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Message-ID: <51249986.3040805@redhat.com>
Date: Wed, 20 Feb 2013 17:38:14 +0800
From: Asias He <asias@...hat.com>
To: Wanlong Gao <gaowanlong@...fujitsu.com>
CC: rusty@...tcorp.com.au, pbonzini@...hat.com, mst@...hat.com,
linux-kernel@...r.kernel.org,
virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH 17/16] virtio-scsi: use virtqueue_add_sgs for command
buffers
On 02/20/2013 04:37 PM, Wanlong Gao wrote:
> Using the new virtqueue_add_sgs function lets us simplify the queueing
> path. In particular, all data protected by the tgt_lock is just gone
> (multiqueue will find a new use for the lock).
>
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> Signed-off-by: Wanlong Gao <gaowanlong@...fujitsu.com>
> ---
> drivers/scsi/virtio_scsi.c | 93 ++++++++++++++++------------------------------
> 1 file changed, 33 insertions(+), 60 deletions(-)
>
> diff --git a/drivers/scsi/virtio_scsi.c b/drivers/scsi/virtio_scsi.c
> index 3449a1f..b002d7b 100644
> --- a/drivers/scsi/virtio_scsi.c
> +++ b/drivers/scsi/virtio_scsi.c
> @@ -59,11 +59,8 @@ struct virtio_scsi_vq {
>
> /* Per-target queue state */
> struct virtio_scsi_target_state {
> - /* Protects sg. Lock hierarchy is tgt_lock -> vq_lock. */
> + /* Never held at the same time as vq_lock. */
> spinlock_t tgt_lock;
> -
> - /* For sglist construction when adding commands to the virtqueue. */
> - struct scatterlist sg[];
> };
>
> /* Driver instance state */
> @@ -351,75 +348,57 @@ static void virtscsi_event_done(struct virtqueue *vq)
> spin_unlock_irqrestore(&vscsi->event_vq.vq_lock, flags);
> };
>
> -static void virtscsi_map_sgl(struct scatterlist *sg, unsigned int *p_idx,
> - struct scsi_data_buffer *sdb)
> -{
> - struct sg_table *table = &sdb->table;
> - struct scatterlist *sg_elem;
> - unsigned int idx = *p_idx;
> - int i;
> -
> - for_each_sg(table->sgl, sg_elem, table->nents, i)
> - sg[idx++] = *sg_elem;
> -
> - *p_idx = idx;
> -}
> -
> /**
> - * virtscsi_map_cmd - map a scsi_cmd to a virtqueue scatterlist
> - * @vscsi : virtio_scsi state
> + * virtscsi_add_cmd - add a virtio_scsi_cmd to a virtqueue
> + * @vq : the struct virtqueue we're talking about
> * @cmd : command structure
> - * @out_num : number of read-only elements
> - * @in_num : number of write-only elements
> * @req_size : size of the request buffer
> * @resp_size : size of the response buffer
> - *
> - * Called with tgt_lock held.
> + * @gfp : flags to use for memory allocations
> */
> -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)
> +static int virtscsi_add_cmd(struct virtqueue *vq,
> + struct virtio_scsi_cmd *cmd,
> + size_t req_size, size_t resp_size, gfp_t gfp)
> {
> struct scsi_cmnd *sc = cmd->sc;
> - struct scatterlist *sg = tgt->sg;
> - unsigned int idx = 0;
> + struct scatterlist *sgs[4], req, resp;
> + struct sg_table *out, *in;
> + unsigned out_num = 0, in_num = 0;
> +
> + out = in = NULL;
>
> - /* Request header. */
> - sg_set_buf(&sg[idx++], &cmd->req, req_size);
> + if (sc && sc->sc_data_direction != DMA_NONE) {
> + if (sc->sc_data_direction != DMA_FROM_DEVICE)
> + out = &scsi_out(sc)->table;
> + if (sc->sc_data_direction != DMA_TO_DEVICE)
> + in = &scsi_in(sc)->table;
> + }
>
> - /* Data-out buffer. */
> - if (sc && sc->sc_data_direction != DMA_FROM_DEVICE)
> - virtscsi_map_sgl(sg, &idx, scsi_out(sc));
> + sg_init_one(&req, &cmd->req, req_size);
> + sgs[out_num++] = &req;
>
> - *out_num = idx;
> + if (out)
> + sgs[out_num++] = out->sgl;
>
> - /* Response header. */
> - sg_set_buf(&sg[idx++], &cmd->resp, resp_size);
> + sg_init_one(&resp, &cmd->resp, resp_size);
> + sgs[out_num + in_num++] = &resp;
>
> - /* Data-in buffer */
Why do you want to drop all the comments?
> - if (sc && sc->sc_data_direction != DMA_TO_DEVICE)
> - virtscsi_map_sgl(sg, &idx, scsi_in(sc));
> + if (in)
> + sgs[out_num + in_num++] = in->sgl;
>
> - *in_num = idx - *out_num;
> + return virtqueue_add_sgs(vq, sgs, out_num, in_num, cmd, gfp);
> }
>
> -static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt,
> - struct virtio_scsi_vq *vq,
> +static int virtscsi_kick_cmd(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 err;
> bool needs_kick = false;
>
> - 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);
> - err = virtqueue_add_buf(vq->vq, tgt->sg, out_num, in_num, cmd, gfp);
> - spin_unlock(&tgt->tgt_lock);
> + spin_lock_irqsave(&vq->vq_lock, flags);
> + err = virtscsi_add_cmd(vq->vq, cmd, req_size, resp_size, gfp);
> if (!err)
> needs_kick = virtqueue_kick_prepare(vq->vq);
>
> @@ -433,7 +412,6 @@ static int virtscsi_kick_cmd(struct virtio_scsi_target_state *tgt,
> 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;
>
> @@ -467,7 +445,7 @@ 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(tgt, &vscsi->req_vq, cmd,
> + if (virtscsi_kick_cmd(&vscsi->req_vq, cmd,
> sizeof cmd->req.cmd, sizeof cmd->resp.cmd,
> GFP_ATOMIC) == 0)
> ret = 0;
> @@ -481,11 +459,10 @@ out:
> 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 = ∁
> - if (virtscsi_kick_cmd(tgt, &vscsi->ctrl_vq, cmd,
> + if (virtscsi_kick_cmd(&vscsi->ctrl_vq, cmd,
> sizeof cmd->req.tmf, sizeof cmd->resp.tmf,
> GFP_NOIO) < 0)
> goto out;
> @@ -591,15 +568,11 @@ static struct virtio_scsi_target_state *virtscsi_alloc_tgt(
> 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);
> -
> + tgt = kmalloc(sizeof(*tgt), gfp_mask);
> if (!tgt)
> return NULL;
>
> spin_lock_init(&tgt->tgt_lock);
> - sg_init_table(tgt->sg, sg_elems + 2);
> return tgt;
> }
>
>
--
Asias
--
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