[RFC 2/6] vhost/scsi: Add preallocation of protection SGLs

["Nicholas A. Bellinger" <nab@daterainc.com>]

From: Nicholas Bellinger <nab@linux-iscsi.org>

This patch updates tcm_vhost_make_nexus() to pre-allocate per descriptor
tcm_vhost_cmd->tvc_prot_sgl[] used to expose protection SGLs from within
virtio-scsi guest memory to vhost-scsi.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Sagi Grimberg <sagig@dev.mellanox.co.il>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
 drivers/vhost/scsi.c |   56 +++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 55 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 31feb47..314cbd4 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -58,6 +58,7 @@
 #define TCM_VHOST_DEFAULT_TAGS 256
 #define TCM_VHOST_PREALLOC_SGLS 2048
 #define TCM_VHOST_PREALLOC_UPAGES 2048
+#define TCM_VHOST_PREALLOC_PROT_SGLS 512
 
 struct vhost_scsi_inflight {
 	/* Wait for the flush operation to finish */
@@ -83,6 +84,7 @@ struct tcm_vhost_cmd {
 	u32 tvc_lun;
 	/* Pointer to the SGL formatted memory from virtio-scsi */
 	struct scatterlist *tvc_sgl;
+	struct scatterlist *tvc_prot_sgl;
 	struct page **tvc_upages;
 	/* Pointer to response */
 	struct virtio_scsi_cmd_resp __user *tvc_resp;
@@ -717,7 +719,7 @@ 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 scatterlist *sg, *prot_sg;
 	struct page **pages;
 	int tag;
 
@@ -736,10 +738,12 @@ vhost_scsi_get_tag(struct vhost_virtqueue *vq,
 
 	cmd = &((struct tcm_vhost_cmd *)se_sess->sess_cmd_map)[tag];
 	sg = cmd->tvc_sgl;
+	prot_sg = cmd->tvc_prot_sgl;
 	pages = cmd->tvc_upages;
 	memset(cmd, 0, sizeof(struct tcm_vhost_cmd));
 
 	cmd->tvc_sgl = sg;
+	cmd->tvc_prot_sgl = prot_sg;
 	cmd->tvc_upages = pages;
 	cmd->tvc_se_cmd.map_tag = tag;
 	cmd->tvc_tag = v_req->tag;
@@ -852,6 +856,47 @@ vhost_scsi_map_iov_to_sgl(struct tcm_vhost_cmd *cmd,
 	return 0;
 }
 
+static int
+vhost_scsi_map_iov_to_prot(struct tcm_vhost_cmd *cmd,
+			   struct iovec *iov,
+			   int niov,
+			   bool write)
+{
+	struct scatterlist *prot_sg = cmd->tvc_prot_sgl;
+	unsigned int prot_sgl_count = 0;
+	int ret, i;
+
+	for (i = 0; i < niov; i++)
+		prot_sgl_count += iov_num_pages(&iov[i]);
+
+	if (prot_sgl_count > TCM_VHOST_PREALLOC_PROT_SGLS) {
+		pr_err("vhost_scsi_map_iov_to_prot() sgl_count: %u greater than"
+			" preallocated TCM_VHOST_PREALLOC_PROT_SGLS: %u\n",
+			prot_sgl_count, TCM_VHOST_PREALLOC_PROT_SGLS);
+		return -ENOBUFS;
+	}
+
+	pr_debug("%s prot_sg %p prot_sgl_count %u\n", __func__,
+		 prot_sg, prot_sgl_count);
+	sg_init_table(prot_sg, prot_sgl_count);
+	cmd->tvc_prot_sgl_count = prot_sgl_count;
+
+	for (i = 0; i < niov; i++) {
+		ret = vhost_scsi_map_to_sgl(cmd, prot_sg, prot_sgl_count, &iov[i],
+					    cmd->tvc_upages, write);
+		if (ret < 0) {
+			for (i = 0; i < cmd->tvc_prot_sgl_count; i++)
+				put_page(sg_page(&cmd->tvc_prot_sgl[i]));
+
+			cmd->tvc_prot_sgl_count = 0;
+			return ret;
+		}
+		prot_sg += ret;
+		prot_sgl_count -= ret;
+	}
+	return 0;
+}
+
 static void tcm_vhost_submission_work(struct work_struct *work)
 {
 	struct tcm_vhost_cmd *cmd =
@@ -1692,6 +1737,7 @@ static void tcm_vhost_free_cmd_map_res(struct tcm_vhost_nexus *nexus,
 		tv_cmd = &((struct tcm_vhost_cmd *)se_sess->sess_cmd_map)[i];
 
 		kfree(tv_cmd->tvc_sgl);
+		kfree(tv_cmd->tvc_prot_sgl);
 		kfree(tv_cmd->tvc_upages);
 	}
 }
@@ -1750,6 +1796,14 @@ static int tcm_vhost_make_nexus(struct tcm_vhost_tpg *tpg,
 			pr_err("Unable to allocate tv_cmd->tvc_upages\n");
 			goto out;
 		}
+
+		tv_cmd->tvc_prot_sgl = kzalloc(sizeof(struct scatterlist) *
+					TCM_VHOST_PREALLOC_PROT_SGLS, GFP_KERNEL);
+		if (!tv_cmd->tvc_prot_sgl) {
+			mutex_unlock(&tpg->tv_tpg_mutex);
+			pr_err("Unable to allocate tv_cmd->tvc_prot_sgl\n");
+			goto out;
+		}
 	}
 	/*
 	 * Since we are running in 'demo mode' this call with generate a
-- 
1.7.10.4