[PATCH bpf-next v2 09/16] bpf: allow struct bpf_wq to be embedded in arraymaps and hashmaps

From: Benjamin Tissoires
Date: Sat Apr 20 2024 - 05:11:51 EST

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Next in thread: Alexei Starovoitov: "Re: [PATCH bpf-next v2 09/16] bpf: allow struct bpf_wq to be embedded in arraymaps and hashmaps"
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Currently bpf_wq_cancel_and_free() is just a placeholder as there is
no memory allocation for bpf_wq just yet.

Again, duplication of the bpf_timer approach

Signed-off-by: Benjamin Tissoires <bentiss@xxxxxxxxxx>

---

changes in v2:
- removed extra fallthrough
---
include/linux/bpf.h | 2 ++
kernel/bpf/arraymap.c | 18 ++++++++++-------
kernel/bpf/hashtab.c | 55 ++++++++++++++++++++++++++++++++++++++++-----------
kernel/bpf/helpers.c | 8 ++++++++
kernel/bpf/syscall.c | 9 +++++++++
5 files changed, 73 insertions(+), 19 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index c7dcfd395555..64bf0cf3ee95 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -534,6 +534,7 @@ static inline void zero_map_value(struct bpf_map *map, void *dst)
void copy_map_value_locked(struct bpf_map *map, void *dst, void *src,
bool lock_src);
void bpf_timer_cancel_and_free(void *timer);
+void bpf_wq_cancel_and_free(void *timer);
void bpf_list_head_free(const struct btf_field *field, void *list_head,
struct bpf_spin_lock *spin_lock);
void bpf_rb_root_free(const struct btf_field *field, void *rb_root,
@@ -2204,6 +2205,7 @@ void bpf_map_free_record(struct bpf_map *map);
struct btf_record *btf_record_dup(const struct btf_record *rec);
bool btf_record_equal(const struct btf_record *rec_a, const struct btf_record *rec_b);
void bpf_obj_free_timer(const struct btf_record *rec, void *obj);
+void bpf_obj_free_workqueue(const struct btf_record *rec, void *obj);
void bpf_obj_free_fields(const struct btf_record *rec, void *obj);
void __bpf_obj_drop_impl(void *p, const struct btf_record *rec, bool percpu);

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 8c1e6d7654bb..580d07b15471 100644
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -428,17 +428,21 @@ static void *array_map_vmalloc_addr(struct bpf_array *array)
return (void *)round_down((unsigned long)array, PAGE_SIZE);
}

-static void array_map_free_timers(struct bpf_map *map)
+static void array_map_free_timers_wq(struct bpf_map *map)
{
struct bpf_array *array = container_of(map, struct bpf_array, map);
int i;

- /* We don't reset or free fields other than timer on uref dropping to zero. */
- if (!btf_record_has_field(map->record, BPF_TIMER))
- return;
+ /* We don't reset or free fields other than timer and workqueue
+ * on uref dropping to zero.
+ */
+ if (btf_record_has_field(map->record, BPF_TIMER))
+ for (i = 0; i < array->map.max_entries; i++)
+ bpf_obj_free_timer(map->record, array_map_elem_ptr(array, i));

- for (i = 0; i < array->map.max_entries; i++)
- bpf_obj_free_timer(map->record, array_map_elem_ptr(array, i));
+ if (btf_record_has_field(map->record, BPF_WORKQUEUE))
+ for (i = 0; i < array->map.max_entries; i++)
+ bpf_obj_free_workqueue(map->record, array_map_elem_ptr(array, i));
}

/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
@@ -782,7 +786,7 @@ const struct bpf_map_ops array_map_ops = {
.map_alloc = array_map_alloc,
.map_free = array_map_free,
.map_get_next_key = array_map_get_next_key,
- .map_release_uref = array_map_free_timers,
+ .map_release_uref = array_map_free_timers_wq,
.map_lookup_elem = array_map_lookup_elem,
.map_update_elem = array_map_update_elem,
.map_delete_elem = array_map_delete_elem,
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 83a9a74260e9..4f8590067c6a 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -240,6 +240,26 @@ static void htab_free_prealloced_timers(struct bpf_htab *htab)
}
}

+static void htab_free_prealloced_wq(struct bpf_htab *htab)
+{
+ u32 num_entries = htab->map.max_entries;
+ int i;
+
+ if (!btf_record_has_field(htab->map.record, BPF_WORKQUEUE))
+ return;
+ if (htab_has_extra_elems(htab))
+ num_entries += num_possible_cpus();
+
+ for (i = 0; i < num_entries; i++) {
+ struct htab_elem *elem;
+
+ elem = get_htab_elem(htab, i);
+ bpf_obj_free_workqueue(htab->map.record,
+ elem->key + round_up(htab->map.key_size, 8));
+ cond_resched();
+ }
+}
+
static void htab_free_prealloced_fields(struct bpf_htab *htab)
{
u32 num_entries = htab->map.max_entries;
@@ -1495,7 +1515,7 @@ static void delete_all_elements(struct bpf_htab *htab)
migrate_enable();
}

-static void htab_free_malloced_timers(struct bpf_htab *htab)
+static void htab_free_malloced_timers_or_wq(struct bpf_htab *htab, bool is_timer)
{
int i;

