2022-03-31 11:59:03

by Jakob Koschel

Subject: [PATCH v2] bpf: replace usage of supported with dedicated list iterator variable

To move the list iterator variable into the list_for_each_entry_*()
macro in the future it should be avoided to use the list iterator
variable after the loop body.

To *never* use the list iterator variable after the loop it was
concluded to use a separate iterator variable instead of a
found boolean [1].

This removes the need to use the found variable (existed & supported)
and simply checking if the variable was set, can determine if the
break/goto was hit.

[1] https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/

Acked-by: Yonghong Song <[email protected]>
Signed-off-by: Jakob Koschel <[email protected]>
---

v1->v2:
- add correct [1] reference (Yonghong Song)

kernel/bpf/bpf_iter.c | 30 ++++++++++++++----------------
1 file changed, 14 insertions(+), 16 deletions(-)

diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
index 110029ede71e..dea920b3b840 100644
--- a/kernel/bpf/bpf_iter.c
+++ b/kernel/bpf/bpf_iter.c
@@ -330,35 +330,34 @@ static void cache_btf_id(struct bpf_iter_target_info *tinfo,
bool bpf_iter_prog_supported(struct bpf_prog *prog)
{
const char *attach_fname = prog->aux->attach_func_name;
+ struct bpf_iter_target_info *tinfo = NULL, *iter;
u32 prog_btf_id = prog->aux->attach_btf_id;
const char *prefix = BPF_ITER_FUNC_PREFIX;
- struct bpf_iter_target_info *tinfo;
int prefix_len = strlen(prefix);
- bool supported = false;

if (strncmp(attach_fname, prefix, prefix_len))
return false;

mutex_lock(&targets_mutex);
- list_for_each_entry(tinfo, &targets, list) {
- if (tinfo->btf_id && tinfo->btf_id == prog_btf_id) {
- supported = true;
+ list_for_each_entry(iter, &targets, list) {
+ if (iter->btf_id && iter->btf_id == prog_btf_id) {
+ tinfo = iter;
break;
}
- if (!strcmp(attach_fname + prefix_len, tinfo->reg_info->target)) {
- cache_btf_id(tinfo, prog);
- supported = true;
+ if (!strcmp(attach_fname + prefix_len, iter->reg_info->target)) {
+ cache_btf_id(iter, prog);
+ tinfo = iter;
break;
}
}
mutex_unlock(&targets_mutex);

- if (supported) {
+ if (tinfo) {
prog->aux->ctx_arg_info_size = tinfo->reg_info->ctx_arg_info_size;
prog->aux->ctx_arg_info = tinfo->reg_info->ctx_arg_info;
}

- return supported;
+ return tinfo != NULL;
}

const struct bpf_func_proto *
@@ -499,12 +498,11 @@ bool bpf_link_is_iter(struct bpf_link *link)
int bpf_iter_link_attach(const union bpf_attr *attr, bpfptr_t uattr,
struct bpf_prog *prog)
{
+ struct bpf_iter_target_info *tinfo = NULL, *iter;
struct bpf_link_primer link_primer;
- struct bpf_iter_target_info *tinfo;
union bpf_iter_link_info linfo;
struct bpf_iter_link *link;
u32 prog_btf_id, linfo_len;
- bool existed = false;
bpfptr_t ulinfo;
int err;

@@ -530,14 +528,14 @@ int bpf_iter_link_attach(const union bpf_attr *attr, bpfptr_t uattr,

prog_btf_id = prog->aux->attach_btf_id;
mutex_lock(&targets_mutex);
- list_for_each_entry(tinfo, &targets, list) {
- if (tinfo->btf_id == prog_btf_id) {
- existed = true;
+ list_for_each_entry(iter, &targets, list) {
+ if (iter->btf_id == prog_btf_id) {
+ tinfo = iter;
break;
}
}
mutex_unlock(&targets_mutex);
- if (!existed)
+ if (!tinfo)
return -ENOENT;

link = kzalloc(sizeof(*link), GFP_USER | __GFP_NOWARN);

base-commit: d888c83fcec75194a8a48ccd283953bdba7b2550
--
2.25.1

2022-04-05 02:20:41

by patchwork-bot+netdevbpf

Subject: Re: [PATCH v2] bpf: replace usage of supported with dedicated list iterator variable

Hello:

This patch was applied to bpf/bpf-next.git (master)
by Andrii Nakryiko <[email protected]>:

On Thu, 31 Mar 2022 11:19:29 +0200 you wrote:
> To move the list iterator variable into the list_for_each_entry_*()
> macro in the future it should be avoided to use the list iterator
> variable after the loop body.
>
> To *never* use the list iterator variable after the loop it was
> concluded to use a separate iterator variable instead of a
> found boolean [1].
>
> [...]

Here is the summary with links:
- [v2] bpf: replace usage of supported with dedicated list iterator variable
https://git.kernel.org/bpf/bpf-next/c/185da3da9379

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html