Re: [Qemu-devel] [RFC PATCH v4 08/28] QEMUSizedBuffer: Introduce two help functions for qsb

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* zhanghailiang (zhang.zhanghailiang@huawei.com) wrote:
> Introduce two new QEMUSizedBuffer APIs which will be used by COLO to buffer
> VM state:
> One is qsb_put_buffer(), which put the content of a given QEMUSizedBuffer
> into QEMUFile, this is used to send buffered VM state to secondary.
> Another is qsb_fill_buffer(), read 'size' bytes of data from the file into
> qsb, this is used to get VM state from socket into a buffer.
> 
> Signed-off-by: Yang Hongyang <yanghy@cn.fujitsu.com>
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>

Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

(I could use these in my postcopy world)

Dave

> ---
>  include/migration/qemu-file.h |  3 ++-
>  migration/qemu-file-buf.c     | 58 +++++++++++++++++++++++++++++++++++++++++++
>  2 files changed, 60 insertions(+), 1 deletion(-)
> 
> diff --git a/include/migration/qemu-file.h b/include/migration/qemu-file.h
> index 745a850..09a0e2a 100644
> --- a/include/migration/qemu-file.h
> +++ b/include/migration/qemu-file.h
> @@ -140,7 +140,8 @@ ssize_t qsb_get_buffer(const QEMUSizedBuffer *, off_t start, size_t count,
>                         uint8_t *buf);
>  ssize_t qsb_write_at(QEMUSizedBuffer *qsb, const uint8_t *buf,
>                       off_t pos, size_t count);
> -
> +void qsb_put_buffer(QEMUFile *f, QEMUSizedBuffer *qsb, int size);
> +int qsb_fill_buffer(QEMUSizedBuffer *qsb, QEMUFile *f, int size);
>  
>  /*
>   * For use on files opened with qemu_bufopen
> diff --git a/migration/qemu-file-buf.c b/migration/qemu-file-buf.c
> index 16a51a1..686f417 100644
> --- a/migration/qemu-file-buf.c
> +++ b/migration/qemu-file-buf.c
> @@ -365,6 +365,64 @@ ssize_t qsb_write_at(QEMUSizedBuffer *qsb, const uint8_t *source,
>      return count;
>  }
>  
> +
> +/**
> + * Put the content of a given QEMUSizedBuffer into QEMUFile.
> + *
> + * @f: A QEMUFile
> + * @qsb: A QEMUSizedBuffer
> + * @size: size of content to write
> + */
> +void qsb_put_buffer(QEMUFile *f, QEMUSizedBuffer *qsb, int size)
> +{
> +    int i, l;
> +
> +    for (i = 0; i < qsb->n_iov && size > 0; i++) {
> +        l = MIN(qsb->iov[i].iov_len, size);
> +        qemu_put_buffer(f, qsb->iov[i].iov_base, l);
> +        size -= l;
> +    }
> +}
> +
> +/*
> + * Read 'size' bytes of data from the file into qsb.
> + * always fill from pos 0 and used after qsb_create().
> + *
> + * It will return size bytes unless there was an error, in which case it will
> + * return as many as it managed to read (assuming blocking fd's which
> + * all current QEMUFile are)
> + */
> +int qsb_fill_buffer(QEMUSizedBuffer *qsb, QEMUFile *f, int size)
> +{
> +    ssize_t rc = qsb_grow(qsb, size);
> +    int pending = size, i;
> +    qsb->used = 0;
> +    uint8_t *buf = NULL;
> +
> +    if (rc < 0) {
> +        return rc;
> +    }
> +
> +    for (i = 0; i < qsb->n_iov && pending > 0; i++) {
> +        int doneone = 0;
> +        /* read until iov full */
> +        while (doneone < qsb->iov[i].iov_len && pending > 0) {
> +            int readone = 0;
> +            buf = qsb->iov[i].iov_base;
> +            readone = qemu_get_buffer(f, buf,
> +                                MIN(qsb->iov[i].iov_len - doneone, pending));
> +            if (readone == 0) {
> +                return qsb->used;
> +            }
> +            buf += readone;
> +            doneone += readone;
> +            pending -= readone;
> +            qsb->used += readone;
> +        }
> +    }
> +    return qsb->used;
> +}
> +
>  typedef struct QEMUBuffer {
>      QEMUSizedBuffer *qsb;
>      QEMUFile *file;
> -- 
> 1.7.12.4
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK