[PATCH-v2,05/11] vhost/scsi: Add ANY_LAYOUT iov -> sgl mapping prerequisites

Commit Message

Nicholas A. Bellinger Feb. 2, 2015, 4:06 a.m. UTC

From: Nicholas Bellinger <[e-mail]>

This patch adds ANY_LAYOUT prerequisites logic for accepting a set of
protection + data payloads via iovec + offset.  Also includes helpers
for calcuating SGLs + invoking vhost_scsi_map_to_sgl() with a known
number of iovecs.

Required by ANY_LAYOUT processing when struct iovec may be offset into
the first outgoing virtio-scsi request header.

v2 changes:
  - Clear ->tvc_sgl_count for vhost_scsi_mapal failure
  - Make vhost_scsi_mapal + vhost_scsi_calc_sgls accept max_niov
  - Minor cleanups

Cc: Michael S. Tsirkin <[e-mail]>
Cc: Paolo Bonzini <[e-mail]>
Signed-off-by: Nicholas Bellinger <[e-mail]>
---
 drivers/vhost/scsi.c | 115 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)

Patch

diff --git a/drivers/vhost/scsi.c b/drivers/vhost/scsi.c
index 049e603..ecbd567 100644
--- a/drivers/vhost/scsi.c
+++ b/drivers/vhost/scsi.c
@@ -909,6 +909,121 @@  vhost_scsi_map_iov_to_prot(struct tcm_vhost_cmd *cmd,
 	return 0;
 }
 
+static int
+vhost_scsi_calc_sgls(struct iovec *iov, size_t off, size_t bytes,
+		     int *niov, int max_niov, int max_sgls)
+{
+	size_t tmp = 0;
+	int sgl_count = 0;
+
+	*niov = 0;
+
+	while (tmp < bytes) {
+		void __user *base = iov[*niov].iov_base + off;
+		size_t len = iov[(*niov)++].iov_len - off;
+
+		if (*niov > max_niov) {
+			pr_err("%s: current *niov %d exceeds max_niov: %d\n",
+			       __func__, *niov, max_niov);
+			return -EINVAL;
+		}
+		sgl_count += iov_num_pages(base, len);
+		tmp += min(len, bytes);
+		off = 0;
+	}
+	if (sgl_count > max_sgls) {
+		pr_err("%s: requested sgl_count: %d exceeds pre-allocated"
+		       " max_sgls: %d\n", __func__, sgl_count, max_sgls);
+		return -ENOBUFS;
+	}
+	return sgl_count;
+}
+
+static int
+vhost_scsi_iov_to_sgl(struct tcm_vhost_cmd *cmd, bool write,
+		      struct iovec *iov, size_t iov_off, int niov,
+		      struct scatterlist *sg, int sg_count)
+{
+	int i, ret;
+
+	for (i = 0; i < niov; i++) {
+		void __user *base = iov[i].iov_base + iov_off;
+		size_t len = iov[i].iov_len - iov_off;
+
+		ret = vhost_scsi_map_to_sgl(cmd, base, len, sg, write);
+		if (ret < 0) {
+			for (i = 0; i < sg_count; i++) {
+				struct page *page = sg_page(&sg[i]);
+				if (page)
+					put_page(page);
+			}
+			return ret;
+		}
+		sg += ret;
+		iov_off = 0;
+	}
+	return 0;
+}
+
+static int
+vhost_scsi_mapal(struct tcm_vhost_cmd *cmd, int max_niov,
+		 size_t prot_bytes, struct iovec *prot_iov, size_t prot_off,
+		 size_t data_bytes, struct iovec *data_iov, size_t data_off)
+{
+	int sgl_count = 0, niov, ret;
+	bool write = (cmd->tvc_data_direction == DMA_FROM_DEVICE);
+
+	if (prot_bytes) {
+		if (!prot_iov) {
+			pr_err("%s: prot_iov is NULL, but prot_bytes: %zu"
+			       "present\n", __func__, prot_bytes);
+			return -EINVAL;
+		}
+		sgl_count = vhost_scsi_calc_sgls(prot_iov, prot_off, prot_bytes,
+						 &niov, max_niov,
+						 TCM_VHOST_PREALLOC_PROT_SGLS);
+		if (sgl_count < 0)
+			return sgl_count;
+
+		sg_init_table(cmd->tvc_prot_sgl, sgl_count);
+		cmd->tvc_prot_sgl_count = sgl_count;
+		pr_debug("%s prot_sg %p prot_sgl_count %u\n", __func__,
+			 cmd->tvc_prot_sgl, cmd->tvc_prot_sgl_count);
+
+		ret = vhost_scsi_iov_to_sgl(cmd, write, prot_iov, prot_off,
+					    niov, cmd->tvc_prot_sgl,
+					    cmd->tvc_prot_sgl_count);
+		if (ret < 0) {
+			cmd->tvc_prot_sgl_count = 0;
+			return ret;
+		}
+		max_niov -= niov;
+	}
+	if (!data_iov) {
+		pr_err("%s: data_iov is NULL, but data_bytes: %zu present\n",
+		       __func__, data_bytes);
+		return -EINVAL;
+	}
+	sgl_count = vhost_scsi_calc_sgls(data_iov, data_off, data_bytes,
+					 &niov, max_niov,
+					 TCM_VHOST_PREALLOC_SGLS);
+	if (sgl_count < 0)
+		return sgl_count;
+
+	sg_init_table(cmd->tvc_sgl, sgl_count);
+	cmd->tvc_sgl_count = sgl_count;
+	pr_debug("%s data_sg %p data_sgl_count %u\n", __func__,
+		  cmd->tvc_sgl, cmd->tvc_sgl_count);
+
+	ret = vhost_scsi_iov_to_sgl(cmd, write, data_iov, data_off, niov,
+				    cmd->tvc_sgl, cmd->tvc_sgl_count);
+	if (ret < 0) {
+		cmd->tvc_sgl_count = 0;
+		return ret;
+	}
+	return 0;
+}
+
 static void tcm_vhost_submission_work(struct work_struct *work)
 {
 	struct tcm_vhost_cmd *cmd =