Introduce BPF_F_ALL_CPUS flag support for percpu_hash and lru_percpu_hash
maps to allow updating values for all CPUs with a single value for both
update_elem and update_batch APIs.
Introduce BPF_F_CPU flag support for percpu_hash and lru_percpu_hash
maps to allow:
* update value for specified CPU for both update_elem and update_batch
APIs.
* lookup value for specified CPU for both lookup_elem and lookup_batch
APIs.
The BPF_F_CPU flag is passed via:
* map_flags along with embedded cpu info.
* elem_flags along with embedded cpu info.
Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
---
v10 -> v11:
- Drop buggy '(u32)map_flags > BPF_F_ALL_CPUS' check in htab_map_check_update_flags().
- Update 'map_flags != BPF_EXIST' to '!(map_flags & BPF_EXIST)' in
__htab_lru_percpu_map_update_elem().
---
include/linux/bpf.h | 4 +-
kernel/bpf/hashtab.c | 96 ++++++++++++++++++++++++++++++--------------
kernel/bpf/syscall.c | 2 +-
3 files changed, 69 insertions(+), 33 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 01a99e3a3e51..f79d2ae27335 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -2761,7 +2761,7 @@ int map_set_for_each_callback_args(struct bpf_verifier_env *env,
struct bpf_func_state *caller,
struct bpf_func_state *callee);
-int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
+int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value, u64 flags);
int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value, u64 flags);
int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
u64 flags);
@@ -3833,6 +3833,8 @@ static inline bool bpf_map_supports_cpu_flags(enum bpf_map_type map_type)
{
switch (map_type) {
case BPF_MAP_TYPE_PERCPU_ARRAY:
+ case BPF_MAP_TYPE_PERCPU_HASH:
+ case BPF_MAP_TYPE_LRU_PERCPU_HASH:
return true;
default:
return false;
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index c8a9b27f8663..c768bf71d60f 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -932,7 +932,7 @@ static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
}
static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
- void *value, bool onallcpus)
+ void *value, bool onallcpus, u64 map_flags)
{
void *ptr;
@@ -943,19 +943,28 @@ static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
bpf_obj_free_fields(htab->map.record, ptr);
} else {
u32 size = round_up(htab->map.value_size, 8);
- int off = 0, cpu;
+ void *val;
+ int cpu;
+
+ if (map_flags & BPF_F_CPU) {
+ cpu = map_flags >> 32;
+ ptr = per_cpu_ptr(pptr, cpu);
+ copy_map_value(&htab->map, ptr, value);
+ bpf_obj_free_fields(htab->map.record, ptr);
+ return;
+ }
for_each_possible_cpu(cpu) {
ptr = per_cpu_ptr(pptr, cpu);
- copy_map_value_long(&htab->map, ptr, value + off);
+ val = (map_flags & BPF_F_ALL_CPUS) ? value : value + size * cpu;
+ copy_map_value(&htab->map, ptr, val);
bpf_obj_free_fields(htab->map.record, ptr);
- off += size;
}
}
}
static void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr,
- void *value, bool onallcpus)
+ void *value, bool onallcpus, u64 map_flags)
{
/* When not setting the initial value on all cpus, zero-fill element
* values for other cpus. Otherwise, bpf program has no way to ensure
@@ -973,7 +982,7 @@ static void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr,
zero_map_value(&htab->map, per_cpu_ptr(pptr, cpu));
}
} else {
- pcpu_copy_value(htab, pptr, value, onallcpus);
+ pcpu_copy_value(htab, pptr, value, onallcpus, map_flags);
}
}
@@ -985,7 +994,7 @@ static bool fd_htab_map_needs_adjust(const struct bpf_htab *htab)
static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
void *value, u32 key_size, u32 hash,
bool percpu, bool onallcpus,
- struct htab_elem *old_elem)
+ struct htab_elem *old_elem, u64 map_flags)
{
u32 size = htab->map.value_size;
bool prealloc = htab_is_prealloc(htab);
