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Date: Sat, 26 Oct 2013 00:06:13 +0800
From: Asias He <asias@...hat.com>
To: Christoph Hellwig <hch@...radead.org>
Cc: Jens Axboe <axboe@...nel.dk>,
Rusty Russell <rusty@...tcorp.com.au>,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] virtio_blk: blk-mq support
On Fri, Oct 25, 2013 at 06:05:01AM -0700, Christoph Hellwig wrote:
> Switch virtio-blk from the dual support for old-style requests and bios
> to use the block-multiqueue. For now pretend to have 4 issue queues
> as Jens pulled that out of his this hair and it worked.
>
> Signed-off-by: Jens Axboe <axboe@...nel.dk>
> Signed-off-by: Christoph Hellwig <hch@....de>
> ---
> drivers/block/virtio_blk.c | 312 +++++++++-----------------------------------
> 1 file changed, 65 insertions(+), 247 deletions(-)
>
> diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
> index 5cdf88b..87f099d 100644
> --- a/drivers/block/virtio_blk.c
> +++ b/drivers/block/virtio_blk.c
> @@ -11,12 +11,11 @@
> #include <linux/string_helpers.h>
> #include <scsi/scsi_cmnd.h>
> #include <linux/idr.h>
> +#include <linux/blk-mq.h>
> +#include <linux/numa.h>
>
> #define PART_BITS 4
>
> -static bool use_bio;
> -module_param(use_bio, bool, S_IRUGO);
> -
> static int major;
> static DEFINE_IDA(vd_index_ida);
>
> @@ -26,13 +25,11 @@ struct virtio_blk
> {
> struct virtio_device *vdev;
> struct virtqueue *vq;
> - wait_queue_head_t queue_wait;
> + spinlock_t vq_lock;
>
> /* The disk structure for the kernel. */
> struct gendisk *disk;
>
> - mempool_t *pool;
> -
> /* Process context for config space updates */
> struct work_struct config_work;
>
> @@ -47,15 +44,11 @@ struct virtio_blk
>
> /* Ida index - used to track minor number allocations. */
> int index;
> -
> - /* Scatterlist: can be too big for stack. */
> - struct scatterlist sg[/*sg_elems*/];
> };
>
> struct virtblk_req
> {
> struct request *req;
> - struct bio *bio;
> struct virtio_blk_outhdr out_hdr;
> struct virtio_scsi_inhdr in_hdr;
> struct work_struct work;
We can drop more things:
diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index 87f099d..c5ca368 100644
--- a/drivers/block/virtio_blk.c
+++ b/drivers/block/virtio_blk.c
@@ -51,20 +51,10 @@ struct virtblk_req
struct request *req;
struct virtio_blk_outhdr out_hdr;
struct virtio_scsi_inhdr in_hdr;
- struct work_struct work;
- struct virtio_blk *vblk;
- int flags;
u8 status;
struct scatterlist sg[];
};
-enum {
- VBLK_IS_FLUSH = 1,
- VBLK_REQ_FLUSH = 2,
- VBLK_REQ_DATA = 4,
- VBLK_REQ_FUA = 8,
-};
-
static inline int virtblk_result(struct virtblk_req *vbr)
{
switch (vbr->status) {
> @@ -84,22 +77,6 @@ static inline int virtblk_result(struct virtblk_req *vbr)
> }
> }
>
> -static inline struct virtblk_req *virtblk_alloc_req(struct virtio_blk *vblk,
> - gfp_t gfp_mask)
> -{
> - struct virtblk_req *vbr;
> -
> - vbr = mempool_alloc(vblk->pool, gfp_mask);
> - if (!vbr)
> - return NULL;
> -
> - vbr->vblk = vblk;
> - if (use_bio)
