Re: [PATCH] fstests: introduce btrfs-map-logical

Re: [PATCH] fstests: introduce btrfs-map-logical

[Qu Wenruo]

At 04/12/2017 08:52 PM, David Sterba wrote:
> On Wed, Apr 12, 2017 at 02:32:02PM +0200, David Sterba wrote:
>> On Wed, Apr 12, 2017 at 09:35:00AM +0800, Qu Wenruo wrote:
>>>
>>>
>>> At 04/12/2017 09:27 AM, Liu Bo wrote:
>>>> A typical use case of 'btrfs-map-logical' is to translate btrfs logical
>>>> address to physical address on each disk.
>>>
>>> Could we avoid usage of btrfs-map-logical here?
>>
>> Agreed.
>>
>>> I understand that we need to do corruption so that we can test if the
>>> repair works, but I'm not sure if the output format will change, or if
>>> the program will get replace by "btrfs inspect-internal" group.
>>
>> In the long-term it will be repleaced, but there's no ETA.
> 
> Possibly, if fstests maintainer agrees, we can add btrfs-map-logical to
> fstests. It's small and uses headers from libbtrfs, so this would become
> a new dependency but I believe is still bearable.
> 
> I'm not sure if we should export all debuging functionality in 'btrfs'
> as this is typically something that a user will never want, not even in
> the emergency environments. There's an overlap in the information to be
> exported but I'd be more inclined to satisfy user needs than testsuite
> needs. So an independent tool would give us more freedom on both sides.
> 
I'm working on the new btrfs-corrupt-block equivalent, considering the 
demand to corrupt on-disk data for recovery test, I could provide tool 
with fundamental corruption support.

Which could corrupt on-disk data, either specified by (root, inode, 
offset, length) or just (logical address, length).
And support to corrupt given mirror or even P/Q for RAID56.
(With btrfs_map_block_v2 from offline scrub)

I'm not sure if I should just replace btrfs-corrupt-block or add a new 
individual prog or add a btrfs subcommand group which is disabled by 
default?

Thanks,
Qu

Re: [PATCH] fstests: introduce btrfs-map-logical

[Eryu Guan]

On Wed, Apr 12, 2017 at 02:52:23PM +0200, David Sterba wrote:
> > > I understand that we need to do corruption so that we can test if the 
> > > repair works, but I'm not sure if the output format will change, or if 
> > > the program will get replace by "btrfs inspect-internal" group.
> > 
> > In the long-term it will be repleaced, but there's no ETA.
> 
> Possibly, if fstests maintainer agrees, we can add btrfs-map-logical to
> fstests. It's small and uses headers from libbtrfs, so this would become
> a new dependency but I believe is still bearable.

IMHO, I think the ability to poke btrfs internal really should be
provided by btrfs-progs package and maintained by btrfs community.
fstests provides some fs-independent c helpers to assist testing, but
not necessarily needs to "understand" filesystem internals.

For historical reason, building fstests requires xfsprogs development
headers, we'd better not introduce new fs-specific dependencies.

Thanks,
Eryu