Re: [PATCH] Btrfs: Do not use data_alloc_cluster in ssd mode

[David Sterba <dsterba@suse.cz>]

On Mon, Jul 24, 2017 at 07:22:03PM +0200, Hans van Kranenburg wrote:
> On 07/24/2017 04:25 PM, David Sterba wrote:
> > On Fri, Jul 21, 2017 at 01:47:11PM +0200, Hans van Kranenburg wrote:
> >> [...]
> >>
> >>     So what now...?
> >>
> >> The changes in here do the following:
> >>
> >> 1. Throw out the current ssd_spread behaviour.
> >> 2. Move the current ssd behaviour to the ssd_spread option.
> >> 3. Make ssd mode data allocation identical to tetris mode, like nossd.
> >> 4. Adjust and clean up filesystem mount messages so that we can easily
> >> identify if a kernel has this patch applied or not, when providing
> >> support to end users.
> >>
> >> Instead of directly cutting out all code related to the data cluster, it
> >> makes sense to take a gradual approach and allow users who are still
> >> able to find a valid reason to prefer the current ssd mode the means to
> >> do so by specifiying the additional ssd_spread option.
> >>
> >> Since there are other uses of the ssd mode, we keep the difference
> >> between nossd and ssd mode. However, the usage of the rotational
> >> attribute warrants some reconsideration in the future.
> >>
> >> [...]
> >> Signed-off-by: Hans van Kranenburg <hans.van.kranenburg@mendix.com>
> > 
> > Thanks for the extensive historical summary, this change really deserves
> > it.
> > 
> > Decoupling the assumptions about the device's block management is really
> > a good thing, mount option 'ssd' should mean that the device just has
> > cheap seeks. Moving the the allocation tweaks to ssd_spread provides a
> > way to keep the behaviour for anybody who wants it.
> > 
> > I'd like to push this change to 4.13-rc3, as I don't think we need more
> > time to let other users to test this. The effects of current ssd
> > implementation have been debated and debugged on IRC for a long time.
> > 
> > Reviewed-by: David Sterba <dsterba@suse.com>
> > 
> 
> Ok, thanks. I'll send out a v2 tonight with the typo / commit id fixes
> etc from the other feedback.

I've fixed them already.