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Subject[PATCH V2 5/6] virtio/console: Allocate scatterlist according to the current pipe size
Date
From: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>

Allocate scatterlist according to the current pipe size.
This allows splicing bigger buffer if the pipe size has
been changed by fcntl.

Changes in v2:
- Just a minor fix for avoiding a confliction with previous patch.

Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
---
drivers/char/virtio_console.c | 23 ++++++++++++-----------
1 files changed, 12 insertions(+), 11 deletions(-)
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index b2fc2ab..e88f843 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -229,7 +229,6 @@ 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);

@@ -482,15 +481,16 @@ struct buffer_token {
void *buf;
struct scatterlist *sg;
} u;
- bool sgpages;
+ /* If sgpages == 0 then buf is used, else sg is used */
+ unsigned int sgpages;
};

-static void reclaim_sg_pages(struct scatterlist *sg)
+static void reclaim_sg_pages(struct scatterlist *sg, unsigned int nrpages)
{
int i;
struct page *page;

- for (i = 0; i < MAX_SPLICE_PAGES; i++) {
+ for (i = 0; i < nrpages; i++) {
page = sg_page(&sg[i]);
if (!page)
break;
@@ -511,7 +511,7 @@ static void reclaim_consumed_buffers(struct port *port)
}
while ((tok = virtqueue_get_buf(port->out_vq, &len))) {
if (tok->sgpages)
- reclaim_sg_pages(tok->u.sg);
+ reclaim_sg_pages(tok->u.sg, tok->sgpages);
else
kfree(tok->u.buf);
kfree(tok);
@@ -581,7 +581,7 @@ static ssize_t send_buf(struct port *port, void *in_buf, size_t in_count,
tok = kmalloc(sizeof(*tok), GFP_ATOMIC);
if (!tok)
return -ENOMEM;
- tok->sgpages = false;
+ tok->sgpages = 0;
tok->u.buf = in_buf;

sg_init_one(sg, in_buf, in_count);
@@ -597,7 +597,7 @@ static ssize_t send_pages(struct port *port, struct scatterlist *sg, int nents,
tok = kmalloc(sizeof(*tok), GFP_ATOMIC);
if (!tok)
return -ENOMEM;
- tok->sgpages = true;
+ tok->sgpages = nents;
tok->u.sg = sg;

return __send_to_port(port, sg, nents, in_count, tok, nonblock);
@@ -797,6 +797,7 @@ out:

struct sg_list {
unsigned int n;
+ unsigned int size;
size_t len;
struct scatterlist *sg;
};
@@ -807,7 +808,7 @@ static int pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
struct sg_list *sgl = sd->u.data;
unsigned int offset, len;

- if (sgl->n == MAX_SPLICE_PAGES)
+ if (sgl->n == sgl->size)
return 0;

/* Try lock this page */
@@ -868,12 +869,12 @@ static ssize_t port_fops_splice_write(struct pipe_inode_info *pipe,

sgl.n = 0;
sgl.len = 0;
- sgl.sg = kmalloc(sizeof(struct scatterlist) * MAX_SPLICE_PAGES,
- GFP_KERNEL);
+ sgl.size = pipe->nrbufs;
+ sgl.sg = kmalloc(sizeof(struct scatterlist) * sgl.size, GFP_KERNEL);
if (unlikely(!sgl.sg))
return -ENOMEM;

- sg_init_table(sgl.sg, MAX_SPLICE_PAGES);
+ sg_init_table(sgl.sg, sgl.size);
ret = __splice_from_pipe(pipe, &sd, pipe_to_sg);
if (likely(ret > 0))
ret = send_pages(port, sgl.sg, sgl.n, sgl.len, true);



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