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

Nicholas A. Bellinger
2014-02-24T05:32:26Z

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