@@ -1043,7 +1052,7 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
pptr = *(void __percpu **)ptr;
}
- pcpu_init_value(htab, pptr, value, onallcpus);
+ pcpu_init_value(htab, pptr, value, onallcpus, map_flags);
if (!prealloc)
htab_elem_set_ptr(l_new, key_size, pptr);
@@ -1147,7 +1156,7 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value,
}
l_new = alloc_htab_elem(htab, key, value, key_size, hash, false, false,
- l_old);
+ l_old, map_flags);
if (IS_ERR(l_new)) {
/* all pre-allocated elements are in use or memory exhausted */
ret = PTR_ERR(l_new);
@@ -1249,6 +1258,15 @@ static long htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value
return ret;
}
+static int htab_map_check_update_flags(bool onallcpus, u64 map_flags)
+{
+ if (unlikely(!onallcpus && map_flags > BPF_EXIST))
+ return -EINVAL;
+ if (unlikely(onallcpus && (map_flags & BPF_F_LOCK)))
+ return -EINVAL;
+ return 0;
+}
+
static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
void *value, u64 map_flags,
bool percpu, bool onallcpus)
@@ -1262,9 +1280,9 @@ static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
u32 key_size, hash;
int ret;
- if (unlikely(map_flags > BPF_EXIST))
- /* unknown flags */
- return -EINVAL;
+ ret = htab_map_check_update_flags(onallcpus, map_flags);
+ if (unlikely(ret))
+ return ret;
WARN_ON_ONCE(!bpf_rcu_lock_held());
@@ -1289,7 +1307,7 @@ static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
/* Update value in-place */
if (percpu) {
pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
- value, onallcpus);
+ value, onallcpus, map_flags);
} else {
void **inner_map_pptr = htab_elem_value(l_old, key_size);
@@ -1298,7 +1316,7 @@ static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
}
} else {
l_new = alloc_htab_elem(htab, key, value, key_size,
- hash, percpu, onallcpus, NULL);
+ hash, percpu, onallcpus, NULL, map_flags);
if (IS_ERR(l_new)) {
ret = PTR_ERR(l_new);
goto err;
@@ -1324,9 +1342,9 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
u32 key_size, hash;
int ret;
- if (unlikely(map_flags > BPF_EXIST))
- /* unknown flags */
- return -EINVAL;
+ ret = htab_map_check_update_flags(onallcpus, map_flags);
+ if (unlikely(ret))
+ return ret;
WARN_ON_ONCE(!bpf_rcu_lock_held());
@@ -1342,7 +1360,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
* to remove older elem from htab and this removal
* operation will need a bucket lock.
*/
- if (map_flags != BPF_EXIST) {
+ if (!(map_flags & BPF_EXIST)) {
l_new = prealloc_lru_pop(htab, key, hash);
if (!l_new)
return -ENOMEM;
@@ -1363,10 +1381,10 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
/* per-cpu hash map can update value in-place */
pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
- value, onallcpus);
+ value, onallcpus, map_flags);
} else {
pcpu_init_value(htab, htab_elem_get_ptr(l_new, key_size),
- value, onallcpus);
+ value, onallcpus, map_flags);
hlist_nulls_add_head_rcu(&l_new->hash_node, head);
l_new = NULL;
}
@@ -1678,9 +1696,9 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
void __user *ukeys = u64_to_user_ptr(attr->batch.keys);
void __user *ubatch = u64_to_user_ptr(attr->batch.in_batch);
u32 batch, max_count, size, bucket_size, map_id;
+ u64 elem_map_flags, map_flags, allowed_flags;
u32 bucket_cnt, total, key_size, value_size;
struct htab_elem *node_to_free = NULL;
- u64 elem_map_flags, map_flags;
struct hlist_nulls_head *head;
struct hlist_nulls_node *n;
unsigned long flags = 0;
@@ -1690,9 +1708,12 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
int ret = 0;
elem_map_flags = attr->batch.elem_flags;
- if ((elem_map_flags & ~BPF_F_LOCK) ||
- ((elem_map_flags & BPF_F_LOCK) && !btf_record_has_field(map->record, BPF_SPIN_LOCK)))
- return -EINVAL;
+ allowed_flags = BPF_F_LOCK;
+ if (!do_delete && is_percpu)
+ allowed_flags |= BPF_F_CPU;
