Re: [Qemu-devel] [PATCH V2 2/4] qemu-nbd: support internal snapshot export

[Paolo Bonzini]

Il 22/09/2013 11:39, Wenchao Xia ha scritto:
> Now it is possible to directly export an internal snapshot, which
> can be used to probe the snapshot's contents without qemu-img
> convert.
> 
> Signed-off-by: Wenchao Xia <address@hidden>
> ---
>  qemu-nbd.c |   54 +++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 files changed, 53 insertions(+), 1 deletions(-)
> 
> diff --git a/qemu-nbd.c b/qemu-nbd.c
> index c26c98e..e450d04 100644
> --- a/qemu-nbd.c
> +++ b/qemu-nbd.c
> @@ -20,6 +20,7 @@
>  #include "block/block.h"
>  #include "block/nbd.h"
>  #include "qemu/main-loop.h"
> +#include "block/snapshot.h"
>  
>  #include <stdarg.h>
>  #include <stdio.h>
> @@ -304,6 +305,23 @@ static void nbd_accept(void *opaque)
>      }
>  }
>  
> +#define SNAPSHOT_OPT_ID         "id"
> +#define SNAPSHOT_OPT_NAME       "name"
> +
> +static QEMUOptionParameter snapshot_options[] = {
> +    {
> +        .name = SNAPSHOT_OPT_ID,
> +        .type = OPT_STRING,
> +        .help = "snapshot id"
> +    },
> +    {
> +        .name = SNAPSHOT_OPT_NAME,
> +        .type = OPT_STRING,
> +        .help = "snapshot name"
> +    },
> +    { NULL }
> +};

I think whatever mechanism you use here to pick a snapshot id or name
should be implemented in qemu-img too.

Also, I think QEMUOptionParameter is being phased out.

>  int main(int argc, char **argv)
>  {
>      BlockDriverState *bs;
> @@ -315,7 +333,10 @@ int main(int argc, char **argv)
>      char *device = NULL;
>      int port = NBD_DEFAULT_PORT;
>      off_t fd_size;
> -    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:t";
> +    QEMUOptionParameter *sn_param = NULL;
> +    const QEMUOptionParameter *sn_param_id, *sn_param_name;
> +    const char *sn_id = NULL, *sn_name = NULL;
> +    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:";
>      struct option lopt[] = {
>          { "help", 0, NULL, 'h' },
>          { "version", 0, NULL, 'V' },
> @@ -328,6 +349,7 @@ int main(int argc, char **argv)
>          { "connect", 1, NULL, 'c' },
>          { "disconnect", 0, NULL, 'd' },
>          { "snapshot", 0, NULL, 's' },
> +        { "snapshot-load", 1, NULL, 'l' },

Please call this option "load-snapshot".

Paolo

>          { "nocache", 0, NULL, 'n' },
>          { "cache", 1, NULL, QEMU_NBD_OPT_CACHE },
>  #ifdef CONFIG_LINUX_AIO
> @@ -428,6 +450,14 @@ int main(int argc, char **argv)
>                  errx(EXIT_FAILURE, "Offset must be positive `%s'", optarg);
>              }
>              break;
> +        case 'l':
> +            sn_param = parse_option_parameters(optarg,
> +                                               snapshot_options, sn_param);
> +            if (!sn_param) {
> +                errx(EXIT_FAILURE,
> +                     "Invalid snapshot-load options '%s'", optarg);
> +            }
> +            /* fall through */
>          case 'r':
>              nbdflags |= NBD_FLAG_READ_ONLY;
>              flags &= ~BDRV_O_RDWR;
> @@ -581,6 +611,24 @@ int main(int argc, char **argv)
>              error_get_pretty(local_err));
>      }
>  
> +    if (sn_param) {
> +        sn_param_id = get_option_parameter(sn_param, SNAPSHOT_OPT_ID);
> +        sn_param_name = get_option_parameter(sn_param, SNAPSHOT_OPT_NAME);
> +        if (sn_param_id) {
> +            sn_id = sn_param_id->value.s;
> +        }
> +        if (sn_param_name) {
> +            sn_name = sn_param_name->value.s;
> +        }
> +        ret = bdrv_snapshot_load_tmp(bs, sn_id, sn_name, &local_err);
> +        if (ret < 0) {
> +            errno = -ret;
> +            err(EXIT_FAILURE,
> +                "Failed to load snapshot, reason:\n%s",
> +                error_get_pretty(local_err));
> +        }
> +    }
> +
>      fd_size = bdrv_getlength(bs);
>  
>      if (partition != -1) {
> @@ -641,6 +689,10 @@ int main(int argc, char **argv)
>          unlink(sockpath);
>      }
>  
> +    if (sn_param) {
> +        free_option_parameters(sn_param);
> +    }
> +
>      if (device) {
>          void *ret;
>          pthread_join(client_thread, &ret);
>