On 10/24/23 6:40 PM, Stanislav Fomichev wrote:
On 10/23, Daniel Borkmann wrote:
[...]
The series looks great! FWIW: Acked-by: Stanislav Fomichev <sdf@xxxxxxxxxx>
Thanks for review!
One small question I have is: We now (and after introduction of tcx) seem to store non-refcounted dev pointers in the bpf_link(s). Is it guaranteed that the dev will outlive the link?
The semantics are the same as it was done in XDP, meaning, the link is in detached state so link->dev is NULL when dev goes away, see also the dev_xdp_uninstall(). We cannot hold a refcount on the dev as otherwise if the link outlives it we get the infamous "unregister_netdev...waiting for <dev>... refcnt = 1" bug.
+ ret = netkit_link_prog_attach(&nkl->link, + attr->link_create.flags, + attr->link_create.netkit.relative_fd, + attr->link_create.netkit.expected_revision); + if (ret) { + nkl->dev = NULL; + bpf_link_cleanup(&link_primer); + goto out;What happens to nkl here? Do we leak it?
No, this is done similarly as in XDP and tcx, that is, bpf_link_cleanup() will trigger eventual release of nlk here : /* Clean up bpf_link and corresponding anon_inode file and FD. After * anon_inode is created, bpf_link can't be just kfree()'d due to deferred * anon_inode's release() call. This helper marks bpf_link as * defunct, releases anon_inode file and puts reserved FD. bpf_prog's refcnt * is not decremented, it's the responsibility of a calling code that failed * to complete bpf_link initialization. * This helper eventually calls link's dealloc callback, but does not call * link's release callback. */ Thanks, Daniel
