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

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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: Nicholas Bellinger <nab@linux-iscsi.org>
This commit is contained in:
Nicholas Bellinger 2015-01-28 00:15:00 -08:00
parent b4078b5fac
commit e8de56b5e7
1 changed files with 93 additions and 0 deletions
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93
drivers/vhost/scsi.c
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@ -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 =