COW a file from snapshot

COW a file from snapshot

[Dave]

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So I've got a daily snapshot of my /home subvolume.  Due to a fat finger, I've
damaged a rather large file so I'd like to pull if from one of these snapshot
backups.  I don't want to simply copy the file since it's many gigs and cp
- --reflink=always doesn't work (produces the error Invalid cross-device link).
Is there a way to recover that file and benefit from COW?
- -- 
- -=[dave]=-

Entropy isn't what it used to be.
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iF4EAREIAAYFAk7wpKUACgkQXM0u5ajNnCgMUQD/Uf0/HygZ9D8StT9Oc6E3+wM/
MBokh6h1iPN2OslJTxgA/RUzFMM2n0+3ORHwvOraJMBJl1P4JfabT31iuemn/BL2
=2cds
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Re: COW a file from snapshot

[Jérôme Poulin]

You would need to apply this patch to your kernel:
http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg09096.html

Is there any chance this patch gets in linux-next ?
I use this feature all the time and it never broke on me.

On Tue, Dec 20, 2011 at 10:07 AM, Dave <dave@thekilempire.com> wrote:
>
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA256
>
> So I've got a daily snapshot of my /home subvolume. =C2=A0Due to a fa=
t finger, I've
> damaged a rather large file so I'd like to pull if from one of these =
snapshot
> backups. =C2=A0I don't want to simply copy the file since it's many g=
igs and cp
> - --reflink=3Dalways doesn't work (produces the error Invalid cross-d=
evice link).
> Is there a way to recover that file and benefit from COW?
> - --
> - -=3D[dave]=3D-
>
> Entropy isn't what it used to be.
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.11 (GNU/Linux)
>
> iF4EAREIAAYFAk7wpKUACgkQXM0u5ajNnCgMUQD/Uf0/HygZ9D8StT9Oc6E3+wM/
> MBokh6h1iPN2OslJTxgA/RUzFMM2n0+3ORHwvOraJMBJl1P4JfabT31iuemn/BL2
> =3D2cds
> -----END PGP SIGNATURE-----
> --
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Re: COW a file from snapshot

[Jérôme Poulin]

Did you get any success with the patch?
Reading the conversation, people seemed to agree that this feature
should be included, anyway, snapshot already share data, why not be
able to copy them?

Other link with title for mailing list reference.
[PATCH 2/2] btrfs: allow cross-subvolume BTRFS_IOC_CLONE
http://permalink.gmane.org/gmane.comp.file-systems.btrfs/9865

On Tue, Dec 20, 2011 at 12:53 PM, J=C3=A9r=C3=B4me Poulin <jeromepoulin=
@gmail.com> wrote:
>
> You would need to apply this patch to your kernel:
> http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg09096.html
>
> Is there any chance this patch gets in linux-next ?
> I use this feature all the time and it never broke on me.
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Re: COW a file from snapshot

[Roman Kapusta]

On Wed, Dec 21, 2011 at 22:31, J=C3=A9r=C3=B4me Poulin <jeromepoulin@gm=
ail.com> wrote:
> Did you get any success with the patch?
> Reading the conversation, people seemed to agree that this feature
> should be included, anyway, snapshot already share data, why not be
> able to copy them?

I'm using btrfs for about two years and this is the key feature I'm
missing all the time. Why is it not part of mainline btrfs already?

>
> Other link with title for mailing list reference.
> [PATCH 2/2] btrfs: allow cross-subvolume BTRFS_IOC_CLONE
> http://permalink.gmane.org/gmane.comp.file-systems.btrfs/9865
>
> On Tue, Dec 20, 2011 at 12:53 PM, J=C3=A9r=C3=B4me Poulin <jeromepoul=
in@gmail.com> wrote:
>>
>> You would need to apply this patch to your kernel:
>> http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg09096.htm=
l
>>
>> Is there any chance this patch gets in linux-next ?
>> I use this feature all the time and it never broke on me.
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Re: COW a file from snapshot

[Chris Samuel]

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On Thu, 22 Dec 2011 07:12:13 PM Roman Kapusta wrote:

> I'm using btrfs for about two years and this is the key feature I'm
> missing all the time. Why is it not part of mainline btrfs already?

Because nobody has written the code to do it yet?

I'm sure the developers would welcome patches for this with open arms!

cheers,
Chris
-- 
 Chris Samuel  :  http://www.csamuel.org/  :  Melbourne, VIC

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Re: COW a file from snapshot

[Gareth Pye]

Chris, I=A0recommend=A0reading the previously linked thread. The suppli=
ed
(and reportedly working) patch was nacked because it violates some
principles or another of file systems. (although from my limited
understanding it only does it in the same way that btrfs snapshots do
in the first place)

On Thu, Dec 22, 2011 at 10:35 PM, Chris Samuel <chris@csamuel.org> wrot=
e:
>
> On Thu, 22 Dec 2011 07:12:13 PM Roman Kapusta wrote:
>
> > I'm using btrfs for about two years and this is the key feature I'm
> > missing all the time. Why is it not part of mainline btrfs already?
>
> Because nobody has written the code to do it yet?
>
> I'm sure the developers would welcome patches for this with open arms=
!
>
> cheers,
> Chris
> --
> =A0Chris Samuel =A0: =A0http://www.csamuel.org/ =A0: =A0Melbourne, VI=
C
>
> This email may come with a PGP signature as a file. Do not panic.
> For more info see: http://en.wikipedia.org/wiki/OpenPGP




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Australian MTG Forum:=A0mtgau.com
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Re: COW a file from snapshot

[Chris Samuel]

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On Thu, 22 Dec 2011 10:57:10 PM Gareth Pye wrote:

> Chris, I recommend reading the previously linked thread.

Mea culpa, I blame reading email out of order after getting out of 
hospital yesterday. :-(

We now return you to your regularly scheduled mailing list..

-- 
 Chris Samuel  :  http://www.csamuel.org/  :  Melbourne, VIC

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Re: COW a file from snapshot

[Sander]

Chris Samuel wrote (ao):
> On Thu, 22 Dec 2011 07:12:13 PM Roman Kapusta wrote:
> > I'm using btrfs for about two years and this is the key feature I'm
> > missing all the time. Why is it not part of mainline btrfs already?
> 
> Because nobody has written the code to do it yet?
> 
> I'm sure the developers would welcome patches for this with open arms!

As posted in this thread by Jerome two days ago:

"You would need to apply this patch to your kernel:
http://www.mail-archive.com/linux-btrfs@vger.kernel.org/msg09096.html

Is there any chance this patch gets in linux-next ?
I use this feature all the time and it never broke on me."


	Sander

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