[PATCH bpf-next v2 19/26] bpf: Convert hashtab.c to rqspinlock

Kumar Kartikeya Dwivedi
2025-02-06T10:55:05Z

Convert hashtab.c from raw_spinlock to rqspinlock, and drop the hashed
per-cpu counter crud from the code base which is no longer necessary.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
kernel/bpf/hashtab.c | 102 ++++++++++++++-----------------------------
1 file changed, 32 insertions(+), 70 deletions(-)

diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 4a9eeb7aef85..9b394e147967 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -16,6 +16,7 @@
#include "bpf_lru_list.h"
#include "map_in_map.h"
#include <linux/bpf_mem_alloc.h>
+#include <asm/rqspinlock.h>

#define HTAB_CREATE_FLAG_MASK \
(BPF_F_NO_PREALLOC | BPF_F_NO_COMMON_LRU | BPF_F_NUMA_NODE | \
@@ -78,7 +79,7 @@
*/
struct bucket {
struct hlist_nulls_head head;
- raw_spinlock_t raw_lock;
+ rqspinlock_t raw_lock;
};

#define HASHTAB_MAP_LOCK_COUNT 8
@@ -104,8 +105,6 @@ struct bpf_htab {
u32 n_buckets; /* number of hash buckets */
u32 elem_size; /* size of each element in bytes */
u32 hashrnd;
- struct lock_class_key lockdep_key;
- int __percpu *map_locked[HASHTAB_MAP_LOCK_COUNT];
};

/* each htab element is struct htab_elem + key + value */
@@ -140,45 +139,26 @@ static void htab_init_buckets(struct bpf_htab *htab)

for (i = 0; i < htab->n_buckets; i++) {
INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);
- raw_spin_lock_init(&htab->buckets[i].raw_lock);
- lockdep_set_class(&htab->buckets[i].raw_lock,
- &htab->lockdep_key);
+ raw_res_spin_lock_init(&htab->buckets[i].raw_lock);
cond_resched();
}
}

-static inline int htab_lock_bucket(const struct bpf_htab *htab,
- struct bucket *b, u32 hash,
- unsigned long *pflags)
+static inline int htab_lock_bucket(struct bucket *b, unsigned long *pflags)
{
unsigned long flags;
+ int ret;

- hash = hash & min_t(u32, HASHTAB_MAP_LOCK_MASK, htab->n_buckets - 1);
-
- preempt_disable();
- local_irq_save(flags);
- if (unlikely(__this_cpu_inc_return(*(htab->map_locked[hash])) != 1)) {
- __this_cpu_dec(*(htab->map_locked[hash]));
- local_irq_restore(flags);
- preempt_enable();
- return -EBUSY;
- }
-
- raw_spin_lock(&b->raw_lock);
+ ret = raw_res_spin_lock_irqsave(&b->raw_lock, flags);
+ if (ret)
+ return ret;
*pflags = flags;
-
return 0;
}

-static inline void htab_unlock_bucket(const struct bpf_htab *htab,
- struct bucket *b, u32 hash,
- unsigned long flags)
+static inline void htab_unlock_bucket(struct bucket *b, unsigned long flags)
{
- hash = hash & min_t(u32, HASHTAB_MAP_LOCK_MASK, htab->n_buckets - 1);
- raw_spin_unlock(&b->raw_lock);
- __this_cpu_dec(*(htab->map_locked[hash]));
- local_irq_restore(flags);
- preempt_enable();
+ raw_res_spin_unlock_irqrestore(&b->raw_lock, flags);
}

static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node);
@@ -483,14 +463,12 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
bool percpu_lru = (attr->map_flags & BPF_F_NO_COMMON_LRU);
bool prealloc = !(attr->map_flags & BPF_F_NO_PREALLOC);
struct bpf_htab *htab;
- int err, i;
+ int err;

htab = bpf_map_area_alloc(sizeof(*htab), NUMA_NO_NODE);
if (!htab)
return ERR_PTR(-ENOMEM);

- lockdep_register_key(&htab->lockdep_key);
-
bpf_map_init_from_attr(&htab->map, attr);

if (percpu_lru) {
@@ -536,15 +514,6 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
if (!htab->buckets)
goto free_elem_count;