+ ret = bpf_map_check_op_flags(map, elem_map_flags, allowed_flags);
+ if (ret)
+ return ret;
map_flags = attr->batch.flags;
if (map_flags)
@@ -1715,7 +1736,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
key_size = htab->map.key_size;
value_size = htab->map.value_size;
size = round_up(value_size, 8);
- if (is_percpu)
+ if (is_percpu && !(elem_map_flags & BPF_F_CPU))
value_size = size * num_possible_cpus();
total = 0;
/* while experimenting with hash tables with sizes ranging from 10 to
@@ -1798,10 +1819,17 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
void __percpu *pptr;
pptr = htab_elem_get_ptr(l, map->key_size);
- for_each_possible_cpu(cpu) {
- copy_map_value_long(&htab->map, dst_val + off, per_cpu_ptr(pptr, cpu));
- check_and_init_map_value(&htab->map, dst_val + off);
- off += size;
+ if (elem_map_flags & BPF_F_CPU) {
+ cpu = elem_map_flags >> 32;
+ copy_map_value(&htab->map, dst_val, per_cpu_ptr(pptr, cpu));
+ check_and_init_map_value(&htab->map, dst_val);
+ } else {
+ for_each_possible_cpu(cpu) {
+ copy_map_value_long(&htab->map, dst_val + off,
+ per_cpu_ptr(pptr, cpu));
+ check_and_init_map_value(&htab->map, dst_val + off);
+ off += size;
+ }
}
} else {
value = htab_elem_value(l, key_size);
@@ -2357,7 +2385,7 @@ static void *htab_lru_percpu_map_lookup_percpu_elem(struct bpf_map *map, void *k
return NULL;
}
-int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
+int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value, u64 map_flags)
{
struct htab_elem *l;
void __percpu *pptr;
@@ -2374,16 +2402,22 @@ int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value)
l = __htab_map_lookup_elem(map, key);
if (!l)
goto out;
+ ret = 0;
/* We do not mark LRU map element here in order to not mess up
* eviction heuristics when user space does a map walk.
*/
pptr = htab_elem_get_ptr(l, map->key_size);
+ if (map_flags & BPF_F_CPU) {
+ cpu = map_flags >> 32;
+ copy_map_value(map, value, per_cpu_ptr(pptr, cpu));
+ check_and_init_map_value(map, value);
+ goto out;
+ }
for_each_possible_cpu(cpu) {
copy_map_value_long(map, value + off, per_cpu_ptr(pptr, cpu));
check_and_init_map_value(map, value + off);
off += size;
}
- ret = 0;
out:
rcu_read_unlock();
return ret;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 238238086b08..7e6cca641026 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -316,7 +316,7 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value,
bpf_disable_instrumentation();
if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH ||
map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) {
- err = bpf_percpu_hash_copy(map, key, value);
+ err = bpf_percpu_hash_copy(map, key, value, flags);
} else if (map->map_type == BPF_MAP_TYPE_PERCPU_ARRAY) {
err = bpf_percpu_array_copy(map, key, value, flags);
} else if (map->map_type == BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE) {
--
2.51.2On Tue, Nov 25, 2025 at 7:00 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>
> Introduce BPF_F_ALL_CPUS flag support for percpu_hash and lru_percpu_hash
> maps to allow updating values for all CPUs with a single value for both
> update_elem and update_batch APIs.
>
> Introduce BPF_F_CPU flag support for percpu_hash and lru_percpu_hash
> maps to allow:
>
> * update value for specified CPU for both update_elem and update_batch
> APIs.
> * lookup value for specified CPU for both lookup_elem and lookup_batch
> APIs.
>
> The BPF_F_CPU flag is passed via:
>
> * map_flags along with embedded cpu info.
> * elem_flags along with embedded cpu info.
>
> Signed-off-by: Leon Hwang <leon.hwang@linux.dev>
> ---
> v10 -> v11:
> - Drop buggy '(u32)map_flags > BPF_F_ALL_CPUS' check in htab_map_check_update_flags().
why?
> - Update 'map_flags != BPF_EXIST' to '!(map_flags & BPF_EXIST)' in
> __htab_lru_percpu_map_update_elem().
