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bpf: Disable migration before calling ops->map_free()

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The freeing of all map elements may invoke bpf_obj_free_fields() to free
the special fields in the map value. Since these special fields may be
allocated from bpf memory allocator, migrate_{disable|enable} pairs are
necessary for the freeing of these special fields.

To simplify reasoning about when migrate_disable() is needed for the
freeing of these special fields, let the caller to guarantee migration
is disabled before invoking bpf_obj_free_fields(). Therefore, disabling
migration before calling ops->map_free() to simplify the freeing of map
values or special fields allocated from bpf memory allocator.

After disabling migration in bpf_map_free(), there is no need for
additional migration_{disable|enable} pairs in these ->map_free()
callbacks. Remove these redundant invocations.

The migrate_{disable|enable} pairs in the underlying implementation of
bpf_obj_free_fields() will be removed by the following patch.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Link: https://lore.kernel.org/r/20250108010728.207536-11-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Hou Tao 2025-01-08 09:07:22 +08:00 committed by Alexei Starovoitov
parent 090d7f2e64
commit 4b7e7cd1c1
4 changed files with 11 additions and 13 deletions
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8
kernel/bpf/bpf_local_storage.c
View File

@ -905,15 +905,11 @@ void bpf_local_storage_map_free(struct bpf_map *map,
while ((selem = hlist_entry_safe(
rcu_dereference_raw(hlist_first_rcu(&b->list)),
struct bpf_local_storage_elem, map_node))) {
if (busy_counter) {
migrate_disable();
if (busy_counter)
this_cpu_inc(*busy_counter);
}
bpf_selem_unlink(selem, true);
if (busy_counter) {
if (busy_counter)
this_cpu_dec(*busy_counter);
migrate_enable();
}
cond_resched_rcu();
}
rcu_read_unlock();

6
kernel/bpf/hashtab.c
View File

@ -1500,10 +1500,9 @@ static void delete_all_elements(struct bpf_htab *htab)
{
int i;
/* It's called from a worker thread, so disable migration here,
* since bpf_mem_cache_free() relies on that.
/* It's called from a worker thread and migration has been disabled,
* therefore, it is OK to invoke bpf_mem_cache_free() directly.
*/
migrate_disable();
for (i = 0; i < htab->n_buckets; i++) {
struct hlist_nulls_head *head = select_bucket(htab, i);
struct hlist_nulls_node *n;
@ -1515,7 +1514,6 @@ static void delete_all_elements(struct bpf_htab *htab)
}
cond_resched();
}
migrate_enable();
}
static void htab_free_malloced_timers_and_wq(struct bpf_htab *htab)

2
kernel/bpf/range_tree.c
View File

@ -259,9 +259,7 @@ void range_tree_destroy(struct range_tree *rt)
while ((rn = range_it_iter_first(rt, 0, -1U))) {
range_it_remove(rn, rt);
migrate_disable();
bpf_mem_free(&bpf_global_ma, rn);
migrate_enable();
}
}

8
kernel/bpf/syscall.c
View File

@ -835,8 +835,14 @@ static void bpf_map_free(struct bpf_map *map)
struct btf_record *rec = map->record;
struct btf *btf = map->btf;
/* implementation dependent freeing */
/* implementation dependent freeing. Disabling migration to simplify
* the free of values or special fields allocated from bpf memory
* allocator.
*/
migrate_disable();
map->ops->map_free(map);
migrate_enable();
/* Delay freeing of btf_record for maps, as map_free
* callback usually needs access to them. It is better to do it here
* than require each callback to do the free itself manually.