[Devel] [PATCH RH9 v3 01/10] drivers/vhost: vhost-blk accelerator for virtio-blk guests
Andrey Zhadchenko
andrey.zhadchenko at virtuozzo.com
Mon Oct 31 14:43:41 MSK 2022
On 10/13/22 19:17, Pavel Tikhomirov wrote:
>
>
> On 10.10.2022 17:56, Andrey Zhadchenko wrote:
>> Although QEMU virtio is quite fast, there is still some room for
>> improvements. Disk latency can be reduced if we handle virito-blk
>> requests
>> in host kernel istead of passing them to QEMU. The patch adds vhost-blk
>> kernel module to do so.
>>
>> Some test setups:
>> fio --direct=1 --rw=randread --bs=4k --ioengine=libaio --iodepth=128
>> QEMU drive options: cache=none
>> filesystem: xfs
>>
>> SSD:
>> | randread, IOPS | randwrite, IOPS |
>> Host | 95.8k | 85.3k |
>> QEMU virtio | 57.5k | 79.4k |
>> QEMU vhost-blk | 95.6k | 84.3k |
>>
>> RAMDISK (vq == vcpu):
>> | randread, IOPS | randwrite, IOPS |
>> virtio, 1vcpu | 123k | 129k |
>> virtio, 2vcpu | 253k (??) | 250k (??) |
>> virtio, 4vcpu | 158k | 154k |
>> vhost-blk, 1vcpu | 110k | 113k |
>> vhost-blk, 2vcpu | 247k | 252k |
>> vhost-blk, 4vcpu | 576k | 567k |
>>
>> https://jira.sw.ru/browse/PSBM-139414
>> Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
>> ---
>> v2:
>> - removed unused VHOST_BLK_VQ
>> - reworked bio handling a bit: now add all pages from signle iov into
>> single bio istead of allocating one bio per page
>> - changed how to calculate sector incrementation
>> - check move_iovec() in vhost_blk_req_handle()
>> - remove snprintf check and better check ret from copy_to_iter for
>> VIRTIO_BLK_ID_BYTES requests
>> - discard vq request if vhost_blk_req_handle() returned negative code
>> - forbid to change nonzero backend in vhost_blk_set_backend(). First of
>> all, QEMU sets backend only once. Also if we want to change backend when
>> we already running requests we need to be much more careful in
>> vhost_blk_handle_guest_kick() as it is not taking any references. If
>> userspace want to change backend that bad it can always reset device.
>> - removed EXPERIMENTAL from Kconfig
>>
>> v3:
>> - a bit reworked bio handling - allocate new bio only if the previous
>> is full
>>
>> drivers/vhost/Kconfig | 12 +
>> drivers/vhost/Makefile | 3 +
>> drivers/vhost/blk.c | 828 +++++++++++++++++++++++++++++++++++++
>> include/uapi/linux/vhost.h | 5 +
>> 4 files changed, 848 insertions(+)
>> create mode 100644 drivers/vhost/blk.c
>>
>> diff --git a/drivers/vhost/Kconfig b/drivers/vhost/Kconfig
>> index 587fbae06182..e1389bf0c10b 100644
>> --- a/drivers/vhost/Kconfig
>> +++ b/drivers/vhost/Kconfig
>> @@ -89,4 +89,16 @@ config VHOST_CROSS_ENDIAN_LEGACY
>> If unsure, say "N".
>> +config VHOST_BLK
>> + tristate "Host kernel accelerator for virtio-blk"
>> + depends on BLOCK && EVENTFD
>> + select VHOST
>> + default n
>> + help
>> + This kernel module can be loaded in host kernel to accelerate
>> + guest vm with virtio-blk driver.
>> +
>> + To compile this driver as a module, choose M here: the module will
>> + be called vhost_blk.
