Re: [PATCH v4 3/4] qemu-io: add -r option to register I/O buffer

[Hanna Czenczek <hreitz@redhat.com>]

On 07.02.23 21:37, Stefan Hajnoczi wrote:
> The blk_register_buf() API is an optimization hint that allows some
> block drivers to avoid I/O buffer housekeeping or bounce buffers.
>
> Add an -r option to register the I/O buffer so that qemu-io can be used
> to test the blk_register_buf() API. The next commit will add a test that
> uses the new option.
>
> Reviewed-by: Eric Blake <eblake@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>   qemu-io-cmds.c | 204 +++++++++++++++++++++++++++++++------------------
>   1 file changed, 129 insertions(+), 75 deletions(-)

Reviewed-by: Hanna Czenczek <hreitz@redhat.com>

> diff --git a/qemu-io-cmds.c b/qemu-io-cmds.c
> index 1f60c23ba4..e7a02f5b99 100644
> --- a/qemu-io-cmds.c
> +++ b/qemu-io-cmds.c
> @@ -414,24 +419,23 @@ static void *qemu_io_alloc_from_file(BlockBackend *blk, size_t len,
>       fclose(f);
>       f = NULL;
>   
> -    if (len > pattern_len) {
> -        len -= pattern_len;
> -        buf += pattern_len;
> -
> -        while (len > 0) {
> -            size_t len_to_copy = MIN(pattern_len, len);
> -
> -            memcpy(buf, buf_origin, len_to_copy);
> +    if (register_buf) {
> +        blk_register_buf(blk, alloc_buf, alloc_len, &error_abort);
> +    }
>   
> -            len -= len_to_copy;
> -            buf += len_to_copy;
> -        }
> +    end = buf + len;
> +    for (char *p = buf + pattern_len; p < end; p += pattern_len) {
> +        memcpy(p, buf, MIN(pattern_len, end - p));
>       }

Cool rewrite of this loop!