Re: btrfs-convert on 24Gb image corrupts files.

[Anand Jain <anand.jain@oracle.com>]

On 5/5/24 13:54, Qu Wenruo wrote:
> 
> 
> 在 2024/5/5 10:26, Anand Jain 写道:
>>
>>> on ext4:
>>>
>>> ilefrag -v
>>> m/root/.mozilla/firefox/s554srh9.default-release/storage/permanent/chrome/idb/3561288849sdhlie.sqlite
>>> Filesystem type is: ef53
>>> File size of
>>> m/root/.mozilla/firefox/s554srh9.default-release/storage/permanent/chrome/idb/3561288849sdhlie.sqlite is 49152 (12 blocks of 4096 bytes)
>>>   ext:     logical_offset:        physical_offset: length:   expected:
>>> flags:
>>>     0:        0..       1:    2217003..   2217004:      2:
>>>     1:        2..      10:    2217019..   2217027:      9:    2217005:
>>>     2:       11..      11:    2217028..   2217028:      1:
>>> last,unwritten,eof
>>> m/root/.mozilla/firefox/s554srh9.default-release/storage/permanent/chrome/idb/3561288849sdhlie.sqlite: 2 extents found
>>>
>>
>>
>> btrfs-convert doesn't support ext4's "unwritten" extents. V2 of the fix
>> is in progress.
>>
>>    [PATCH 0/4] btrfs-progs: add support ext4 unwritten file extent
> 
> But the reporter also tried your patchset already:
> 
>  > *********
>  >
>  > Tried the four patches from:
> https://lore.kernel.org/linux-btrfs/6d2a19ced4551bfcf2a5d841921af7f84c4ea950.1714722726.git.anand.jain@oracle.com/
> 
>  > on the https://github.com/kdave/btrfs-progs.git tree - no change.
>  >
>  > **********
> 
> Any clue why it doesn't work?
> 
> Anyway, for now I'd prefer to change those unwritten extents just to holes.
> 
> Remember every file extent is shared between the inode and the ext4
> image, meaning even if we created the preallocated extents correctly,
> any newer write would be COWed anyway.
> 
> Thus for now, I believe changing the unwritten extents to holes would be
> much easier.
> 

Ah. I missed that part. Thanks for highlighting.

The data size and extent size might not align. In v2, I'll detect
this and handle it. I'm still figuring out how to split merged
blocks into separate extents, so that prealloc flag/as a hole
can be set on only appropriate extent size.

Thanks, Anand

> Thanks,
> Qu
>>
>>
>> Thanks, Anand
>>