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[SCSI] virtio-scsi: split scatterlist per target
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To improve performance for I/O to different targets, add a separate
scatterlist for each of them.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
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Paolo Bonzini authored and James Bottomley committed Jul 20, 2012
1 parent bce750b commit 2bd37f0
Showing 1 changed file with 94 additions and 47 deletions.
141 changes: 94 additions & 47 deletions drivers/scsi/virtio_scsi.c
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Original file line number Diff line number Diff line change
Expand Up @@ -50,18 +50,24 @@ struct virtio_scsi_vq {
struct virtqueue *vq;
};

/* Per-target queue state */
struct virtio_scsi_target_state {
/* Protects sg. Lock hierarchy is tgt_lock -> vq_lock. */
spinlock_t tgt_lock;

/* For sglist construction when adding commands to the virtqueue. */
struct scatterlist sg[];
};

/* Driver instance state */
struct virtio_scsi {
/* Protects sg[]. The lock hierarchy is sg_lock -> vq_lock. */
spinlock_t sg_lock;

struct virtio_device *vdev;

struct virtio_scsi_vq ctrl_vq;
struct virtio_scsi_vq event_vq;
struct virtio_scsi_vq req_vq;

/* For sglist construction when adding commands to the virtqueue. */
struct scatterlist sg[];
struct virtio_scsi_target_state *tgt[];
};

static struct kmem_cache *virtscsi_cmd_cache;
Expand Down Expand Up @@ -230,25 +236,17 @@ static void virtscsi_map_sgl(struct scatterlist *sg, unsigned int *p_idx,
* @req_size : size of the request buffer
* @resp_size : size of the response buffer
*
* Called with vq_lock held.
* Called with tgt_lock held.
*/
static void virtscsi_map_cmd(struct virtio_scsi *vscsi,
static void virtscsi_map_cmd(struct virtio_scsi_target_state *tgt,
struct virtio_scsi_cmd *cmd,
unsigned *out_num, unsigned *in_num,
size_t req_size, size_t resp_size)
{
struct scsi_cmnd *sc = cmd->sc;
struct scatterlist *sg = vscsi->sg;
struct scatterlist *sg = tgt->sg;
unsigned int idx = 0;

if (sc) {
struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
BUG_ON(scsi_sg_count(sc) > shost->sg_tablesize);

/* TODO: check feature bit and fail if unsupported? */
BUG_ON(sc->sc_data_direction == DMA_BIDIRECTIONAL);
}

/* Request header. */
sg_set_buf(&sg[idx++], &cmd->req, req_size);

Expand All @@ -268,20 +266,21 @@ static void virtscsi_map_cmd(struct virtio_scsi *vscsi,
*in_num = idx - *out_num;
}

static int virtscsi_kick_cmd(struct virtio_scsi *vscsi, struct virtio_scsi_vq *vq,
static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt,
struct virtio_scsi_vq *vq,
struct virtio_scsi_cmd *cmd,
size_t req_size, size_t resp_size, gfp_t gfp)
{
unsigned int out_num, in_num;
unsigned long flags;
int ret;

spin_lock_irqsave(&vscsi->sg_lock, flags);
virtscsi_map_cmd(vscsi, cmd, &out_num, &in_num, req_size, resp_size);
spin_lock_irqsave(&tgt->tgt_lock, flags);
virtscsi_map_cmd(tgt, cmd, &out_num, &in_num, req_size, resp_size);

spin_lock(&vq->vq_lock);
ret = virtqueue_add_buf(vq->vq, vscsi->sg, out_num, in_num, cmd, gfp);
spin_unlock(&vscsi->sg_lock);
ret = virtqueue_add_buf(vq->vq, tgt->sg, out_num, in_num, cmd, gfp);
spin_unlock(&tgt->tgt_lock);
if (ret >= 0)
ret = virtqueue_kick_prepare(vq->vq);

Expand All @@ -295,9 +294,16 @@ static int virtscsi_kick_cmd(struct virtio_scsi *vscsi, struct virtio_scsi_vq *v
static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc)
{
struct virtio_scsi *vscsi = shost_priv(sh);
struct virtio_scsi_target_state *tgt = vscsi->tgt[sc->device->id];
struct virtio_scsi_cmd *cmd;
int ret;

struct Scsi_Host *shost = virtio_scsi_host(vscsi->vdev);
BUG_ON(scsi_sg_count(sc) > shost->sg_tablesize);

/* TODO: check feature bit and fail if unsupported? */
BUG_ON(sc->sc_data_direction == DMA_BIDIRECTIONAL);

dev_dbg(&sc->device->sdev_gendev,
"cmd %p CDB: %#02x\n", sc, sc->cmnd[0]);

Expand All @@ -322,7 +328,7 @@ static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc)
BUG_ON(sc->cmd_len > VIRTIO_SCSI_CDB_SIZE);
memcpy(cmd->req.cmd.cdb, sc->cmnd, sc->cmd_len);

if (virtscsi_kick_cmd(vscsi, &vscsi->req_vq, cmd,
if (virtscsi_kick_cmd(tgt, &vscsi->req_vq, cmd,
sizeof cmd->req.cmd, sizeof cmd->resp.cmd,
GFP_ATOMIC) >= 0)
ret = 0;
Expand All @@ -334,10 +340,11 @@ static int virtscsi_queuecommand(struct Scsi_Host *sh, struct scsi_cmnd *sc)
static int virtscsi_tmf(struct virtio_scsi *vscsi, struct virtio_scsi_cmd *cmd)
{
DECLARE_COMPLETION_ONSTACK(comp);
struct virtio_scsi_target_state *tgt = vscsi->tgt[cmd->sc->device->id];
int ret = FAILED;

cmd->comp = &comp;
if (virtscsi_kick_cmd(vscsi, &vscsi->ctrl_vq, cmd,
if (virtscsi_kick_cmd(tgt, &vscsi->ctrl_vq, cmd,
sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
GFP_NOIO) < 0)
goto out;
Expand Down Expand Up @@ -437,11 +444,49 @@ static void virtscsi_init_vq(struct virtio_scsi_vq *virtscsi_vq,
virtscsi_vq->vq = vq;
}

static struct virtio_scsi_target_state *virtscsi_alloc_tgt(
struct virtio_device *vdev, int sg_elems)
{
struct virtio_scsi_target_state *tgt;
gfp_t gfp_mask = GFP_KERNEL;