- for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++) {
- htab->map_locked[i] = bpf_map_alloc_percpu(&htab->map,
- sizeof(int),
- sizeof(int),
- GFP_USER);
- if (!htab->map_locked[i])
- goto free_map_locked;
- }
-
if (htab->map.map_flags & BPF_F_ZERO_SEED)
htab->hashrnd = 0;
else
@@ -607,15 +576,12 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
free_map_locked:
if (htab->use_percpu_counter)
percpu_counter_destroy(&htab->pcount);
- for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++)
- free_percpu(htab->map_locked[i]);
bpf_map_area_free(htab->buckets);
bpf_mem_alloc_destroy(&htab->pcpu_ma);
bpf_mem_alloc_destroy(&htab->ma);
free_elem_count:
bpf_map_free_elem_count(&htab->map);
free_htab:
- lockdep_unregister_key(&htab->lockdep_key);
bpf_map_area_free(htab);
return ERR_PTR(err);
}
@@ -817,7 +783,7 @@ static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
b = __select_bucket(htab, tgt_l->hash);
head = &b->head;

- ret = htab_lock_bucket(htab, b, tgt_l->hash, &flags);
+ ret = htab_lock_bucket(b, &flags);
if (ret)
return false;

@@ -828,7 +794,7 @@ static bool htab_lru_map_delete_node(void *arg, struct bpf_lru_node *node)
break;
}

- htab_unlock_bucket(htab, b, tgt_l->hash, flags);
+ htab_unlock_bucket(b, flags);

if (l == tgt_l)
check_and_free_fields(htab, l);
@@ -1147,7 +1113,7 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value,
*/
}

- ret = htab_lock_bucket(htab, b, hash, &flags);
+ ret = htab_lock_bucket(b, &flags);
if (ret)
return ret;

@@ -1198,7 +1164,7 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value,
check_and_free_fields(htab, l_old);
}
}
- htab_unlock_bucket(htab, b, hash, flags);
+ htab_unlock_bucket(b, flags);
if (l_old) {
if (old_map_ptr)
map->ops->map_fd_put_ptr(map, old_map_ptr, true);
@@ -1207,7 +1173,7 @@ static long htab_map_update_elem(struct bpf_map *map, void *key, void *value,
}
return 0;
err:
- htab_unlock_bucket(htab, b, hash, flags);
+ htab_unlock_bucket(b, flags);
return ret;
}

@@ -1254,7 +1220,7 @@ static long htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value
copy_map_value(&htab->map,
l_new->key + round_up(map->key_size, 8), value);

- ret = htab_lock_bucket(htab, b, hash, &flags);
+ ret = htab_lock_bucket(b, &flags);
if (ret)
goto err_lock_bucket;

@@ -1275,7 +1241,7 @@ static long htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value
ret = 0;

err:
- htab_unlock_bucket(htab, b, hash, flags);
+ htab_unlock_bucket(b, flags);

err_lock_bucket:
if (ret)
@@ -1312,7 +1278,7 @@ static long __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
b = __select_bucket(htab, hash);
head = &b->head;

- ret = htab_lock_bucket(htab, b, hash, &flags);
+ ret = htab_lock_bucket(b, &flags);
if (ret)
return ret;

@@ -1337,7 +1303,7 @@ static long __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
}
ret = 0;
err:
- htab_unlock_bucket(htab, b, hash, flags);
+ htab_unlock_bucket(b, flags);
return ret;
}

@@ -1378,7 +1344,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
return -ENOMEM;
}

- ret = htab_lock_bucket(htab, b, hash, &flags);
+ ret = htab_lock_bucket(b, &flags);
if (ret)
goto err_lock_bucket;

@@ -1402,7 +1368,7 @@ static long __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
}
ret = 0;
err:
- htab_unlock_bucket(htab, b, hash, flags);
+ htab_unlock_bucket(b, flags);
err_lock_bucket:
if (l_new) {
bpf_map_dec_elem_count(&htab->map);
@@ -1444,7 +1410,7 @@ static long htab_map_delete_elem(struct bpf_map *map, void *key)
b = __select_bucket(htab, hash);
head = &b->head;

