On 25 Sep 2009, at 22:49, Artem Belevich wrote:
> Our bootloader implementation does not know how to read gang blocks.
> Compare the code from OpenSolaris' variant of grub with what we have
> and find the differences:
>
> Search for zio_read_data here:
> http://bitbucket.org/osunix/osunix-gate/src/1cca4617b3a8/usr/src/grub/grub-0.97/stage2/fsys_zfs.c
>
> And compare with our zio_read here:
> http://fxr.watson.org/fxr/source/boot/zfs/zfsimpl.c?im=excerpts#L900
>
> We seem to be missing gang block check. That would explain why zfsboot
> works only sometimes. If all the files are written using regular
> blocks, then we're OK. However, some time later (i.e. during upgrade
> or after an edit), some data can end up written to disk in a gang
> block and that would make zfsboot choke.
This sounds plausible - I never managed to see a gang block while I
was working on this.