Hi all, 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. Thanks in advance. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Mar 27, 2012 at 12:19 PM, Alex <alex@bpmit.com> wrote:> Hi all, > > 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. > > Thanks in advance. > >I don''t think this is possible. The closest thing I can think of is to take a snapshot of the volume, move the directory to the top of the subvolume, then delete all other content.. ... That seems like an awful amount of work, but it''ll preserve the contents of the directory without making duplicates.> > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 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 -- Matthias G. Eckermann Senior Product Manager SUSE® Linux Enterprise SUSE LINUX Products GmbH Maxfeldstraße 5 90409 Nürnberg Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer, HRB 16746 (AG Nürnberg) -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Mar 28, 2012 at 5:24 AM, Matthias G. Eckermann <mge@suse.com> wrote:> 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.So this is cross-subvolume reflinks? I thought the code for that wasn''t merged yet? -- Fajar -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Mar 28, 2012 at 08:46:13AM +0700, Fajar A. Nugraha wrote:> On Wed, Mar 28, 2012 at 5:24 AM, Matthias G. Eckermann <mge@suse.com> wrote: > > 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. > > So this is cross-subvolume reflinks? I thought the code for that > wasn''t merged yet?Matthias was using SLES kernel, the cross-subvolume reflink patch is present there, he was not aware it''s not merged upstream. david -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, Mar 27, 2012 at 05:19:06PM +0000, Alex wrote:> Can I create/convert a existing (btrfs) directory into a subvolume?For the reference there''s an entry at the wiki: http://btrfs.ipv5.de/index.php?title=UseCases#Can_I_take_a_snapshot_of_a_directory.3F as noted in the thread, this relies on the unmerged cross-subvolume reflink patch. david -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
David Sterba <dave <at> jikos.cz> writes:> > On Tue, Mar 27, 2012 at 05:19:06PM +0000, Alex wrote: > > Can I create/convert a existing (btrfs) directory into a subvolume? > > For the reference there''s an entry at the wiki: > >http://btrfs.ipv5.de/index.php?title=UseCases#Can_I_take_a_snapshot_of_a_directory.3F>Thank you all for your replies. Kind regards. (happily experimenting with btrfs in a 3.3 kernel!) Al. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Hello Liu On 03/28/2012 04:18 AM, Liu Bo wrote:> On 03/28/2012 06:24 AM, Matthias G. Eckermann wrote:>> # 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.Could you elaborate which would be the issue ? "cp --reflink"-ing a file is not different than snapshotting a file. In any case I could mount a snapshot and not the source subvolume.> > 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 majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > . >-- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 03/29/2012 12:54 AM, Goffredo Baroncelli wrote:>> > > Could you elaborate which would be the issue ? > "cp --reflink"-ing a file is not different than snapshotting a file. In > any case I could mount a snapshot and not the source subvolume. > > >We already have a debate about this "cross-link device": http://comments.gmane.org/gmane.comp.file-systems.btrfs/9864 "cp --reflink" will use clone feature, which can share data among files, but metadata is preserved individually. My case is that I can mount both a subvolume and a snapshot via "-o subvol=xxx" or "-o subvolid=xxx". thanks, liubo -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thursday 29 of March 2012 09:24:44 Liu Bo wrote:> On 03/29/2012 12:54 AM, Goffredo Baroncelli wrote: > > Could you elaborate which would be the issue ? > > "cp --reflink"-ing a file is not different than snapshotting a file. In > > any case I could mount a snapshot and not the source subvolume. > > We already have a debate about this "cross-link device": > http://comments.gmane.org/gmane.comp.file-systems.btrfs/9864 > > "cp --reflink" will use clone feature, which can share data