Re: [Qemu-devel] [PATCH 2/2] block: add-cow support snapshot_blkdev

[Dong Xu Wang]

image file will be created automaticly, file name is formated as:
sprintf(image_file, "%s.raw", snapshot_file);

I just add ".raw" to the file name of #1 in you comments as file name of #2.

On Wed, Mar 7, 2012 at 21:10, Stefan Hajnoczi <address@hidden> wrote:
> On Thu, Mar 1, 2012 at 2:49 AM, Dong Xu Wang <address@hidden> wrote:
>> From: Dong Xu Wang <address@hidden>
>>
>> We can not use raw to support snapshot_file, but add-cow can do this.
>>
>> CC: Marcelo Tosatti <address@hidden>
>> CC: Kevin Wolf <address@hidden>
>> CC: Stefan Hajnoczi <address@hidden>
>> Signed-off-by: Dong Xu Wang <address@hidden>
>> ---
>>  blockdev.c              |   53 
>> ++++++++++++++++++++++++++++++++++++++++++----
>>  docs/live-block-ops.txt |    8 ++++++-
>>  2 files changed, 55 insertions(+), 6 deletions(-)
>>
>> diff --git a/blockdev.c b/blockdev.c
>> index d78aa51..c820fcb 100644
>> --- a/blockdev.c
>> +++ b/blockdev.c
>> @@ -687,12 +687,55 @@ void qmp_blockdev_snapshot_sync(const char *device, 
>> const char *snapshot_file,
>>         return;
>>     }
>>
>> -    ret = bdrv_img_create(snapshot_file, format, bs->filename,
>> -                          bs->drv->format_name, NULL, -1, flags);
>> -    if (ret) {
>> -        error_set(errp, QERR_UNDEFINED_ERROR);
>> -        return;
>> +    if (strcmp(format, "add-cow")) {
>> +        ret = bdrv_img_create(snapshot_file, format, bs->filename,
>> +                              bs->drv->format_name, NULL, -1, flags);
>> +        if (ret) {
>> +            error_set(errp, QERR_UNDEFINED_ERROR);
>> +            return;
>> +        }
>
> I'm confused here because I thought we need three files:
> 1. The .add-cow file containing the bitmap
> 2. The cow image file containing allocated sectors
> 3. The backing file containing the original image
>
> We're only passing in snapshot_file and bs->filename.  How will #2,
> the cow file, be created?
>
> Stefan
>