From: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
This patch remembers which smap triggers the allocation
of a 'struct bpf_local_storage' object. The local_storage is
allocated during the very first selem added to the owner.
The smap pointer is needed when using the bpf_mem_cache_free
in a later patch because it needs to free to the correct
smap's bpf_mem_alloc object.
When a selem is being removed, it needs to check if it is
the selem that triggers the creation of the local_storage.
If it is, the local_storage->smap pointer will be reset to NULL.
This NULL reset is done under the local_storage->lock in
bpf_selem_unlink_storage_nolock() when a selem is being removed.
Also note that the local_storage may not go away even
local_storage->smap is NULL because there may be other
selem still stored in the local_storage.
Signed-off-by: Martin KaFai Lau <martin.lau@xxxxxxxxxx>
---
include/linux/bpf_local_storage.h | 1 +
kernel/bpf/bpf_local_storage.c | 4 ++++
2 files changed, 5 insertions(+)
diff --git a/include/linux/bpf_local_storage.h b/include/linux/bpf_local_storage.h
index 5908a954ddc2..613b1805ed9f 100644
--- a/include/linux/bpf_local_storage.h
+++ b/include/linux/bpf_local_storage.h
@@ -83,6 +83,7 @@ struct bpf_local_storage_elem {
struct bpf_local_storage {
struct bpf_local_storage_data __rcu *cache[BPF_LOCAL_STORAGE_CACHE_SIZE];
+ struct bpf_local_storage_map __rcu *smap;
struct hlist_head list; /* List of bpf_local_storage_elem */
void *owner; /* The object that owns the above "list" of
* bpf_local_storage_elem.
diff --git a/kernel/bpf/bpf_local_storage.c b/kernel/bpf/bpf_local_storage.c
index 70df8dcb2066..5585dbfd9c66 100644
--- a/kernel/bpf/bpf_local_storage.c
+++ b/kernel/bpf/bpf_local_storage.c
@@ -213,6 +213,9 @@ static bool bpf_selem_unlink_storage_nolock(struct bpf_local_storage *local_stor
kfree_rcu(selem, rcu);
}
+ if (rcu_access_pointer(local_storage->smap) == smap)
+ RCU_INIT_POINTER(local_storage->smap, NULL);
+
return free_local_storage;
}
@@ -368,6 +371,7 @@ int bpf_local_storage_alloc(void *owner,
goto uncharge;
}
+ RCU_INIT_POINTER(storage->smap, smap);
INIT_HLIST_HEAD(&storage->list);
raw_spin_lock_init(&storage->lock);
storage->owner = owner;
--
2.34.1
