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Commit e8de56b5 authored by Nicholas Bellinger's avatar Nicholas Bellinger
Browse files

vhost/scsi: Add ANY_LAYOUT iov -> sgl mapping prerequisites 



This patch adds ANY_LAYOUT prerequisites logic for accepting a set of
protection + data payloads via iov_iter.  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.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarNicholas Bellinger <nab@linux-iscsi.org>
parent b4078b5f

drivers/vhost/scsi.c

+93 −0
Original line number Diff line number Diff line
@@ -914,6 +914,99 @@ vhost_scsi_map_iov_to_prot(struct tcm_vhost_cmd *cmd, 
	return 0;

}



static int

vhost_scsi_calc_sgls(struct iov_iter *iter, size_t bytes, int max_sgls)

{

	int sgl_count = 0;



	if (!iter || !iter->iov) {

		pr_err("%s: iter->iov is NULL, but expected bytes: %zu"

		       " present\n", __func__, bytes);

		return -EINVAL;

	}



	sgl_count = iov_iter_npages(iter, 0xffff);

	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 -EINVAL;

	}

	return sgl_count;

}



static int

vhost_scsi_iov_to_sgl(struct tcm_vhost_cmd *cmd, bool write,

		      struct iov_iter *iter, struct scatterlist *sg,

		      int sg_count)

{

	size_t off = iter->iov_offset;

	int i, ret;



	for (i = 0; i < iter->nr_segs; i++) {

		void __user *base = iter->iov[i].iov_base + off;

		size_t len = iter->iov[i].iov_len - 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;

		off = 0;

	}

	return 0;

}



static int

vhost_scsi_mapal(struct tcm_vhost_cmd *cmd,

		 size_t prot_bytes, struct iov_iter *prot_iter,

		 size_t data_bytes, struct iov_iter *data_iter)

{

	int sgl_count, ret;

	bool write = (cmd->tvc_data_direction == DMA_FROM_DEVICE);



	if (prot_bytes) {

		sgl_count = vhost_scsi_calc_sgls(prot_iter, prot_bytes,

						 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_iter,

					    cmd->tvc_prot_sgl,

					    cmd->tvc_prot_sgl_count);

		if (ret < 0) {

			cmd->tvc_prot_sgl_count = 0;

			return ret;

		}

	}

	sgl_count = vhost_scsi_calc_sgls(data_iter, data_bytes,

					 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_iter,

				    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 =