Re: fix read repair on compressed extents

[Boris Burkov <boris@bur.io>]

On Wed, Jun 29, 2022 at 10:42:01AM +0200, Christoph Hellwig wrote:
> Any chance to get a review on this one?

Hi, I'm taking a look, and wanted to confirm my test procedure for
examining your patches is correct.

I applied this series and:
btrfs: repair all known bad mirrors
on top of for-next

and I applied
btrfs read repair: more tests
to my xfstests

Under that setup, the new btrfs/270 fails on step 4 checking if
the repair worked (the output looks all random rather than aa's)

Am I missing something?

Thanks,
Boris

> 
> On Thu, Jun 23, 2022 at 07:53:34AM +0200, Christoph Hellwig wrote:
> > Hi all,
> > 
> > while looking into the repair code I found that read repair of compressed
> > extents is current fundamentally broken, in that repair tries to write
> > the uncompressed data into a corrupted extent during a repair.  This is
> > demonstrated by the "btrfs: test read repair on a corrupted compressed
> > extent" test submitted to xfstests.
> > 
> > This series fixes that, but is a bit invaside as it requires both
> > refactoring of the compression code and changes to the repair code to
> > not look up the logic address on every repair attempt.  On the plus
> > side it removes a whole lot of code.
> > 
> > It is based on the for-next branch plus my "btrfs: repair all known bad
> > mirrors" patch.
> > 
> > Diffstat:
> >  compression.c |  287 ++++++++++++++++------------------------------------------
> >  compression.h |   11 --
> >  ctree.h       |    4 
> >  extent_io.c   |   93 +++++++-----------
> >  extent_io.h   |    9 -
> >  inode.c       |   34 +++---
> >  6 files changed, 148 insertions(+), 290 deletions(-)
> ---end quoted text---