Re: [Qemu-devel] [RFC v2 6/8] qemu-img: add measure subcommand

[Max Reitz <mreitz@redhat.com>]

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On 15.03.2017 10:29, Stefan Hajnoczi wrote:
> The measure subcommand calculates the size required by a new image file.
> This can be used by users or management tools that need to allocate
> space on an LVM volume, SAN LUN, etc before creating or converting an
> image file.
> 
> Suggested-by: Maor Lipchuk <mlipchuk@redhat.com>
> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
> ---
>  qemu-img.c       | 213 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>  qemu-img-cmds.hx |   9 +++

Looking forward to the documentation in the non-RFC version. O:-)

>  2 files changed, 222 insertions(+)
> 
> diff --git a/qemu-img.c b/qemu-img.c
> index 98b836b..e8c6dcc 100644
> --- a/qemu-img.c
> +++ b/qemu-img.c
> @@ -59,6 +59,7 @@ enum {
>      OPTION_PATTERN = 260,
>      OPTION_FLUSH_INTERVAL = 261,
>      OPTION_NO_DRAIN = 262,
> +    OPTION_SIZE = 263,
>  };
>  
>  typedef enum OutputFormat {
> @@ -4287,6 +4288,218 @@ out:
>      return 0;
>  }
>  
> +static void dump_json_block_measure_info(BlockMeasureInfo *info)
> +{
> +    QString *str;
> +    QObject *obj;
> +    Visitor *v = qobject_output_visitor_new(&obj);
> +
> +    visit_type_BlockMeasureInfo(v, NULL, &info, &error_abort);
> +    visit_complete(v, &obj);
> +    str = qobject_to_json_pretty(obj);
> +    assert(str != NULL);
> +    printf("%s\n", qstring_get_str(str));
> +    qobject_decref(obj);
> +    visit_free(v);
> +    QDECREF(str);
> +}
> +
> +static int img_measure(int argc, char **argv)
> +{
> +    static const struct option long_options[] = {
> +        {"help", no_argument, 0, 'h'},
> +        {"image-opts", no_argument, 0, OPTION_IMAGE_OPTS},
> +        {"object", required_argument, 0, OPTION_OBJECT},
> +        {"output", required_argument, 0, OPTION_OUTPUT},
> +        {"size", required_argument, 0, OPTION_SIZE},
> +        {0, 0, 0, 0}
> +    };
> +    OutputFormat output_format = OFORMAT_HUMAN;
> +    BlockBackend *in_blk = NULL;
> +    BlockDriver *drv;
> +    const char *filename = NULL;
> +    const char *fmt = NULL;
> +    const char *out_fmt = "raw";
> +    char *options = NULL;
> +    char *snapshot_name = NULL;
> +    QemuOpts *opts = NULL;
> +    QemuOpts *object_opts = NULL;
> +    QemuOpts *sn_opts = NULL;
> +    QemuOptsList *create_opts = NULL;
> +    bool image_opts = false;
> +    uint64_t img_size = ~0ULL;
> +    BlockMeasureInfo info;
> +    Error *local_err = NULL;
> +    int ret = 1;
> +    int c;
> +
> +    while ((c = getopt_long(argc, argv, "hf:O:o:l:",
> +                            long_options, NULL)) != -1) {
> +        switch (c) {
> +        case '?':
> +        case 'h':
> +            help();
> +            break;
> +        case 'f':
> +            fmt = optarg;
> +            break;
> +        case 'O':
> +            out_fmt = optarg;
> +            break;
> +        case 'o':
> +            if (!is_valid_option_list(optarg)) {
> +                error_report("Invalid option list: %s", optarg);
> +                goto out;
> +            }
> +            if (!options) {
> +                options = g_strdup(optarg);
> +            } else {
> +                char *old_options = options;
> +                options = g_strdup_printf("%s,%s", options, optarg);
> +                g_free(old_options);
> +            }
> +            break;
> +        case 'l':
> +            if (strstart(optarg, SNAPSHOT_OPT_BASE, NULL)) {
> +                sn_opts = qemu_opts_parse_noisily(&internal_snapshot_opts,
> +                                                  optarg, false);
> +                if (!sn_opts) {
> +                    error_report("Failed in parsing snapshot param '%s'",
> +                                 optarg);
> +                    goto out;
> +                }
> +            } else {
> +                snapshot_name = optarg;
> +            }
> +            break;
> +        case OPTION_OBJECT:
> +            object_opts = qemu_opts_parse_noisily(&qemu_object_opts,
> +                                                  optarg, true);
> +            if (!object_opts) {
> +                goto out;
> +            }
> +            break;
> +        case OPTION_IMAGE_OPTS:
> +            image_opts = true;
> +            break;
> +        case OPTION_OUTPUT:
> +            if (!strcmp(optarg, "json")) {
> +                output_format = OFORMAT_JSON;
> +            } else if (!strcmp(optarg, "human")) {
> +                output_format = OFORMAT_HUMAN;
> +            } else {
> +                error_report("--output must be used with human or json "
> +                             "as argument.");
> +                goto out;
> +            }
> +            break;
> +        case OPTION_SIZE:
> +        {
> +            int64_t sval;
> +
> +            sval = cvtnum(optarg);
> +            if (sval < 0) {
> +                if (sval == -ERANGE) {
> +                    error_report("Image size must be less than 8 EiB!");
> +                } else {
> +                    error_report("Invalid image size specified! You may use "
> +                                 "k, M, G, T, P or E suffixes for ");
> +                    error_report("kilobytes, megabytes, gigabytes, terabytes, "
> +                                 "petabytes and exabytes.");

BTW, I love how we say "EiB" in these error messages but the non-i
suffixes the user can specify are still power-of-two units.

