This is an implementation of the new rw_page interface. It primarily
demonstrates a low-impact, low-reward method for adding support to a
driver. I don't expect it to improve performance; in fact I expect it
to worsen performance slightly since there are still memory allocations
in the I/O path.
Please don't apply this patch.
Signed-off-by: Matthew Wilcox <matthew.r.wilcox@xxxxxxxxx>
---
drivers/block/virtio_blk.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 44 insertions(+)
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 6a680d4..4c1c9ad 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -110,11 +110,22 @@ static int __virtblk_add_req(struct virtqueue *vq,
return virtqueue_add_sgs(vq, sgs, num_out, num_in, vbr, GFP_ATOMIC);
}
+#define rw_to_dmad(rw) (((rw) == WRITE) ? DMA_TO_DEVICE : DMA_FROM_DEVICE)
+
static inline void virtblk_request_done(struct virtblk_req *vbr)
{
struct request *req = vbr->req;
int error = virtblk_result(vbr);
+ if ((unsigned long)req & 1) {
+ struct virtio_blk *vblk = (void *)((unsigned long)req & ~1UL);
+ int rw = (vbr->out_hdr.type & VIRTIO_BLK_T_OUT) ? WRITE : READ;
+ struct page *page = sg_page(vbr->sg);
+ dma_unmap_sg(&vblk->vdev->dev, vbr->sg, 1, rw_to_dmad(rw));
+ page_endio(page, rw, error);
+ return;
+ }
+
if (req->cmd_type == REQ_TYPE_BLOCK_PC) {
req->resid_len = vbr->in_hdr.residual;
req->sense_len = vbr->in_hdr.sense_len;
@@ -239,6 +250,38 @@ static int virtblk_get_id(struct gendisk *disk, char *id_str)
return err;
}
+static int virtblk_rw_page(struct block_device *bdev, sector_t sector,
+ struct page *page, int rw)
+{
+ unsigned long flags;
+ struct virtio_blk *vblk = bdev->bd_disk->private_data;
+ struct virtblk_req *vbr;
+ int err;
+
+ vbr = kmalloc(sizeof(*vbr) + sizeof(struct scatterlist), GFP_NOFS);
+ if (!vbr)
+ return -ENOMEM;
+
+ vbr->req = (void *)((unsigned long)vblk | 1);
+ vbr->out_hdr.type = (rw == WRITE) ? VIRTIO_BLK_T_OUT : VIRTIO_BLK_T_IN;
+ vbr->out_hdr.sector = sector;
+ vbr->out_hdr.ioprio = 0;
+
+ sg_init_table(vbr->sg, 1);
+ sg_set_page(vbr->sg, page, PAGE_CACHE_SIZE, 0);
+ sg_mark_end(vbr->sg);
+ if (dma_map_sg(&vblk->vdev->dev, vbr->sg, 1, rw_to_dmad(rw))) {
+ kfree(vbr);
+ return -ENOMEM;
+ }
+
+ spin_lock_irqsave(&vblk->vq_lock, flags);
+ err = __virtblk_add_req(vblk->vq, vbr, vbr->sg, 1);
+ virtqueue_kick(vblk->vq);
+ spin_unlock_irqrestore(&vblk->vq_lock, flags);
+ return err;
+}
+
static int virtblk_ioctl(struct block_device *bdev, fmode_t mode,
unsigned int cmd, unsigned long data)
{
@@ -278,6 +321,7 @@ static int virtblk_getgeo(struct block_device *bd, struct hd_geometry *geo)
}
static const struct block_device_operations virtblk_fops = {
+ .rw_page = virtblk_rw_page,
.ioctl = virtblk_ioctl,
.owner = THIS_MODULE,
.getgeo = virtblk_getgeo,
--
1.8.5.2
--
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