[RFC 3/6] vhost/scsi: Add T10 PI IOV -> SGL memory mapping logic

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

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

This patch adds vhost_scsi_map_iov_to_prot() to perform the mapping of
T10 data integrity memory between virtio iov + struct scatterlist using
get_user_pages_fast() following existing code.

As with vhost_scsi_map_iov_to_sgl(), this does sanity checks against the
total prot_sgl_count vs. pre-allocated SGLs, and loops across protection
iovs using vhost_scsi_map_to_sgl() to perform the actual memory mapping.

Also update tcm_vhost_release_cmd() to release associated tvc_prot_sgl[]
struct page.

Cc: Martin K. Petersen <martin.petersen@oracle.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.de>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sagi Grimberg <sagig@dev.mellanox.co.il>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
---
 drivers/vhost/scsi.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 314cbd4..0cf5948 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -80,6 +80,7 @@ struct tcm_vhost_cmd {
 	u64 tvc_tag;
 	/* The number of scatterlists associated with this cmd */
 	u32 tvc_sgl_count;
+	u32 tvc_prot_sgl_count;
 	/* Saved unpacked SCSI LUN for tcm_vhost_submission_work() */
 	u32 tvc_lun;
 	/* Pointer to the SGL formatted memory from virtio-scsi */
@@ -458,12 +459,16 @@ static void tcm_vhost_release_cmd(struct se_cmd *se_cmd)
 	struct tcm_vhost_cmd *tv_cmd = container_of(se_cmd,
 				struct tcm_vhost_cmd, tvc_se_cmd);
 	struct se_session *se_sess = se_cmd->se_sess;
+	int i;
 
 	if (tv_cmd->tvc_sgl_count) {
-		u32 i;
 		for (i = 0; i < tv_cmd->tvc_sgl_count; i++)
 			put_page(sg_page(&tv_cmd->tvc_sgl[i]));
 	}
+	if (tv_cmd->tvc_prot_sgl_count) {
+		for (i = 0; i < tv_cmd->tvc_prot_sgl_count; i++)
+			put_page(sg_page(&tv_cmd->tvc_prot_sgl[i]));
+	}
 
 	tcm_vhost_put_inflight(tv_cmd->inflight);
 	percpu_ida_free(&se_sess->sess_tag_pool, se_cmd->map_tag);
-- 
1.7.10.4