Re: [PATCH v3 0/9] Btrfs: free space B-tree

["Holger Hoffstätte" <holger.hoffstaette@googlemail.com>]

On 09/14/15 08:04, Omar Sandoval wrote:
> I went back and fixed the issues that came up since v2. Changes below. I
> removed Josef's Reviewed-by on patch 9 because it was completely
> rewritten to change the mount options like Dave suggested. These are
> still based on 4.2

I decided to take one for the team and try this.

Merging it into my custom 4.1++ tree (with btrfs at ~4.3) worked flawlessly,
just as the -progs bits. \o/

Upgrading existing filesystems works fine and performance on my peasant
systems with SATA SSDs and rust is still good; not worse but also not
noticeably better. Maybe it is and I just didn't notice; otherwise I guess
that's good for a cache which is not really supposed to be noticeable. :)

Unmounting, remounting, btrfs check all also seem to work as expected.

Two questions:

1) I believe the previous postings mentioned that the fst inherits the
metadata properties - does this mean that e.g. on a single rotational
disk with data=single,metadata=dup the fst is also dup? Is this good,
bad, intentional? I guess it might prevent some of the problems with
corrupted v1 caches that some people had.

2) the following:

> - Changed the free_space_tree option to space_cache=v2 and made clear_cache
>   clear the free space tree. If the free space tree has been created,
>   the mount will fail unless space_cache=v2 or nospace_cache,clear_cache
>   is given because we cannot allow the free space tree to get out of
>   date.

also all seem to work in my testing (wrt. the clearing/downgrading to v1),
but once a volume has been upgraded to v2 fst, a simple mount does not need
to specify space_cache=v2 again; it seems to stick until cleared/downgraded.
Not sure if that is what you meant to say.

Long story short: +1 excellent job and:
Tested-by: Holger Hoffstätte <holger.hoffstaette@googlemail.com>

cheers!

Holger