@@ -1507,24 +1527,35 @@ static void htab_free_malloced_timers(struct bpf_htab *htab)

hlist_nulls_for_each_entry(l, n, head, hash_node) {
/* We only free timer on uref dropping to zero */
- bpf_obj_free_timer(htab->map.record, l->key + round_up(htab->map.key_size, 8));
+ if (is_timer)
+ bpf_obj_free_timer(htab->map.record,
+ l->key + round_up(htab->map.key_size, 8));
+ else
+ bpf_obj_free_workqueue(htab->map.record,
+ l->key + round_up(htab->map.key_size, 8));
}
cond_resched_rcu();
}
rcu_read_unlock();
}

-static void htab_map_free_timers(struct bpf_map *map)
+static void htab_map_free_timers_and_wq(struct bpf_map *map)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);

- /* We only free timer on uref dropping to zero */
- if (!btf_record_has_field(htab->map.record, BPF_TIMER))
- return;
- if (!htab_is_prealloc(htab))
- htab_free_malloced_timers(htab);
- else
- htab_free_prealloced_timers(htab);
+ /* We only free timer and workqueue on uref dropping to zero */
+ if (btf_record_has_field(htab->map.record, BPF_TIMER)) {
+ if (!htab_is_prealloc(htab))
+ htab_free_malloced_timers_or_wq(htab, true);
+ else
+ htab_free_prealloced_timers(htab);
+ }
+ if (btf_record_has_field(htab->map.record, BPF_WORKQUEUE)) {
+ if (!htab_is_prealloc(htab))
+ htab_free_malloced_timers_or_wq(htab, false);
+ else
+ htab_free_prealloced_wq(htab);
+ }
}

/* Called when map->refcnt goes to zero, either from workqueue or from syscall */
@@ -2260,7 +2291,7 @@ const struct bpf_map_ops htab_map_ops = {
.map_alloc = htab_map_alloc,
.map_free = htab_map_free,
.map_get_next_key = htab_map_get_next_key,
- .map_release_uref = htab_map_free_timers,
+ .map_release_uref = htab_map_free_timers_and_wq,
.map_lookup_elem = htab_map_lookup_elem,
.map_lookup_and_delete_elem = htab_map_lookup_and_delete_elem,
.map_update_elem = htab_map_update_elem,
@@ -2281,7 +2312,7 @@ const struct bpf_map_ops htab_lru_map_ops = {
.map_alloc = htab_map_alloc,
.map_free = htab_map_free,
.map_get_next_key = htab_map_get_next_key,
- .map_release_uref = htab_map_free_timers,
+ .map_release_uref = htab_map_free_timers_and_wq,
.map_lookup_elem = htab_lru_map_lookup_elem,
.map_lookup_and_delete_elem = htab_lru_map_lookup_and_delete_elem,
.map_lookup_elem_sys_only = htab_lru_map_lookup_elem_sys,
diff --git a/kernel/bpf/helpers.c b/kernel/bpf/helpers.c
index 78847f444f79..9fd12d480b8b 100644
--- a/kernel/bpf/helpers.c
+++ b/kernel/bpf/helpers.c
@@ -1468,6 +1468,14 @@ void bpf_timer_cancel_and_free(void *val)
kfree_rcu(t, cb.rcu);
}

+/* This function is called by map_delete/update_elem for individual element and
+ * by ops->map_release_uref when the user space reference to a map reaches zero.
+ */
+void bpf_wq_cancel_and_free(void *val)
+{
+ BTF_TYPE_EMIT(struct bpf_wq);
+}
+
BPF_CALL_2(bpf_kptr_xchg, void *, map_value, void *, ptr)
{
unsigned long *kptr = map_value;
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 0848e4141b00..63e368337483 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -661,6 +661,13 @@ void bpf_obj_free_timer(const struct btf_record *rec, void *obj)
bpf_timer_cancel_and_free(obj + rec->timer_off);
}

+void bpf_obj_free_workqueue(const struct btf_record *rec, void *obj)
+{
+ if (WARN_ON_ONCE(!btf_record_has_field(rec, BPF_WORKQUEUE)))
+ return;
+ bpf_wq_cancel_and_free(obj + rec->wq_off);
+}
+
void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
{
const struct btf_field *fields;
@@ -682,6 +689,7 @@ void bpf_obj_free_fields(const struct btf_record *rec, void *obj)
bpf_timer_cancel_and_free(field_ptr);
break;
case BPF_WORKQUEUE:
+ bpf_wq_cancel_and_free(field_ptr);
break;
case BPF_KPTR_UNREF:
WRITE_ONCE(*(u64 *)field_ptr, 0);
@@ -1119,6 +1127,7 @@ static int map_check_btf(struct bpf_map *map, struct bpf_token *token,
}
break;
case BPF_TIMER:
+ case BPF_WORKQUEUE:
if (map->map_type != BPF_MAP_TYPE_HASH &&
map->map_type != BPF_MAP_TYPE_LRU_HASH &&
map->map_type != BPF_MAP_TYPE_ARRAY) {

--
2.44.0

Next message: Benjamin Tissoires: "[PATCH bpf-next v2 10/16] selftests/bpf: add bpf_wq tests"
Previous message: Benjamin Tissoires: "[PATCH bpf-next v2 08/16] bpf: add support for KF_ARG_PTR_TO_WORKQUEUE"
In reply to: Benjamin Tissoires: "[PATCH bpf-next v2 08/16] bpf: add support for KF_ARG_PTR_TO_WORKQUEUE"
Next in thread: Alexei Starovoitov: "Re: [PATCH bpf-next v2 09/16] bpf: allow struct bpf_wq to be embedded in arraymaps and hashmaps"
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