> bpf: keep module BTF until the vmlinux BTF is available

TL;DR: Nits only: in kernel/bpf/btf.c, btf_drop_deferred_vmlinux_regs() could
reuse the new btf_free_deferred_regs() helper, and the module and vmlinux
apply loops look duplicated. No bug.

> diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c
> index 96241dc62dc3..4d51fb212218 100644
> --- a/kernel/bpf/btf.c
> +++ b/kernel/bpf/btf.c

[ ... ]

> @@ -10967,6 +11252,16 @@ static void btf_apply_deferred_regs(struct btf *btf, struct list_head *regs)
>  	}
>  }
>
> +static void btf_free_deferred_regs(struct list_head *regs)
> +{
> +	struct btf_deferred_reg *reg, *tmp;
> +
> +	list_for_each_entry_safe(reg, tmp, regs, list) {
> +		list_del(&reg->list);
> +		btf_free_deferred_reg(reg);
> +	}
> +}
> +

This isn't a bug, but could btf_drop_deferred_vmlinux_regs() call the new
btf_free_deferred_regs(&regs) instead of keeping its own copy of the loop?

The tail of btf_drop_deferred_vmlinux_regs() still open-codes the same
thing on its local list:

    list_for_each_entry_safe(reg, tmp, &regs, list) {
        list_del(&reg->list);
        btf_free_deferred_reg(reg);
    }

The splice / unlock / apply / relock loop in btf_module_apply_regs() is
also the same as the one in btf_apply_deferred_vmlinux_regs(), just with a
different mutex.


---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md

CI run summary: https://github.com/kernel-patches/bpf/actions/runs/36938681172