This is useful for some setups like swiotlb or VDUSE where the DMA
operations are expensive and/or need to be performed with a write lock.
After applying this patch, fio read test goes from 1201MiB/s to 1211MiB/s.
Signed-off-by: Eugenio Pérez <eperezma@xxxxxxxxxx>
---
drivers/virtio/virtio_ring.c | 2 ++
fs/fuse/virtio_fs.c | 25 +++++++++++++++++++++++--
2 files changed, 25 insertions(+), 2 deletions(-)
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index e49912fa77c5..eb22bfcb9100 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -580,6 +580,7 @@ int virtqueue_map_sgs(struct virtqueue *_vq,
goto unmap_release;
sg_dma_address(sg) = addr;
+ sg_dma_len(sg) = sg->length;
mapped_sg++;
}
}
@@ -592,6 +593,7 @@ int virtqueue_map_sgs(struct virtqueue *_vq,
goto unmap_release;
sg_dma_address(sg) = addr;
+ sg_dma_len(sg) = sg->length;
mapped_sg++;
}
}
diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index 1344c5782a7c..2b558b05d0f8 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -836,8 +836,21 @@ static void virtio_fs_requests_done_work(struct work_struct *work)
/* End requests */
list_for_each_entry_safe(req, next, &reqs, list) {
+ struct scatterlist *stack_sgs[6];
+ struct scatterlist **sgs = stack_sgs;
+ unsigned int total_sgs = req->out_sgs + req->in_sgs;
+
list_del_init(&req->list);
+ /* TODO replace magic 6 by a macro */
+ if (total_sgs > 6)
+ sgs = kmalloc_array(total_sgs, sizeof(sgs[0]), GFP_ATOMIC);
+
+ for (unsigned int i = 0; i < total_sgs; ++i)
+ sgs[i] = &req->sg[i];
+
+ virtqueue_unmap_sgs(vq, sgs, req->out_sgs, req->in_sgs);
+
/* blocking async request completes in a worker context */
if (req->args->may_block) {
struct virtio_fs_req_work *w;
@@ -850,6 +863,9 @@ static void virtio_fs_requests_done_work(struct work_struct *work)
} else {
virtio_fs_request_complete(req, fsvq);
}
+
+ if (sgs != stack_sgs)
+ kfree(sgs);
}
/* Try to push previously queued requests, as the queue might no longer be full */
@@ -1426,6 +1442,11 @@ static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
sgs[i] = &req->sg[i];
WARN_ON(req->out_sgs + req->in_sgs != total_sgs);
+ // TODO can we change this ptr out of the lock?
+ vq = fsvq->vq;
+ // TODO handle this and following errors
+ ret = virtqueue_map_sgs(vq, sgs, req->out_sgs, req->in_sgs);
+ BUG_ON(ret < 0);
spin_lock(&fsvq->lock);
if (!fsvq->connected) {
@@ -1434,8 +1455,8 @@ static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
goto out;
}
- vq = fsvq->vq;
- ret = virtqueue_add_sgs(vq, sgs, req->out_sgs, req->in_sgs, req, GFP_ATOMIC);
+ ret = virtqueue_add_sgs_premapped(vq, sgs, req->out_sgs,
+ req->in_sgs, req, GFP_ATOMIC);
if (ret < 0) {
spin_unlock(&fsvq->lock);
goto out;
--
2.48.1
