On 03/28/2012 06:24 AM, Matthias G. Eckermann wrote: > Hello Alex and all, > > On 2012-03-27 T 17:19 +0000 Alex wrote: > >> Just a quick question but can't find an obvious answer. >> >> Can I create/convert a existing (btrfs) directory into a >> subvolume? >> >> It would be very helpful when transferring 'partitions' >> into btrfs. I found a similar question way back in >> google, but that site is down now generally. > > As far as I am aware, this is not possible directly. My > approach to this would be using copy with reflinks: > > ------------------------------< snip >------------------------------ > > ## migrate /var/lib/lxc/installserver > ## from directory to btrfs subvolume > > # du -ks /var/lib/lxc/installserver > 500332 /var/lib/lxc/installserver > > # mv /var/lib/lxc/installserver /var/lib/lxc/installserver_tmp > > # btrfs subvol create /var/lib/lxc/installserver > Create subvolume '/var/lib/lxc/installserver' > > # time cp -a --reflink /var/lib/lxc/installserver_tmp/rootfs > /var/lib/lxc/installserver >
This is too much weird. AFAIK, clone between different subvolumes should be forbidden. So this would get a "Invalid cross-device link", because an individual subvolume can be mounted directly. thanks, liubo > real 0m1.367s > user 0m0.148s > sys 0m1.108s > > ## Now remove /var/lib/lxc/installserver_tmp (or not) > > ------------------------------< snap >------------------------------ > > Just to compare this with a "mv": > > ------------------------------< snip >------------------------------ > > ## Go back to former state > > # btrfs subvol delete /var/lib/lxc/installserver > Delete subvolume '/var/lib/lxc/installserver' > > # btrfs subvol create /var/lib/lxc/installserver > Create subvolume '/var/lib/lxc/installserver' > > # time mv /var/lib/lxc/installserver_tmp/rootfs /var/lib/lxc/installserver/ > > real 0m12.917s > user 0m0.208s > sys 0m2.508s > > ------------------------------< snap >------------------------------ > > While the time measurement might be flawed due to the subvol > actions inbetween, caching etc.: I tried several times, and > "cp --reflinks" always is multiple times faster than "mv" in > my environment. > > Or did I misunderstand your question? > > so long - > MgE > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