/* We need extra sg elements at head and tail. */
tgt = kmalloc(sizeof(*tgt) + sizeof(tgt->sg[0]) * (sg_elems + 2),
gfp_mask);

if (!tgt)
return NULL;

spin_lock_init(&tgt->tgt_lock);
sg_init_table(tgt->sg, sg_elems + 2);
return tgt;
}

static void virtscsi_remove_vqs(struct virtio_device *vdev)
{
struct Scsi_Host *sh = virtio_scsi_host(vdev);
struct virtio_scsi *vscsi = shost_priv(sh);
u32 i, num_targets;

/* Stop all the virtqueues. */
vdev->config->reset(vdev);

num_targets = sh->max_id;
for (i = 0; i < num_targets; i++) {
kfree(vscsi->tgt[i]);
vscsi->tgt[i] = NULL;
}

vdev->config->del_vqs(vdev);
}

static int virtscsi_init(struct virtio_device *vdev,
struct virtio_scsi *vscsi)
struct virtio_scsi *vscsi, int num_targets)
{
int err;
struct virtqueue *vqs[3];
u32 i, sg_elems;

vq_callback_t *callbacks[] = {
virtscsi_ctrl_done,
virtscsi_event_done,
Expand All @@ -464,47 +509,57 @@ static int virtscsi_init(struct virtio_device *vdev,

virtscsi_config_set(vdev, cdb_size, VIRTIO_SCSI_CDB_SIZE);
virtscsi_config_set(vdev, sense_size, VIRTIO_SCSI_SENSE_SIZE);
return 0;

/* We need to know how many segments before we allocate. */
sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;

for (i = 0; i < num_targets; i++) {
vscsi->tgt[i] = virtscsi_alloc_tgt(vdev, sg_elems);
if (!vscsi->tgt[i]) {
err = -ENOMEM;
goto out;
}
}
err = 0;

out:
if (err)
virtscsi_remove_vqs(vdev);
return err;
}

static int __devinit virtscsi_probe(struct virtio_device *vdev)
{
struct Scsi_Host *shost;
struct virtio_scsi *vscsi;
int err;
u32 sg_elems;
u32 sg_elems, num_targets;
u32 cmd_per_lun;

/* We need to know how many segments before we allocate.
* We need an extra sg elements at head and tail.
*/
sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;

/* Allocate memory and link the structs together. */
num_targets = virtscsi_config_get(vdev, max_target) + 1;
shost = scsi_host_alloc(&virtscsi_host_template,
sizeof(*vscsi) + sizeof(vscsi->sg[0]) * (sg_elems + 2));
sizeof(*vscsi)
+ num_targets * sizeof(struct virtio_scsi_target_state));

if (!shost)
return -ENOMEM;

sg_elems = virtscsi_config_get(vdev, seg_max) ?: 1;
shost->sg_tablesize = sg_elems;
vscsi = shost_priv(shost);
vscsi->vdev = vdev;
vdev->priv = shost;

/* Random initializations. */
spin_lock_init(&vscsi->sg_lock);
sg_init_table(vscsi->sg, sg_elems + 2);

err = virtscsi_init(vdev, vscsi);
err = virtscsi_init(vdev, vscsi, num_targets);
if (err)
goto virtscsi_init_failed;

cmd_per_lun = virtscsi_config_get(vdev, cmd_per_lun) ?: 1;
shost->cmd_per_lun = min_t(u32, cmd_per_lun, shost->can_queue);
shost->max_sectors = virtscsi_config_get(vdev, max_sectors) ?: 0xFFFF;
shost->max_lun = virtscsi_config_get(vdev, max_lun) + 1;
shost->max_id = virtscsi_config_get(vdev, max_target) + 1;
shost->max_id = num_targets;
shost->max_channel = 0;
shost->max_cmd_len = VIRTIO_SCSI_CDB_SIZE;
err = scsi_add_host(shost, &vdev->dev);
Expand All @@ -522,14 +577,6 @@ static int __devinit virtscsi_probe(struct virtio_device *vdev)
return err;
}

static void virtscsi_remove_vqs(struct virtio_device *vdev)
{
/* Stop all the virtqueues. */
vdev->config->reset(vdev);

vdev->config->del_vqs(vdev);
}

static void __devexit virtscsi_remove(struct virtio_device *vdev)
{
struct Scsi_Host *shost = virtio_scsi_host(vdev);
Expand All @@ -552,7 +599,7 @@ static int virtscsi_restore(struct virtio_device *vdev)
struct Scsi_Host *sh = virtio_scsi_host(vdev);
struct virtio_scsi *vscsi = shost_priv(sh);

return virtscsi_init(vdev, vscsi);
return virtscsi_init(vdev, vscsi, sh->max_id);
}
#endif

Expand Down

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