mainline inclusion
from mainline-v5.12-rc1
commit 20f2505f
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I4GII8?from=project-issue
CVE: NA

--------------

When we attach a bpf program to cgroup/getsockopt any other getsockopt()
syscall starts incurring kzalloc/kfree cost.

Let add a small buffer on the stack and use it for small (majority)
{s,g}etsockopt values. The buffer is small enough to fit into
the cache line and cover the majority of simple options (most
of them are 4 byte ints).

It seems natural to do the same for setsockopt, but it's a bit more
involved when the BPF program modifies the data (where we have to
kmalloc). The assumption is that for the majority of setsockopt
calls (which are doing pure BPF options or apply policy) this
will bring some benefit as well.

Without this patch (we remove about 1% __kmalloc):
     3.38%     0.07%  tcp_mmap  [kernel.kallsyms]  [k] __cgroup_bpf_run_filter_getsockopt
            |
             --3.30%--__cgroup_bpf_run_filter_getsockopt
                       |
                        --0.81%--__kmalloc
Signed-off-by: NStanislav Fomichev <sdf@google.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20210115163501.805133-3-sdf@google.comSigned-off-by: NLu Jialin <lujialin4@huawei.com>
Reviewed-by: Wei Yongjun<weiyongjun1@huawei.com>
Reviewed-by: Nweiyang wang <wangweiyang2@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>