Re: [PATCH 07/18] btrfs: create qgroup earlier in snapshot creation

[Boris Burkov <boris@bur.io>]

On Thu, Jul 13, 2023 at 10:26:00AM -0400, Josef Bacik wrote:
> On Wed, Jul 05, 2023 at 04:20:44PM -0700, Boris Burkov wrote:
> > Pull creating the qgroup earlier in the snapshot. This allows simple
> > quotas qgroups to see all the metadata writes related to the snapshot
> > being created and to be born with the root node accounted.
> > 
> > Signed-off-by: Boris Burkov <boris@bur.io>
> > ---
> >  fs/btrfs/qgroup.c      | 3 +++
> >  fs/btrfs/transaction.c | 5 +++++
> >  2 files changed, 8 insertions(+)
> > 
> > diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
> > index 75afd8212bc0..8419270f7417 100644
> > --- a/fs/btrfs/qgroup.c
> > +++ b/fs/btrfs/qgroup.c
> > @@ -1670,6 +1670,9 @@ int btrfs_create_qgroup(struct btrfs_trans_handle *trans, u64 qgroupid)
> >  	struct btrfs_qgroup *qgroup;
> >  	int ret = 0;
> >  
> > +	if (btrfs_qgroup_mode(fs_info) == BTRFS_QGROUP_MODE_DISABLED)
> > +		return 0;
> > +
> >  	mutex_lock(&fs_info->qgroup_ioctl_lock);
> >  	if (!fs_info->quota_root) {
> >  		ret = -ENOTCONN;
> > diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> > index f644c7c04d53..2bb5a64f6d84 100644
> > --- a/fs/btrfs/transaction.c
> > +++ b/fs/btrfs/transaction.c
> > @@ -1716,6 +1716,11 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
> >  	}
> >  	btrfs_release_path(path);
> >  
> > +	ret = btrfs_create_qgroup(trans, objectid);
> > +	if (ret) {
> > +		btrfs_abort_transaction(trans, ret);
> > +		goto fail;
> > +	}
> 
> Newline please.
> 
> How is this ok with normal qgroups?  We weren't creating a qgroup at snapshot
> creation time at all it seems, so I don't understand how this is ok for qgroups.

qgroup_account_snapshot calls btrfs_qgroup_inherit which contains a
separate implementation of qgroup creation.

> Thanks,
> 
> Josef