Messages in this thread Patch in this message | | | Date | Wed, 11 Oct 2023 13:32:02 +0800 | Subject | Re: [PATCH bpf-next v4 4/8] bpf: Introduce css open-coded iterator kfuncs | From | Chuyi Zhou <> |
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在 2023/10/11 12:44, Chuyi Zhou 写道: > > > 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; > > } >
or we can change the BUILD_BUG_ON check, like bpf_timer_kern in bpf_timer_init:
--- a/kernel/bpf/cgroup_iter.c +++ b/kernel/bpf/cgroup_iter.c @@ -310,7 +310,7 @@ __bpf_kfunc int bpf_iter_css_new(struct bpf_iter_css *it, { 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(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));
kit->start = NULL; diff --git a/kernel/bpf/task_iter.c b/kernel/bpf/task_iter.c index 773be9a221f5..0772545568f1 100644 --- a/kernel/bpf/task_iter.c +++ b/kernel/bpf/task_iter.c @@ -877,7 +877,7 @@ __bpf_kfunc int bpf_iter_task_new(struct bpf_iter_task *it, { struct bpf_iter_task_kern *kit = (void *)it;
- BUILD_BUG_ON(sizeof(struct bpf_iter_task_kern) != sizeof(struct bpf_iter_task)); + BUILD_BUG_ON(sizeof(struct bpf_iter_task_kern) > sizeof(struct bpf_iter_task)); BUILD_BUG_ON(__alignof__(struct bpf_iter_task_kern) != __alignof__(struct bpf_iter_task));
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