1// SPDX-License-Identifier: GPL-2.0
2/*
3 * virtio_pmem.c: Virtio pmem Driver
4 *
5 * Discovers persistent memory range information
6 * from host and provides a virtio based flushing
7 * interface.
8 */
9#include "virtio_pmem.h"
10#include "nd.h"
11
12 /* The interrupt handler */
13void virtio_pmem_host_ack(struct virtqueue *vq)
14{
15	struct virtio_pmem *vpmem = vq->vdev->priv;
16	struct virtio_pmem_request *req_data, *req_buf;
17	unsigned long flags;
18	unsigned int len;
19
20	spin_lock_irqsave(&vpmem->pmem_lock, flags);
21	while ((req_data = virtqueue_get_buf(vq, &len)) != NULL) {
22		req_data->done = true;
23		wake_up(&req_data->host_acked);
24
25		if (!list_empty(&vpmem->req_list)) {
26			req_buf = list_first_entry(&vpmem->req_list,
27					struct virtio_pmem_request, list);
28			req_buf->wq_buf_avail = true;
29			wake_up(&req_buf->wq_buf);
30			list_del(&req_buf->list);
31		}
32	}
33	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
34}
35EXPORT_SYMBOL_GPL(virtio_pmem_host_ack);
36
37 /* The request submission function */
38static int virtio_pmem_flush(struct nd_region *nd_region)
39{
40	struct virtio_device *vdev = nd_region->provider_data;
41	struct virtio_pmem *vpmem  = vdev->priv;
42	struct virtio_pmem_request *req_data;
43	struct scatterlist *sgs[2], sg, ret;
44	unsigned long flags;
45	int err, err1;
46
47	might_sleep();
48	req_data = kmalloc(sizeof(*req_data), GFP_KERNEL);
49	if (!req_data)
50		return -ENOMEM;
51
52	req_data->done = false;
53	init_waitqueue_head(&req_data->host_acked);
54	init_waitqueue_head(&req_data->wq_buf);
55	INIT_LIST_HEAD(&req_data->list);
56	req_data->req.type = cpu_to_le32(VIRTIO_PMEM_REQ_TYPE_FLUSH);
57	sg_init_one(&sg, &req_data->req, sizeof(req_data->req));
58	sgs[0] = &sg;
59	sg_init_one(&ret, &req_data->resp.ret, sizeof(req_data->resp));
60	sgs[1] = &ret;
61
62	spin_lock_irqsave(&vpmem->pmem_lock, flags);
63	 /*
64	  * If virtqueue_add_sgs returns -ENOSPC then req_vq virtual
65	  * queue does not have free descriptor. We add the request
66	  * to req_list and wait for host_ack to wake us up when free
67	  * slots are available.
68	  */
69	while ((err = virtqueue_add_sgs(vpmem->req_vq, sgs, 1, 1, req_data,
70					GFP_ATOMIC)) == -ENOSPC) {
71
72		dev_info(&vdev->dev, "failed to send command to virtio pmem device, no free slots in the virtqueue\n");
73		req_data->wq_buf_avail = false;
74		list_add_tail(&req_data->list, &vpmem->req_list);
75		spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
76
77		/* A host response results in "host_ack" getting called */
78		wait_event(req_data->wq_buf, req_data->wq_buf_avail);
79		spin_lock_irqsave(&vpmem->pmem_lock, flags);
80	}
81	err1 = virtqueue_kick(vpmem->req_vq);
82	spin_unlock_irqrestore(&vpmem->pmem_lock, flags);
83	/*
84	 * virtqueue_add_sgs failed with error different than -ENOSPC, we can't
85	 * do anything about that.
86	 */
87	if (err || !err1) {
88		dev_info(&vdev->dev, "failed to send command to virtio pmem device\n");
89		err = -EIO;
90	} else {
91		/* A host repsonse results in "host_ack" getting called */
92		wait_event(req_data->host_acked, req_data->done);
93		err = le32_to_cpu(req_data->resp.ret);
94	}
95
96	kfree(req_data);
97	return err;
98};
99
100/* The asynchronous flush callback function */
101int async_pmem_flush(struct nd_region *nd_region, struct bio *bio)
102{
103	/*
104	 * Create child bio for asynchronous flush and chain with
105	 * parent bio. Otherwise directly call nd_region flush.
106	 */
107	if (bio && bio->bi_iter.bi_sector != -1) {
108		struct bio *child = bio_alloc(bio->bi_bdev, 0,
109					      REQ_OP_WRITE | REQ_PREFLUSH,
110					      GFP_ATOMIC);
111
112		if (!child)
113			return -ENOMEM;
114		bio_clone_blkg_association(child, bio);
115		child->bi_iter.bi_sector = -1;
116		bio_chain(child, bio);
117		submit_bio(child);
118		return 0;
119	}
120	if (virtio_pmem_flush(nd_region))
121		return -EIO;
122
123	return 0;
124};
125EXPORT_SYMBOL_GPL(async_pmem_flush);
126MODULE_LICENSE("GPL");
127