Re: Regression in v5.14-rc1: f2165627319f btrfs: compression: don't try to compress if we don't have enough pages

David Sterba
2021-08-26T19:38:54Z

On Mon, Aug 23, 2021 at 01:17:15PM +0200, David Sterba wrote:
> On Sun, Aug 22, 2021 at 01:51:15AM -0400, Zygo Blaxell wrote:
> > Before this commit:
> >
> > # head /dev/zero -c 4095 > inline
> > # compsize inline
> > Type Perc Disk Usage Uncompressed Referenced
> > TOTAL 0% 18B 3.9K 3.9K
> > zstd 0% 18B 3.9K 3.9K
> >
> > After this commit:
> >
> > # head /dev/zero -c 4095 > inline
> > # compsize inline
> > Processed 1 file, 1 regular extents (1 refs), 0 inline.
> > Type Perc Disk Usage Uncompressed Referenced
> > TOTAL 100% 4.0K 4.0K 4.0K
> > none 100% 4.0K 4.0K 4.0K
> >
> > This change makes the metadata sizes of trees of small files (e.g. source
> > checkouts) blow up.
> >
> > It looks like we need to look at the offset of the extent, as well as
> > its length.
>
> Thanks for the report, my bad, I'll look into it.

The patch has been reverted in Linus' tree so it'll be in 5.14 final and
will be in the upcoming stable updates according to their release
schedule.