Re: [Qemu-devel] [PATCH] qemu-img: change opening method for the output in dd

[Fam Zheng <famz@redhat.com>]

On Thu, 08/11 06:02, Reda Sallahi wrote:
> dd was creating an output image regardless of whether there was one already
> created. With this patch we try to open first the output image and resize it
> if necessary.
> 
> Signed-off-by: Reda Sallahi <fullmanet@gmail.com>
> ---
> Depends on:
> [PATCH v2] qemu-img: add conv=notrunc option to dd
> 
>  qemu-img.c | 91 +++++++++++++++++++++++++++++++++++++++++++++++++++-----------
>  1 file changed, 76 insertions(+), 15 deletions(-)
> 
> diff --git a/qemu-img.c b/qemu-img.c
> index 7c546c1..dfa0e63 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -3919,6 +3919,8 @@ static int img_dd(int argc, char **argv)
>      char *tmp;
>      BlockDriver *drv = NULL, *proto_drv = NULL;
>      BlockBackend *blk1 = NULL, *blk2 = NULL;
> +    BlockDriverState *bs = NULL;
> +    QDict *qoptions = NULL;
>      QemuOpts *opts = NULL;
>      QemuOptsList *create_opts = NULL;
>      Error *local_err = NULL;
> @@ -4080,22 +4082,60 @@ static int img_dd(int argc, char **argv)
>          size = dd.count * in.bsz;
>      }
>  
> -    /* Overflow means the specified offset is beyond input image's size */
> -    if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz ||
> -                              size < in.bsz * in.offset)) {
> -        qemu_opt_set_number(opts, BLOCK_OPT_SIZE, 0, &error_abort);
> -    } else {
> -        qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
> -                            size - in.bsz * in.offset, &error_abort);
> -    }
> +    qoptions = qdict_new();
> +    qdict_put(qoptions, "driver", qstring_from_str(out_fmt));
>  
> -    ret = bdrv_create(drv, out.filename, opts, &local_err);
> -    if (ret < 0) {
> -        error_reportf_err(local_err,
> -                          "%s: error while creating output image: ",
> -                          out.filename);
> -        ret = -1;
> -        goto out;
> +    bs = bdrv_open(out.filename, NULL, qoptions, BDRV_O_RDWR, &local_err);

What about --image-opts? With that we need to open it like img_open.

> +
> +    if (!bs) {
> +        drv = bdrv_find_format(out_fmt);
> +        if (!drv) {
> +            error_report("Unknown file format");
> +            ret = -1;
> +            goto out;
> +        }
> +        proto_drv = bdrv_find_protocol(out.filename, true, &local_err);

local_err is likely set here, you cannot pass it again without freeing it
first.

> +
> +        if (!proto_drv) {
> +            error_report_err(local_err);
> +            ret = -1;
> +            goto out;
> +        }
> +        if (!drv->create_opts) {
> +            error_report("Format driver '%s' does not support image creation",
> +                         drv->format_name);
> +            ret = -1;
> +            goto out;
> +        }
> +        if (!proto_drv->create_opts) {
> +            error_report("Protocol driver '%s' does not support image creation",
> +                         proto_drv->format_name);
> +            ret = -1;
> +            goto out;
> +        }
> +        create_opts = qemu_opts_append(create_opts, drv->create_opts);
> +        create_opts = qemu_opts_append(create_opts, proto_drv->create_opts);
> +
> +        opts = qemu_opts_create(create_opts, NULL, 0, &error_abort);
> +
> +        /* Overflow means the specified offset is beyond input image's size */
> +        if (dd.flags & C_SKIP && (in.offset > INT64_MAX / in.bsz ||
> +                                  size < in.offset * in.bsz)) {
> +            qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
> +                                0, &error_abort);
> +        } else {
> +            qemu_opt_set_number(opts, BLOCK_OPT_SIZE,
> +                                size - in.offset * in.bsz, &error_abort);
> +        }
> +
> +        ret = bdrv_create(drv, out.filename, opts, &local_err);
> +        if (ret < 0) {
> +            error_reportf_err(local_err,
> +                              "%s: error while creating output image: ",
> +                              out.filename);
> +            ret = -1;
> +            goto out;
> +        }
>      }
>  
>      blk2 = img_open(image_opts, out.filename, out_fmt, BDRV_O_RDWR,

Isn't this duplicated to the above bdrv_open? Maybe they should be unified to
one.

> @@ -4117,6 +4157,26 @@ static int img_dd(int argc, char **argv)
>          in_pos = in.offset * in.bsz;
>      }
>  
> +    if (bs) {
> +        int64_t blk2sz = blk_getlength(blk2);
> +        if (blk2sz < 0) {
> +            error_report("Failed to get size for '%s'", in.filename);
> +            ret = -1;
> +            goto out;
> +        }
> +
> +        if (!(dd.conv & C_NOTRUNC)) {
> +            blk_truncate(blk2, 0);
> +        }
> +        if (!(dd.flags & C_SKIP) || (in.offset <= INT64_MAX / in.bsz &&
> +                                  size >= in.offset * in.bsz)) {
> +            if (!(dd.conv & C_NOTRUNC) ||
> +                blk2sz < size - in.offset * in.bsz) {
> +                blk_truncate(blk2, size - in.offset * in.bsz);
> +            }
> +        }
> +    }
> +
>      in.buf = g_new(uint8_t, in.bsz);
>  
>      for (out_pos = 0; in_pos < size; block_count++) {
> @@ -4152,6 +4212,7 @@ out:
>      qemu_opts_free(create_opts);
>      blk_unref(blk1);
>      blk_unref(blk2);
> +    bdrv_unref(bs);
>      g_free(in.filename);
>      g_free(out.filename);
>      g_free(in.buf);
> -- 
> 2.9.2
> 

Fam