> - sg_init_table(vbr->sg, vblk->sg_elems);
> -
> - return vbr;
> -}
> -
> static int __virtblk_add_req(struct virtqueue *vq,
> struct virtblk_req *vbr,
> struct scatterlist *data_sg,
> @@ -143,83 +120,8 @@ static int __virtblk_add_req(struct virtqueue *vq,
> return virtqueue_add_sgs(vq, sgs, num_out, num_in, vbr, GFP_ATOMIC);
> }
>
> -static void virtblk_add_req(struct virtblk_req *vbr, bool have_data)
> -{
> - struct virtio_blk *vblk = vbr->vblk;
> - DEFINE_WAIT(wait);
> - int ret;
> -
> - spin_lock_irq(vblk->disk->queue->queue_lock);
> - while (unlikely((ret = __virtblk_add_req(vblk->vq, vbr, vbr->sg,
> - have_data)) < 0)) {
> - prepare_to_wait_exclusive(&vblk->queue_wait, &wait,
> - TASK_UNINTERRUPTIBLE);
> -
> - spin_unlock_irq(vblk->disk->queue->queue_lock);
> - io_schedule();
> - spin_lock_irq(vblk->disk->queue->queue_lock);
> -
> - finish_wait(&vblk->queue_wait, &wait);
> - }
> -
> - virtqueue_kick(vblk->vq);
> - spin_unlock_irq(vblk->disk->queue->queue_lock);
> -}
> -
> -static void virtblk_bio_send_flush(struct virtblk_req *vbr)
> -{
> - vbr->flags |= VBLK_IS_FLUSH;
> - vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
> - vbr->out_hdr.sector = 0;
> - vbr->out_hdr.ioprio = 0;
> -
> - virtblk_add_req(vbr, false);
> -}
> -
> -static void virtblk_bio_send_data(struct virtblk_req *vbr)
> -{
> - struct virtio_blk *vblk = vbr->vblk;
> - struct bio *bio = vbr->bio;
> - bool have_data;
> -
> - vbr->flags &= ~VBLK_IS_FLUSH;
> - vbr->out_hdr.type = 0;
> - vbr->out_hdr.sector = bio->bi_sector;
> - vbr->out_hdr.ioprio = bio_prio(bio);
> -
> - if (blk_bio_map_sg(vblk->disk->queue, bio, vbr->sg)) {
> - have_data = true;
> - if (bio->bi_rw & REQ_WRITE)
> - vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
> - else
> - vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
> - } else
> - have_data = false;
> -
> - virtblk_add_req(vbr, have_data);
> -}
> -
> -static void virtblk_bio_send_data_work(struct work_struct *work)
> -{
> - struct virtblk_req *vbr;
> -
> - vbr = container_of(work, struct virtblk_req, work);
> -
> - virtblk_bio_send_data(vbr);
> -}
> -
> -static void virtblk_bio_send_flush_work(struct work_struct *work)
> -{
> - struct virtblk_req *vbr;
> -
> - vbr = container_of(work, struct virtblk_req, work);
> -
> - virtblk_bio_send_flush(vbr);
> -}
> -
> static inline void virtblk_request_done(struct virtblk_req *vbr)
> {
> - struct virtio_blk *vblk = vbr->vblk;
> struct request *req = vbr->req;
> int error = virtblk_result(vbr);
>
> @@ -231,90 +133,43 @@ static inline void virtblk_request_done(struct virtblk_req *vbr)
> req->errors = (error != 0);
> }
>
> - __blk_end_request_all(req, error);
> - mempool_free(vbr, vblk->pool);
> -}
> -
> -static inline void virtblk_bio_flush_done(struct virtblk_req *vbr)
> -{
> - struct virtio_blk *vblk = vbr->vblk;
> -
> - if (vbr->flags & VBLK_REQ_DATA) {
> - /* Send out the actual write data */
> - INIT_WORK(&vbr->work, virtblk_bio_send_data_work);
> - queue_work(virtblk_wq, &vbr->work);
