* Fwd: Backref walking utilities
[not found] <29C9FCE8-F9FB-425A-B346-09939CC0A9FE@gmail.com>
@ 2011-05-23 11:42 ` João Eduardo Luís
2011-05-25 20:47 ` Phillip Susi
0 siblings, 1 reply; 2+ messages in thread
From: João Eduardo Luís @ 2011-05-23 11:42 UTC (permalink / raw)
To: linux-btrfs
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My apologies. Sent this from my mobile and forgot to send it to the list.
---
João Eduardo Luís
gpg key: 477C26E5 from pool.keyserver.eu
Begin forwarded message:
> From: João Eduardo Luís <jecluis@gmail.com>
> Date: May 23, 2011 11:22:51 AM GMT+01:00
> To: Hugo Mills <hugo@carfax.org.uk>
> Subject: Re: Backref walking utilities
>
>
> On May 23, 2011, at 11:15 AM, Hugo Mills wrote:
>
>> On Mon, May 23, 2011 at 12:02:21PM +0200, Arne Jansen wrote:
>>> Hi liubo,
>>>
>>> On 23.05.2011 11:53, liubo wrote:
>>>> As one of my plans, I'm going to take this project over unless someone has been working on it.
>>>
>>> Jan Schmidt has a patch for scrub nearly ready, that does some
>>> ref-walking to report affected files to the user. While this is
>>> kernel code and you're planning to add user-space code, it might
>>> still be possible to share some of it. Maybe the efforts can be
>>> coordinated.
>>
>> Another use for walking backrefs for a block (or an extent) is to
>> work out the differential size of a snapshot -- i.e. how much space
>> will be freed up if the snapshot is deleted. (You need to look at
>> every extent of every file in the snapshot, and work out whether those
>> extents are used anywhere outside the subvolume).
>
> Which, I believe, would be useful if one wanted to merge two diverging snapshots into one.
>
> As I'm doing some research on this topic, I would be thankful if anyone pointed me to Jan Schmidt's patch.
>
>
> - J
>
> ---
> João Eduardo Luís
> gpg key: 477C26E5 from pool.keyserver.eu
>
>
>
>
>
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