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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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