From: Hou Tao <houtao1@xxxxxxxxxx>
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@xxxxxxxxxx>
---
kernel/bpf/bpf_local_storage.c | 8 ++------
kernel/bpf/hashtab.c | 6 ++----
kernel/bpf/range_tree.c | 2 --
kernel/bpf/syscall.c | 8 +++++++-
4 files changed, 11 insertions(+), 13 deletions(-)
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index 615a3034baeb5..12cf6382175e1 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -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();
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 7f09943c6ee22..772304f9519ba 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -1519,10 +1519,9 @@ 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;
@@ -1534,7 +1533,6 @@ 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)
diff --git a/kernel/bpf/range_tree.c b/kernel/bpf/range_tree.c
index 5bdf9aadca3a6..37b80a23ae1ae 100644
--- a/kernel/bpf/range_tree.c
+++ b/kernel/bpf/range_tree.c
@@ -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();
}
}
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 4e88797fdbebb..5d24204929461 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -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.
--
2.29.2
