Messages in this thread | | | Date | Wed, 11 Oct 2023 12:44:08 +0800 | Subject | Re: [PATCH bpf-next v4 4/8] bpf: Introduce css open-coded iterator kfuncs | From | Chuyi Zhou <> |
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在 2023/10/7 20:45, Chuyi Zhou 写道: > This Patch adds kfuncs bpf_iter_css_{new,next,destroy} which allow > creation and manipulation of struct bpf_iter_css in open-coded iterator > style. These kfuncs actually wrapps css_next_descendant_{pre, post}. > css_iter can be used to: > > 1) iterating a sepcific cgroup tree with pre/post/up order > > 2) iterating cgroup_subsystem in BPF Prog, like > for_each_mem_cgroup_tree/cpuset_for_each_descendant_pre in kernel. > > The API design is consistent with cgroup_iter. bpf_iter_css_new accepts > parameters defining iteration order and starting css. Here we also reuse > BPF_CGROUP_ITER_DESCENDANTS_PRE, BPF_CGROUP_ITER_DESCENDANTS_POST, > BPF_CGROUP_ITER_ANCESTORS_UP enums. > > Signed-off-by: Chuyi Zhou <zhouchuyi@bytedance.com> > Acked-by: Tejun Heo <tj@kernel.org> > --- > kernel/bpf/cgroup_iter.c | 59 +++++++++++++++++++ > kernel/bpf/helpers.c | 3 + > .../testing/selftests/bpf/bpf_experimental.h | 6 ++ > 3 files changed, 68 insertions(+) > > diff --git a/kernel/bpf/cgroup_iter.c b/kernel/bpf/cgroup_iter.c > index 810378f04fbc..9c6ad892ae82 100644 > --- a/kernel/bpf/cgroup_iter.c > +++ b/kernel/bpf/cgroup_iter.c > @@ -294,3 +294,62 @@ static int __init bpf_cgroup_iter_init(void) > } > > late_initcall(bpf_cgroup_iter_init); > + > +struct bpf_iter_css { > + __u64 __opaque[3]; > +} __attribute__((aligned(8))); > + > +struct bpf_iter_css_kern { > + struct cgroup_subsys_state *start; > + struct cgroup_subsys_state *pos; > + unsigned int flags; > +} __attribute__((aligned(8))); > + > +__bpf_kfunc int bpf_iter_css_new(struct bpf_iter_css *it, > + struct cgroup_subsys_state *start, unsigned int flags) > +{ > + struct bpf_iter_css_kern *kit = (void *)it; > + > + BUILD_BUG_ON(sizeof(struct bpf_iter_css_kern) != sizeof(struct bpf_iter_css)); > + BUILD_BUG_ON(__alignof__(struct bpf_iter_css_kern) != __alignof__(struct bpf_iter_css)); > +
This would cause the fail of netdev/build_32bit CI (https://netdev.bots.linux.dev/static/nipa/790929/13412333/build_32bit/stderr):
tools/testing/selftests/kvm/settings: warning: ignored by one of the .gitignore files ../kernel/bpf/cgroup_iter.c:308:17: warning: no previous prototype for ‘bpf_iter_css_new’ [-Wmissing-prototypes] 308 | __bpf_kfunc int bpf_iter_css_new(struct bpf_iter_css *it, | ^~~~~~~~~~~~~~~~ ../kernel/bpf/cgroup_iter.c:332:41: warning: no previous prototype for ‘bpf_iter_css_next’ [-Wmissing-prototypes] 332 | __bpf_kfunc struct cgroup_subsys_state *bpf_iter_css_next(struct bpf_iter_css *it) | ^~~~~~~~~~~~~~~~~ ../kernel/bpf/cgroup_iter.c:353:18: warning: no previous prototype for ‘bpf_iter_css_destroy’ [-Wmissing-prototypes] 353 | __bpf_kfunc void bpf_iter_css_destroy(struct bpf_iter_css *it) | ^~~~~~~~~~~~~~~~~~~~ In file included from <command-line>: ../kernel/bpf/cgroup_iter.c: In function ‘bpf_iter_css_new’: ./../include/linux/compiler_types.h:425:45: error: call to ‘__compiletime_assert_322’ declared with attribute error: BUILD_BUG_ON failed: sizeof(struct bpf_iter_css_kern) != sizeof(struct bpf_iter_css) 425 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) | ^ ./../include/linux/compiler_types.h:406:25: note: in definition of macro ‘__compiletime_assert’ 406 | prefix ## suffix(); \ | ^~~~~~ ./../include/linux/compiler_types.h:425:9: note: in expansion of macro ‘_compiletime_assert’ 425 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) | ^~~~~~~~~~~~~~~~~~~ ../include/linux/build_bug.h:39:37: note: in expansion of macro ‘compiletime_assert’ 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) | ^~~~~~~~~~~~~~~~~~ ../include/linux/build_bug.h:50:9: note: in expansion of macro ‘BUILD_BUG_ON_MSG’ 50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) | ^~~~~~~~~~~~~~~~ ../kernel/bpf/cgroup_iter.c:313:9: note: in expansion of macro ‘BUILD_BUG_ON’ 313 | BUILD_BUG_ON(sizeof(struct bpf_iter_css_kern) != sizeof(struct bpf_iter_css));
The reason seems on 32-bit machine, sizeof(struct bpf_iter_css) is 24 and sizeof(struct bpf_iter_css_kern) is 16.
I was wondering whether the BUILD_BUG_ON check is necessary. Looking at the struct bpf_list_node and struct bpf_list_node_kern wich are very similay to bpf_iter_css, I didn't see the BUILD_BUG_ON check when convert from (struct bpf_list_node *) to (struct bpf_list_node_kern *)
/* Non-opaque version of bpf_list_node in uapi/linux/bpf.h */ struct bpf_list_node_kern { struct list_head list_head; void *owner; } __attribute__((aligned(8)));
struct bpf_list_node { __u64 :64; __u64 :64; __u64 :64; } __attribute__((aligned(8)));
__bpf_kfunc int bpf_list_push_back_impl(struct bpf_list_head *head, struct bpf_list_node *node, void *meta__ign, u64 off) { struct bpf_list_node_kern *n = (void *)node;
}
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