Re: [Qemu-devel] [PATCH V3 2/7] qemu-nbd: support internal snapshot export

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

于 2013/10/2 0:08, Paolo Bonzini 写道:
> Il 26/09/2013 02:16, 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>
>> ---
>>   block/snapshot.c         |   18 ++++++++++++++++++
>>   include/block/snapshot.h |    6 ++++++
>>   qemu-nbd.c               |   35 ++++++++++++++++++++++++++++++++++-
>>   3 files changed, 58 insertions(+), 1 deletions(-)
>>
>> diff --git a/block/snapshot.c b/block/snapshot.c
>> index 2ae3099..b371c27 100644
>> --- a/block/snapshot.c
>> +++ b/block/snapshot.c
>> @@ -25,6 +25,24 @@
>>   #include "block/snapshot.h"
>>   #include "block/block_int.h"
>>
>> +QemuOptsList internal_snapshot_opts = {
>> +    .name = "snapshot",
>> +    .head = QTAILQ_HEAD_INITIALIZER(internal_snapshot_opts.head),
>> +    .desc = {
>> +        {
>> +            .name = SNAPSHOT_OPT_ID,
> Why not just use "id" and "name"?
>
Later it is used by code:
qemu_opt_get(sn_opts, SNAPSHOT_OPT_ID),
The macro is used to avoid type it twice in the codes, shouldn't it be used?

Another reason not using "id" is because string "id" is treated as 
special case
in opts_parse() so I choosed string "snapshot.id".

>> +            .type = QEMU_OPT_STRING,
>> +            .help = "snapshot id"
>> +        },{
>> +            .name = SNAPSHOT_OPT_NAME,
>> +            .type = QEMU_OPT_STRING,
>> +            .help = "snapshot name"
>> +        },{
>> +            /* end of list */
>> +        }
>> +    },
>> +};
>> +
>>   int bdrv_snapshot_find(BlockDriverState *bs, QEMUSnapshotInfo *sn_info,
>>                          const char *name)
>>   {
>> diff --git a/include/block/snapshot.h b/include/block/snapshot.h
>> index d05bea7..c524a49 100644
>> --- a/include/block/snapshot.h
>> +++ b/include/block/snapshot.h
>> @@ -27,6 +27,12 @@
>>
>>   #include "qemu-common.h"
>>   #include "qapi/error.h"
>> +#include "qemu/option.h"
>> +
>> +#define SNAPSHOT_OPT_ID         "snapshot.id"
>> +#define SNAPSHOT_OPT_NAME       "snapshot.name"
>> +
>> +extern QemuOptsList internal_snapshot_opts;
>>
>>   typedef struct QEMUSnapshotInfo {
>>       char id_str[128]; /* unique snapshot id */
>> diff --git a/qemu-nbd.c b/qemu-nbd.c
>> index c26c98e..6588a1f 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>
>> @@ -315,7 +316,9 @@ 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";
>> +    QemuOpts *sn_opts = NULL;
>> +    const char *sn_id_or_name = NULL;
>> +    const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:L:";
>>       struct option lopt[] = {
>>           { "help", 0, NULL, 'h' },
>>           { "version", 0, NULL, 'V' },
>> @@ -328,6 +331,8 @@ int main(int argc, char **argv)
>>           { "connect", 1, NULL, 'c' },
>>           { "disconnect", 0, NULL, 'd' },
>>           { "snapshot", 0, NULL, 's' },
>> +        { "load-snapshot", 1, NULL, 'l' },
> Just omit the long option here...
>
>> +        { "load-snapshot1", 1, NULL, 'L' },
> ... and call this "load-snapshot".
>
> Paolo
>
OK, I will change as:

{ NULL, 1, NULL, 'l' },

{ "load-snapshot", 1, NULL, 'L' },

>>           { "nocache", 0, NULL, 'n' },
>>           { "cache", 1, NULL, QEMU_NBD_OPT_CACHE },
>>   #ifdef CONFIG_LINUX_AIO
>> @@ -428,6 +433,14 @@ int main(int argc, char **argv)
>>                   errx(EXIT_FAILURE, "Offset must be positive `%s'", optarg);
>>               }
>>               break;
>> +        case 'l':
>> +            sn_id_or_name = optarg;
>> +            nbdflags |= NBD_FLAG_READ_ONLY;
>> +            flags&= ~BDRV_O_RDWR;
>> +            break;
>> +        case 'L':
>> +            sn_opts = qemu_opts_parse(&internal_snapshot_opts, optarg, 0);
>> +            /* fall through */
>>           case 'r':
>>               nbdflags |= NBD_FLAG_READ_ONLY;
>>               flags&= ~BDRV_O_RDWR;
>> @@ -581,6 +594,22 @@ int main(int argc, char **argv)
>>               error_get_pretty(local_err));
>>       }
>>
>> +    if (sn_opts) {
>> +        ret = bdrv_snapshot_load_tmp(bs,
>> +                                     qemu_opt_get(sn_opts, SNAPSHOT_OPT_ID),
>> +                                     qemu_opt_get(sn_opts, SNAPSHOT_OPT_NAME),
>> +&local_err);
>> +    } else if (sn_id_or_name) {
>> +        ret = bdrv_snapshot_load_tmp_by_id_or_name(bs, sn_id_or_name,
>> +&local_err);
>> +    }
>> +    if (ret<  0) {
>> +        errno = -ret;
>> +        err(EXIT_FAILURE,
>> +            "Failed to load snapshot: %s",
>> +            error_get_pretty(local_err));
>> +    }
>> +
>>       fd_size = bdrv_getlength(bs);
>>
>>       if (partition != -1) {
>> @@ -641,6 +670,10 @@ int main(int argc, char **argv)
>>           unlink(sockpath);
>>       }
>>
>> +    if (sn_opts) {
>> +        qemu_opts_del(sn_opts);
>> +    }
>> +
>>       if (device) {
>>           void *ret;
>>           pthread_join(client_thread,&ret);
>>
>