How to map extents to files

How to map extents to files

[Nikolaus Rath]

Hello,

For one of my btrfs volumes, btrfsck reports a lot of the following
warnings:

[...]
checking extents
bad extent [138477568, 138510336), type mismatch with chunk
bad extent [140091392, 140148736), type mismatch with chunk
bad extent [140148736, 140201984), type mismatch with chunk
bad extent [140836864, 140865536), type mismatch with chunk
[...]

Is there a way to discover which files are affected by this (in
particular so that I can take a look at them before and after a btrfsck
--repair)?


Best,
-Nikolaus

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Re: How to map extents to files

[Qu Wenruo]

At 06/02/2016 11:06 AM, Nikolaus Rath wrote:
> Hello,
>
> For one of my btrfs volumes, btrfsck reports a lot of the following
> warnings:
>
> [...]
> checking extents
> bad extent [138477568, 138510336), type mismatch with chunk
> bad extent [140091392, 140148736), type mismatch with chunk
> bad extent [140148736, 140201984), type mismatch with chunk
> bad extent [140836864, 140865536), type mismatch with chunk
> [...]
>
> Is there a way to discover which files are affected by this (in
> particular so that I can take a look at them before and after a btrfsck
> --repair)?
>
>
> Best,
> -Nikolaus
>
Which version is the progs? If the fs is not converted from ext2/3/4, it 
may be a false alert.

Thanks,
Qu

Re: How to map extents to files

[Nikolaus Rath]

On Jun 02 2016, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
> At 06/02/2016 11:06 AM, Nikolaus Rath wrote:
>> Hello,
>>
>> For one of my btrfs volumes, btrfsck reports a lot of the following
>> warnings:
>>
>> [...]
>> checking extents
>> bad extent [138477568, 138510336), type mismatch with chunk
>> bad extent [140091392, 140148736), type mismatch with chunk
>> bad extent [140148736, 140201984), type mismatch with chunk
>> bad extent [140836864, 140865536), type mismatch with chunk
>> [...]
>>
>> Is there a way to discover which files are affected by this (in
>> particular so that I can take a look at them before and after a btrfsck
>> --repair)?
>
> Which version is the progs? If the fs is not converted from ext2/3/4,
> it may be a false alert.

Version is 4.4.1. The fs may very well have been converted from ext4,
but I can't tell for sure.


Best,
-Nikolaus

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Re: How to map extents to files

[Qu Wenruo]

At 06/02/2016 10:56 PM, Nikolaus Rath wrote:
> On Jun 02 2016, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
>> At 06/02/2016 11:06 AM, Nikolaus Rath wrote:
>>> Hello,
>>>
>>> For one of my btrfs volumes, btrfsck reports a lot of the following
>>> warnings:
>>>
>>> [...]
>>> checking extents
>>> bad extent [138477568, 138510336), type mismatch with chunk
>>> bad extent [140091392, 140148736), type mismatch with chunk
>>> bad extent [140148736, 140201984), type mismatch with chunk
>>> bad extent [140836864, 140865536), type mismatch with chunk
>>> [...]
>>>
>>> Is there a way to discover which files are affected by this (in
>>> particular so that I can take a look at them before and after a btrfsck
>>> --repair)?
>>
>> Which version is the progs? If the fs is not converted from ext2/3/4,
>> it may be a false alert.
>
> Version is 4.4.1. The fs may very well have been converted from ext4,
> but I can't tell for sure.
>
>
> Best,
> -Nikolaus
>

Sorry for the late reply.

For such case, btrfsck --repair is unable to fix it, as btrfs-progs is 
not able to balance extents.

Normally, a full balance would fix it.


I would try to update btrfs-progs to 4.5 and recheck, to see if it's a 
false alert.
If not, then remove unused snapshots and then do the full balance.

It's recommended to delete unused snapshots, as if there are too many 
snapshots, balance may be quite slow.

