On 2/7/25 12:41 PM, Dongli Zhang wrote:
> The vhost-scsi I/O queue uses vhost_scsi_cmd. Pre-allocate the log buffer
> during vhost_scsi_cmd allocation, and free it when vhost_scsi_cmd is
> reclaimed.
>
> The cached log buffer will be uses in upcoming patches to log write
> descriptors for the I/O queue. The core idea is to cache the log in the
> per-command log buffer in the submission path, and use them to log write
> descriptors in the completion path.
>
> Suggested-by: Joao Martins <joao.m.martins@xxxxxxxxxx>
> Signed-off-by: Dongli Zhang <dongli.zhang@xxxxxxxxxx>
> ---
> drivers/vhost/scsi.c | 21 +++++++++++++++++++++
> 1 file changed, 21 insertions(+)
>
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index ee2310555740..5e6221cbbe9e 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -98,6 +98,11 @@ struct vhost_scsi_cmd {
> unsigned char tvc_cdb[VHOST_SCSI_MAX_CDB_SIZE];
> /* Sense buffer that will be mapped into outgoing status */
> unsigned char tvc_sense_buf[TRANSPORT_SENSE_BUFFER];
> + /*
> + * Dirty write descriptors of this command.
> + */
> + struct vhost_log *tvc_log;
> + unsigned int tvc_log_num;
> /* Completed commands list, serviced from vhost worker thread */
> struct llist_node tvc_completion_list;
> /* Used to track inflight cmd */
> @@ -619,6 +624,7 @@ vhost_scsi_get_cmd(struct vhost_virtqueue *vq, struct vhost_scsi_tpg *tpg,
> struct vhost_scsi_nexus *tv_nexus;
> struct scatterlist *sg, *prot_sg;
> struct iovec *tvc_resp_iov;
> + struct vhost_log *log;
> struct page **pages;
> int tag;
>
> @@ -639,6 +645,7 @@ vhost_scsi_get_cmd(struct vhost_virtqueue *vq, struct vhost_scsi_tpg *tpg,
> prot_sg = cmd->tvc_prot_sgl;
> pages = cmd->tvc_upages;
> tvc_resp_iov = cmd->tvc_resp_iov;
> + log = cmd->tvc_log;
> memset(cmd, 0, sizeof(*cmd));
> cmd->tvc_sgl = sg;
> cmd->tvc_prot_sgl = prot_sg;
> @@ -652,6 +659,7 @@ vhost_scsi_get_cmd(struct vhost_virtqueue *vq, struct vhost_scsi_tpg *tpg,
> cmd->tvc_nexus = tv_nexus;
> cmd->inflight = vhost_scsi_get_inflight(vq);
> cmd->tvc_resp_iov = tvc_resp_iov;
> + cmd->tvc_log = log;
>
> memcpy(cmd->tvc_cdb, cdb, VHOST_SCSI_MAX_CDB_SIZE);
>
> @@ -1604,6 +1612,7 @@ static void vhost_scsi_destroy_vq_cmds(struct vhost_virtqueue *vq)
> kfree(tv_cmd->tvc_prot_sgl);
> kfree(tv_cmd->tvc_upages);
> kfree(tv_cmd->tvc_resp_iov);
> + kfree(tv_cmd->tvc_log);
> }
>
> sbitmap_free(&svq->scsi_tags);
> @@ -1666,6 +1675,18 @@ static int vhost_scsi_setup_vq_cmds(struct vhost_virtqueue *vq, int max_cmds)
> pr_err("Unable to allocate tv_cmd->tvc_prot_sgl\n");
> goto out;
> }
> +
> + /*
> + * tv_cmd->tvc_log and vq->log need to have the same max
> + * length.
> + */
> + tv_cmd->tvc_log = kcalloc(vq->dev->iov_limit,
> + sizeof(struct vhost_log),
> + GFP_KERNEL);
VHOST_F_LOG_ALL is normally set when the migration starts right?
I mean it's done before the initial setup when the above code is run so
is it possible to do the allocation when vhost_scsi_set_features is passed
VHOST_F_LOG_ALL? We then don't allocate a bunch of mem for a feature that
may never be used.
