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(GFP_ATOMIC, 0);
109
110		if (!child)
111			return -ENOMEM;
112		bio_copy_dev(child, bio);
113		child->bi_opf = REQ_PREFLUSH;
114		child->bi_iter.bi_sector = -1;
115		bio_chain(child, bio);
116		submit_bio(child);
117		return 0;
118	}
119	if (virtio_pmem_flush(nd_region))
120		return -EIO;
121
122	return 0;
123};
124EXPORT_SYMBOL_GPL(async_pmem_flush);
125MODULE_LICENSE("GPL");