Re: Grow btrfs partition & filesystem backwards

[Goffredo Baroncelli <kreijack@inwind.it>]

On Wednesday, 09 November, 2011 08:36:24 Chris Mason wrote:
> The only choice for an online operation is to make a new partition in
> front of the old one and just add that as a second disk in btrfs.
>=20
> The slow method of shifting the bytes down is probably a better long
> term choice.
>=20
> -chris

Hi Chris,

does the chunk tree be able to map the sectors "before" ? If so we shou=
ld only=20
"shift down" the map logical->physical in the chunk tree/device tree.

The only exception should be the superblock which has to be moved.

At the mount time we should pass a parameter which set how the data sho=
uld be=20
moved backward. Then the kernel remap the chunk tree/device tree.

I don't know if the gains is greater than the work, but from a theoreti=
cal=20
point of view, it should be doable..



>=20
> On Wed, Nov 09, 2011 at 06:40:06AM -0600, Billy Crook wrote:
> > I think the biggest point of contention is that with all the stuff
> > going on in the background in btrfs, its difficult to be sure that =
the
> > resize operation has completed.  With grows, you don't have to worr=
y.
> > With shrinks, if you truncate the block device too soon, you will
> > corrupt the filesystem.
> >=20
> > 2011/11/9 Ernst Sj=F6strand <ernstp@gmail.com>:
> > > Gparted can do that, it just takes a very long time because it mo=
ves
> > > everything back first.
> > >=20
> > > Regards
> > > //Ernst
> > >=20
> > > On Wed, Nov 9, 2011 at 05:23, Jordan Windsor <jordanw2@gmail.com>=
 wrote:
> > >> Hello,
> > >> I was wondering how I would go about growing a btrfs filesystem
> > >> backwards, I don't have any space to store the files temporally,
> > >> I'd
> > >> need to do it in place.
> > >> Thanks.
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> >=20
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>=20
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