On Fri, Sep 11, 2015 at 09:25:25AM +0800, Qu Wenruo wrote:
> Josef Bacik wrote on 2015/09/10 16:27 -0400:
> >When dropping a snapshot we need to account for the qgroup changes. If we
> >drop
> >the snapshot in all one go then the backref code will fail to find blocks
> >from
> >the snapshot we dropped since it won't be able to find the root in the fs
> >root
> >cache. This can lead to us failing to find refs from other roots that
> >pointed
> >at blocks in the now deleted root. To handle this we need to not remove the
> >fs
> >roots from the cache until after we process the qgroup operations. Do this
> >by
> >adding dropped roots to a list on the transaction, and letting the
> >transaction
> >remove the roots at the same time it drops the commit roots. This will keep
> >all
> >of the backref searching code in sync properly, and fixes a problem Mark was
> >seeing with snapshot delete and qgroups. Thanks,Btrfs: keep dropped roots in
> >cache until transaciton commit
>
> Mark will definitely be happy with this patch, as quite a good basis
> for snapshot deletion.
Indeed. My tests against a kernel with Josefs patches and my snapshot
deletion code seem to be passing. I'll have something on the list shortly.
Thanks,
--Mark
--
Mark Fasheh
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