>> +
>> endif
>> diff --git a/drivers/vhost/Makefile b/drivers/vhost/Makefile
>> index f3e1897cce85..c76cc4f5fcd8 100644
>> --- a/drivers/vhost/Makefile
>> +++ b/drivers/vhost/Makefile
>> @@ -17,3 +17,6 @@ obj-$(CONFIG_VHOST) += vhost.o
>> obj-$(CONFIG_VHOST_IOTLB) += vhost_iotlb.o
>> vhost_iotlb-y := iotlb.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 000000000000..933c9c50b0a6
>> --- /dev/null
>> +++ b/drivers/vhost/blk.c
>> @@ -0,0 +1,828 @@
>> +// SPDX-License-Identifier: GPL-2.0-only
>> +/*
>> + * Copyright (C) 2011 Taobao, Inc.
>> + * Author: Liu Yuan <tailai.ly at taobao.com>
>> + *
>> + * Copyright (C) 2012 Red Hat, Inc.
>> + * Author: Asias He <asias at redhat.com>
>> + *
>> + * Copyright (c) 2022 Virtuozzo International GmbH.
>> + * Author: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
>> + *
>> + * virtio-blk host kernel accelerator.
>> + */
>> +
>> +#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.h"
>> +
>> +enum {
>> + VHOST_BLK_FEATURES = VHOST_FEATURES |
>> + (1ULL << VIRTIO_RING_F_INDIRECT_DESC) |
>> + (1ULL << VIRTIO_RING_F_EVENT_IDX) |
>> + (1ULL << VIRTIO_BLK_F_MQ) |
>> + (1ULL << VIRTIO_BLK_F_FLUSH),
>> +};
>> +
>> +/*
>> + * Max number of bytes transferred before requeueing the job.
>> + * Using this limit prevents one virtqueue from starving others.
>> + */
>> +#define VHOST_DEV_WEIGHT 0x80000
>> +
>> +/*
>> + * Max number of packets transferred before requeueing the job.
>> + * Using this limit prevents one virtqueue from starving others with
>> + * pkts.
>> + */
>> +#define VHOST_DEV_PKT_WEIGHT 256
>> +
>> +#define VHOST_BLK_VQ_MAX 8
>> +
>> +#define VHOST_MAX_METADATA_IOV 1
>> +
>> +#define VHOST_BLK_SECTOR_BITS 9
>> +#define VHOST_BLK_SECTOR_SIZE (1 << VHOST_BLK_SECTOR_BITS)
>> +#define VHOST_BLK_SECTOR_MASK (VHOST_BLK_SECTOR_SIZE - 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[VHOST_MAX_METADATA_IOV];
>> +
>> + sector_t sector;
>> + int bi_opf;
>> + u16 head;
>> + long len;
>> + int bio_err;
>> +
>> + struct vhost_blk_vq *blk_vq;
>> +};
>> +
>> +struct vhost_blk_vq {
>> + struct vhost_virtqueue vq;
>> + struct vhost_blk_req *req;
>> + struct iovec iov[UIO_MAXIOV];
>> + struct llist_head llhead;
>> + struct vhost_work work;
>> +};
>> +
>> +struct vhost_blk {
>> + wait_queue_head_t flush_wait;
>> + struct vhost_blk_vq vqs[VHOST_BLK_VQ_MAX];
>> + atomic_t req_inflight[2];
>> + spinlock_t flush_lock;
>> + struct vhost_dev dev;
>> + int during_flush;
>> + struct file *backend;
>> + int index;
>> +};
>> +
>> +static int gen;
>> +
>> +static int move_iovec(struct iovec *from, struct iovec *to,
>> + size_t len, int iov_count_from, int iov_count_to)
>> +{
>> + int moved_seg = 0, spent_seg = 0;
>> + size_t size;
>> +
>> + while (len && spent_seg < iov_count_from && moved_seg <
>> iov_count_to) {
>> + if (from->iov_len == 0) {
>> + ++from;
>> + ++spent_seg;
>> + 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;
>> + ++moved_seg;
>> + ++spent_seg;
>> + }
>> +
>> + return len ? -1 : moved_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 iov_iter iter;
>> + int ret;
>> +
>> + iov_iter_init(&iter, WRITE, req->status, ARRAY_SIZE(req->status),
>> sizeof(status));
>> + ret = copy_to_iter(&status, sizeof(status), &iter);
