Re: [Qemu-devel] [PATCH] add qemu-img convert -C option (skip target volume creation)

[Fam Zheng <famz@redhat.com>]

On Sun, 08/11 18:31, Alex Bligh wrote:
> Add a -C option to skip volume creation on qemu-img convert.
> This is useful for targets such as rbd / ceph, where the
> target volume may already exist; we cannot always rely on
> qemu-img convert to create the image, as dependent on the
> output format, there may be parameters which are not possible
> to specify through the qemu-img convert command line.
> 
> Code:
> 
> Author: Alexandre Derumier <aderumier@odiso.com>
> Signed-off-by: Alexandre Derumier <aderumier@odiso.com>
> Signed-off-by: Alex Bligh <alex@alex.org.uk>
> 
> Documentaton:
> 
> Author: Alex Bligh <alex@alex.org.uk>
> Signed-off-by: Alex Bligh <alex@alex.org.uk>
> ---
>  qemu-img-cmds.hx |    4 ++--
>  qemu-img.c       |   37 ++++++++++++++++++++++---------------
>  qemu-img.texi    |   15 ++++++++++++++-
>  3 files changed, 38 insertions(+), 18 deletions(-)
> 
> diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
> index 4ca7e95..74ced81 100644
> --- a/qemu-img-cmds.hx
> +++ b/qemu-img-cmds.hx
> @@ -34,9 +34,9 @@ STEXI
>  ETEXI
>  
>  DEF("convert", img_convert,
> -    "convert [-c] [-p] [-q] [-f fmt] [-t cache] [-O output_fmt] [-o options] [-s snapshot_name] [-S sparse_size] filename [filename2 [...]] output_filename")
> +    "convert [-c] [-p] [-q] [-C] [-f fmt] [-t cache] [-O output_fmt] [-o options] [-s snapshot_name] [-S sparse_size] filename [filename2 [...]] output_filename")
>  STEXI
> -@item convert [-c] [-p] [-q] [-f @var{fmt}] [-t @var{cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}
> +@item convert [-c] [-p] [-q] [-C] [-f @var{fmt}] [-t @var{cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}
>  ETEXI
>  
>  DEF("info", img_info,
> diff --git a/qemu-img.c b/qemu-img.c
> index b9a848d..5b6ae15 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -103,6 +103,7 @@ static void help(void)
>             "  '-S' indicates the consecutive number of bytes that must contain only zeros\n"
>             "       for qemu-img to create a sparse image during conversion\n"
>             "  '--output' takes the format in which the output must be done (human or json)\n"
> +           "  '-C' skips the target volume creation (useful for rbd)\n"

The statement "useful for rbd" is not very informative, maybe you could
use "'-C' skips the target volume creation (assuming it already exists)".

>             "\n"
>             "Parameters to check subcommand:\n"
>             "  '-r' tries to repair any inconsistencies that are found during the check.\n"
> @@ -1116,7 +1117,7 @@ out3:
>  
>  static int img_convert(int argc, char **argv)
>  {
> -    int c, ret = 0, n, n1, bs_n, bs_i, compress, cluster_size, cluster_sectors;
> +    int c, ret = 0, n, n1, bs_n, bs_i, compress, cluster_size, cluster_sectors, skipcreate;

This line is too long, please break it.

>      int progress = 0, flags;
>      const char *fmt, *out_fmt, *cache, *out_baseimg, *out_filename;
>      BlockDriver *drv, *proto_drv;
> @@ -1139,8 +1140,9 @@ static int img_convert(int argc, char **argv)
>      cache = "unsafe";
>      out_baseimg = NULL;
>      compress = 0;
> +    skipcreate = 0;
>      for(;;) {
> -        c = getopt(argc, argv, "f:O:B:s:hce6o:pS:t:q");
> +        c = getopt(argc, argv, "f:O:B:s:hce6o:pS:t:qC");
>          if (c == -1) {
>              break;
>          }
> @@ -1161,6 +1163,9 @@ static int img_convert(int argc, char **argv)
>          case 'c':
>              compress = 1;
>              break;
> +        case 'C':
> +            skipcreate = 1;
> +            break;
>          case 'e':
>              error_report("option -e is deprecated, please use \'-o "
>                    "encryption\' instead!");
> @@ -1329,20 +1334,22 @@ static int img_convert(int argc, char **argv)
>          }
>      }
>  
> -    /* Create the new image */
> -    ret = bdrv_create(drv, out_filename, param);
> -    if (ret < 0) {
> -        if (ret == -ENOTSUP) {
> -            error_report("Formatting not supported for file format '%s'",
> -                         out_fmt);
> -        } else if (ret == -EFBIG) {
> -            error_report("The image size is too large for file format '%s'",
> -                         out_fmt);
> -        } else {
> -            error_report("%s: error while converting %s: %s",
> -                         out_filename, out_fmt, strerror(-ret));
> +    if (!skipcreate) {
> +        /* Create the new image */
> +        ret = bdrv_create(drv, out_filename, param);
> +        if (ret < 0) {
> +            if (ret == -ENOTSUP) {
> +                 error_report("Formatting not supported for file format '%s'",
> +                              out_fmt);
> +            } else if (ret == -EFBIG) {
> +                 error_report("The image size is too large for file format '%s'",
> +                              out_fmt);
> +            } else {
> +                error_report("%s: error while converting %s: %s",
> +                             out_filename, out_fmt, strerror(-ret));
> +            }
> +            goto out;
>          }
> -        goto out;
>      }
>  
>      flags = BDRV_O_RDWR;
> diff --git a/qemu-img.texi b/qemu-img.texi
> index 69f1bda..9e5ba36 100644
> --- a/qemu-img.texi
> +++ b/qemu-img.texi
> @@ -96,6 +96,14 @@ Second image format
>  Strict mode - fail on on different image size or sector allocation
>  @end table
>  
> +Parameters to convert subcommand:
> +
> +@table @option
> +
> +@item -C
> +Skip the creation of the target volume
> +@end table
> +
>  Command description:
>  
>  @table @option
> @@ -171,7 +179,7 @@ Error on reading data
>  
>  @end table
>  
> -@item convert [-c] [-p] [-f @var{fmt}] [-t @var{cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}
> +@item convert [-c] [-p] [-C] [-f @var{fmt}] [-t @var{cache}] [-O @var{output_fmt}] [-o @var{options}] [-s @var{snapshot_name}] [-S @var{sparse_size}] @var{filename} [@var{filename2} [...]] @var{output_filename}
>  
>  Convert the disk image @var{filename} or a snapshot @var{snapshot_name} to disk image @var{output_filename}
>  using format @var{output_fmt}. It can be optionally compressed (@code{-c}
> @@ -190,6 +198,11 @@ created as a copy on write image of the specified base image; the
>  @var{backing_file} should have the same content as the input's base image,
>  however the path, image format, etc may differ.
>  
> +If the @code{-C} option is specified, the target volume creation will be
> +skipped. This is useful for formats such as @code{rbd} if the target
> +volume has already been created with site specific options that cannot
> +be supplied through qemu-img.
> +
>  @item info [-f @var{fmt}] [--output=@var{ofmt}] [--backing-chain] @var{filename}
>  
>  Give information about the disk image @var{filename}. Use it in
> -- 
> 1.7.9.5
> 
> 

-- 
Fam