Message-Id: <1354412033-32372-1-git-send-email-asias@redhat.com>
Date:	Sun,  2 Dec 2012 09:33:53 +0800
From:	Asias He <asias@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Rusty Russell <rusty@...tcorp.com.au>,
	Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@...radead.org>,
	"David S. Miller" <davem@...emloft.net>, kvm@...r.kernel.org,
	virtualization@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: [PATCH] vhost-blk: Add vhost-blk support v6

vhost-blk is an in-kernel virito-blk device accelerator.

Due to lack of proper in-kernel AIO interface, this version converts
guest's I/O request to bio and use submit_bio() to submit I/O directly.
So this version any supports raw block device as guest's disk image,
e.g. /dev/sda, /dev/ram0. We can add file based image support to
vhost-blk once we have in-kernel AIO interface. There are some work in
progress for in-kernel AIO interface from Dave Kleikamp and Zach Brown:

   http://marc.info/?l=linux-fsdevel&m=133312234313122

Performance evaluation:
-----------------------------
LKVM: Fio with libaio ioengine on 1 Fusion IO device
IOPS(k)    Before    After    Improvement
seq-read   107       121      +13.0%
seq-write  130       179      +37.6%
rnd-read   102       122      +19.6%
rnd-write  125       159      +27.0%

QEMU: Fio with libaio ioengine on 1 Fusion IO device
IOPS(k)    Before    After    Improvement
seq-read   76        123      +61.8%
seq-write  139       173      +24.4%
rnd-read   73        120      +64.3%
rnd-write  75        156      +108.0%

QEMU: Fio with libaio ioengine on 1 Ramdisk device
IOPS(k)    Before    After    Improvement
seq-read   138       437      +216%
seq-write  191       436      +128%
rnd-read   137       426      +210%
rnd-write  140       415      +196%

QEMU: Fio with libaio ioengine on 8 Ramdisk device
50% read + 50% write
IOPS(k)    Before    After    Improvement
randrw     64/64     189/189  +195%/+195%

Userspace bits:
-----------------------------
1) LKVM
The latest vhost-blk userspace bits for kvm tool can be found here:
git@...hub.com:asias/linux-kvm.git blk.vhost-blk

2) QEMU
The latest vhost-blk userspace prototype for QEMU can be found here:
git@...hub.com:asias/qemu.git blk.vhost-blk

Changes in v6:
- Use inline req_page_list to reduce kmalloc
- Switch to single thread model, thanks mst!
- Wait until requests fired before vhost_blk_flush to be finished

Changes in v5:
- Do not assume the buffer layout
- Fix wakeup race

Changes in v4:
- Mark req->status as userspace pointer
- Use __copy_to_user() instead of copy_to_user() in vhost_blk_set_status()
- Add if (need_resched()) schedule() in blk thread
- Kill vhost_blk_stop_vq() and move it into vhost_blk_stop()
- Use vq_err() instead of pr_warn()
- Fail un Unsupported request
- Add flush in vhost_blk_set_features()

Changes in v3:
- Sending REQ_FLUSH bio instead of vfs_fsync, thanks Christoph!
- Check file passed by user is a raw block device file

Acked-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Asias He <asias@...hat.com>
---
 drivers/vhost/Kconfig     |   1 +
 drivers/vhost/Kconfig.blk |  10 +
 drivers/vhost/Makefile    |   2 +
 drivers/vhost/blk.c       | 724 ++++++++++++++++++++++++++++++++++++++++++++++
 drivers/vhost/blk.h       |   8 +
 5 files changed, 745 insertions(+)
 create mode 100644 drivers/vhost/Kconfig.blk
 create mode 100644 drivers/vhost/blk.c
 create mode 100644 drivers/vhost/blk.h

diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
index 202bba6..acd8038 100644
--- a/drivers/vhost/Kconfig
+++ b/drivers/vhost/Kconfig
@@ -11,4 +11,5 @@ config VHOST_NET
 
