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Subject[PATCH 2/2] virtio_blk: blk-mq support
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@kernel.dk>
Signed-off-by: Christoph Hellwig <hch@lst.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;
@@ -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



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