qemu-img convert is freezing for some DMG files.

[Julio Faracco]

Recently, I created a file using hdiutil from MacOS (using Zlib compression):

$ hdiutil create -volname MyVolName -srcfolder /path/to/my/vol/ -ov -format UDZO myvolname.dmg

But, when I try to convert this volume using qemu-img convert, this command is freezing.

I'm using the upstream version to test it.

It is freezing inside the binary search method to retrieve the chunk.

But, I still don't know why.

I'm attaching the file as an example.

It can be mounted using MacOS or other Linux apps like hfsleuth and darling-dmg.

[yuchenlin (npes87184)]

I have submitted a patch to prevent hanging in binary search.
See: http://lists.nongnu.org/archive/html/qemu-devel/2018-12/msg05453.html?fbclid=IwAR0ObsaZ4kVMVv6MWIdq0ZCAN5tGhDsd9GmFv8_v7HBTl94Cu5EkRZ3z4n4

Thanks,
Yu-Chen Lin

[Julio Faracco (jcfaracco)]

I'm almost sure that we need other improvements beyond fixing binary search deadlock.

It is returning read errors when you apply your patch.

[yuchenlin (npes87184)]

Because of lacking zero chunk table, reading zero sector will return EIO.
I have submitted a series to fix this problem.

Please refer to this series: http://lists.nongnu.org/archive/html/qemu-devel/2018-12/msg05637.html

Thanks,
Yu-Chen Lin

[Julio Faracco (jcfaracco)]

Hi Yu-Chen.

The series looks good. It fixed the problems related to zero chunk. Nice work!

I added a comment that I reviewed your patch considering my scenarios here. At least, It contributes to merge your changes.

[Julio Faracco (jcfaracco)]

Additional info: tested with version 3.0.0. So, before pushing my commits. Conclusion: This is not a new bug.

[Thomas Huth (th-huth)]

Since QEMU 4.0 has been released now, I assume we can close this ticket as "Fix released"? Or is there still anything left to do here?

[yuchenlin (npes87184)]

I re-test the dmg img with QEMU 4.0 again, and it works.

In my opinion, the bug can be closed as "Fix released".

Thanks.

[Thomas Huth (th-huth)]

Thanks for testing. So I'm marking this now as "Fix released".