> - } else {
> - bio_endio(vbr->bio, virtblk_result(vbr));
> - mempool_free(vbr, vblk->pool);
> - }
> -}
> -
> -static inline void virtblk_bio_data_done(struct virtblk_req *vbr)
> -{
> - struct virtio_blk *vblk = vbr->vblk;
> -
> - if (unlikely(vbr->flags & VBLK_REQ_FUA)) {
> - /* Send out a flush before end the bio */
> - vbr->flags &= ~VBLK_REQ_DATA;
> - INIT_WORK(&vbr->work, virtblk_bio_send_flush_work);
> - queue_work(virtblk_wq, &vbr->work);
> - } else {
> - bio_endio(vbr->bio, virtblk_result(vbr));
> - mempool_free(vbr, vblk->pool);
> - }
> -}
> -
> -static inline void virtblk_bio_done(struct virtblk_req *vbr)
> -{
> - if (unlikely(vbr->flags & VBLK_IS_FLUSH))
> - virtblk_bio_flush_done(vbr);
> - else
> - virtblk_bio_data_done(vbr);
> + blk_mq_end_io(req, error);
> }
>
> static void virtblk_done(struct virtqueue *vq)
> {
> struct virtio_blk *vblk = vq->vdev->priv;
> - bool bio_done = false, req_done = false;
> + bool req_done = false;
> struct virtblk_req *vbr;
> unsigned long flags;
> unsigned int len;
>
> - spin_lock_irqsave(vblk->disk->queue->queue_lock, flags);
> + spin_lock_irqsave(&vblk->vq_lock, flags);
> do {
> virtqueue_disable_cb(vq);
> while ((vbr = virtqueue_get_buf(vblk->vq, &len)) != NULL) {
> - if (vbr->bio) {
> - virtblk_bio_done(vbr);
> - bio_done = true;
> - } else {
> - virtblk_request_done(vbr);
> - req_done = true;
> - }
> + virtblk_request_done(vbr);
> + req_done = true;
> }
> } while (!virtqueue_enable_cb(vq));
> + spin_unlock_irqrestore(&vblk->vq_lock, flags);
> +
> /* In case queue is stopped waiting for more buffers. */
> if (req_done)
> - blk_start_queue(vblk->disk->queue);
> - spin_unlock_irqrestore(vblk->disk->queue->queue_lock, flags);
> -
> - if (bio_done)
> - wake_up(&vblk->queue_wait);
> + blk_mq_start_stopped_hw_queues(vblk->disk->queue);
> }
>
> -static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
> - struct request *req)
> +static int virtio_queue_rq(struct blk_mq_hw_ctx *hctx, struct request *req)
> {
> + struct virtio_blk *vblk = hctx->queue->queuedata;
> + struct virtblk_req *vbr = req->special;
> + unsigned long flags;
> unsigned int num;
> - struct virtblk_req *vbr;
> + const bool last = (req->cmd_flags & REQ_END) != 0;
>
> - vbr = virtblk_alloc_req(vblk, GFP_ATOMIC);
> - if (!vbr)
> - /* When another request finishes we'll try again. */
> - return false;
> + BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
>
> vbr->req = req;
> - vbr->bio = NULL;
> if (req->cmd_flags & REQ_FLUSH) {
> vbr->out_hdr.type = VIRTIO_BLK_T_FLUSH;
> vbr->out_hdr.sector = 0;
> @@ -342,7 +197,7 @@ static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
> }
> }
>
> - num = blk_rq_map_sg(q, vbr->req, vblk->sg);
> + num = blk_rq_map_sg(hctx->queue, vbr->req, vbr->sg);
> if (num) {
> if (rq_data_dir(vbr->req) == WRITE)
> vbr->out_hdr.type |= VIRTIO_BLK_T_OUT;
> @@ -350,63 +205,18 @@ static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
> vbr->out_hdr.type |= VIRTIO_BLK_T_IN;