>> + if (ret != sizeof(status)) {
>> + vq_err(&req->blk_vq->vq, "Failed to write status\n");
>> + return -EFAULT;
>> + }
>> +
>> + return 0;
>> +}
>> +
>> +static void vhost_blk_req_done(struct bio *bio)
>> +{
>> + struct vhost_blk_req *req = bio->bi_private;
>> + struct vhost_blk *blk = req->blk;
>> +
>> + req->bio_err = blk_status_to_errno(bio->bi_status);
>> +
>> + if (atomic_dec_and_test(&req->bio_nr)) {
>> + llist_add(&req->llnode, &req->blk_vq->llhead);
>> + vhost_work_queue(&blk->dev, &req->blk_vq->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->bi_opf)
>> + set_page_dirty_lock(pl->pages[j]);
>> + put_page(pl->pages[j]);
>> + }
>> + }
>> + }
>> +
>> + if (!req->use_inline)
>> + kfree(req->pl);
>> +}
>> +
>> +static int vhost_blk_bio_make_simple(struct vhost_blk_req *req,
>> + struct block_device *bdev)
>> +{
>> + struct bio *bio;
>> +
>> + req->use_inline = true;
>> + req->pl = NULL;
>> + req->bio = req->inline_bio;
>> +
>> + bio = bio_alloc(GFP_KERNEL, 1);
>> + if (!bio)
>> + return -ENOMEM;
>> +
>> + bio->bi_iter.bi_sector = req->sector;
>> + bio_set_dev(bio, bdev);
>> + bio->bi_private = req;
>> + bio->bi_end_io = vhost_blk_req_done;
>> + bio->bi_opf = req->bi_opf;
>> + req->bio[0] = bio;
>> +
>> + atomic_set(&req->bio_nr, 1);
>> +
>> + return 0;
>> +}
>> +
>> +static struct page **vhost_blk_prepare_req(struct vhost_blk_req *req,
>> + int total_pages, int iov_nr)
>> +{
>> + int pl_len, page_len, bio_len;
>> + void *buf;
>> +
>> + req->use_inline = false;
>> + pl_len = iov_nr * sizeof(req->pl[0]);
>> + page_len = total_pages * sizeof(struct page *);
>> + bio_len = total_pages * sizeof(struct bio *);
>> +
>> + buf = kmalloc(pl_len + page_len + bio_len, GFP_KERNEL);
>> + if (!buf)
>> + return NULL;
>> +
>> + req->pl = buf;
>> + req->bio = buf + pl_len + page_len;
>> +
>> + return buf + pl_len;
>> +}
>> +
>> +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;
>> +
>> + if (unlikely(req->bi_opf == REQ_OP_FLUSH))
>> + return vhost_blk_bio_make_simple(req, bdev);
>> +
>> + pages_nr_total = 0;
>> + for (i = 0; i < iov_nr; i++)
>> + pages_nr_total += iov_num_pages(&iov[i]);
>> +
>> + if (pages_nr_total > NR_INLINE) {
>> + pages = vhost_blk_prepare_req(req, pages_nr_total, iov_nr);
>> + if (!pages)
>> + return -ENOMEM;
>> + } 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;
>> +
>> + ret = get_user_pages_fast(iov_base, pages_nr,
>> + !req->bi_opf, 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, pos;
>> +
>> + 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)) {
>> + bio = bio_alloc(GFP_KERNEL, pages_nr);
>> + if (!bio)
>> + goto fail;
>> + bio->bi_iter.bi_sector = req->sector;
>> + bio_set_dev(bio, bdev);
>> + bio->bi_private = req;
>> + bio->bi_end_io = vhost_blk_req_done;
>> + bio->bi_opf = req->bi_opf;
>> + req->bio[bio_nr++] = bio;
>> + }
>> +
>> + iov_base += len;
>> + iov_len -= len;
>> +
>> + pos = (iov_base & VHOST_BLK_SECTOR_MASK) + iov_len;
>> + req->sector += pos >> VHOST_BLK_SECTOR_BITS;
>> + }
>> +
>> + pages += pages_nr;
>> + }
>> + 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->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 = I_BDEV(inode);
>> + 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 total_iov_nr,
