quoted

quoted

quoted

This really wants some luo helper

'luo alloc array'
'luo restore array'
'luo free array'

We can just add kho_{preserve,restore}_vmalloc(). I've drafted it here:
https://git.kernel.org/pub/scm/linux/kernel/git/rppt/linux.git/log/?h=kho/vmalloc/v1

The patch looks okay to me, but it doesn't support holes in vmap
areas. While that is likely acceptable for vmalloc, it could be a
problem if we want to preserve memfd with holes and using vmap
preservation as a method, which would require a different approach.
Still, this would help with preserving memfd.

I agree. I think we should do it the other way round. Build a sparse
array first, and then use that to build vmap preservation. Our emails

Yes, sparse array support would help both: vmalloc and memfd preservation.

seem to have crossed, but see my reply to Mike [0] that describes my
idea a bit more, along with WIP code.

[0] https://lore.kernel.org/lkml/mafs0ldmyw1hp.fsf@kernel.org/ (local)

quoted

However, I wonder if we should add a separate preservation library on
top of the kho and not as part of kho (or at least keep them in a
separate file from core logic). This would allow us to preserve more
advanced data structures such as this and define preservation version
control, similar to Jason's store_object/restore_object proposal.

This is how I have done it in my code: created a separate file called
kho_array.c. If we have enough such data structures, we can probably
move it under kernel/liveupdate/lib/.

Yes, let's place it under kernel/liveupdate/lib/. We will add more
preservation types over time.

As for the store_object/restore_object proposal: see an alternate idea
at [1].

[1] https://lore.kernel.org/lkml/mafs0h5xmw12a.fsf@kernel.org/ (local)

What you are proposing makes sense. We can update the LUO API to be
responsible for passing the compatible string outside of the data
payload. However, I think we first need to settle on the actual API
for storing and restoring a versioned blob of data and place that code
into kernel/liveupdate/lib/. Depending on which API we choose, we can
then modify the LUO to work accordingly.

--
Regards,
Pratyush Yadav