 if STAGING
 source "drivers/vhost/Kconfig.tcm"
+source "drivers/vhost/Kconfig.blk"
 endif
diff --git a/drivers/vhost/Kconfig.blk b/drivers/vhost/Kconfig.blk
new file mode 100644
index 0000000..ff8ab76
--- /dev/null
+++ b/drivers/vhost/Kconfig.blk
@@ -0,0 +1,10 @@
+config VHOST_BLK
+	tristate "Host kernel accelerator for virtio blk (EXPERIMENTAL)"
+	depends on BLOCK &&  EXPERIMENTAL && m
+	---help---
+	  This kernel module can be loaded in host kernel to accelerate
+	  guest block with virtio_blk. Not to be confused with virtio_blk
+	  module itself which needs to be loaded in guest kernel.
+
+	  To compile this driver as a module, choose M here: the module will
+	  be called vhost_blk.
diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile
index a27b053..1a8a4a5 100644
--- a/drivers/vhost/Makefile
+++ b/drivers/vhost/Makefile
@@ -2,3 +2,5 @@ obj-$(CONFIG_VHOST_NET) += vhost_net.o
 vhost_net-y := vhost.o net.o
 
 obj-$(CONFIG_TCM_VHOST) += tcm_vhost.o
+obj-$(CONFIG_VHOST_BLK) += vhost_blk.o
+vhost_blk-y := blk.o
diff --git a/drivers/vhost/blk.c b/drivers/vhost/blk.c
new file mode 100644
index 0000000..e4ca4b6
--- /dev/null
+++ b/drivers/vhost/blk.c
@@ -0,0 +1,724 @@
+/*
+ * Copyright (C) 2011 Taobao, Inc.
+ * Author: Liu Yuan <tailai.ly@...bao.com>
+ *
+ * Copyright (C) 2012 Red Hat, Inc.
+ * Author: Asias He <asias@...hat.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.
+ *
+ * virtio-blk server in host kernel.
+ */
+
+#include <linux/miscdevice.h>
+#include <linux/module.h>
+#include <linux/vhost.h>
+#include <linux/virtio_blk.h>
+#include <linux/mutex.h>
+#include <linux/file.h>
+#include <linux/kthread.h>
+#include <linux/blkdev.h>
+#include <linux/llist.h>
+
+#include "vhost.c"
+#include "vhost.h"
+#include "blk.h"
+
+static DEFINE_IDA(vhost_blk_index_ida);
+
+enum {
+	VHOST_BLK_VQ_REQ = 0,
+	VHOST_BLK_VQ_MAX = 1,
+};
+
+struct req_page_list {
+	struct page **pages;
+	int pages_nr;
+};
+
+#define NR_INLINE 16
+
+struct vhost_blk_req {
+	struct req_page_list inline_pl[NR_INLINE];
+	struct page *inline_page[NR_INLINE];
+	struct bio *inline_bio[NR_INLINE];
+	struct req_page_list *pl;
+	int during_flush;
+	bool use_inline;
+
+	struct llist_node llnode;
+
+	struct vhost_blk *blk;
+
+	struct iovec *iov;
+	int iov_nr;
+
+	struct bio **bio;
+	atomic_t bio_nr;
+
+	struct iovec status[1];
+
+	sector_t sector;
+	int write;
+	u16 head;
+	long len;
+};
+
+struct vhost_blk {
+	wait_queue_head_t flush_wait;
+	struct iovec iov[UIO_MAXIOV];
+	struct vhost_blk_req *reqs;
+	struct vhost_virtqueue vq;
+	struct llist_head llhead;
+	atomic_t req_inflight[2];
+	struct vhost_work work;
+	spinlock_t flush_lock;
+	struct vhost_dev dev;
+	int during_flush;
+	u16 reqs_nr;
+	int index;
+};
+
+static int move_iovec(struct iovec *from, struct iovec *to,
+		      size_t len, int iov_count)
+{
+	int seg = 0;
+	size_t size;
+
+	while (len && seg < iov_count) {
+		if (from->iov_len == 0) {
+			++from;
+			continue;
+		}
+		size = min(from->iov_len, len);
+		to->iov_base = from->iov_base;
+		to->iov_len = size;