>> + struct file *file)
>> +{
>> + struct vhost_blk *blk = container_of(vq->dev, struct vhost_blk,
>> dev);
>> + struct vhost_blk_vq *blk_vq = container_of(vq, struct
>> vhost_blk_vq, vq);
>> + unsigned char id[VIRTIO_BLK_ID_BYTES];
>> + struct vhost_blk_req *req;
>> + struct iov_iter iter;
>> + int ret, len;
>> + u8 status;
>> +
>> + req = &blk_vq->req[head];
>> + req->blk_vq = blk_vq;
>> + req->head = head;
>> + req->blk = blk;
>> + req->sector = hdr->sector;
>> + req->iov = blk_vq->iov;
>> +
>> + req->len = iov_length(vq->iov, total_iov_nr) - sizeof(status);
>> + req->iov_nr = move_iovec(vq->iov, req->iov, req->len,
>> total_iov_nr,
>> + ARRAY_SIZE(blk_vq->iov));
>> +
>> + ret = move_iovec(vq->iov, req->status, sizeof(status), total_iov_nr,
>> + ARRAY_SIZE(req->status));
>> + if (ret < 0 || req->iov_nr < 0)
>> + return -EINVAL;
>> +
>> + switch (hdr->type) {
>> + case VIRTIO_BLK_T_OUT:
>> + req->bi_opf = REQ_OP_WRITE;
>> + ret = vhost_blk_req_submit(req, file);
>> + break;
>> + case VIRTIO_BLK_T_IN:
>> + req->bi_opf = REQ_OP_READ;
>> + ret = vhost_blk_req_submit(req, file);
>> + break;
>> + case VIRTIO_BLK_T_FLUSH:
>> + req->bi_opf = REQ_OP_FLUSH;
>> + ret = vhost_blk_req_submit(req, file);
>> + break;
>> + case VIRTIO_BLK_T_GET_ID:
>> + len = snprintf(id, VIRTIO_BLK_ID_BYTES, "vhost-blk%d",
>> blk->index);
>> + iov_iter_init(&iter, WRITE, req->iov, req->iov_nr, req->len);
>> + ret = copy_to_iter(id, len, &iter);
>> + status = ret != len ? 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;
>> +}
>> +
>> +static void vhost_blk_handle_guest_kick(struct vhost_work *work)
>> +{
>> + struct virtio_blk_outhdr hdr;
>> + struct vhost_blk_vq *blk_vq;
>> + struct vhost_virtqueue *vq;
>> + struct iovec hdr_iovec[VHOST_MAX_METADATA_IOV];
>> + struct vhost_blk *blk;
>> + struct iov_iter iter;
>> + 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);
>> + blk_vq = container_of(vq, struct vhost_blk_vq, vq);
>> +
>> + f = vhost_vq_get_backend(vq);
>> + if (!f)
>> + return;
>> +
>> + vhost_disable_notify(&blk->dev, vq);
>> + for (;;) {
>> + head = vhost_get_vq_desc(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;
>> + }
>
> > Maybe vhost_discard_vq_desc here?
> >
> > Looking on implementation in get_rx_bufs using both vhost_get_vq_desc
> > and counterpart vhost_discard_vq_desc we need to call
> > vhost_discard_vq_desc on error everywhere.
head == vq->num is not an error. This mean vq is empty. No need to
discard anything.
> >
> > Also as you have loop here maybe you need to do count like headcount in
> > get_rx_bufs and do: vhost_discard_vq_desc(vq, headcount); not
> > vhost_discard_vq_desc(vq, 1); as you do below.
vhost-net does a batching there. We only process one request at a time
so discard also only last one in case of error (as previous is already
in-progress)
> >
> > I honestly don't understand what vhost_get_vq_desc actually does, maybe
> > some explanation here would be helpful to understand what the right
> > error path logic should be.
vhost_get_vq_desc() reads the virtqueue content and creates a series of
iovecs based on the request. vhost_discard_vq_desc() just reverses
internal virtqueue state so next vhost_get_vq_desc() will create iovecs
for the same requests again.
