdr.type & VIRTIO_BLK_T_OUT) == 0)
+ dir = DMA_FROM_DEVICE;
+
+ virtqueue_add_sg(&buf, vbr->sg, vbr->sg_count, dir);
+ }
+
+ dir = DMA_FROM_DEVICE;
+ sg_init_one(&sg, &vbr->status, sizeof(vbr->status));
+ virtqueue_add_sg_single(&buf, &sg, dir);
+
+ virtqueue_end_buf(&buf);
+ return 0;
}
-static void virtblk_add_req(struct virtblk_req *vbr,
- unsigned int out, unsigned int in)
+static void virtblk_add_req(struct virtblk_req *vbr)
{
struct virtio_blk *vblk = vbr->vblk;
DEFINE_WAIT(wait);
int ret;
spin_lock_irq(vblk->disk->queue->queue_lock);
- while (unlikely((ret = __virtblk_add_req(vblk->vq, vbr,
- out, in)) < 0)) {
+ while (unlikely((ret = __virtblk_add_req(vblk->vq, vbr)) < 0)) {
prepare_to_wait_exclusive(&vblk->queue_wait, &wait,
TASK_UNINTERRUPTIBLE);
@@ -134,22 +164,18 @@ static void virtblk_add_req(struct virtblk_req *vbr,
static void virtblk_bio_send_flush(struct virtblk_req *vbr)
{
- unsigned int out = 0, in = 0;
-
vbr->flags |= VBLK_IS_FLUSH;
vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
vbr->out_hdr.sector = 0;
vbr->out_hdr.ioprio = 0;
- sg_set_buf(&vbr->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
- sg_set_buf(&vbr->sg[out + in++], &vbr->status, sizeof(vbr->status));
+ vbr->sg_count = 0;
- virtblk_add_req(vbr, out, in);
+ virtblk_add_req(vbr);
}
static void virtblk_bio_send_data(struct virtblk_req *vbr)
{
struct virtio_blk *vblk = vbr->vblk;
- unsigned int num, out = 0, in = 0;
struct bio *bio = vbr->bio;
vbr->flags &= ~VBLK_IS_FLUSH;
@@ -157,24 +183,15 @@ static void virtblk_bio_send_data(struct virtblk_req *vbr)
vbr->out_hdr.sector = bio->bi_sector;
vbr->out_hdr.ioprio = bio_prio(bio);
- sg_set_buf(&vbr->sg[out++], &vbr->out_hdr, sizeof(vbr->out_hdr));
-
- num = blk_bio_map_sg(vblk->disk->queue, bio, vbr->sg + out);
-
- sg_set_buf(&vbr->sg[num + out + in++], &vbr->status,
- sizeof(vbr->status));
-
- if (num) {
- if (bio->bi_rw & REQ_WRITE) {
+ vbr->sg_count = blk_bio_map_sg(vblk->disk->queue, bio, vbr->sg);
+ if (vbr->sg_count) {
+ if (bio->bi_rw & REQ_WRITE)
vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
- out += num;
- } else {
+ else
vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
- in += num;
- }
}
- virtblk_add_req(vbr, out, in);
+ virtblk_add_req(vbr);
}
static void virtblk_bio_send_data_work(struct work_struct *work)
--
1.7.1
--
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