+		from->iov_len -= size;
+		from->iov_base += size;
+		len -= size;
+		++from;
+		++to;
+		++seg;
+	}
+	return seg;
+}
+
+static inline int iov_num_pages(struct iovec *iov)
+{
+	return (PAGE_ALIGN((unsigned long)iov->iov_base + iov->iov_len) -
+	       ((unsigned long)iov->iov_base & PAGE_MASK)) >> PAGE_SHIFT;
+}
+
+static inline int vhost_blk_set_status(struct vhost_blk_req *req, u8 status)
+{
+	struct vhost_blk *blk = req->blk;
+	int ret;
+
+	ret = memcpy_toiovecend(req->status, &status, 0, sizeof(status));
+
+	if (ret) {
+		vq_err(&blk->vq, "Failed to write status\n");
+		return -EFAULT;
+	}
+
+	return 0;
+}
+
+static void vhost_blk_req_done(struct bio *bio, int err)
+{
+	struct vhost_blk_req *req = bio->bi_private;
+	struct vhost_blk *blk = req->blk;
+
+	if (err)
+		req->len = err;
+
+	if (atomic_dec_and_test(&req->bio_nr)) {
+		llist_add(&req->llnode, &blk->llhead);
+		vhost_work_queue(&blk->dev, &blk->work);
+	}
+
+	bio_put(bio);
+}
+
+static void vhost_blk_req_umap(struct vhost_blk_req *req)
+{
+	struct req_page_list *pl;
+	int i, j;
+
+	if (req->pl) {
+		for (i = 0; i < req->iov_nr; i++) {
+			pl = &req->pl[i];
+			for (j = 0; j < pl->pages_nr; j++) {
+				if (!req->write)
+					set_page_dirty_lock(pl->pages[j]);
+				page_cache_release(pl->pages[j]);
+			}
+		}
+	}
+
+	if (!req->use_inline)
+		kfree(req->pl);
+}
+
+static int vhost_blk_bio_make(struct vhost_blk_req *req,
+			      struct block_device *bdev)
+{
+	int pages_nr_total, i, j, ret;
+	struct iovec *iov = req->iov;
+	int iov_nr = req->iov_nr;
+	struct page **pages, *page;
+	struct bio *bio = NULL;
+	int bio_nr = 0;
+	void *buf;
+
+	pages_nr_total = 0;
+	for (i = 0; i < iov_nr; i++)
+		pages_nr_total += iov_num_pages(&iov[i]);
+
+	if (unlikely(req->write == WRITE_FLUSH)) {
+		req->use_inline = true;
+		req->pl = NULL;
+		req->bio = req->inline_bio;
+
+		bio = bio_alloc(GFP_KERNEL, 1);
+		if (!bio)
+			return -ENOMEM;
+
+		bio->bi_sector  = req->sector;
+		bio->bi_bdev    = bdev;
+		bio->bi_private = req;
+		bio->bi_end_io  = vhost_blk_req_done;
+		req->bio[bio_nr++] = bio;
+
+		goto out;
+	}
+
+	if (pages_nr_total > NR_INLINE) {
+		int pl_len, page_len, bio_len;
+
+		req->use_inline = false;
+		pl_len = iov_nr * sizeof(req->pl[0]);
+		page_len = pages_nr_total * sizeof(struct page *);
+		bio_len = pages_nr_total * sizeof(struct bio *);
+
+		buf = kmalloc(pl_len + page_len + bio_len, GFP_KERNEL);
+		if (!buf)
+			return -ENOMEM;
+
+		req->pl	= buf;
+		pages = buf + pl_len;
+		req->bio = buf + pl_len + page_len;
+	} else {
+		req->use_inline = true;
+		req->pl = req->inline_pl;
+		pages = req->inline_page;
+		req->bio = req->inline_bio;
+	}
+
+	req->iov_nr = 0;
+	for (i = 0; i < iov_nr; i++) {
+		int pages_nr = iov_num_pages(&iov[i]);
+		unsigned long iov_base, iov_len;
+		struct req_page_list *pl;
+
+		iov_base = (unsigned long)iov[i].iov_base;
+		iov_len  = (unsigned long)iov[i].iov_len;
+
+		/* TODO: Limit the total number of pages pinned */
+		ret = get_user_pages_fast(iov_base, pages_nr,
+					  !req->write, pages);
