[Qemu-devel] [PATCH V2 5/6] virtio/console: Allocate scatterlist according to the current pipe size

[Yoshihiro YUNOMAE]

From: Masami Hiramatsu <address@hidden>

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 <address@hidden>
---

 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);