It is hard to say what a correct error path logic looks like as
resulting code iovec is inside a request (so what if it is malformed?)
>
> You seem to miss this comment in v2:
> https://lists.openvz.org/pipermail/devel/2022-September/079964.html
>
>> + break;
>> + }
>> +
>> + ret = move_iovec(vq->iov, hdr_iovec, sizeof(hdr), in + out,
>> ARRAY_SIZE(hdr_iovec));
>> + if (ret < 0) {
>> + vq_err(vq, "virtio_blk_hdr is too split!");
>> + vhost_discard_vq_desc(vq, 1);
>> + break;
>> + }
>> +
>> + iov_iter_init(&iter, READ, hdr_iovec, ARRAY_SIZE(hdr_iovec),
>> sizeof(hdr));
>> + ret = copy_from_iter(&hdr, sizeof(hdr), &iter);
>> + if (ret != sizeof(hdr)) {
>> + vq_err(vq, "Failed to get block header: read %d bytes
>> instead of %ld!\n",
>> + ret, sizeof(hdr));
>> + vhost_discard_vq_desc(vq, 1);
>> + break;
>> + }
>> +
>> + if (vhost_blk_req_handle(vq, &hdr, head, out + in, f) < 0) {
>> + vhost_discard_vq_desc(vq, 1);
>> + break;
>> + }
>> +
>> + if (!llist_empty(&blk_vq->llhead)) {
>> + vhost_poll_queue(&vq->poll);
>> + break;
>> + }
>> + }
>> +}
>> +
>> +static void vhost_blk_handle_host_kick(struct vhost_work *work)
>> +{
>> + struct vhost_blk_vq *blk_vq;
>> + struct vhost_virtqueue *vq;
>> + struct vhost_blk_req *req;
>> + struct llist_node *llnode;
>> + struct vhost_blk *blk = NULL;
>> + bool added, zero;
>> + u8 status;
>> + int ret;
>> +
>> + blk_vq = container_of(work, struct vhost_blk_vq, work);
>> + vq = &blk_vq->vq;
>> + llnode = llist_del_all(&blk_vq->llhead);
>> + added = false;
>> + while (llnode) {
>> + req = llist_entry(llnode, struct vhost_blk_req, llnode);
>> + llnode = llist_next(llnode);
>> +
>> + if (!blk)
>> + blk = req->blk;
>> +
>> + vhost_blk_req_umap(req);
>> +
>> + status = req->bio_err == 0 ? VIRTIO_BLK_S_OK :
>> VIRTIO_BLK_S_IOERR;
>> + ret = vhost_blk_set_status(req, status);
>> + if (unlikely(ret))
>> + continue;
>> +
>> + vhost_add_used(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, vq);
>> +}
>> +
>> +static void vhost_blk_flush(struct vhost_blk *blk)
>> +{
>> + int i;
>> +
>> + spin_lock(&blk->flush_lock);
>> + blk->during_flush = 1;
>> + spin_unlock(&blk->flush_lock);
>> +
>> + for (i = 0; i < VHOST_BLK_VQ_MAX; i++)
>> + vhost_poll_flush(&blk->vqs[i].vq.poll);
>> + vhost_work_dev_flush(&blk->dev);
>> + /*
>> + * 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_drop_backends(struct vhost_blk *blk)
>> +{
>> + struct vhost_virtqueue *vq;
>> + int i;
>> +
>> + for (i = 0; i < VHOST_BLK_VQ_MAX; i++) {
>> + vq = &blk->vqs[i].vq;
>> +
>> + mutex_lock(&vq->mutex);
>> + vhost_vq_set_backend(vq, NULL);
>> + mutex_unlock(&vq->mutex);
>> + }
>> +}
>> +
>> +static int vhost_blk_open(struct inode *inode, struct file *file)
>> +{
