On 03/15, Jose Fernandez wrote: > This patch enhances the BPF helpers by adding a kfunc to retrieve the > cgroup v2 ID of a specific task, addressing a previous limitation where > only bpf_task_get_cgroup1 was available for cgroup v1. The new kfunc is > particularly useful for scenarios where obtaining the cgroup ID of a > task other than the "current" one is necessary, which the existing > bpf_get_current_cgroup_id helper cannot accommodate. A specific use case > at Netflix involved the sched_switch tracepoint, where we had to get > the cgroup IDs of both the previous and next tasks. > > The bpf_task_get_cgroup_id kfunc returns a task's cgroup ID, correctly > implementing RCU read locking and unlocking for safe data access, and > leverages existing cgroup.h helpers to fetch the cgroup and its ID. > > Signed-off-by: Jose Fernandez <[email protected]> > Reviewed-by: Tycho Andersen <[email protected]> > --- > kernel/bpf/helpers.c | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c > index a89587859571..8038b2bd3488 100644 > --- a/kernel/bpf/helpers.c > +++ b/kernel/bpf/helpers.c > @@ -2266,6 +2266,27 @@ bpf_task_get_cgroup1(struct task_struct *task, int > hierarchy_id) > return NULL; > return cgrp; > } > + > +/** > + * bpf_task_get_cgroup_id - Get the cgroup ID of a task. > + * @task: The target task > + * > + * This function returns the ID of the task's default cgroup, primarily > + * designed for use with cgroup v2. In cgroup v1, the concept of default > + * cgroup varies by subsystem, and while this function will work with > + * cgroup v1, it's recommended to use bpf_task_get_cgroup1 instead. > + */ > +__bpf_kfunc u64 bpf_task_get_cgroup_id(struct task_struct *task) > +{ > + struct cgroup *cgrp; > + u64 cgrp_id; > + > + rcu_read_lock(); > + cgrp = task_dfl_cgroup(task); > + cgrp_id = cgroup_id(cgrp); > + rcu_read_unlock(); > + return cgrp_id; > +} > #endif /* CONFIG_CGROUPS */ > > /** > @@ -2573,6 +2594,7 @@ BTF_ID_FLAGS(func, bpf_cgroup_ancestor, KF_ACQUIRE | > KF_RCU | KF_RET_NULL) > BTF_ID_FLAGS(func, bpf_cgroup_from_id, KF_ACQUIRE | KF_RET_NULL) > BTF_ID_FLAGS(func, bpf_task_under_cgroup, KF_RCU) > BTF_ID_FLAGS(func, bpf_task_get_cgroup1, KF_ACQUIRE | KF_RCU | KF_RET_NULL) > +BTF_ID_FLAGS(func, bpf_task_get_cgroup_id, KF_RCU)
Any reason we are not returning 'struct cgroup' pointer? That should allow using other kfuncs that are all 'struct cgrop' based as well.
