Re: [PATCH 2/2] Btrfs: make snapshot-aware defrag as a mount option

[Liu Bo <bo.li.liu@oracle.com>]

On 10/31/2012 07:31 AM, David Sterba wrote:
> On Sat, Oct 27, 2012 at 06:28:41PM +0800, Liu Bo wrote:
>> This feature works on our crucial write endio path, so if we've got
>> lots of fragments to process, it will be kind of a disaster to the
>> performance, so I make such a change.
>>
>> One can benifit from it while mounting with '-o snap_aware_defrag'.
> 
> I vote for a more fine grained control over this feature, ie.  via
> 'btrfs fi defrag', off by default (current behaviour). The defrag ioctl
> is the only place that actually calls set_extent_defrag, so this will
> not affect normal operation and is fully in hands of the user who runs
> defrag.
> 

Besides 'btrfs fi defrag', mounting with autodefrag may also do the same thing.

But controlling by 'btrfs fi defrag' can actually be a good idea.

thanks,
liubo

> Do you have a usecase for setting it through the mount option?
> 
> thanks,
> david
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