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

[Wenchao Xia <xiawenc@linux.vnet.ibm.com>]

于 2013/9/23 18:25, Paolo Bonzini 写道:
> 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<xiawenc@linux.vnet.ibm.com>
>> ---
>>   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.
qemu-img already pick up snapshot by mixed id and name, do you like to 
add a new
interface like the above(Keep old interface untouched for compatiablity)?

> Also, I think QEMUOptionParameter is being phased out.
>
Is QemuOptsList the recommanded method?

>>   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".
>
OK.


> 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);
>>