Re: [PATCH-v5 4/6] vhost/scsi: Add pre-allocation for tv_cmd SGL +upages memory

[Asias He]

On Sat, Aug 31, 2013 at 02:52:34AM +0000, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
> 
> This patch adds support for pre-allocation of per tv_cmd descriptor
> scatterlist + user-space page pointer memory using se_sess->sess_cmd_map
> within tcm_vhost_make_nexus() code.
> 
> This includes sanity checks within vhost_scsi_map_to_sgl()
> to reject I/O that exceeds these initial hardcoded values, and
> the necessary cleanup in tcm_vhost_make_nexus() failure path +
> tcm_vhost_drop_nexus().
> 
> v3 changes:
>   - Rebase to v3.11-rc5 code
> 
> Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
> Cc: Asias He <asias@xxxxxxxxxx>
> Cc: Kent Overstreet <kmo@xxxxxxxxxxxxx>
> Signed-off-by: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>

Reviewed-by: Asias He <asias@xxxxxxxxxx>

> ---
>  drivers/vhost/scsi.c |   99 ++++++++++++++++++++++++++++++++++++++++----------
>  1 files changed, 80 insertions(+), 19 deletions(-)
> 
> diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
> index 8cd545a..d52a3a0 100644
> --- a/drivers/vhost/scsi.c
> +++ b/drivers/vhost/scsi.c
> @@ -56,6 +56,8 @@
>  #define TCM_VHOST_NAMELEN 256
>  #define TCM_VHOST_MAX_CDB_SIZE 32
>  #define TCM_VHOST_DEFAULT_TAGS 256
> +#define TCM_VHOST_PREALLOC_SGLS 2048
> +#define TCM_VHOST_PREALLOC_PAGES 2048
>  
>  struct vhost_scsi_inflight {
>  	/* Wait for the flush operation to finish */
> @@ -81,6 +83,7 @@ struct tcm_vhost_cmd {
>  	u32 tvc_lun;
>  	/* Pointer to the SGL formatted memory from virtio-scsi */
>  	struct scatterlist *tvc_sgl;
> +	struct page **tvc_upages;
>  	/* Pointer to response */
>  	struct virtio_scsi_cmd_resp __user *tvc_resp;
>  	/* Pointer to vhost_scsi for our device */
> @@ -458,8 +461,6 @@ static void tcm_vhost_release_cmd(struct se_cmd *se_cmd)
>  		u32 i;
>  		for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
>  			put_page(sg_page(&tv_cmd->tvc_sgl[i]));
> -
> -		kfree(tv_cmd->tvc_sgl);
>          }
>  
>  	tcm_vhost_put_inflight(tv_cmd->inflight);
> @@ -716,6 +717,8 @@ vhost_scsi_get_tag(struct vhost_virtqueue *vq,
>  	struct tcm_vhost_cmd *cmd;
>  	struct tcm_vhost_nexus *tv_nexus;
>  	struct se_session *se_sess;
> +	struct scatterlist *sg;
> +	struct page **pages;
>  	int tag;
>  
>  	tv_nexus = tpg->tpg_nexus;
> @@ -727,8 +730,12 @@ vhost_scsi_get_tag(struct vhost_virtqueue *vq,
>  
>  	tag = percpu_ida_alloc(&se_sess->sess_tag_pool, GFP_KERNEL);
>  	cmd = &((struct tcm_vhost_cmd *)se_sess->sess_cmd_map)[tag];
> +	sg = cmd->tvc_sgl;
> +	pages = cmd->tvc_upages;
>  	memset(cmd, 0, sizeof(struct tcm_vhost_cmd));
>  
> +	cmd->tvc_sgl = sg;
> +	cmd->tvc_upages = pages;
>  	cmd->tvc_se_cmd.map_tag = tag;
>  	cmd->tvc_tag = v_req->tag;