+		if (ret != pages_nr)
+			goto fail;
+
+		req->iov_nr++;
+		pl = &req->pl[i];
+		pl->pages_nr = pages_nr;
+		pl->pages = pages;
+
+		for (j = 0; j < pages_nr; j++) {
+			unsigned int off, len;
+			page = pages[j];
+			off = iov_base & ~PAGE_MASK;
+			len = PAGE_SIZE - off;
+			if (len > iov_len)
+				len = iov_len;
+
+			while (!bio || bio_add_page(bio, page, len, off) <= 0) {
+				bio = bio_alloc(GFP_KERNEL, pages_nr_total);
+				if (!bio)
+					goto fail;
+				bio->bi_sector  = req->sector;
+				bio->bi_bdev    = bdev;
+				bio->bi_private = req;
+				bio->bi_end_io  = vhost_blk_req_done;
+				req->bio[bio_nr++] = bio;
+			}
+			req->sector	+= len >> 9;
+			iov_base	+= len;
+			iov_len		-= len;
+		}
+
+		pages += pages_nr;
+	}
+out:
+	atomic_set(&req->bio_nr, bio_nr);
+	return 0;
+
+fail:
+	for (i = 0; i < bio_nr; i++)
+		bio_put(req->bio[i]);
+	vhost_blk_req_umap(req);
+	return -ENOMEM;
+}
+
+static inline void vhost_blk_bio_send(struct vhost_blk_req *req)
+{
+	struct blk_plug plug;
+	int i, bio_nr;
+
+	bio_nr = atomic_read(&req->bio_nr);
+	blk_start_plug(&plug);
+	for (i = 0; i < bio_nr; i++)
+		submit_bio(req->write, req->bio[i]);
+	blk_finish_plug(&plug);
+}
+
+static int vhost_blk_req_submit(struct vhost_blk_req *req, struct file *file)
+{
+
+	struct inode *inode = file->f_mapping->host;
+	struct block_device *bdev = inode->i_bdev;
+	int ret;
+
+	ret = vhost_blk_bio_make(req, bdev);
+	if (ret < 0)
+		return ret;
+
+	vhost_blk_bio_send(req);
+
+	spin_lock(&req->blk->flush_lock);
+	req->during_flush = req->blk->during_flush;
+	atomic_inc(&req->blk->req_inflight[req->during_flush]);
+	spin_unlock(&req->blk->flush_lock);
+
+	return ret;
+}
+
+static int vhost_blk_req_handle(struct vhost_virtqueue *vq,
+				struct virtio_blk_outhdr *hdr,
+				u16 head, u16 out, u16 in,
+				struct file *file)
+{
+	struct vhost_blk *blk = container_of(vq->dev, struct vhost_blk, dev);
+	unsigned char id[VIRTIO_BLK_ID_BYTES];
+	struct vhost_blk_req *req;
+	int ret, len;
+	u8 status;
+
+	req		= &blk->reqs[head];
+	req->head	= head;
+	req->blk	= blk;
+	req->sector	= hdr->sector;
+	req->iov	= blk->iov;
+
+	req->len	= iov_length(vq->iov, out + in) - sizeof(status);
+	req->iov_nr	= move_iovec(vq->iov, req->iov, req->len, out + in);
+
+	move_iovec(vq->iov, req->status, sizeof(status), out + in);
+
+	switch (hdr->type) {
+	case VIRTIO_BLK_T_OUT:
+		req->write = WRITE;
+		ret = vhost_blk_req_submit(req, file);
+		break;
+	case VIRTIO_BLK_T_IN:
+		req->write = READ;
+		ret = vhost_blk_req_submit(req, file);
+		break;
+	case VIRTIO_BLK_T_FLUSH:
+		req->write = WRITE_FLUSH;
+		ret = vhost_blk_req_submit(req, file);
+		break;
+	case VIRTIO_BLK_T_GET_ID:
+		ret = snprintf(id, VIRTIO_BLK_ID_BYTES,
+			       "vhost-blk%d", blk->index);
+		if (ret < 0)
+			break;
+		len = ret;
+		ret = memcpy_toiovecend(req->iov, id, 0, len);
+		status = ret < 0 ? VIRTIO_BLK_S_IOERR : VIRTIO_BLK_S_OK;
+		ret = vhost_blk_set_status(req, status);
+		if (ret)
+			break;
+		vhost_add_used_and_signal(&blk->dev, vq, head, len);
+		break;
+	default:
