[sheepdog] [PATCH v2] dog: allow vdi snapshot without snapshot tag

[Hitoshi Mitake]

At Fri, 19 Sep 2014 10:40:38 +0800,
Ruoyu wrote:
> 
> 
> On 2014年09月19日 10:30, Hitoshi Mitake wrote:
> > At Fri, 19 Sep 2014 10:22:07 +0800,
> > Ruoyu wrote:
> >> The problem is still existed.
> > Really? On my environment, I couldn't reproduce the problem. Can I see
> > your command sequence?
> $ dog/dog cluster format
> __
> ()'`;
> /\|`
> / | Caution! The cluster is not empty.
> (/_)_|_ Are you sure you want to continue? [yes/no]: yes
> using backend plain store
> $ dog/dog vdi create test 4M -P
> 100.0 % [=====================================================] 4.0 MB /
> 4.0 MB
> $ dog/dog vdi snapshot test <-- it is allowed
> $ dog/dog vdi snapshot test <-- should be forbidden
> $ dog/dog vdi list <-- both snapshots tagged with ""
> Name Id Size Used Shared Creation time VDI id Copies Tag
> s test 1 4.0 MB 4.0 MB 0.0 MB 2014-09-19 10:36 7c2b25 3
> s test 2 4.0 MB 0.0 MB 4.0 MB 2014-09-19 10:36 7c2b26 3
> test 0 4.0 MB 0.0 MB 4.0 MB 2014-09-19 10:36 7c2b27 3

Ah, sorry. The empty snapshot tag "" is a thing which should be
ignored. So the above behavior is correct. Current master forbids it
and Valerio reported it as a problem.

v2 patch forbids command sequence like this:

$ dog/dog vdi snapshot test -s asdf
$ dog/dog vdi snapshot test -s asdf
Failed to create snapshot for test, maybe snapshot id (0) or tag (asdf) is existed

Actually, v2 can pass 030 test which consists a test case for
duplicated snapshot tags.

Thanks,
Hitoshi

> 
> >
> >> How about disabling empty snapshot tag which will make it simple?
> > It introduces big incompatibility. I want to avoid it.
> >
> > Thanks,
> > Hitoshi
> >
> >> On 2014年09月19日 09:37, Hitoshi Mitake wrote:
> >>> The commit a21bf27906b23448b92cca9943e1019105ffac2f makes
> >>> $ dog vdi snapshot <vdi>
> >>> fail if the <vdi> is an ordinal vdi because newly created VDIs have
> >>> snapid 0. This patch avoids the failure with checking the VDI is
> >>> snapshot or not.
> >>>
> >>> Cc: Ruoyu <liangry at ucweb.com>
> >>> Signed-off-by: Hitoshi Mitake <mitake.hitoshi at lab.ntt.co.jp>
> >>> ---
> >>>   dog/vdi.c | 30 ++++++++++++++++++++++--------
> >>>   1 file changed, 22 insertions(+), 8 deletions(-)
> >>>
> >>> v2: correct vdi existence checking
> >>>
> >>> diff --git a/dog/vdi.c b/dog/vdi.c
> >>> index fa6130e..58b0a71 100644
> >>> --- a/dog/vdi.c
> >>> +++ b/dog/vdi.c
> >>> @@ -567,6 +567,7 @@ static int vdi_snapshot(int argc, char **argv)
> >>>   	int vs_count = 0;
> >>>   	struct node_id owners[SD_MAX_COPIES];
> >>>   	int nr_owners = 0, nr_issued_prevent_inode_update = 0;
> >>> +	bool fail_if_snapshot = false;
> >>>   
> >>>   	if (vdi_cmd_data.snapshot_id != 0) {
> >>>   		sd_err("Please specify a non-integer value for "
> >>> @@ -584,16 +585,29 @@ static int vdi_snapshot(int argc, char **argv)
> >>>   	case SD_RES_NO_TAG:
> >>>   		break;
> >>>   	default:
> >>> -		sd_err("Failed to create snapshot for %s, maybe "
> >>> -			"snapshot id (%d) or tag (%s) is existed",
> >>> -			vdiname, vdi_cmd_data.snapshot_id,
> >>> -			vdi_cmd_data.snapshot_tag);
> >>> -		return EXIT_FAILURE;
> >>> +		fail_if_snapshot = true;
> >>> +		break;
> >>>   	}
> >>>   
> >>> -	ret = read_vdi_obj(vdiname, 0, "", &vid, inode, SD_INODE_HEADER_SIZE);
> >>> -	if (ret != EXIT_SUCCESS)
> >>> -		return ret;
> >>> +	if (fail_if_snapshot) {
> >>> +		ret = dog_read_object(vid_to_vdi_oid(vid), inode,
> >>> +				      SD_INODE_HEADER_SIZE, 0, true);
> >>> +		if (ret != EXIT_SUCCESS)
> >>> +			return ret;
> >>> +
> >>> +		if (vdi_is_snapshot(inode)) {
> >>> +			sd_err("Failed to create snapshot for %s, maybe "
> >>> +			       "snapshot id (%d) or tag (%s) is existed",
> >>> +			       vdiname, vdi_cmd_data.snapshot_id,
> >>> +			       vdi_cmd_data.snapshot_tag);
> >>> +			return EXIT_FAILURE;
> >>> +		}
> >>> +	} else {
> >>> +		ret = read_vdi_obj(vdiname, 0, "", &vid, inode,
> >>> +				   SD_INODE_HEADER_SIZE);
> >>> +		if (ret != EXIT_SUCCESS)
> >>> +			return ret;
> >>> +	}
> >>>   
> >>>   	if (inode->store_policy) {
> >>>   		sd_err("creating a snapshot of hypervolume is not supported");
> >>
> 
>