(Also, this error message explicitly says "kilobytes" and so on instead
of "kibibytes". I'm fine with it not least because it's pre-existing,
though. (Furthermore, I'd rather have it be "EB" than the latter message
contain "kibibytes, mebibytes" and so on.))

> +                }
> +                goto out;
> +            }
> +            img_size = (uint64_t)sval;
> +        }
> +        break;
> +        }
> +    }
> +
> +    if (qemu_opts_foreach(&qemu_object_opts,
> +                          user_creatable_add_opts_foreach,
> +                          NULL, NULL)) {
> +        goto out;
> +    }
> +
> +    if (argc - optind > 1) {
> +        error_report("At most one filename argument is allowed.");

Not exactly like convert, then. :-(

But, yeah, it wouldn't really work for the current interface and we can
always extend it later.

(But maybe that means the interface could be better. Maybe this central
function here could collect a statistics of allocated/zero/free/...
clusters of the input image (with a cluster size somehow specified by
the output image driver, however that's supposed to work...) and pass it
to the output driver. That would also save us from replicating the input
block query code for all of the block drivers that implement
bdrv_measure().)

Max

> +        goto out;
> +    } else if (argc - optind == 1) {
> +        filename = argv[optind];
> +    }
> +
> +    if (!filename &&
> +        (object_opts || image_opts || fmt || snapshot_name || sn_opts)) {
> +        error_report("--object, --image-opts, -f, and -l "
> +                     "require a filename argument.");
> +        goto out;
> +    }
> +    if (filename && img_size != ~0ULL) {
> +        error_report("--size N cannot be used together with a filename.");
> +        goto out;
> +    }
> +    if (!filename && img_size == ~0ULL) {
> +        error_report("Either --size N or one filename must be specified.");
> +        goto out;
> +    }
> +
> +    if (filename) {
> +        in_blk = img_open(image_opts, filename, fmt, 0, false, false);
> +        if (!in_blk) {
> +            goto out;
> +        }
> +    }
> +
> +    drv = bdrv_find_format(out_fmt);
> +    if (!drv) {
> +        error_report("Unknown file format '%s'", out_fmt);
> +        goto out;
> +    }
> +    if (!drv->create_opts) {
> +        error_report("Format driver '%s' does not support image creation",
> +                     drv->format_name);
> +        goto out;
> +    }
> +
> +    create_opts = qemu_opts_append(create_opts, drv->create_opts);
> +    opts = qemu_opts_create(create_opts, NULL, 0, &error_abort);
> +    if (options) {
> +        qemu_opts_do_parse(opts, options, NULL, &local_err);
> +        if (local_err) {
> +            error_report_err(local_err);
> +            error_report("Invalid options for file format '%s'", out_fmt);
> +            goto out;
> +        }
> +    }
> +    if (img_size != ~0ULL) {
> +        qemu_opt_set_number(opts, BLOCK_OPT_SIZE, img_size, &error_abort);
> +    }
> +
> +    bdrv_measure(drv, opts, in_blk ? blk_bs(in_blk) : NULL, &info, &local_err);
> +    if (local_err) {
> +        error_report_err(local_err);
> +        goto out;
> +    }
> +
> +    if (output_format == OFORMAT_HUMAN) {
> +        printf("required bytes: %" PRIu64 "\n", info.required_bytes);
> +        printf("fully allocated bytes: %" PRIu64 "\n",
> +               info.fully_allocated_bytes);
> +    } else {
> +        dump_json_block_measure_info(&info);
> +    }
> +
> +    ret = 0;
> +
> +out:
> +    qemu_opts_del(object_opts);
> +    qemu_opts_del(opts);
> +    qemu_opts_del(sn_opts);
> +    qemu_opts_free(create_opts);
> +    g_free(options);
> +    blk_unref(in_blk);
> +    return ret;
> +}
>  
>  static const img_cmd_t img_cmds[] = {
>  #define DEF(option, callback, arg_string)        \
> diff --git a/qemu-img-cmds.hx b/qemu-img-cmds.hx
> index 9c9702c..57ef70f 100644
> --- a/qemu-img-cmds.hx
> +++ b/qemu-img-cmds.hx
> @@ -85,5 +85,14 @@ DEF("amend", img_amend,
>      "amend [--object objectdef] [--image-opts] [-p] [-q] [-f fmt] [-t cache] -o options filename")
>  STEXI
>  @item amend [--object @var{objectdef}] [--image-opts] [-p] [-q] [-f @var{fmt}] [-t @var{cache}] -o @var{options} @var{filename}
> +ETEXI
> +
> +DEF("measure", img_measure,
> +"measure [--output=ofmt] [-O output_fmt] [-o options] [--size N | [--object objectdef] [--image-opts] [-f fmt] [-l snapshot_param] filename]")
> +STEXI
> +@item measure [--output=@var{ofmt}] [-O @var{output_fmt}] [-o @var{options}] [--size @var{N} | [--object @var{objectdef}] [--image-opts] [-f @var{fmt}] [-l @var{snapshot_param}] @var{filename}]
> +ETEXI
> +
> +STEXI
>  @end table
>  ETEXI
> 



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