> ---
> include/linux/bpf.h | 4 +-
> kernel/bpf/hashtab.c | 96 ++++++++++++++++++++++++++++++--------------
> kernel/bpf/syscall.c | 2 +-
> 3 files changed, 69 insertions(+), 33 deletions(-)
>
> diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> index 01a99e3a3e51..f79d2ae27335 100644
> --- a/include/linux/bpf.h
> +++ b/include/linux/bpf.h
> @@ -2761,7 +2761,7 @@ int map_set_for_each_callback_args(struct bpf_verifier_env *env,
> struct bpf_func_state *caller,
> struct bpf_func_state *callee);
>
> -int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value);
> +int bpf_percpu_hash_copy(struct bpf_map *map, void *key, void *value, u64 flags);
> int bpf_percpu_array_copy(struct bpf_map *map, void *key, void *value, u64 flags);
> int bpf_percpu_hash_update(struct bpf_map *map, void *key, void *value,
> u64 flags);
> @@ -3833,6 +3833,8 @@ static inline bool bpf_map_supports_cpu_flags(enum bpf_map_type map_type)
> {
> switch (map_type) {
> case BPF_MAP_TYPE_PERCPU_ARRAY:
> + case BPF_MAP_TYPE_PERCPU_HASH:
> + case BPF_MAP_TYPE_LRU_PERCPU_HASH:
> return true;
> default:
> return false;
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index c8a9b27f8663..c768bf71d60f 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -932,7 +932,7 @@ static void free_htab_elem(struct bpf_htab *htab, struct htab_elem *l)
> }
>
> static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
> - void *value, bool onallcpus)
> + void *value, bool onallcpus, u64 map_flags)
> {
> void *ptr;
>
> @@ -943,19 +943,28 @@ static void pcpu_copy_value(struct bpf_htab *htab, void __percpu *pptr,
> bpf_obj_free_fields(htab->map.record, ptr);
> } else {
> u32 size = round_up(htab->map.value_size, 8);
> - int off = 0, cpu;
> + void *val;
> + int cpu;
> +
> + if (map_flags & BPF_F_CPU) {
> + cpu = map_flags >> 32;
> + ptr = per_cpu_ptr(pptr, cpu);
> + copy_map_value(&htab->map, ptr, value);
> + bpf_obj_free_fields(htab->map.record, ptr);
> + return;
> + }
>
> for_each_possible_cpu(cpu) {
> ptr = per_cpu_ptr(pptr, cpu);
> - copy_map_value_long(&htab->map, ptr, value + off);
> + val = (map_flags & BPF_F_ALL_CPUS) ? value : value + size * cpu;
> + copy_map_value(&htab->map, ptr, val);
> bpf_obj_free_fields(htab->map.record, ptr);
> - off += size;
> }
> }
> }
>
> static void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr,
> - void *value, bool onallcpus)
> + void *value, bool onallcpus, u64 map_flags)
> {
> /* When not setting the initial value on all cpus, zero-fill element
> * values for other cpus. Otherwise, bpf program has no way to ensure
> @@ -973,7 +982,7 @@ static void pcpu_init_value(struct bpf_htab *htab, void __percpu *pptr,
> zero_map_value(&htab->map, per_cpu_ptr(pptr, cpu));
> }
> } else {
> - pcpu_copy_value(htab, pptr, value, onallcpus);
> + pcpu_copy_value(htab, pptr, value, onallcpus, map_flags);
> }
> }
>
> @@ -985,7 +994,7 @@ static bool fd_htab_map_needs_adjust(const struct bpf_htab *htab)
> static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
> void *value, u32 key_size, u32 hash,
> bool percpu, bool onallcpus,
> - struct htab_elem *old_elem)
> + struct htab_elem *old_elem, u64 map_flags)
> {
> u32 size = htab->map.value_size;
> bool prealloc = htab_is_prealloc(htab);
> @@ -1043,7 +1052,7 @@ static struct htab_elem *alloc_htab_elem(struct bpf_htab *htab, void *key,
> pptr = *(void __percpu **)ptr;
> }
>
> - pcpu_init_value(htab, pptr, value, onallcpus);
> + pcpu_init_value(htab, pptr, value, onallcpus, map_flags);
>
> if (!prealloc)
> htab_elem_set_ptr(l_new, key_size, pptr);
> @@ -1147,7 +1156,7 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value,
> }
>
> l_new = alloc_htab_elem(htab, key, value, key_size, hash, false, false,
> - l_old);
> + l_old, map_flags);
> if (IS_ERR(l_new)) {
> /* all pre-allocated elements are in use or memory exhausted */
> ret = PTR_ERR(l_new);
> @@ -1249,6 +1258,15 @@ static long htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value
> return ret;
> }
>
> +static int htab_map_check_update_flags(bool onallcpus, u64 map_flags)
> +{
