Re: [PATCH v6 07/13] kho: add support for linked-block serialization

[Pasha Tatashin <pasha.tatashin@soleen.com>]

On 06-03 09:49, Mike Rapoport wrote:
> On Wed, 03 Jun 2026 03:28:58 +0000, Pasha Tatashin <pasha.tatashin@soleen.com> wrote:
> > diff --git a/include/linux/kho/abi/block.h b/include/linux/kho/abi/block.h
> > new file mode 100644
> > index 000000000000..8641c20b379b
> > --- /dev/null
> > +++ b/include/linux/kho/abi/block.h
> > @@ -0,0 +1,56 @@
> > [ ... skip 25 lines ... ]
> > +#define _LINUX_KHO_ABI_BLOCK_H
> > +
> > +#include <asm/page.h>
> > +#include <linux/types.h>
> > +
> > +#define KHO_BLOCK_ABI_COMPATIBLE	"kho-block-v1"
> 
> It's never used by block set and after looking at the following patches I
> found that it's appended to LUO compatible string.
> 
> While this works for LUO, I think it should be kho_block_set_restore()
> responsibility to verify the compatibility.

It should work for any component that relies on  kho_block. My proposal 
is to use this method for other common KHO data structures (e.g.,  kho 
vmalloc,  kho radix, future kho xarray). There is no need for them to 
carry the compatibility string in their metadata, as whoever uses them 
will include their compatibility string.

For now, reviewers will have to make sure that if the ABI header content 
is changed, the compatibility string is updated.

> > diff --git a/kernel/liveupdate/kho_block.c b/kernel/liveupdate/kho_block.c
> > new file mode 100644
> > index 000000000000..4f147c308e6b
> > --- /dev/null
> > +++ b/kernel/liveupdate/kho_block.c
> > @@ -0,0 +1,411 @@
> > [ ... skip 121 lines ... ]
> > +/**
> > + * kho_block_set_grow - Expand the block set to accommodate the target count.
> > + * @bs:    The block set.
> > + * @count: The target number of valid entries to accommodate.
> > + *
> > + * Acts as a runtime notifier when new resources (such as files or sessions)
> 
> Not sure I understand what "runtime notifier" means in this context.

It came from discussion with Pratyush, but I think we are on the same 
page what they are, and I will just remove this.

> 
> > [ ... skip 11 lines ... ]
> > +
> > +	while (count > bs->nblocks * bs->count_per_block) {
> > +		int err = kho_block_set_grow_one(bs);
> > +
> > +		if (err)
> > +			return err;
> 
> This leaks memory if more than one block is added.
> 
> > [ ... skip 31 lines ... ]
> > + * unregistered, allowing the block set to release and unallocate redundant
> > + * preserved memory blocks. Checks if the last block in the set can be removed
> > + * because the remaining entry count is fully accommodated by the preceding blocks.
> > + *
> > + * Note: It is the caller's responsibility to ensure that entries are removed
> > + * in LIFO (last-in, first-out) order (the reverse order of their insertion).
> 
> I think "in LIFO order" is sufficient :)

Oh, I keep removing those :-)

> > [ ... skip 173 lines ... ]
> > +		it->i = 0;
> > +	}
> > +
> > +	entry = kho_block_entry(it, it->i++);
> > +	it->block->ser->count = it->i;
> > +	return entry;
> 
> This looks way better than the previous version :)
> Thanks!

Thank you. I will send a new version of this patch as a reply to this 
email to avoid cluttering the mailing list.

Pasha

> 
> -- 
> Sincerely yours,
> Mike.
>