>  	cmd->tvc_task_attr = v_req->task_attr;
> @@ -746,7 +753,8 @@ vhost_scsi_get_tag(struct vhost_virtqueue *vq,
>   * Returns the number of scatterlist entries used or -errno on error.
>   */
>  static int
> -vhost_scsi_map_to_sgl(struct scatterlist *sgl,
> +vhost_scsi_map_to_sgl(struct tcm_vhost_cmd *tv_cmd,
> +		      struct scatterlist *sgl,
>  		      unsigned int sgl_count,
>  		      struct iovec *iov,
>  		      int write)
> @@ -758,13 +766,25 @@ vhost_scsi_map_to_sgl(struct scatterlist *sgl,
>  	struct page **pages;
>  	int ret, i;
>  
> +	if (sgl_count > TCM_VHOST_PREALLOC_SGLS) {
> +		pr_err("vhost_scsi_map_to_sgl() psgl_count: %u greater than"
> +		       " preallocated TCM_VHOST_PREALLOC_SGLS: %u\n",
> +			sgl_count, TCM_VHOST_PREALLOC_SGLS);
> +		return -ENOBUFS;
> +	}
> +
>  	pages_nr = iov_num_pages(iov);
>  	if (pages_nr > sgl_count)
>  		return -ENOBUFS;
>  
> -	pages = kmalloc(pages_nr * sizeof(struct page *), GFP_KERNEL);
> -	if (!pages)
> -		return -ENOMEM;
> +	if (pages_nr > TCM_VHOST_PREALLOC_PAGES) {
> +		pr_err("vhost_scsi_map_to_sgl() pages_nr: %u greater than"
> +		       " preallocated TCM_VHOST_PREALLOC_PAGES: %u\n",
> +			pages_nr, TCM_VHOST_PREALLOC_PAGES);
> +		return -ENOBUFS;
> +	}
> +
> +	pages = tv_cmd->tvc_upages;
>  
>  	ret = get_user_pages_fast((unsigned long)ptr, pages_nr, write, pages);
>  	/* No pages were pinned */
> @@ -789,7 +809,6 @@ vhost_scsi_map_to_sgl(struct scatterlist *sgl,
>  	}
>  
>  out:
> -	kfree(pages);
>  	return ret;
>  }
>  
> @@ -813,24 +832,20 @@ vhost_scsi_map_iov_to_sgl(struct tcm_vhost_cmd *cmd,
>  
>  	/* TODO overflow checking */
>  
> -	sg = kmalloc(sizeof(cmd->tvc_sgl[0]) * sgl_count, GFP_ATOMIC);
> -	if (!sg)
> -		return -ENOMEM;
> -	pr_debug("%s sg %p sgl_count %u is_err %d\n", __func__,
> -	       sg, sgl_count, !sg);
> +	sg = cmd->tvc_sgl;
> +	pr_debug("%s sg %p sgl_count %u\n", __func__, sg, sgl_count);
>  	sg_init_table(sg, sgl_count);
>  
> -	cmd->tvc_sgl = sg;
>  	cmd->tvc_sgl_count = sgl_count;
>  
>  	pr_debug("Mapping %u iovecs for %u pages\n", niov, sgl_count);
>  	for (i = 0; i < niov; i++) {
> -		ret = vhost_scsi_map_to_sgl(sg, sgl_count, &iov[i], write);
> +		ret = vhost_scsi_map_to_sgl(cmd, sg, sgl_count, &iov[i],
> +					    write);
>  		if (ret < 0) {
>  			for (i = 0; i < cmd->tvc_sgl_count; i++)
>  				put_page(sg_page(&cmd->tvc_sgl[i]));
> -			kfree(cmd->tvc_sgl);
> -			cmd->tvc_sgl = NULL;
> +
>  			cmd->tvc_sgl_count = 0;
>  			return ret;
>  		}
> @@ -1660,11 +1675,31 @@ static void tcm_vhost_drop_nodeacl(struct se_node_acl *se_acl)
>  	kfree(nacl);
>  }
>  
> +static void tcm_vhost_free_cmd_map_res(struct tcm_vhost_nexus *nexus,
> +				       struct se_session *se_sess)
> +{
> +	struct tcm_vhost_cmd *tv_cmd;
> +	unsigned int i;
