On Mon, Apr 10, 2023 at 12:07:48PM -0700, Dave Marchevsky wrote: > Currently, BPF programs can interact with the lifetime of refcounted > local kptrs in the following ways: > > bpf_obj_new - Initialize refcount to 1 as part of new object creation > bpf_obj_drop - Decrement refcount and free object if it's 0 > collection add - Pass ownership to the collection. No change to > refcount but collection is responsible for > bpf_obj_dropping it > > In order to be able to add a refcounted local kptr to multiple > collections we need to be able to increment the refcount and acquire a > new owning reference. This patch adds a kfunc, bpf_refcount_acquire, > implementing such an operation. > > bpf_refcount_acquire takes a refcounted local kptr and returns a new > owning reference to the same underlying memory as the input. The input > can be either owning or non-owning. To reinforce why this is safe, > consider the following code snippets: > > struct node *n = bpf_obj_new(typeof(*n)); // A > struct node *m = bpf_refcount_acquire(m); // B typo. should probably be bpf_refcount_acquire(n) ?