among files, but > metadata is preserved individually. > > My case is that I can mount both a subvolume and a snapshot via "-o > subvol=xxx" or "-o subvolid=xxx".And how is this different from regular snapshot of subvolume? In the end you get two files pointing to same data on the disk while having different metadata. Let me rephrase it: People don''t want to be able to do: mount /dev/lvm/btrfs /mnt/a -t btrfs -o subvol=volA mount /dev/lvm/btrfs /mnt/b -t btrfs -o subvol=volB cp --reflink=always /mnt/a/file /mnt/b Just like you can''t do hardlinks over `mount --bind` mountpoints, you shouldn''t be able to cp reflink over mountpoints. That''s expected as this *does* break VFS semantics. *But* people want to be able to do this: mount /dev/lvm/btrfs /mnt/ -t btrfs btrfs subvol create /mnt/subvol big-file-creator > /mnt/subvol/BIG-file btrfs subvol snapshot /mnt/subvol /mnt/subvol-bak big-file-editor /mnt/subvol/BIG-file rm /mnt/subvol-bak/BIG-file cp --reflink=always /mnt/subvol/BIG-file /mnt/subvol-bak/BIG-file This does not cross any VFS boundaries. Regards, -- Hubert Kario QBS - Quality Business Software 02-656 Warszawa, ul. Ksawerów 30/85 tel. +48 (22) 646-61-51, 646-74-24 www.qbs.com.pl -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, May 01, 2012 at 07:09:21PM +0200, Hubert Kario wrote:> Let me rephrase it: > > People don''t want to be able to do: > > mount /dev/lvm/btrfs /mnt/a -t btrfs -o subvol=volA > mount /dev/lvm/btrfs /mnt/b -t btrfs -o subvol=volB > cp --reflink=always /mnt/a/file /mnt/b > > Just like you can''t do hardlinks over `mount --bind` mountpoints, you > shouldn''t be able to cp reflink over mountpoints. That''s expected as this > *does* break VFS semantics.Proposed fix (incremental on top of the cross-subvol): --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -2321,6 +2321,10 @@ static noinline long btrfs_ioctl_clone(struct file *file, unsigned long srcfd, goto out_drop_write; } + ret = -EXDEV; + if (src_file->f_path.mnt != file->f_path.mnt) + goto out_fput; + src = src_file->f_dentry->d_inode; ret = -EINVAL; david -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wednesday 02 of May 2012 18:33:37 David Sterba wrote:> On Tue, May 01, 2012 at 07:09:21PM +0200, Hubert Kario wrote: > > Let me rephrase it: > > > > People don''t want to be able to do: > > > > mount /dev/lvm/btrfs /mnt/a -t btrfs -o subvol=volA > > mount /dev/lvm/btrfs /mnt/b -t btrfs -o subvol=volB > > cp --reflink=always /mnt/a/file /mnt/b > > > > Just like you can''t do hardlinks over `mount --bind` mountpoints, you > > shouldn''t be able to cp reflink over mountpoints. That''s expected as this > > *does* break VFS semantics. > > Proposed fix (incremental on top of the cross-subvol):I''m a noob as far as kernel development is concerned so take my comments for what they''re worth.> --- a/fs/btrfs/ioctl.c > +++ b/fs/btrfs/ioctl.c > @@ -2321,6 +2321,10 @@ static noinline long btrfs_ioctl_clone(struct file > *file, unsigned long srcfd, goto out_drop_write; > } > > + ret = -EXDEV; > + if (src_file->f_path.mnt != file->f_path.mnt)I''m not sure about this comparision. Is the f_path struct member used just as reference to some general kernel structure?> + goto out_fput; > + > src = src_file->f_dentry->d_inode; > > ret = -EINVAL;Other that that, looks OK. Regards, -- Hubert Kario QBS - Quality Business Software 02-656 Warszawa, ul. Ksawerów 30/85 tel. +48 (22) 646-61-51, 646-74-24 www.qbs.com.pl
On Thu, May 03, 2012 at 03:26:20PM +0200, Hubert Kario wrote:> > --- a/fs/btrfs/ioctl.c > > +++ b/fs/btrfs/ioctl.c > > @@ -2321,6 +2321,10 @@ static noinline long btrfs_ioctl_clone(struct file > > *file, unsigned long srcfd, goto out_drop_write; > > } > > > > + ret = -EXDEV; > > + if (src_file->f_path.mnt != file->f_path.mnt) > > I''m not sure about this comparision. Is the f_path struct member used just as > reference to some general kernel structure?f_path is ''struct path'' pointer obtained from a ''struct file'' hence the ''f_'' prefix, this is a naming scheme used in vfs. Patch updated in my git repo (branch dev/cross-subvol-clone-v2). david -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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