Re: [PATCH] vhost-blk: Add vhost-blk support v5
From: Asias He
Date: Tue Nov 20 2012 - 01:38:02 EST
On 11/20/2012 04:26 AM, Michael S. Tsirkin wrote:
> On Mon, Nov 19, 2012 at 04:53:42PM +0800, Asias He wrote:
>> 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:
>> -----------------------------
>> 1) LKVM
>> Fio with libaio ioengine on Fusion IO device using kvm tool
>> 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%
>>
>> 2) QEMU
>> Fio with libaio ioengine on Fusion IO device using QEMU
>> 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%
>
> Could you compare with dataplane qemu as well please?
Well, I will try to collect it.
>
>>
>> Userspace bits:
>> -----------------------------
>> 1) LKVM
>> The latest vhost-blk userspace bits for kvm tool can be found here:
>> git@xxxxxxxxxx:asias/linux-kvm.git blk.vhost-blk
>>
>> 2) QEMU
>> The latest vhost-blk userspace prototype for QEMU can be found here:
>> git@xxxxxxxxxx:asias/qemu.git blk.vhost-blk
>>
>> 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
>>
>> Signed-off-by: Asias He <asias@xxxxxxxxxx>
>
> Since there are files shared by this and vhost net
> it's easiest for me to merge this all through the
> vhost tree.
>
> Jens, could you ack this and the bio usage in this driver
> please?
>
>> ---
>> drivers/vhost/Kconfig | 1 +
>> drivers/vhost/Kconfig.blk | 10 +
>> drivers/vhost/Makefile | 2 +
>> drivers/vhost/blk.c | 697 ++++++++++++++++++++++++++++++++++++++++++++++
>> drivers/vhost/blk.h | 8 +
>> 5 files changed, 718 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..f0f118a
>> --- /dev/null
>> +++ b/drivers/vhost/blk.c
>> @@ -0,0 +1,697 @@
>> +/*
>> + * Copyright (C) 2011 Taobao, Inc.
>> + * Author: Liu Yuan <tailai.ly@xxxxxxxxxx>
>> + *
>> + * Copyright (C) 2012 Red Hat, Inc.
>> + * Author: Asias He <asias@xxxxxxxxxx>
>> + *
>> + * 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;
>> +};
>> +
>> +struct vhost_blk_req {
>> + struct llist_node llnode;
>> + struct req_page_list *pl;
>> + 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 {
>> + struct task_struct *host_kick;
>
> Could you please add a comment here explaining why
> is this better than using the builtin vhost thread?
With separate thread model, the request submit and request completion
can be handled in parallel. I have measured significant performance
improvement with this model. In the long term, It would be nice if the
vhost core can provide multiple thread support.
>> + struct iovec iov[UIO_MAXIOV];
>> + struct vhost_blk_req *reqs;
>> + struct vhost_virtqueue vq;
>> + struct llist_head llhead;
>> + struct vhost_dev dev;
>> + 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 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 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_enable_vq(struct vhost_blk *blk,
>> + struct vhost_virtqueue *vq)
>> +{
>> + wake_up_process(blk->host_kick);
>> +}
>> +
>> +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);
>> + wake_up_process(blk->host_kick);
>> + }
>> +
>> + 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) {
>> + kfree(req->bio);
>> + return;
>> + }
>> +
>> + 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]);
>> + }
>> + }
>> +
>> + kfree(req->pl);
>> +}
>> +
>> +static int vhost_blk_bio_make(struct vhost_blk_req *req,
>> + struct block_device *bdev)
>> +{
>> + int pl_len, page_len, bio_len;
>> + 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->pl = NULL;
>> + req->bio = kmalloc(sizeof(struct bio *), GFP_KERNEL);
>> + bio = bio_alloc(GFP_KERNEL, 1);
>> + if (!bio) {
>> + kfree(req->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;
>> + }
>> +
>> + 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;
>> +
>> + 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 */
>
> What's the plan here? Is there some limit if e.g. aio is used?
The problem is there is no easy way to find a proper limit number. May
be 16 * vq size number of pages as you sugguested.
With aio, we do not touch this code path at all.
>> + 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);
>> + 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);
>> +
>> + return ret;
>> +}
>> +
>> +static int vhost_blk_req_done_thread(void *data)
>> +{
>> + mm_segment_t oldfs = get_fs();
>> + struct vhost_blk *blk = data;
>> + struct vhost_virtqueue *vq;
>> + struct llist_node *llnode;
>> + struct vhost_blk_req *req;
>> + bool added;
>> + u8 status;
>> + int ret;
>> +
>> + vq = &blk->vq;
>> + set_fs(USER_DS);
>> + use_mm(blk->dev.mm);
>> + for (;;) {
>> + set_current_state(TASK_INTERRUPTIBLE);
>> + llnode = llist_del_all(&blk->llhead);
>> + if (!llnode) {
>> + schedule();
>> + if (unlikely(kthread_should_stop()))
>> + break;
>> + continue;
>> + }
>> + set_current_state(TASK_RUNNING);
>> +
>> + if (need_resched())
>> + schedule();
>> +
>> + 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;
>> + }
>> + if (likely(added))
>> + vhost_signal(&blk->dev, &blk->vq);
>> + }
>> + unuse_mm(blk->dev.mm);
>> + set_fs(oldfs);
>> + return 0;
>> +}
>> +
>> +static void vhost_blk_flush(struct vhost_blk *blk)
>> +{
>> + vhost_poll_flush(&blk->vq.poll);
>> +}
>> +
>> +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;
>> +}
>> +
>> +/* Handle guest request */
>> +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 IO request */
>> +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;
>> + }
>> +}
>> +
>> +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;
>> +
>> + ret = vhost_dev_init(&blk->dev, &blk->vq, VHOST_BLK_VQ_MAX);
>> + if (ret < 0)
>> + goto out_dev;
>> + file->private_data = blk;
>> +
>> + blk->host_kick = kthread_create(vhost_blk_req_done_thread,
>> + blk, "vhost-blk-%d", current->pid);
>> + if (IS_ERR(blk->host_kick)) {
>> + ret = PTR_ERR(blk->host_kick);
>> + goto out_dev;
>> + }
>> +
>> + 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);
>> + kthread_stop(blk->host_kick);
>> + 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);
>> + vhost_blk_enable_vq(blk, vq);
>> +
>> + 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 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
--
Asias
--
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