> }
>
> - if (__virtblk_add_req(vblk->vq, vbr, vblk->sg, num) < 0) {
> - mempool_free(vbr, vblk->pool);
> - return false;
> - }
> -
> - return true;
> -}
> -
> -static void virtblk_request(struct request_queue *q)
> -{
> - struct virtio_blk *vblk = q->queuedata;
> - struct request *req;
> - unsigned int issued = 0;
> -
> - while ((req = blk_peek_request(q)) != NULL) {
> - BUG_ON(req->nr_phys_segments + 2 > vblk->sg_elems);
> -
> - /* If this request fails, stop queue and wait for something to
> - finish to restart it. */
> - if (!do_req(q, vblk, req)) {
> - blk_stop_queue(q);
> - break;
> - }
> - blk_start_request(req);
> - issued++;
> - }
> -
> - if (issued)
> + spin_lock_irqsave(&vblk->vq_lock, flags);
> + if (__virtblk_add_req(vblk->vq, vbr, vbr->sg, num) < 0) {
> + spin_unlock_irqrestore(&vblk->vq_lock, flags);
> + blk_mq_stop_hw_queue(hctx);
> virtqueue_kick(vblk->vq);
> -}
> -
> -static void virtblk_make_request(struct request_queue *q, struct bio *bio)
> -{
> - struct virtio_blk *vblk = q->queuedata;
> - struct virtblk_req *vbr;
> -
> - BUG_ON(bio->bi_phys_segments + 2 > vblk->sg_elems);
> -
> - vbr = virtblk_alloc_req(vblk, GFP_NOIO);
> - if (!vbr) {
> - bio_endio(bio, -ENOMEM);
> - return;
> + return BLK_MQ_RQ_QUEUE_BUSY;
> }
> + spin_unlock_irqrestore(&vblk->vq_lock, flags);
>
> - vbr->bio = bio;
> - vbr->flags = 0;
> - if (bio->bi_rw & REQ_FLUSH)
> - vbr->flags |= VBLK_REQ_FLUSH;
> - if (bio->bi_rw & REQ_FUA)
> - vbr->flags |= VBLK_REQ_FUA;
> - if (bio->bi_size)
> - vbr->flags |= VBLK_REQ_DATA;
> -
> - if (unlikely(vbr->flags & VBLK_REQ_FLUSH))
> - virtblk_bio_send_flush(vbr);
> - else
> - virtblk_bio_send_data(vbr);
> + if (last)
> + virtqueue_kick(vblk->vq);
> + return BLK_MQ_RQ_QUEUE_OK;
> }
>
> /* return id (s/n) string for *disk to *id_str
> @@ -680,12 +490,35 @@ static const struct device_attribute dev_attr_cache_type_rw =
> __ATTR(cache_type, S_IRUGO|S_IWUSR,
> virtblk_cache_type_show, virtblk_cache_type_store);
>
> +static struct blk_mq_ops virtio_mq_ops = {
> + .queue_rq = virtio_queue_rq,
> + .map_queue = blk_mq_map_queue,
> + .alloc_hctx = blk_mq_alloc_single_hw_queue,
> + .free_hctx = blk_mq_free_single_hw_queue,
> +};
> +
> +static struct blk_mq_reg virtio_mq_reg = {
> + .ops = &virtio_mq_ops,
> + .nr_hw_queues = 4,
> + .queue_depth = 64,
> + .numa_node = NUMA_NO_NODE,
> + .flags = BLK_MQ_F_SHOULD_MERGE,
> +};
> +
> +static void virtblk_init_vbr(void *data, struct blk_mq_hw_ctx *hctx,
> + struct request *rq, unsigned int nr)
> +{
> + struct virtio_blk *vblk = data;
> + struct virtblk_req *vbr = rq->special;
> +
> + sg_init_table(vbr->sg, vblk->sg_elems);
> +}
> +
> static int virtblk_probe(struct virtio_device *vdev)
> {
> struct virtio_blk *vblk;
> struct request_queue *q;
> int err, index;
> - int pool_size;
>
> u64 cap;
> u32 v, blk_size, sg_elems, opt_io_size;
> @@ -709,17 +542,14 @@ static int virtblk_probe(struct virtio_device *vdev)
>
> /* We need an extra sg elements at head and tail. */
