On Fri, 4 Sep 2020, Mikulas Patocka wrote:
> Hmm, so I've found another bug in dax mode.
>
> If you extract the Linux kernel tree on dax-based ext2 filesystem (use the
> real ext2 driver, not ext4), and then you run make twice, the second
> invocation will rebuild everything. It seems like a problem with
> timestamps.
>
> mount -t ext2 -o dax /dev/pmem0 /mnt/ext2/
> cd /mnt/ext2/usr/src/git/linux-2.6
> make clean
> make -j12
> make -j12 <--- this rebuilds the whole tree, althought it shouldn't
>
> I wasn't able to bisect it because this bug seems to be present in every
> kernel I tried (back to 4.16.0). Ext4 doesn't seem to have this bug.
>
> Mikulas
I've found out the root cause for this bug (XFS has it too) and I'm
sending patches.
Mikulas