+		vq_err(vq, "Unsupported request type %d\n", hdr->type);
+		status = VIRTIO_BLK_S_UNSUPP;
+		ret = vhost_blk_set_status(req, status);
+		if (ret)
+			break;
+		vhost_add_used_and_signal(&blk->dev, vq, head, 0);
+	}
+
+	return ret;
+}
+
+/* Guest kick us for I/O submit */
+static void vhost_blk_handle_guest_kick(struct vhost_work *work)
+{
+	struct virtio_blk_outhdr hdr;
+	struct vhost_virtqueue *vq;
+	struct vhost_blk *blk;
+	int in, out, ret;
+	struct file *f;
+	u16 head;
+
+	vq = container_of(work, struct vhost_virtqueue, poll.work);
+	blk = container_of(vq->dev, struct vhost_blk, dev);
+
+	/* TODO: check that we are running from vhost_worker? */
+	f = rcu_dereference_check(vq->private_data, 1);
+	if (!f)
+		return;
+
+	vhost_disable_notify(&blk->dev, vq);
+	for (;;) {
+		head = vhost_get_vq_desc(&blk->dev, vq, vq->iov,
+					 ARRAY_SIZE(vq->iov),
+					 &out, &in, NULL, NULL);
+		if (unlikely(head < 0))
+			break;
+
+		if (unlikely(head == vq->num)) {
+			if (unlikely(vhost_enable_notify(&blk->dev, vq))) {
+				vhost_disable_notify(&blk->dev, vq);
+				continue;
+			}
+			break;
+		}
+		move_iovec(vq->iov, vq->hdr, sizeof(hdr), out);
+		ret = memcpy_fromiovecend((unsigned char *)&hdr, vq->hdr, 0,
+					   sizeof(hdr));
+		if (ret < 0) {
+			vq_err(vq, "Failed to get block header!\n");
+			vhost_discard_vq_desc(vq, 1);
+			break;
+		}
+
+		if (vhost_blk_req_handle(vq, &hdr, head, out, in, f) < 0)
+			break;
+
+		if (!llist_empty(&blk->llhead)) {
+			vhost_poll_queue(&vq->poll);
+			break;
+		}
+	}
+}
+
+/* Host kick us for I/O completion */
+static void vhost_blk_handle_host_kick(struct vhost_work *work)
+{
+
+	struct vhost_virtqueue *vq;
+	struct vhost_blk_req *req;
+	struct llist_node *llnode;
+	struct vhost_blk *blk;
+	bool added, zero;
+	u8 status;
+	int ret;
+
+	blk = container_of(work, struct vhost_blk, work);
+	vq = &blk->vq;
+
+	llnode = llist_del_all(&blk->llhead);
+	added = false;
+	while (llnode) {
+		req = llist_entry(llnode, struct vhost_blk_req, llnode);
+		llnode = llist_next(llnode);
+
+		vhost_blk_req_umap(req);
+
+		status = req->len > 0 ?  VIRTIO_BLK_S_OK : VIRTIO_BLK_S_IOERR;
+		ret = vhost_blk_set_status(req, status);
+		if (unlikely(ret))
+			continue;
+		vhost_add_used(&blk->vq, req->head, req->len);
+		added = true;
+
+		spin_lock(&req->blk->flush_lock);
+		zero = atomic_dec_and_test(
+				&req->blk->req_inflight[req->during_flush]);
+		if (zero && !req->during_flush)
+			wake_up(&blk->flush_wait);
+		spin_unlock(&req->blk->flush_lock);
+
+	}
+	if (likely(added))
+		vhost_signal(&blk->dev, &blk->vq);
+}
+
+static void vhost_blk_flush(struct vhost_blk *blk)
+{
+	spin_lock(&blk->flush_lock);
+	blk->during_flush = 1;
+	spin_unlock(&blk->flush_lock);
+
+	vhost_poll_flush(&blk->vq.poll);
+	vhost_work_flush(&blk->dev, &blk->work);
+	/*
+	 * Wait until requests fired before the flush to be finished
+	 * req_inflight[0] is used to track the requests fired before the flush
+	 * req_inflight[1] is used to track the requests fired during the flush
+	 */
