* Create subvolume from a directory?
@ 2012-03-27 17:19 Alex
2012-03-27 20:42 ` Chester
` (2 more replies)
0 siblings, 3 replies; 14+ messages in thread
From: Alex @ 2012-03-27 17:19 UTC (permalink / raw)
To: linux-btrfs
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.
^ permalink raw reply [flat|nested] 14+ messages in thread* Re: Create subvolume from a directory? 2012-03-27 17:19 Create subvolume from a directory? Alex @ 2012-03-27 20:42 ` Chester 2012-03-27 22:24 ` Matthias G. Eckermann 2012-03-28 9:24 ` David Sterba 2 siblings, 0 replies; 14+ messages in thread From: Chester @ 2012-03-27 20:42 UTC (permalink / raw) To: Alex; +Cc: linux-btrfs 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.. =2E.. 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 =A0http://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 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-03-27 17:19 Create subvolume from a directory? Alex 2012-03-27 20:42 ` Chester @ 2012-03-27 22:24 ` Matthias G. Eckermann 2012-03-28 1:46 ` Fajar A. Nugraha 2012-03-28 2:18 ` Liu Bo 2012-03-28 9:24 ` David Sterba 2 siblings, 2 replies; 14+ messages in thread From: Matthias G. Eckermann @ 2012-03-27 22:24 UTC (permalink / raw) To: Alex, linux-btrfs 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. >=20 > Can I create/convert a existing (btrfs) directory into a > subvolume? >=20 > 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=20 ## 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/l= xc/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/installser= ver/ real 0m12.917s user 0m0.208s=20 sys 0m2.508s=20 ------------------------------< 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 --=20 Matthias G. Eckermann Senior Product Manager SUSE=C2=AE Linux Ent= erprise SUSE LINUX Products GmbH Maxfeldstra=C3=9Fe 5 90409 N=C3=BCrn= berg Germany GF: Jeff Hawn, Jennifer Guild, Felix Imend=C3=B6rffer, HRB 16746 (AG N=C3= =BCrnberg) -- 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 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-03-27 22:24 ` Matthias G. Eckermann @ 2012-03-28 1:46 ` Fajar A. Nugraha 2012-03-28 9:20 ` David Sterba 2012-03-28 2:18 ` Liu Bo 1 sibling, 1 reply; 14+ messages in thread From: Fajar A. Nugraha @ 2012-03-28 1:46 UTC (permalink / raw) To: Matthias G. Eckermann; +Cc: Alex, linux-btrfs 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 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-03-28 1:46 ` Fajar A. Nugraha @ 2012-03-28 9:20 ` David Sterba 0 siblings, 0 replies; 14+ messages in thread From: David Sterba @ 2012-03-28 9:20 UTC (permalink / raw) To: Fajar A. Nugraha; +Cc: Matthias G. Eckermann, Alex, linux-btrfs 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 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-03-27 22:24 ` Matthias G. Eckermann 2012-03-28 1:46 ` Fajar A. Nugraha @ 2012-03-28 2:18 ` Liu Bo 2012-03-28 16:54 ` Goffredo Baroncelli 1 sibling, 1 reply; 14+ messages in thread From: Liu Bo @ 2012-03-28 2:18 UTC (permalink / raw) To: Matthias G. Eckermann; +Cc: Alex, linux-btrfs 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 > ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-03-28 2:18 ` Liu Bo @ 2012-03-28 16:54 ` Goffredo Baroncelli 2012-03-29 1:24 ` Liu Bo 0 siblings, 1 reply; 14+ messages in thread From: Goffredo Baroncelli @ 2012-03-28 16:54 UTC (permalink / raw) To: Liu Bo; +Cc: Matthias G. Eckermann, Alex, linux-btrfs 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 > . > ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-03-28 16:54 ` Goffredo Baroncelli @ 2012-03-29 1:24 ` Liu Bo 2012-05-01 17:09 ` Hubert Kario 0 siblings, 1 reply; 14+ messages in thread From: Liu Bo @ 2012-03-29 1:24 UTC (permalink / raw) To: kreijack; +Cc: Matthias G. Eckermann, Alex, linux-btrfs 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 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-03-29 1:24 ` Liu Bo @ 2012-05-01 17:09 ` Hubert Kario 2012-05-02 16:33 ` David Sterba 0 siblings, 1 reply; 14+ messages in thread From: Hubert Kario @ 2012-05-01 17:09 UTC (permalink / raw) To: Liu Bo; +Cc: