btrfs: extended inode refs

btrfs: extended inode refs

[Norbert Veber]

Hi,


I am trying to switch my BackupPC filesystem to btrfs, so I upgraded to
kernel 3.7.5 as I understand it has support for more hard links.
However I still get the 'too many hard links error'.

I looked at Mark Fasheh's patch, and from my rudimentary udnerstanding
it seems like I need to set BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF in the
superblock.

Is there any way to edit the superblock of an existing filesystem to
enable extended inode refs so that more hard links can be used?

I even went as far as backing up the filesystem, re-formatting using the
mkfs in the latest git version of btrfs-progs, and restoring but it
still doesnt work - too many hard links.  Aparently the mkfs patch wasnt
even applied in git yet?

$ grep -ir BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF .
$ 

Does this mean I shouldnt be using the feature just yet? :P

Thanks,

Norbert

Re: btrfs: extended inode refs

[David Sterba]

On Thu, Jan 31, 2013 at 10:33:37AM -0500, Norbert Veber wrote:
> I looked at Mark Fasheh's patch, and from my rudimentary udnerstanding
> it seems like I need to set BTRFS_FEATURE_INCOMPAT_EXTENDED_IREF in the
> superblock.
> 
> Is there any way to edit the superblock of an existing filesystem to
> enable extended inode refs so that more hard links can be used?

I've once written a one-shot super block "editor" that modified super_flag, if
you feel like updating it to tweak the incompat bits, here it is

http://repo.or.cz/w/btrfs-progs-unstable/devel.git/commit/0c4a8413af17909c6909f8ad96d3cf72c7c3a537

Otherwise, Mark's patches add the incompat bit unconditionally, we need
a way how to make it tunable in the same way as other mkfs do. I'd say
to take them as-is now and extend mkfs later.

david

Re: btrfs: extended inode refs

[Norbert Veber]

On Thu, Jan 31, 2013 at 06:34:04PM +0100, David Sterba wrote:
> Otherwise, Mark's patches add the incompat bit unconditionally, we need
> a way how to make it tunable in the same way as other mkfs do. I'd say
> to take them as-is now and extend mkfs later.

Well I guess its more of a job for btrfstune.  Same way as tune2fs can
enable all of their features.

Having to reformat seems uncecessary.

Re: btrfs: extended inode refs

[David Sterba]

On Thu, Jan 31, 2013 at 01:25:26PM -0500, Norbert Veber wrote:
> On Thu, Jan 31, 2013 at 06:34:04PM +0100, David Sterba wrote:
> > Otherwise, Mark's patches add the incompat bit unconditionally, we need
> > a way how to make it tunable in the same way as other mkfs do. I'd say
> > to take them as-is now and extend mkfs later.
> 
> Well I guess its more of a job for btrfstune.  Same way as tune2fs can
> enable all of their features.

Right.

> Having to reformat seems uncecessary.

Right.

david