+	wait_event(blk->flush_wait, !atomic_read(&blk->req_inflight[0]));
+
+	spin_lock(&blk->flush_lock);
+	blk->during_flush = 0;
+	spin_unlock(&blk->flush_lock);
+}
+
+static inline void vhost_blk_stop(struct vhost_blk *blk, struct file **file)
+{
+	struct vhost_virtqueue *vq = &blk->vq;
+	struct file *f;
+
+	mutex_lock(&vq->mutex);
+	f = rcu_dereference_protected(vq->private_data,
+				      lockdep_is_held(&vq->mutex));
+	rcu_assign_pointer(vq->private_data, NULL);
+	mutex_unlock(&vq->mutex);
+
+	*file = f;
+}
+
+static int vhost_blk_open(struct inode *inode, struct file *file)
+{
+	struct vhost_blk *blk;
+	int ret;
+
+	blk = kzalloc(sizeof(*blk), GFP_KERNEL);
+	if (!blk) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	ret = ida_simple_get(&vhost_blk_index_ida, 0, 0, GFP_KERNEL);
+	if (ret < 0)
+		goto out_dev;
+	blk->index = ret;
+
+	blk->vq.handle_kick = vhost_blk_handle_guest_kick;
+	atomic_set(&blk->req_inflight[0], 0);
+	atomic_set(&blk->req_inflight[1], 0);
+	blk->during_flush = 0;
+	spin_lock_init(&blk->flush_lock);
+	init_waitqueue_head(&blk->flush_wait);
+
+	ret = vhost_dev_init(&blk->dev, &blk->vq, VHOST_BLK_VQ_MAX);
+	if (ret < 0)
+		goto out_dev;
+	file->private_data = blk;
+
+	vhost_work_init(&blk->work, vhost_blk_handle_host_kick);
+
+	return ret;
+out_dev:
+	kfree(blk);
+out:
+	return ret;
+}
+
+static int vhost_blk_release(struct inode *inode, struct file *f)
+{
+	struct vhost_blk *blk = f->private_data;
+	struct file *file;
+
+	ida_simple_remove(&vhost_blk_index_ida, blk->index);
+	vhost_blk_stop(blk, &file);
+	vhost_blk_flush(blk);
+	vhost_dev_cleanup(&blk->dev, false);
+	if (file)
+		fput(file);
+	kfree(blk->reqs);
+	kfree(blk);
+
+	return 0;
+}
+
+static int vhost_blk_set_features(struct vhost_blk *blk, u64 features)
+{
+	mutex_lock(&blk->dev.mutex);
+	blk->dev.acked_features = features;
+	vhost_blk_flush(blk);
+	mutex_unlock(&blk->dev.mutex);
+
+	return 0;
+}
+
+static long vhost_blk_set_backend(struct vhost_blk *blk, unsigned index, int fd)
+{
+	struct vhost_virtqueue *vq = &blk->vq;
+	struct file *file, *oldfile;
+	struct inode *inode;
+	int ret;
+
+	mutex_lock(&blk->dev.mutex);
+	ret = vhost_dev_check_owner(&blk->dev);
+	if (ret)
+		goto out_dev;
+
+	if (index >= VHOST_BLK_VQ_MAX) {
+		ret = -ENOBUFS;
+		goto out_dev;
+	}
+
+	mutex_lock(&vq->mutex);
+
+	if (!vhost_vq_access_ok(vq)) {
+		ret = -EFAULT;
+		goto out_vq;
+	}
+
+	file = fget(fd);
+	if (IS_ERR(file)) {
+		ret = PTR_ERR(file);
+		goto out_vq;
+	}
+
+	/* Only raw block device is supported for now */
+	inode = file->f_mapping->host;
+	if (!S_ISBLK(inode->i_mode)) {
+		ret = -EFAULT;
+		goto out_file;
+	}
+
+	oldfile = rcu_dereference_protected(vq->private_data,
+			lockdep_is_held(&vq->mutex));
+	if (file != oldfile) {
+		rcu_assign_pointer(vq->private_data, file);
+
+		ret = vhost_init_used(vq);
+		if (ret)
+			goto out_file;
+	}
+
+	mutex_unlock(&vq->mutex);
+
+	if (oldfile) {
+		vhost_blk_flush(blk);
+		fput(oldfile);
+	}
+
+	mutex_unlock(&blk->dev.mutex);
+	return 0;
+
+out_file:
+	fput(file);
+out_vq:
+	mutex_unlock(&vq->mutex);
