Re: Add stripes filter

[David Sterba <dsterba@suse.cz>]

On Tue, Sep 29, 2015 at 12:21:39PM +0000, Hugo Mills wrote:
> On Tue, Sep 29, 2015 at 08:10:19AM -0400, Austin S Hemmelgarn wrote:
> > On 2015-09-29 08:00, David Sterba wrote:
> > >On Mon, Sep 28, 2015 at 05:57:05PM +0000, Gabríel Arthúr Pétursson wrote:
> > >>The attached patches to linux and btrfs-progs add support for filtering
> > >>based on the number of strips in a block when balancing.
> > >
> > >What usecase do you want to address? As I understand it, this would help
> > >the raid56 rebalancing to process only blockgroups that are not spread
> > >accross enough devices.
> 
>    Exactly. Last week, I was trying to help Gabríel on IRC with a
> close-to-full filesystem balance it to add some new devices in a
> parity RAID configuration. He'd added the devices and balanced, but
> the usage was unequal across the devices. The only way I could think
> of dealing with it with the current tools was either to do a full
> balance repeatedly until it worked itself out, or to delve into the
> metadata with btrfs-debug-tree, and balance selected block groups
> individually.
> 
>    I whinged that we needed a filter to pick just the block groups
> that weren't "as full as possible", and Gabríel picked up the idea and
> ran with it.

That's great, thanks. The stripe filters are really missing.