> +
> +	if (!se_sess->sess_cmd_map)
> +		return;
> +
> +	for (i = 0; i < TCM_VHOST_DEFAULT_TAGS; i++) {
> +		tv_cmd = &((struct tcm_vhost_cmd *)se_sess->sess_cmd_map)[i];
> +
> +		kfree(tv_cmd->tvc_sgl);
> +		kfree(tv_cmd->tvc_upages);
> +	}
> +}
> +
>  static int tcm_vhost_make_nexus(struct tcm_vhost_tpg *tpg,
>  				const char *name)
>  {
>  	struct se_portal_group *se_tpg;
> +	struct se_session *se_sess;
>  	struct tcm_vhost_nexus *tv_nexus;
> +	struct tcm_vhost_cmd *tv_cmd;
> +	unsigned int i;
>  
>  	mutex_lock(&tpg->tv_tpg_mutex);
>  	if (tpg->tpg_nexus) {
> @@ -1692,6 +1727,26 @@ static int tcm_vhost_make_nexus(struct tcm_vhost_tpg *tpg,
>  		kfree(tv_nexus);
>  		return -ENOMEM;
>  	}
> +	se_sess = tv_nexus->tvn_se_sess;
> +	for (i = 0; i < TCM_VHOST_DEFAULT_TAGS; i++) {
> +		tv_cmd = &((struct tcm_vhost_cmd *)se_sess->sess_cmd_map)[i];
> +
> +		tv_cmd->tvc_sgl = kzalloc(sizeof(struct scatterlist) *
> +					TCM_VHOST_PREALLOC_SGLS, GFP_KERNEL);
> +		if (!tv_cmd->tvc_sgl) {
> +			mutex_unlock(&tpg->tv_tpg_mutex);
> +			pr_err("Unable to allocate tv_cmd->tvc_sgl\n");
> +			goto out;
> +		}
> +
> +		tv_cmd->tvc_upages = kzalloc(sizeof(struct page *) *
> +					TCM_VHOST_PREALLOC_PAGES, GFP_KERNEL);
> +		if (!tv_cmd->tvc_upages) {
> +			mutex_unlock(&tpg->tv_tpg_mutex);
> +			pr_err("Unable to allocate tv_cmd->tvc_upages\n");
> +			goto out;
> +		}
> +	}
>  	/*
>  	 * Since we are running in 'demo mode' this call with generate a
>  	 * struct se_node_acl for the tcm_vhost struct se_portal_group with
> @@ -1703,9 +1758,7 @@ static int tcm_vhost_make_nexus(struct tcm_vhost_tpg *tpg,
>  		mutex_unlock(&tpg->tv_tpg_mutex);
>  		pr_debug("core_tpg_check_initiator_node_acl() failed"
>  				" for %s\n", name);
> -		transport_free_session(tv_nexus->tvn_se_sess);
> -		kfree(tv_nexus);
> -		return -ENOMEM;
> +		goto out;
>  	}
>  	/*
>  	 * Now register the TCM vhost virtual I_T Nexus as active with the
> @@ -1717,6 +1770,12 @@ static int tcm_vhost_make_nexus(struct tcm_vhost_tpg *tpg,
>  
>  	mutex_unlock(&tpg->tv_tpg_mutex);
>  	return 0;
> +
> +out:
> +	tcm_vhost_free_cmd_map_res(tv_nexus, se_sess);
> +	transport_free_session(se_sess);
> +	kfree(tv_nexus);
> +	return -ENOMEM;
>  }
>  
>  static int tcm_vhost_drop_nexus(struct tcm_vhost_tpg *tpg)
> @@ -1756,6 +1815,8 @@ static int tcm_vhost_drop_nexus(struct tcm_vhost_tpg *tpg)
>  	pr_debug("TCM_vhost_ConfigFS: Removing I_T Nexus to emulated"
>  		" %s Initiator Port: %s\n", tcm_vhost_dump_proto_id(tpg->tport),
>  		tv_nexus->tvn_se_sess->se_node_acl->initiatorname);
> +
> +	tcm_vhost_free_cmd_map_res(tv_nexus, se_sess);
>  	/*
>  	 * Release the SCSI I_T Nexus to the emulated vhost Target Port
>  	 */
> -- 
> 1.7.2.5
> 

-- 
Asias
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