> + if (unlikely(!onallcpus && map_flags > BPF_EXIST))
> + return -EINVAL;
> + if (unlikely(onallcpus && (map_flags & BPF_F_LOCK)))
> + return -EINVAL;
> + return 0;
> +}
> +
> static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
> void *value, u64 map_flags,
> bool percpu, bool onallcpus)
> @@ -1262,9 +1280,9 @@ static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
> u32 key_size, hash;
> int ret;
>
> - if (unlikely(map_flags > BPF_EXIST))
> - /* unknown flags */
> - return -EINVAL;
> + ret = htab_map_check_update_flags(onallcpus, map_flags);
> + if (unlikely(ret))
> + return ret;
>
> WARN_ON_ONCE(!bpf_rcu_lock_held());
>
> @@ -1289,7 +1307,7 @@ static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
> /* Update value in-place */
> if (percpu) {
> pcpu_copy_value(htab, htab_elem_get_ptr(l_old, key_size),
> - value, onallcpus);
> + value, onallcpus, map_flags);
> } else {
> void **inner_map_pptr = htab_elem_value(l_old, key_size);
>
> @@ -1298,7 +1316,7 @@ static long htab_map_update_elem_in_place(struct bpf_map *map, void *key,
> }
> } else {
> l_new = alloc_htab_elem(htab, key, value, key_size,
> - hash, percpu, onallcpus, NULL);
> + hash, percpu, onallcpus, NULL, map_flags);
> if (IS_ERR(l_new)) {
> ret = PTR_ERR(l_new);
> goto err;
> @@ -1324,9 +1342,9 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
> u32 key_size, hash;
> int ret;
>
> - if (unlikely(map_flags > BPF_EXIST))
> - /* unknown flags */
> - return -EINVAL;
> + ret = htab_map_check_update_flags(onallcpus, map_flags);
> + if (unlikely(ret))
> + return ret;
>
> WARN_ON_ONCE(!bpf_rcu_lock_held());
>
> @@ -1342,7 +1360,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
> * to remove older elem from htab and this removal
> * operation will need a bucket lock.
> */
> - if (map_flags != BPF_EXIST) {
> + if (!(map_flags & BPF_EXIST)) {
> l_new = prealloc_lru_pop(htab, key, hash);
> if (!l_new)
> return -ENOMEM;
It's not in the diff, but this is broken.
You tried to allow BPF_EXIST combination here, but didn't update
check_flags(),
so BPF_[NO]EXIST | BPF_F_CPU combination check_flags() will always
return 0, so BPF_[NO]EXIST flag will make no difference.
When you add features, always always add unit tests.
Patch 8 is not it. It's testing F_CPU. It doesn't check
that BPF_EXIST | BPF_F_CPU correctly errors when an element doesn't exist.
v10 was close, but then you decided to add this BPF_EXIST feature
and did it in a sloppy way. Why ?
Focus on one thing only. Land it and then do the next one.
11 revisions and still no go... it is not a good sign.
pw-bot: cr
On 26/11/25 07:11, Alexei Starovoitov wrote:
> On Tue, Nov 25, 2025 at 7:00 AM Leon Hwang <leon.hwang@linux.dev> wrote:
>>
[...]
>> @@ -1342,7 +1360,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
>> * to remove older elem from htab and this removal
>> * operation will need a bucket lock.
>> */
>> - if (map_flags != BPF_EXIST) {
>> + if (!(map_flags & BPF_EXIST)) {
>> l_new = prealloc_lru_pop(htab, key, hash);
>> if (!l_new)
>> return -ENOMEM;
>
> It's not in the diff, but this is broken.
> You tried to allow BPF_EXIST combination here, but didn't update
> check_flags(),
>
> so BPF_[NO]EXIST | BPF_F_CPU combination check_flags() will always
> return 0, so BPF_[NO]EXIST flag will make no difference.
>
> When you add features, always always add unit tests.
> Patch 8 is not it. It's testing F_CPU. It doesn't check
> that BPF_EXIST | BPF_F_CPU correctly errors when an element doesn't exist.
>
> v10 was close, but then you decided to add this BPF_EXIST feature
> and did it in a sloppy way. Why ?
> Focus on one thing only. Land it and then do the next one.
> 11 revisions and still no go... it is not a good sign.
>
Yeah, you're right.
The intention of v11 was solely to address the unstable lru_percpu_hash
map test — not to introduce support for the BPF_EXIST combination.
Given that, the approach in v11 was not the right way to fix the
instability. I'll investigate the underlying cause first and then work
on a better fix.
Thanks,
Leon
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