>> + struct vhost_blk *blk;
>> + struct vhost_virtqueue **vqs;
>> + int ret = 0, i = 0;
>> +
>> + blk = kvzalloc(sizeof(*blk), GFP_KERNEL);
>> + if (!blk) {
>> + ret = -ENOMEM;
>> + goto out;
>> + }
>> +
>> + vqs = kcalloc(VHOST_BLK_VQ_MAX, sizeof(*vqs), GFP_KERNEL);
>> + if (!vqs) {
>> + ret = -ENOMEM;
>> + goto out_blk;
>> + }
>> +
>> + for (i = 0; i < VHOST_BLK_VQ_MAX; i++) {
>> + blk->vqs[i].vq.handle_kick = vhost_blk_handle_guest_kick;
>> + vqs[i] = &blk->vqs[i].vq;
>> + }
>> +
>> + blk->index = gen++;
>> +
>> + 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);
>> +
>> + vhost_dev_init(&blk->dev, vqs, VHOST_BLK_VQ_MAX, UIO_MAXIOV,
>> + VHOST_DEV_WEIGHT, VHOST_DEV_PKT_WEIGHT, true, NULL);
>> + file->private_data = blk;
>> +
>> + for (i = 0; i < VHOST_BLK_VQ_MAX; i++)
>> + vhost_work_init(&blk->vqs[i].work, vhost_blk_handle_host_kick);
>> +
>> + return ret;
>> +out_blk:
>> + kvfree(blk);
>> +out:
>> + return ret;
>> +}
>> +
>> +static int vhost_blk_release(struct inode *inode, struct file *f)
>> +{
>> + struct vhost_blk *blk = f->private_data;
>> + int i;
>> +
>> + vhost_blk_drop_backends(blk);
>> + vhost_blk_flush(blk);
>> + vhost_dev_stop(&blk->dev);
>> + if (blk->backend)
>> + fput(blk->backend);
>> + vhost_dev_cleanup(&blk->dev);
>> + for (i = 0; i < VHOST_BLK_VQ_MAX; i++)
>> + kvfree(blk->vqs[i].req);
>> + kfree(blk->dev.vqs);
>> + kvfree(blk);
>> +
>> + return 0;
>> +}
>> +
>> +static int vhost_blk_set_features(struct vhost_blk *blk, u64 features)
>> +{
>> + struct vhost_virtqueue *vq;
>> + int i;
>> +
>> + mutex_lock(&blk->dev.mutex);
>> + if ((features & (1 << VHOST_F_LOG_ALL)) &&
>> + !vhost_log_access_ok(&blk->dev)) {
>> + mutex_unlock(&blk->dev.mutex);
>> + return -EFAULT;
>> + }
>> +
>> + for (i = 0; i < VHOST_BLK_VQ_MAX; i++) {
>> + vq = &blk->vqs[i].vq;
>> + mutex_lock(&vq->mutex);
>> + vq->acked_features = features & (VHOST_BLK_FEATURES);
>> + mutex_unlock(&vq->mutex);
>> + }
>> +
>> + vhost_blk_flush(blk);
>> + mutex_unlock(&blk->dev.mutex);
>> +
>> + return 0;
>> +}
>> +
>> +static long vhost_blk_set_backend(struct vhost_blk *blk, int fd)
>> +{
>> + struct vhost_virtqueue *vq;
>> + struct file *file;
>> + struct inode *inode;
>> + int ret, i;
>> +
>> + mutex_lock(&blk->dev.mutex);
>> + ret = vhost_dev_check_owner(&blk->dev);
>> + if (ret)
>> + goto out_dev;
>> +
>> + if (blk->backend) {
>> + ret = -EBUSY;
>> + goto out_dev;
>> + }
>> +
>> + file = fget(fd);
>> + if (IS_ERR(file)) {
>> + ret = PTR_ERR(file);
>> + goto out_dev;
>> + }
>> +
>> + inode = file->f_mapping->host;
>> + if (!S_ISBLK(inode->i_mode)) {
>> + ret = -EFAULT;
>> + goto out_file;
>> + }
>> +
>> + for (i = 0; i < VHOST_BLK_VQ_MAX; i++) {
>> + vq = &blk->vqs[i].vq;