Thanks,
Qu

Re: How to map extents to files

[Henk Slager]

On Fri, Jun 10, 2016 at 10:17 AM, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
>
>
> At 06/02/2016 10:56 PM, Nikolaus Rath wrote:
>>
>> On Jun 02 2016, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
>>>
>>> At 06/02/2016 11:06 AM, Nikolaus Rath wrote:
>>>>
>>>> Hello,
>>>>
>>>> For one of my btrfs volumes, btrfsck reports a lot of the following
>>>> warnings:
>>>>
>>>> [...]
>>>> checking extents
>>>> bad extent [138477568, 138510336), type mismatch with chunk
>>>> bad extent [140091392, 140148736), type mismatch with chunk
>>>> bad extent [140148736, 140201984), type mismatch with chunk
>>>> bad extent [140836864, 140865536), type mismatch with chunk
>>>> [...]
>>>>
>>>> Is there a way to discover which files are affected by this (in
>>>> particular so that I can take a look at them before and after a btrfsck
>>>> --repair)?
>>>
>>>
>>> Which version is the progs? If the fs is not converted from ext2/3/4,
>>> it may be a false alert.
>>
>>
>> Version is 4.4.1. The fs may very well have been converted from ext4,
>> but I can't tell for sure.
>>
>>
>> Best,
>> -Nikolaus
>>
>
> Sorry for the late reply.
>
> For such case, btrfsck --repair is unable to fix it, as btrfs-progs is not
> able to balance extents.
>
> Normally, a full balance would fix it.
>
>
> I would try to update btrfs-progs to 4.5 and recheck, to see if it's a false
> alert.
> If not, then remove unused snapshots and then do the full balance.
>
> It's recommended to delete unused snapshots, as if there are too many
> snapshots, balance may be quite slow.

You might want to try to balance only the ranges that are problematic
if a recent kernel+tools still report this bad extents.

AFAIK, in the 'bad extent [X, Y), type mismatch with chunk' text, the
X and Y are logical byte numbers (virtual addresses).
You can list all chunks with this:
https://github.com/knorrie/btrfs-heatmap/blob/master/show_usage.py

To force balance of this [X, Y) range, run   btrfs balance start -v
-dvrange=X..Y <mountpoint>
or    -mvrange or -svrange  if [X, Y) is in a metadata resp. system chunk.

The  btrfs-debugfs python script in the
git://git.kernel.org/pub/scm/linux/kernel/git/kdave/btrfs-progs.git
sources might also help, but it does not list system and metadata
chunks.

After such a filtered balance, you should see at least one new chunk
added (just see the highest virtual addr)

In case the [X, Y) are physical, have a look at the man btrfs-balance
drange filter.
I currently don't know an answer to your post subject, but maybe less
important as [X, Y) might also be not file contents
related.

Re: How to map extents to files

[Nikolaus Rath]

On Jun 10 2016, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
> At 06/02/2016 10:56 PM, Nikolaus Rath wrote:
>> On Jun 02 2016, Qu Wenruo <quwenruo@cn.fujitsu.com> wrote:
>>> At 06/02/2016 11:06 AM, Nikolaus Rath wrote:
>>>> Hello,
>>>>
>>>> For one of my btrfs volumes, btrfsck reports a lot of the following
>>>> warnings:
>>>>
>>>> [...]
>>>> checking extents
>>>> bad extent [138477568, 138510336), type mismatch with chunk
>>>> bad extent [140091392, 140148736), type mismatch with chunk
>>>> bad extent [140148736, 140201984), type mismatch with chunk
>>>> bad extent [140836864, 140865536), type mismatch with chunk
>>>> [...]
>>>>
>>>> Is there a way to discover which files are affected by this (in
>>>> particular so that I can take a look at them before and after a btrfsck
>>>> --repair)?
>>>
>>> Which version is the progs? If the fs is not converted from ext2/3/4,
>>> it may be a false alert.
>>
>> Version is 4.4.1. The fs may very well have been converted from ext4,
>> but I can't tell for sure.
>
> For such case, btrfsck --repair is unable to fix it, as btrfs-progs is
> not able to balance extents.
>
> Normally, a full balance would fix it.
>
>
> I would try to update btrfs-progs to 4.5 and recheck, to see if it's a
> false alert.
> If not, then remove unused snapshots and then do the full balance.

Newest btrfs-progs reported the same error, and a full balance fixed
it. Thank you!

Best,
Nikolaus

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Re: How to map extents to files

[Nikolaus Rath]

On Jun 01 2016, Nikolaus Rath <Nikolaus@rath.org> wrote:
> Hello,
>
> For one of my btrfs volumes, btrfsck reports a lot of the following
> warnings:
>
> [...]
> checking extents
> bad extent [138477568, 138510336), type mismatch with chunk
> bad extent [140091392, 140148736), type mismatch with chunk
> bad extent [140148736, 140201984), type mismatch with chunk
> bad extent [140836864, 140865536), type mismatch with chunk
> [...]
>
> Is there a way to discover which files are affected by this (in
> particular so that I can take a look at them before and after a btrfsck
> --repair)?

Hmm. Anyone? Is there really no way to figure out what might be affected
if I attempt a repair?


Best,
-Nikolaus

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