+out_dev:
+	mutex_unlock(&blk->dev.mutex);
+	return ret;
+}
+
+static long vhost_blk_reset_owner(struct vhost_blk *blk)
+{
+	struct file *file = NULL;
+	int err;
+
+	mutex_lock(&blk->dev.mutex);
+	err = vhost_dev_check_owner(&blk->dev);
+	if (err)
+		goto done;
+	vhost_blk_stop(blk, &file);
+	vhost_blk_flush(blk);
+	err = vhost_dev_reset_owner(&blk->dev);
+done:
+	mutex_unlock(&blk->dev.mutex);
+	if (file)
+		fput(file);
+	return err;
+}
+
+static int vhost_blk_setup(struct vhost_blk *blk)
+{
+	blk->reqs_nr = blk->vq.num;
+
+	blk->reqs = kmalloc(sizeof(struct vhost_blk_req) * blk->reqs_nr,
+			    GFP_KERNEL);
+	if (!blk->reqs)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static long vhost_blk_ioctl(struct file *f, unsigned int ioctl,
+			    unsigned long arg)
+{
+	struct vhost_blk *blk = f->private_data;
+	void __user *argp = (void __user *)arg;
+	struct vhost_vring_file backend;
+	u64 __user *featurep = argp;
+	u64 features;
+	int ret;
+
+	switch (ioctl) {
+	case VHOST_BLK_SET_BACKEND:
+		if (copy_from_user(&backend, argp, sizeof(backend)))
+			return -EFAULT;
+		return vhost_blk_set_backend(blk, backend.index, backend.fd);
+	case VHOST_GET_FEATURES:
+		features = VHOST_BLK_FEATURES;
+		if (copy_to_user(featurep, &features, sizeof(features)))
+			return -EFAULT;
+		return 0;
+	case VHOST_SET_FEATURES:
+		if (copy_from_user(&features, featurep, sizeof(features)))
+			return -EFAULT;
+		if (features & ~VHOST_BLK_FEATURES)
+			return -EOPNOTSUPP;
+		return vhost_blk_set_features(blk, features);
+	case VHOST_RESET_OWNER:
+		return vhost_blk_reset_owner(blk);
+	default:
+		mutex_lock(&blk->dev.mutex);
+		ret = vhost_dev_ioctl(&blk->dev, ioctl, arg);
+		if (!ret && ioctl == VHOST_SET_VRING_NUM)
+			ret = vhost_blk_setup(blk);
+		vhost_blk_flush(blk);
+		mutex_unlock(&blk->dev.mutex);
+		return ret;
+	}
+}
+
+static const struct file_operations vhost_blk_fops = {
+	.owner          = THIS_MODULE,
+	.open           = vhost_blk_open,
+	.release        = vhost_blk_release,
+	.llseek		= noop_llseek,
+	.unlocked_ioctl = vhost_blk_ioctl,
+};
+
+static struct miscdevice vhost_blk_misc = {
+	MISC_DYNAMIC_MINOR,
+	"vhost-blk",
+	&vhost_blk_fops,
+};
+
+static int vhost_blk_init(void)
+{
+	return misc_register(&vhost_blk_misc);
+}
+
+static void vhost_blk_exit(void)
+{
+	misc_deregister(&vhost_blk_misc);
+}
+
+module_init(vhost_blk_init);
+module_exit(vhost_blk_exit);
+
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("Asias He");
+MODULE_DESCRIPTION("Host kernel accelerator for virtio_blk");
diff --git a/drivers/vhost/blk.h b/drivers/vhost/blk.h
new file mode 100644
index 0000000..2f674f0
--- /dev/null
+++ b/drivers/vhost/blk.h
@@ -0,0 +1,8 @@
+#include <linux/vhost.h>
+
+enum {
+	VHOST_BLK_FEATURES = (1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
+			     (1ULL << VIRTIO_RING_F_EVENT_IDX),
+};
+/* VHOST_BLK specific defines */
+#define VHOST_BLK_SET_BACKEND _IOW(VHOST_VIRTIO, 0x50, struct vhost_vring_file)
-- 
1.7.11.7

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