On 2/23/21 2:28 PM, Song Liu wrote:
To access per-task data, BPF programs usually creates a hash table with
pid as the key. This is not ideal because:
1. The user need to estimate the proper size of the hash table, which may
be inaccurate;
2. Big hash tables are slow;
3. To clean up the data properly during task terminations, the user need
to write extra logic.
Task local storage overcomes these issues and offers a better option for
these per-task data. Task local storage is only available to BPF_LSM. Now
enable it for tracing programs.
Unlike LSM programs, tracing programs can be called in IRQ contexts.
Helpers that access task local storage are updated to use
raw_spin_lock_irqsave() instead of raw_spin_lock_bh().
Tracing programs can attach to functions on the task free path, e.g.
exit_creds(). To avoid allocating task local storage after
bpf_task_storage_free(). bpf_task_storage_get() is updated to not allocate
new storage when the task is not refcounted (task->usage == 0).
Reported-by: kernel test robot <lkp@xxxxxxxxx>
For a patch like this, typically we do not put the above
Reported-by here as it is not really reported by the
kernel test robot. If no revision is required, maybe
maintainer can remove it before applying.
Acked-by: KP Singh <kpsingh@xxxxxxxxxx>
Signed-off-by: Song Liu <songliubraving@xxxxxx>
---
include/linux/bpf.h | 7 ++++++
include/linux/bpf_lsm.h | 22 -----------------
include/linux/bpf_types.h | 2 +-
include/linux/sched.h | 5 ++++
kernel/bpf/Makefile | 3 +--
kernel/bpf/bpf_local_storage.c | 28 +++++++++++++---------
kernel/bpf/bpf_lsm.c | 4 ----
kernel/bpf/bpf_task_storage.c | 43 +++++++++-------------------------
kernel/fork.c | 5 ++++
kernel/trace/bpf_trace.c | 4 ++++
10 files changed, 51 insertions(+), 72 deletions(-)
[...]