kreijack, Matthias G. Eckermann, Alex, linux-btrfs 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= =2E In > > any case I could mount a snapshot and not the source subvolume. >=20 > We already have a debate about this "cross-link device": > http://comments.gmane.org/gmane.comp.file-systems.btrfs/9864 >=20 > "cp --reflink" will use clone feature, which can share data among fil= es, but > metadata is preserved individually. >=20 > My case is that I can mount both a subvolume and a snapshot via "-o > subvol=3Dxxx" or "-o subvolid=3Dxxx". And how is this different from regular snapshot of subvolume? In the en= d you=20 get two files pointing to same data on the disk while having different=20 metadata. Let me rephrase it: People don't want to be able to do: mount /dev/lvm/btrfs /mnt/a -t btrfs -o subvol=3DvolA mount /dev/lvm/btrfs /mnt/b -t btrfs -o subvol=3DvolB cp --reflink=3Dalways /mnt/a/file /mnt/b Just like you can't do hardlinks over `mount --bind` mountpoints, you=20 shouldn't be able to cp reflink over mountpoints. That's expected as th= is=20 *does* break VFS semantics. *But* people want to be able to do this:=20 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=3Dalways /mnt/subvol/BIG-file /mnt/subvol-bak/BIG-file This does not cross any VFS boundaries. Regards, --=20 Hubert Kario QBS - Quality Business Software 02-656 Warszawa, ul. Ksawer=F3w 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 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-05-01 17:09 ` Hubert Kario @ 2012-05-02 16:33 ` David Sterba 2012-05-03 13:26 ` Hubert Kario 0 siblings, 1 reply; 14+ messages in thread From: David Sterba @ 2012-05-02 16:33 UTC (permalink / raw) To: Hubert Kario; +Cc: Liu Bo, kreijack, Matthias G. Eckermann, Alex, linux-btrfs 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 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-05-02 16:33 ` David Sterba @ 2012-05-03 13:26 ` Hubert Kario 2012-05-14 12:36 ` David Sterba 0 siblings, 1 reply; 14+ messages in thread From: Hubert Kario @ 2012-05-03 13:26 UTC (permalink / raw) To: dave; +Cc: Liu Bo, kreijack, Matthias G. Eckermann, Alex, linux-btrfs [-- Attachment #1: Type: text/plain, Size: 1424 bytes --] 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 [-- Attachment #2: smime.p7s --] [-- Type: application/pkcs7-signature, Size: 2346 bytes --] ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-05-03 13:26 ` Hubert Kario @ 2012-05-14 12:36 ` David Sterba 0 siblings, 0 replies; 14+ messages in thread From: David Sterba @ 2012-05-14 12:36 UTC (permalink / raw) To: Hubert Kario Cc: dave, Liu Bo, kreijack, Matthias G. Eckermann, Alex, linux-btrfs 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 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-03-27 17:19 Create subvolume from a directory? Alex 2012-03-27 20:42 ` Chester 2012-03-27 22:24 ` Matthias G. Eckermann @ 2012-03-28 9:24 ` David Sterba 2012-03-28 11:11 ` Alex 2 siblings, 1 reply; 14+ messages in thread From: David Sterba @ 2012-03-28 9:24 UTC (permalink / raw) To: Alex; +Cc: linux-btrfs 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 ^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: Create subvolume from a directory? 2012-03-28 9:24 ` David Sterba @ 2012-03-28 11:11 ` Alex 0 siblings, 0 replies; 14+ messages in thread From: Alex @ 2012-03-28 11:11 UTC (permalink / raw) To: linux-btrfs 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. ^ permalink raw reply [flat|nested] 14+ messages in thread
end of thread, other threads:[~2012-05-14 12:36 UTC | newest] Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2012-03-27 17:19 Create subvolume from a directory? Alex 2012-03-27 20:42 ` Chester 2012-03-27 22:24 ` Matthias G. Eckermann 2012-03-28 1:46 ` Fajar A. Nugraha 2012-03-28 9:20 ` David Sterba 2012-03-28 2:18 ` Liu Bo 2012-03-28 16:54 ` Goffredo Baroncelli 2012-03-29 1:24 ` Liu Bo 2012-05-01 17:09 ` Hubert Kario 2012-05-02 16:33 ` David Sterba 2012-05-03 13:26 ` Hubert Kario 2012-05-14 12:36 ` David Sterba 2012-03-28 9:24 ` David Sterba 2012-03-28 11:11 ` Alex
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