From: Hou Tao <houtao1@xxxxxxxxxx>
bpf_selem_free() has the following three callers:
(1) bpf_local_storage_update
It will be invoked through ->map_update_elem syscall or helpers for
storage map. Migration has already been disabled in these running
contexts.
(2) bpf_sk_storage_clone
It has already disabled migration before invoking bpf_selem_free().
(3) bpf_selem_free_list
bpf_selem_free_list() has three callers: bpf_selem_unlink_storage(),
bpf_local_storage_update() and bpf_local_storage_destroy().
The callers of bpf_selem_unlink_storage() includes: storage map
->map_delete_elem syscall, storage map delete helpers and
bpf_local_storage_map_free(). These contexts have already disabled
migration when invoking bpf_selem_unlink() which invokes
bpf_selem_unlink_storage() and bpf_selem_free_list() correspondingly.
bpf_local_storage_update() has been analyzed as the first caller above.
bpf_local_storage_destroy() is invoked when freeing the local storage
for the kernel object. Now cgroup, task, inode and sock storage have
already disabled migration before invoking bpf_local_storage_destroy().
After the analyses above, it is safe to remove migrate_{disable|enable}
from bpf_selem_free(). Also add a cant_migrate() check in
bpf_selem_free().
Signed-off-by: Hou Tao <houtao1@xxxxxxxxxx>
---
kernel/bpf/bpf_local_storage.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index d67ba116aee8..f196093db0a0 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -235,6 +235,8 @@ void bpf_selem_free(struct bpf_local_storage_elem *selem,
struct bpf_local_storage_map *smap,
bool reuse_now)
{
+ cant_migrate();
+
if (!smap->bpf_ma) {
/* Only task storage has uptrs and task storage
* has moved to bpf_mem_alloc. Meaning smap->bpf_ma == true
@@ -258,9 +260,7 @@ void bpf_selem_free(struct bpf_local_storage_elem *selem,
* bpf_mem_cache_free will be able to reuse selem
* immediately.
*/
- migrate_disable();
bpf_mem_cache_free(&smap->selem_ma, selem);
- migrate_enable();
return;
}
--
2.29.2
