Re: What to do about snapshot-aware defrag

[Martin <m_btrfs@ml1.co.uk>]

OK... I'll jump in...

On 30/05/14 21:43, Josef Bacik wrote:
> Hello,
> 
> TL;DR: I want to only do snapshot-aware defrag on inodes in snapshots
> that haven't changed since the snapshot was taken.  Yay or nay (with a
> reason why for nay)

[...]
> 
> === Summary and what I need ===
> 
> Option 1: Only relink inodes that haven't changed since the snapshot was
> taken.
> 
> Pros:
> -Faster
> -Simpler
> -Less duplicated code, uses existing functions for tricky operations so
> less likely to introduce weird bugs.
> 
> Cons:
> -Could possibly lost some of the snapshot-awareness of the defrag.  If
> you just touch a file we would not do the relinking and you'd end up
> with twice the space usage.
[...]


Obvious way to go for fast KISS.


One question:

Will option one mean that we always need to mount with noatime or
read-only to allow snapshot defragging to do anything?


Regards,
Martin