Re: [PATCH 0/3] Btrfs in-band de-duplication test cases

[Eryu Guan <eguan@redhat.com>]

On Tue, Mar 21, 2017 at 03:36:54PM +0800, Qu Wenruo wrote:
> 
> 
> At 03/21/2017 03:23 PM, Eryu Guan wrote:
> > On Thu, Mar 16, 2017 at 09:50:24AM +0800, Qu Wenruo wrote:
> > > Btrfs in-band de-duplication test cases for in-memory backend, which covers
> > > the bugs exposed during the development.
> > 
> > Sorry, I'm having trouble enabling inband dedupe in tests, I always get
> > ioctl failure, $seqres.full shows:
> > 
> > btrfs-progs v4.10-5-g23d4fd5
> > See https://urldefense.proofpoint.com/v2/url?u=http-3A__btrfs.wiki.kernel.org&d=DwIBAg&c=RoP1YumCXCgaWHvlZYR8PQcxBKCX5YTpkKY057SbK10&r=-yMrTV4jriXR7ieyzzjV-QgHBD0UDw8ixoR77aMeAHE&m=fSE-SZFHxYOtme73LUGhdAkjjKVeu59aewsxj3KYT8Q&s=wL4wtAJyaJ3YtkcV6849DAoedG_3c8E0ngquYDlE9ns&e=  for more information.
> > 
> > Label:              (null)
> > UUID:               3d2cedd0-64ae-4667-ba09-9c12e28ecadd
> > Node size:          16384
> > Sector size:        4096
> > Filesystem size:    15.00GiB
> > Block group profiles:
> >   Data:             single            8.00MiB
> >   Metadata:         DUP               1.00GiB
> >   System:           DUP               8.00MiB
> > SSD detected:       no
> > Incompat features:  extref, skinny-metadata
> > Number of devices:  1
> > Devices:
> >    ID        SIZE  PATH
> >     1    15.00GiB  /dev/mapper/systemvg-testlv2
> > 
> > # /usr/local/bin/btrfs dedupe enable -f -s inmemory -b 64K /scratch
> > ERROR: failed to (enable) inband deduplication: Inappropriate ioctl for device
> > ERROR: unsupported dedupe limit combination: nr: 0, mem: 0
> 
> What I forgot to mention is that, the inband dedupe feature is an
> experimental feature, so CONFIG_BTRFS_DEBUG is needed to use this feature.

OK, I'll rebuild with BTRFS_DEBUG and try again, thanks for the info!
But IMHO, giving out experimental message in dmesg seems sufficient,
like what XFS reflink feature does.

> 
> Sorry for the inconvenience.
> 
> I'll add also add the CONFIG_BTRFS_DEBUG check for /sys/fs/btrfs/feature/,
> so it won't export inband dedupe to users.

I'd suggest that adding a new require rule to check if inband dedupe is
supported by current kernel, by enabling inband dedupe and see the
result, so that we don't need to update the CONFIG_BTRFS_DEBUG check
when this feature is moved out of BTRFS_DEBUG.

Thanks,
Eryu
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