- ret = htab_lock_bucket(htab, b, hash, &flags);
+ ret = htab_lock_bucket(b, &flags);
if (ret)
return ret;

@@ -1454,7 +1420,7 @@ static long htab_map_delete_elem(struct bpf_map *map, void *key)
else
ret = -ENOENT;

- htab_unlock_bucket(htab, b, hash, flags);
+ htab_unlock_bucket(b, flags);

if (l)
free_htab_elem(htab, l);
@@ -1480,7 +1446,7 @@ static long htab_lru_map_delete_elem(struct bpf_map *map, void *key)
b = __select_bucket(htab, hash);
head = &b->head;

- ret = htab_lock_bucket(htab, b, hash, &flags);
+ ret = htab_lock_bucket(b, &flags);
if (ret)
return ret;

@@ -1491,7 +1457,7 @@ static long htab_lru_map_delete_elem(struct bpf_map *map, void *key)
else
ret = -ENOENT;

- htab_unlock_bucket(htab, b, hash, flags);
+ htab_unlock_bucket(b, flags);
if (l)
htab_lru_push_free(htab, l);
return ret;
@@ -1558,7 +1524,6 @@ static void htab_map_free_timers_and_wq(struct bpf_map *map)
static void htab_map_free(struct bpf_map *map)
{
struct bpf_htab *htab = container_of(map, struct bpf_htab, map);
- int i;

/* bpf_free_used_maps() or close(map_fd) will trigger this map_free callback.
* bpf_free_used_maps() is called after bpf prog is no longer executing.
@@ -1583,9 +1548,6 @@ static void htab_map_free(struct bpf_map *map)
bpf_mem_alloc_destroy(&htab->ma);
if (htab->use_percpu_counter)
percpu_counter_destroy(&htab->pcount);
- for (i = 0; i < HASHTAB_MAP_LOCK_COUNT; i++)
- free_percpu(htab->map_locked[i]);
- lockdep_unregister_key(&htab->lockdep_key);
bpf_map_area_free(htab);
}

@@ -1628,7 +1590,7 @@ static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
b = __select_bucket(htab, hash);
head = &b->head;

- ret = htab_lock_bucket(htab, b, hash, &bflags);
+ ret = htab_lock_bucket(b, &bflags);
if (ret)
return ret;

@@ -1665,7 +1627,7 @@ static int __htab_map_lookup_and_delete_elem(struct bpf_map *map, void *key,
hlist_nulls_del_rcu(&l->hash_node);

out_unlock:
- htab_unlock_bucket(htab, b, hash, bflags);
+ htab_unlock_bucket(b, bflags);

if (l) {
if (is_lru_map)
@@ -1787,7 +1749,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
head = &b->head;
/* do not grab the lock unless need it (bucket_cnt > 0). */
if (locked) {
- ret = htab_lock_bucket(htab, b, batch, &flags);
+ ret = htab_lock_bucket(b, &flags);
if (ret) {
rcu_read_unlock();
bpf_enable_instrumentation();
@@ -1810,7 +1772,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
/* Note that since bucket_cnt > 0 here, it is implicit
* that the locked was grabbed, so release it.
*/
- htab_unlock_bucket(htab, b, batch, flags);
+ htab_unlock_bucket(b, flags);
rcu_read_unlock();
bpf_enable_instrumentation();
goto after_loop;
@@ -1821,7 +1783,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
/* Note that since bucket_cnt > 0 here, it is implicit
* that the locked was grabbed, so release it.
*/
- htab_unlock_bucket(htab, b, batch, flags);
+ htab_unlock_bucket(b, flags);
rcu_read_unlock();
bpf_enable_instrumentation();
kvfree(keys);
@@ -1884,7 +1846,7 @@ __htab_map_lookup_and_delete_batch(struct bpf_map *map,
dst_val += value_size;
}

- htab_unlock_bucket(htab, b, batch, flags);
+ htab_unlock_bucket(b, flags);
locked = false;

while (node_to_free) {
--
2.43.5