On Wed, Dec 18, 2019 at 02:50:39PM -0800, Andrii Nakryiko wrote: > There are cases in which BPF resource (program, map, etc) has to outlive > userspace program that "installed" it in the system in the first place. > When BPF program is attached, libbpf returns bpf_link object, which > is supposed to be destroyed after no longer necessary through > bpf_link__destroy() API. Currently, bpf_link destruction causes both automatic > detachment and frees up any resources allocated to for bpf_link in-memory > representation. This is inconvenient for the case described above because of > coupling of detachment and resource freeing. > > This patch introduces bpf_link__disconnect() API call, which marks bpf_link as > disconnected from its underlying BPF resouces. This means that when bpf_link > is destroyed later, all its memory resources will be freed, but BPF resource > itself won't be detached. > > This design allows to follow strict and resource-leak-free design by default, > while giving easy and straightforward way for user code to opt for keeping BPF > resource attached beyond lifetime of a bpf_link. For some BPF programs (i.e., > FS-based tracepoints, kprobes, raw tracepoint, etc), user has to make sure to > pin BPF program to prevent kernel to automatically detach it on process exit. > This should typically be achived by pinning BPF program (or map in some cases) > in BPF FS. Thanks for the patch. Acked-by: Martin KaFai Lau <kafai@xxxxxx>
