Re: [patch 0/2] Control filesystem balances (kernel side)

[Hugo Mills <hugo-lkml@carfax.org.uk>]

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On Sat, Oct 30, 2010 at 07:44:35PM +0200, Goffredo Baroncelli wrote:
> On Saturday, 30 October, 2010, Hugo Mills wrote:
> >    One fundamental question, though -- is the progress monitor
> > function best implemented as an ioctl, as I've done here, or should it
> > be two or three sysfs files? I'm thinking of /proc/mdstat...
> > Obviously, /proc/mdstat would never get into /sys, but exposing the
> > "expected" and "remaining" values as files has an attractive
> > simplicity to it.
> 
> I like the idea that these info should be put under sysfs. Something like
> 
> /sys/btrfs/<filesystem-uuid>/

/sys/fs/btrfs/<uuid> I think. Also:
/sys/fs/btrfs/<label> as a symlink to the <uuid> directory.

>                              balance	-> info on balancing

For the one-value-per-file rule of sysfs, this should probably be
balance_expected and balance_completed, each holding a count of block
groups.

>                              devices	-> list of device (a directory of
>                                            links or a file which contains 
>                                            the list of devices)
>                              subvolumes/ -> info on subvolume(s)
>                              label       -> label of the filesystem
>                              <other btrfs filesystem related knoba>

   The other one that struck me earlier today as being useful was
tracking the progress of a dev delete operation. But that'll come
later.

> Obviously we need another btrfs command to extract an uuid from a btrfs 
> filesystem like:
> 
> # btrfs filesystem get-uuid /path/to/a/btrfs/filesystem
> f9b9c413-0dc8-4e3f-94f2-86faa702f519

   Possibly a slightly more general "fi metadata" with switches for
UUID and label?

# btrfs fi metadata [-u|--uuid] /path
# btrfs fi metadata [-l|--label] /path

   Hugo.

-- 
=== Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk ===
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