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Message-ID: <20250729182550.185356-8-ameryhung@gmail.com>
Date: Tue, 29 Jul 2025 11:25:45 -0700
From: Amery Hung <ameryhung@...il.com>
To: bpf@...r.kernel.org
Cc: netdev@...r.kernel.org,
alexei.starovoitov@...il.com,
andrii@...nel.org,
daniel@...earbox.net,
memxor@...il.com,
kpsingh@...nel.org,
martin.lau@...nel.org,
yonghong.song@...ux.dev,
song@...nel.org,
haoluo@...gle.com,
ameryhung@...il.com,
kernel-team@...a.com
Subject: [RFC PATCH bpf-next v1 07/11] bpf: Remove cgroup local storage percpu counter
The percpu counter in cgroup local storage is no longer needed as the
underlying bpf_local_storage can now handle deadlock with the help of
rqspinlock. Remove the percpu counter and related migrate_{disable,
enable}.
Signed-off-by: Amery Hung <ameryhung@...il.com>
---
kernel/bpf/bpf_cgrp_storage.c | 57 ++++-------------------------------
1 file changed, 6 insertions(+), 51 deletions(-)
diff --git a/kernel/bpf/bpf_cgrp_storage.c b/kernel/bpf/bpf_cgrp_storage.c
index 68a2ad1fc3d4..4f9cfa032870 100644
--- a/kernel/bpf/bpf_cgrp_storage.c
+++ b/kernel/bpf/bpf_cgrp_storage.c
@@ -11,29 +11,6 @@
DEFINE_BPF_STORAGE_CACHE(cgroup_cache);
-static DEFINE_PER_CPU(int, bpf_cgrp_storage_busy);
-
-static void bpf_cgrp_storage_lock(void)
-{
- cant_migrate();
- this_cpu_inc(bpf_cgrp_storage_busy);
-}
-
-static void bpf_cgrp_storage_unlock(void)
-{
- this_cpu_dec(bpf_cgrp_storage_busy);
-}
-
-static bool bpf_cgrp_storage_trylock(void)
-{
- cant_migrate();
- if (unlikely(this_cpu_inc_return(bpf_cgrp_storage_busy) != 1)) {
- this_cpu_dec(bpf_cgrp_storage_busy);
- return false;
- }
- return true;
-}
-
static struct bpf_local_storage __rcu **cgroup_storage_ptr(void *owner)
{
struct cgroup *cg = owner;
@@ -45,18 +22,14 @@ void bpf_cgrp_storage_free(struct cgroup *cgroup)
{
struct bpf_local_storage *local_storage;
- migrate_disable();
rcu_read_lock();
local_storage = rcu_dereference(cgroup->bpf_cgrp_storage);
if (!local_storage)
goto out;
- bpf_cgrp_storage_lock();
bpf_local_storage_destroy(local_storage);
- bpf_cgrp_storage_unlock();
out:
rcu_read_unlock();
- migrate_enable();
}
static struct bpf_local_storage_data *
@@ -85,9 +58,7 @@ static void *bpf_cgrp_storage_lookup_elem(struct bpf_map *map, void *key)
if (IS_ERR(cgroup))
return ERR_CAST(cgroup);
- bpf_cgrp_storage_lock();
sdata = cgroup_storage_lookup(cgroup, map, true);
- bpf_cgrp_storage_unlock();
cgroup_put(cgroup);
return sdata ? sdata->data : NULL;
}
@@ -104,10 +75,8 @@ static long bpf_cgrp_storage_update_elem(struct bpf_map *map, void *key,
if (IS_ERR(cgroup))
return PTR_ERR(cgroup);
- bpf_cgrp_storage_lock();
sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map,
value, map_flags, false, GFP_ATOMIC);
- bpf_cgrp_storage_unlock();
cgroup_put(cgroup);
return PTR_ERR_OR_ZERO(sdata);
}
@@ -133,9 +102,7 @@ static long bpf_cgrp_storage_delete_elem(struct bpf_map *map, void *key)
if (IS_ERR(cgroup))
return PTR_ERR(cgroup);
- bpf_cgrp_storage_lock();
err = cgroup_storage_delete(cgroup, map);
- bpf_cgrp_storage_unlock();
cgroup_put(cgroup);
return err;
}
@@ -152,7 +119,7 @@ static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
static void cgroup_storage_map_free(struct bpf_map *map)
{
- bpf_local_storage_map_free(map, &cgroup_cache, &bpf_cgrp_storage_busy);
+ bpf_local_storage_map_free(map, &cgroup_cache, NULL);
}
/* *gfp_flags* is a hidden argument provided by the verifier */
@@ -160,7 +127,6 @@ BPF_CALL_5(bpf_cgrp_storage_get, struct bpf_map *, map, struct cgroup *, cgroup,
void *, value, u64, flags, gfp_t, gfp_flags)
{
struct bpf_local_storage_data *sdata;
- bool nobusy;
WARN_ON_ONCE(!bpf_rcu_lock_held());
if (flags & ~(BPF_LOCAL_STORAGE_GET_F_CREATE))
@@ -169,38 +135,27 @@ BPF_CALL_5(bpf_cgrp_storage_get, struct bpf_map *, map, struct cgroup *, cgroup,
if (!cgroup)
return (unsigned long)NULL;
- nobusy = bpf_cgrp_storage_trylock();
-
- sdata = cgroup_storage_lookup(cgroup, map, nobusy);
+ sdata = cgroup_storage_lookup(cgroup, map, NULL);
if (sdata)
- goto unlock;
+ goto out;
/* only allocate new storage, when the cgroup is refcounted */
if (!percpu_ref_is_dying(&cgroup->self.refcnt) &&
- (flags & BPF_LOCAL_STORAGE_GET_F_CREATE) && nobusy)
+ (flags & BPF_LOCAL_STORAGE_GET_F_CREATE))
sdata = bpf_local_storage_update(cgroup, (struct bpf_local_storage_map *)map,
value, BPF_NOEXIST, false, gfp_flags);
-unlock:
- if (nobusy)
- bpf_cgrp_storage_unlock();
+out:
return IS_ERR_OR_NULL(sdata) ? (unsigned long)NULL : (unsigned long)sdata->data;
}
BPF_CALL_2(bpf_cgrp_storage_delete, struct bpf_map *, map, struct cgroup *, cgroup)
{
- int ret;
-
WARN_ON_ONCE(!bpf_rcu_lock_held());
if (!cgroup)
return -EINVAL;
- if (!bpf_cgrp_storage_trylock())
- return -EBUSY;
-
- ret = cgroup_storage_delete(cgroup, map);
- bpf_cgrp_storage_unlock();
- return ret;
+ return cgroup_storage_delete(cgroup, map);
}
const struct bpf_map_ops cgrp_storage_map_ops = {
--
2.47.3
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