[PATCH] virtiofs: Enable multiple request queues

[Connor Kuehl]

Distribute requests across the multiqueue complex automatically based
on the IRQ affinity.

Suggested-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Signed-off-by: Connor Kuehl <ckuehl@xxxxxxxxxx>
---
 fs/fuse/virtio_fs.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/fs/fuse/virtio_fs.c b/fs/fuse/virtio_fs.c
index bcb8a02e2d8b..dcdc8b7b1ad5 100644
--- a/fs/fuse/virtio_fs.c
+++ b/fs/fuse/virtio_fs.c
@@ -30,6 +30,10 @@
 static DEFINE_MUTEX(virtio_fs_mutex);
 static LIST_HEAD(virtio_fs_instances);
 
+struct virtio_fs_vq;
+
+DEFINE_PER_CPU(struct virtio_fs_vq *, this_cpu_fsvq);
+
 enum {
 	VQ_HIPRIO,
 	VQ_REQUEST
@@ -673,6 +677,7 @@ static int virtio_fs_setup_vqs(struct virtio_device *vdev,
 	struct virtqueue **vqs;
 	vq_callback_t **callbacks;
 	const char **names;
+	struct irq_affinity desc = { .pre_vectors = 1, .nr_sets = 1, };
 	unsigned int i;
 	int ret = 0;
 
@@ -681,6 +686,9 @@ static int virtio_fs_setup_vqs(struct virtio_device *vdev,
 	if (fs->num_request_queues == 0)
 		return -EINVAL;
 
+	fs->num_request_queues = min_t(unsigned int, nr_cpu_ids,
+				       fs->num_request_queues);
+
 	fs->nvqs = VQ_REQUEST + fs->num_request_queues;
 	fs->vqs = kcalloc(fs->nvqs, sizeof(fs->vqs[VQ_HIPRIO]), GFP_KERNEL);
 	if (!fs->vqs)
@@ -710,12 +718,24 @@ static int virtio_fs_setup_vqs(struct virtio_device *vdev,
 		names[i] = fs->vqs[i].name;
 	}
 
-	ret = virtio_find_vqs(vdev, fs->nvqs, vqs, callbacks, names, NULL);
+	ret = virtio_find_vqs(vdev, fs->nvqs, vqs, callbacks, names, &desc);
 	if (ret < 0)
 		goto out;
 
-	for (i = 0; i < fs->nvqs; i++)
+	for (i = 0; i < fs->nvqs; i++) {
+		const struct cpumask *mask;
+		unsigned int cpu;
+
 		fs->vqs[i].vq = vqs[i];
+		if (i == VQ_HIPRIO)
+			continue;
+
+		mask = vdev->config->get_vq_affinity(vdev, i);
+		for_each_cpu(cpu, mask) {
+			struct virtio_fs_vq **cpu_vq = per_cpu_ptr(&this_cpu_fsvq, cpu);
+			*cpu_vq = &fs->vqs[i];
+		}
+	}
 
 	virtio_fs_start_all_queues(fs);
 out:
@@ -877,8 +897,6 @@ static int virtio_fs_probe(struct virtio_device *vdev)
 	if (ret < 0)
 		goto out;
 
-	/* TODO vq affinity */
-
 	ret = virtio_fs_setup_dax(vdev, fs);
 	if (ret < 0)
 		goto out_vqs;
@@ -1225,7 +1243,6 @@ static int virtio_fs_enqueue_req(struct virtio_fs_vq *fsvq,
 static void virtio_fs_wake_pending_and_unlock(struct fuse_iqueue *fiq)
 __releases(fiq->lock)
 {
-	unsigned int queue_id = VQ_REQUEST; /* TODO multiqueue */
 	struct virtio_fs *fs;
 	struct fuse_req *req;
 	struct virtio_fs_vq *fsvq;
@@ -1245,7 +1262,8 @@ __releases(fiq->lock)
 		 req->in.h.nodeid, req->in.h.len,
 		 fuse_len_args(req->args->out_numargs, req->args->out_args));
 
-	fsvq = &fs->vqs[queue_id];
+	fsvq = this_cpu_read(this_cpu_fsvq);
+
 	ret = virtio_fs_enqueue_req(fsvq, req, false);
 	if (ret < 0) {
 		if (ret == -ENOMEM || ret == -ENOSPC) {
-- 
2.30.2