Re: [PATCH] bcachefs: support REMAP_FILE_DEDUP in bch2_remap_file_range

[Brian Foster <bfoster@redhat.com>]

On Mon, May 13, 2024 at 11:42:42PM +0000, Reed Riley wrote:
> On Monday, May 13th, 2024 at 5:34 AM, Brian Foster <bfoster@redhat.com> wrote:
> 
> > On Sat, May 11, 2024 at 12:20:12AM +0000, Reed Riley wrote:
> > 
> > > By removing the early-exit when REMAP_FILE_DEDUP is set, we should be
> > > able to support the fideduperange ioctl, albeit less efficiently than if
> > > we handled some of the extent locking and comparison logic inside
> > > bcachefs. Extent comparison logic already exists inside of
> > > `__generic_remap_file_range_prep`.
> > > 
> > > Signed-off-by: Reed Riley reed@riley.engineer
> > > ---
> > 
> > 
> > Seems reasonable:
> > 
> > Reviewed-by: Brian Foster bfoster@redhat.com
> > 
> > 
> > Have you run any tests just to make sure there are no surprises? If not,
> > it looks like xfs_io has a 'dedupe' command that would make it easy to
> > run a quick test or two from the command line. fstests has a bunch of
> > tests in the dedupe group (which I presume this patch should now allow
> > to run on bcachefs) as well.
> 
> I worked with Kent to run his CI tests against the patch (https://evilpiepirate.org/~testdashboard/ci?branch=bcachefs-fideduperange&commit=1945149c8d7549b924cd88f57f0cd938b3bb7125) and also used xfs_io to do some basic sanity checks.
> 

Ah, great. I threw this up on my test branch yesterday as well just to
see what happens. It looks like it enabled more tests (likely the
fstests that _require_dedupe), which is good to see.

> Specifically, I sanity checked that:
>  1. fideduperange doesn’t dedupe if file content doesn’t match,
>  2. fideduperange does dedupe stuff when they do (according to filefrag -v reporting shared extents), and
>  3. That neither of the above operations changed file checksums.
> 

Makes sense. Thanks!

Brian

> I’d be happy to run more tests if anyone can suggest them?
> 
> > 
> > Brian
> > 
> > > fs/bcachefs/fs-io.c | 3 ---
> > > 1 file changed, 3 deletions(-)
> > > 
> > > diff --git a/fs/bcachefs/fs-io.c b/fs/bcachefs/fs-io.c
> > > index 20b40477425f..4f513f22a66a 100644
> > > --- a/fs/bcachefs/fs-io.c
> > > +++ b/fs/bcachefs/fs-io.c
> > > @@ -857,9 +857,6 @@ loff_t bch2_remap_file_range(struct file *file_src, loff_t pos_src,
> > > if (remap_flags & ~(REMAP_FILE_DEDUP|REMAP_FILE_ADVISORY))
> > > return -EINVAL;
> > > 
> > > - if (remap_flags & REMAP_FILE_DEDUP)
> > > - return -EOPNOTSUPP;
> > > -
> > > if ((pos_src & (block_bytes(c) - 1)) ||
> > > (pos_dst & (block_bytes(c) - 1)))
> > > return -EINVAL;
> > > --
> > > 2.44.0
>