virtio/console: Add splice_write support

Enable to use splice_write from pipe to virtio-console port.
This steals pages from pipe and directly send it to host.

Note that this may accelerate only the guest to host path.

Changes in v2:
 - Use GFP_KERNEL instead of GFP_ATOMIC in syscall context function.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Masami Hiramatsu 2012-08-09 21:30:39 +09:00 committed by Rusty Russell
parent 925a6f0bf8
commit eb5e89fc70

View File

@ -24,6 +24,8 @@
#include <linux/err.h>
#include <linux/freezer.h>
#include <linux/fs.h>
#include <linux/splice.h>
#include <linux/pagemap.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/poll.h>
@ -227,6 +229,7 @@ struct port {
bool guest_connected;
};
#define MAX_SPLICE_PAGES 32
/* This is the very early arch-specified put chars function. */
static int (*early_put_chars)(u32, const char *, int);
@ -474,26 +477,52 @@ static ssize_t send_control_msg(struct port *port, unsigned int event,
return 0;
}
struct buffer_token {
union {
void *buf;
struct scatterlist *sg;
} u;
bool sgpages;
};
static void reclaim_sg_pages(struct scatterlist *sg)
{
int i;
struct page *page;
for (i = 0; i < MAX_SPLICE_PAGES; i++) {
page = sg_page(&sg[i]);
if (!page)
break;
put_page(page);
}
kfree(sg);
}
/* Callers must take the port->outvq_lock */
static void reclaim_consumed_buffers(struct port *port)
{
void *buf;
struct buffer_token *tok;
unsigned int len;
if (!port->portdev) {
/* Device has been unplugged. vqs are already gone. */
return;
}
while ((buf = virtqueue_get_buf(port->out_vq, &len))) {
kfree(buf);
while ((tok = virtqueue_get_buf(port->out_vq, &len))) {
if (tok->sgpages)
reclaim_sg_pages(tok->u.sg);
else
kfree(tok->u.buf);
kfree(tok);
port->outvq_full = false;
}
}
static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count,
bool nonblock)
static ssize_t __send_to_port(struct port *port, struct scatterlist *sg,
int nents, size_t in_count,
struct buffer_token *tok, bool nonblock)
{
struct scatterlist sg[1];
struct virtqueue *out_vq;
ssize_t ret;
unsigned long flags;
@ -505,8 +534,7 @@ static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count,
reclaim_consumed_buffers(port);
sg_init_one(sg, in_buf, in_count);
ret = virtqueue_add_buf(out_vq, sg, 1, 0, in_buf, GFP_ATOMIC);
ret = virtqueue_add_buf(out_vq, sg, nents, 0, tok, GFP_ATOMIC);
/* Tell Host to go! */
virtqueue_kick(out_vq);
@ -544,6 +572,37 @@ static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count,
return in_count;
}
static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count,
bool nonblock)
{
struct scatterlist sg[1];
struct buffer_token *tok;
tok = kmalloc(sizeof(*tok), GFP_ATOMIC);
if (!tok)
return -ENOMEM;
tok->sgpages = false;
tok->u.buf = in_buf;
sg_init_one(sg, in_buf, in_count);
return __send_to_port(port, sg, 1, in_count, tok, nonblock);
}
static ssize_t send_pages(struct port *port, struct scatterlist *sg, int nents,
size_t in_count, bool nonblock)
{
struct buffer_token *tok;
tok = kmalloc(sizeof(*tok), GFP_ATOMIC);
if (!tok)
return -ENOMEM;
tok->sgpages = true;
tok->u.sg = sg;
return __send_to_port(port, sg, nents, in_count, tok, nonblock);
}
/*
* Give out the data that's requested from the buffer that we have
* queued up.
@ -725,6 +784,66 @@ static ssize_t port_fops_write(struct file *filp, const char __user *ubuf,
return ret;
}
struct sg_list {
unsigned int n;
size_t len;
struct scatterlist *sg;
};
static int pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
struct splice_desc *sd)
{
struct sg_list *sgl = sd->u.data;
unsigned int len = 0;
if (sgl->n == MAX_SPLICE_PAGES)
return 0;
/* Try lock this page */
if (buf->ops->steal(pipe, buf) == 0) {
/* Get reference and unlock page for moving */
get_page(buf->page);
unlock_page(buf->page);
len = min(buf->len, sd->len);
sg_set_page(&(sgl->sg[sgl->n]), buf->page, len, buf->offset);
sgl->n++;
sgl->len += len;
}
return len;
}
/* Faster zero-copy write by splicing */
static ssize_t port_fops_splice_write(struct pipe_inode_info *pipe,
struct file *filp, loff_t *ppos,
size_t len, unsigned int flags)
{
struct port *port = filp->private_data;
struct sg_list sgl;
ssize_t ret;
struct splice_desc sd = {
.total_len = len,
.flags = flags,
.pos = *ppos,
.u.data = &sgl,
};
sgl.n = 0;
sgl.len = 0;
sgl.sg = kmalloc(sizeof(struct scatterlist) * MAX_SPLICE_PAGES,
GFP_KERNEL);
if (unlikely(!sgl.sg))
return -ENOMEM;
sg_init_table(sgl.sg, MAX_SPLICE_PAGES);
ret = __splice_from_pipe(pipe, &sd, pipe_to_sg);
if (likely(ret > 0))
ret = send_pages(port, sgl.sg, sgl.n, sgl.len, true);
return ret;
}
static unsigned int port_fops_poll(struct file *filp, poll_table *wait)
{
struct port *port;
@ -856,6 +975,7 @@ static const struct file_operations port_fops = {
.open = port_fops_open,
.read = port_fops_read,
.write = port_fops_write,
.splice_write = port_fops_splice_write,
.poll = port_fops_poll,
.release = port_fops_release,
.fasync = port_fops_fasync,