Hi Ivo, (thanks for the cc) Ivo De Decker <ivodd@debian.org> (2017-04-23): > Thanks for investigating this in detail. > > The changes introduced in os-prober 1.72 (just before the freeze) are > meant to provide a fix for #701814, which has been around for quite some > time. The dmsetup patch was tested on a regular installation. There > probably wasn't that much testing in d-i, which explains why your > investigation shows it probably don't work at all. The issue doesn't show > up that often, because the code path isn't used in most cases (see below). I had tried to reproduce setups from reporters to debug this further but unfortunately I wasn't successful… > The dmsetup code will only be used when grub-mount doesn't work on the > device. This means the dmsetup code path is only used when there is a > partition that can't be mounted by grub-mount (that was the case in > #853277). Your tests show something similar: there is a partition that > cannot be mounted by grub-mount, which means the dmsetup path is used. And > that seems to be broken (at least in d-i). It's nice to know which part(s) doesn't work, this is good news. > Given that grub-mount should be able to handle almost all common cases and > that the dmsetup path probably doesn't work at all in d-i, my proposal > would be to remove (or disable) the dmsetup code path and only rely on > grub-mount. ACK, ignoring something we can't grub-mount looks like a better idea than just waiting forever. We can still try and find a solution for those cases later on, and think of backporting it once it's been tested for a while. > This will still fix the original issue in #701814, and it will fix the > issues with the dmsetup code path (there is also #853927 and #853163). The > 'cost' of this change would be that devices which contain a partition that > can't be mounted by grub-mount, but can be mounted by the kernel, will no > longer be probed for other operating systems. I don't know if there are > common examples like that. Another option is to revert to the original > code path without dmsetup, but that would reintroduce #701814. I think reverting to the previous breakage shouldn't happen at all… KiBi.
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