> sg_elems += 2;
> - vdev->priv = vblk = kmalloc(sizeof(*vblk) +
> - sizeof(vblk->sg[0]) * sg_elems, GFP_KERNEL);
> + vdev->priv = vblk = kmalloc(sizeof(*vblk), GFP_KERNEL);
> if (!vblk) {
> err = -ENOMEM;
> goto out_free_index;
> }
>
> - init_waitqueue_head(&vblk->queue_wait);
> vblk->vdev = vdev;
> vblk->sg_elems = sg_elems;
> - sg_init_table(vblk->sg, vblk->sg_elems);
> mutex_init(&vblk->config_lock);
>
> INIT_WORK(&vblk->config_work, virtblk_config_changed_work);
> @@ -728,31 +558,27 @@ static int virtblk_probe(struct virtio_device *vdev)
> err = init_vq(vblk);
> if (err)
> goto out_free_vblk;
> -
> - pool_size = sizeof(struct virtblk_req);
> - if (use_bio)
> - pool_size += sizeof(struct scatterlist) * sg_elems;
> - vblk->pool = mempool_create_kmalloc_pool(1, pool_size);
> - if (!vblk->pool) {
> - err = -ENOMEM;
> - goto out_free_vq;
> - }
> + spin_lock_init(&vblk->vq_lock);
>
> /* FIXME: How many partitions? How long is a piece of string? */
> vblk->disk = alloc_disk(1 << PART_BITS);
> if (!vblk->disk) {
> err = -ENOMEM;
> - goto out_mempool;
> + goto out_free_vq;
> }
>
> - q = vblk->disk->queue = blk_init_queue(virtblk_request, NULL);
> + virtio_mq_reg.cmd_size =
> + sizeof(struct virtblk_req) +
> + sizeof(struct scatterlist) * sg_elems;
> +
> + q = vblk->disk->queue = blk_mq_init_queue(&virtio_mq_reg, vblk);
> if (!q) {
> err = -ENOMEM;
> goto out_put_disk;
> }
>
> - if (use_bio)
> - blk_queue_make_request(q, virtblk_make_request);
> + blk_mq_init_commands(q, virtblk_init_vbr, vblk);
> +
> q->queuedata = vblk;
>
> virtblk_name_format("vd", index, vblk->disk->disk_name, DISK_NAME_LEN);
> @@ -857,8 +683,6 @@ out_del_disk:
> blk_cleanup_queue(vblk->disk->queue);
> out_put_disk:
> put_disk(vblk->disk);
> -out_mempool:
> - mempool_destroy(vblk->pool);
> out_free_vq:
> vdev->config->del_vqs(vdev);
> out_free_vblk:
> @@ -890,7 +714,6 @@ static void virtblk_remove(struct virtio_device *vdev)
>
> refc = atomic_read(&disk_to_dev(vblk->disk)->kobj.kref.refcount);
> put_disk(vblk->disk);
> - mempool_destroy(vblk->pool);
> vdev->config->del_vqs(vdev);
> kfree(vblk);
>
> @@ -914,10 +737,7 @@ static int virtblk_freeze(struct virtio_device *vdev)
>
> flush_work(&vblk->config_work);
>
> - spin_lock_irq(vblk->disk->queue->queue_lock);
> - blk_stop_queue(vblk->disk->queue);
> - spin_unlock_irq(vblk->disk->queue->queue_lock);
> - blk_sync_queue(vblk->disk->queue);
> + blk_mq_stop_hw_queues(vblk->disk->queue);
>
> vdev->config->del_vqs(vdev);
> return 0;
> @@ -930,11 +750,9 @@ static int virtblk_restore(struct virtio_device *vdev)
>
> vblk->config_enable = true;
> ret = init_vq(vdev->priv);
> - if (!ret) {
> - spin_lock_irq(vblk->disk->queue->queue_lock);
> - blk_start_queue(vblk->disk->queue);
> - spin_unlock_irq(vblk->disk->queue->queue_lock);
> - }
> + if (!ret)
> + blk_mq_start_stopped_hw_queues(vblk->disk->queue);
> +
> return ret;
> }
> #endif
> --
> 1.7.10.4
>
>
--
Asias
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