>> + if (!vhost_vq_access_ok(vq)) {
>> + ret = -EFAULT;
>> + goto out_drop;
>> + }
>> +
>> + mutex_lock(&vq->mutex);
>> + vhost_vq_set_backend(vq, file);
>> + ret = vhost_vq_init_access(vq);
>> + mutex_unlock(&vq->mutex);
>> + }
>> +
>> + blk->backend = file;
>> +
>> + mutex_unlock(&blk->dev.mutex);
>> + return 0;
>> +
>> +out_drop:
>> + vhost_blk_drop_backends(blk);
>> +out_file:
>> + fput(file);
>> +out_dev:
>> + mutex_unlock(&blk->dev.mutex);
>> + return ret;
>> +}
>> +
>> +static long vhost_blk_reset_owner(struct vhost_blk *blk)
>> +{
>> + struct vhost_iotlb *umem;
>> + int err, i;
>> +
>> + mutex_lock(&blk->dev.mutex);
>> + err = vhost_dev_check_owner(&blk->dev);
>> + if (err)
>> + goto done;
>> + umem = vhost_dev_reset_owner_prepare();
>> + if (!umem) {
>> + err = -ENOMEM;
>> + goto done;
>> + }
>> + vhost_blk_drop_backends(blk);
>> + if (blk->backend) {
>> + fput(blk->backend);
>> + blk->backend = NULL;
>> + }
>> + vhost_blk_flush(blk);
>> + vhost_dev_stop(&blk->dev);
>> + vhost_dev_reset_owner(&blk->dev, umem);
>> +
>> + for (i = 0; i < VHOST_BLK_VQ_MAX; i++) {
>> + kvfree(blk->vqs[i].req);
>> + blk->vqs[i].req = NULL;
>> + }
>> +
>> +done:
>> + mutex_unlock(&blk->dev.mutex);
>> + return err;
>> +}
>> +
>> +static int vhost_blk_setup(struct vhost_blk *blk, void __user *argp)
>> +{
>> + struct vhost_vring_state s;
>> +
>> + if (copy_from_user(&s, argp, sizeof(s)))
>> + return -EFAULT;
>> +
>> + if (blk->vqs[s.index].req)
>> + return 0;
>> +
>> + blk->vqs[s.index].req = kvmalloc(sizeof(struct vhost_blk_req) *
>> s.num, GFP_KERNEL);
>> + if (!blk->vqs[s.index].req)
>> + 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.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, argp);
>> + if (ret == -ENOIOCTLCMD)
>> + ret = vhost_vring_ioctl(&blk->dev, ioctl, argp);
>> + if (!ret && ioctl == VHOST_SET_VRING_NUM)
>> + ret = vhost_blk_setup(blk, argp);
>> + 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,
>> +};
>> +module_misc_device(vhost_blk_misc);
>> +
>> +MODULE_VERSION("0.0.1");
>> +MODULE_LICENSE("GPL v2");
>> +MODULE_AUTHOR("Andrey Zhadchenko");
>> +MODULE_DESCRIPTION("Host kernel accelerator for virtio_blk");
>> diff --git a/include/uapi/linux/vhost.h b/include/uapi/linux/vhost.h
>> index c998860d7bbc..13caf114bcde 100644
>> --- a/include/uapi/linux/vhost.h
>> +++ b/include/uapi/linux/vhost.h
>> @@ -150,4 +150,9 @@
>> /* Get the valid iova range */
>> #define VHOST_VDPA_GET_IOVA_RANGE _IOR(VHOST_VIRTIO, 0x78, \
>> struct vhost_vdpa_iova_range)
>> +
>> +/* VHOST_BLK specific defines */
>> +#define VHOST_BLK_SET_BACKEND _IOW(VHOST_VIRTIO, 0xFF, \
>> + struct vhost_vring_file)
>> +
>> #endif
>
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