From: YiFei Zhu <zhuyifei@xxxxxxxxxx>
This change comes in several parts:
One, the restriction that the CGROUP_STORAGE map can only be used
by one program is removed. This results in the removal of the field
'aux' in struct bpf_cgroup_storage_map, and removal of relevant
code associated with the field, and removal of now-noop functions
bpf_free_cgroup_storage and bpf_cgroup_storage_release.
Second, because there could be multiple attach types to the same
cgroup, the attach type is completely ignored on comparison in
the map key. Newly added keys have it zeroed. The only value in
the key that still matters is the cgroup inode. bpftool map dump
will also show an attach type of zero.
Third, because the storages are now shared, the storages cannot
be unconditionally freed on program detach. There could be two
ways to solve this issue:
* A. Reference count the usage of the storages, and free when the
last program is detached.
* B. Free only when the storage is impossible to be referred to
again, i.e. when either the cgroup_bpf it is attached to, or
the map itself, is freed.
Option A has the side effect that, when the user detach and
reattach a program, whether the program gets a fresh storage
depends on whether there is another program attached using that
storage. This could trigger races if the user is multi-threaded,
and since nondeterminism in data races is evil, go with option B.
The both the map and the cgroup_bpf now tracks their associated
storages, and the storage unlink and free are removed from
cgroup_bpf_detach and added to cgroup_bpf_release and
cgroup_storage_map_free. The latter also new holds the cgroup_mutex
to prevent any races with the former.
Fourth, on attach, we reuse the old storage if the key already
exists in the map. Because the rbtree traversal holds the spinlock
of the map, during which we can't allocate a new storage if we
don't find an old storage, instead we preallocate the storage
unconditionally, and free the preallocated storage if we find an
old storage in the map. This results in a change of semantics in
bpf_cgroup_storage{,s}_link, and rename cgroup_storage_insert to
cgroup_storage_lookup_insert that does both lookup and conditionally
insert or free. bpf_cgroup_storage{,s}_link also tracks exactly
which storages are reused in an array of bools, so it can unlink
and free the new storages in the event that attachment failed
later than link. bpf_cgroup_storages_{free,unlink} accepts the
bool array in order to facilitate that.
Signed-off-by: YiFei Zhu <zhuyifei@xxxxxxxxxx>
---
include/linux/bpf-cgroup.h | 15 +++---
include/uapi/linux/bpf.h | 2 +-
kernel/bpf/cgroup.c | 69 +++++++++++++++------------
kernel/bpf/core.c | 12 -----
kernel/bpf/local_storage.c | 85 ++++++++++++++++------------------
tools/include/uapi/linux/bpf.h | 2 +-
6 files changed, 91 insertions(+), 94 deletions(-)
diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h
index 2c6f26670acc..c83cd8862298 100644
--- a/include/linux/bpf-cgroup.h
+++ b/include/linux/bpf-cgroup.h
@@ -46,7 +46,8 @@ struct bpf_cgroup_storage {
};
struct bpf_cgroup_storage_map *map;
struct bpf_cgroup_storage_key key;
- struct list_head list;
+ struct list_head list_map;
+ struct list_head list_cg;
struct rb_node node;
struct rcu_head rcu;
};
@@ -78,6 +79,9 @@ struct cgroup_bpf {
struct list_head progs[MAX_BPF_ATTACH_TYPE];
u32 flags[MAX_BPF_ATTACH_TYPE];
+ /* list of cgroup shared storages */
+ struct list_head storages;
+
/* temp storage for effective prog array used by prog_attach/detach */
struct bpf_prog_array *inactive;
@@ -164,12 +168,11 @@ static inline void bpf_cgroup_storage_set(struct bpf_cgroup_storage
struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(struct bpf_prog *prog,
enum bpf_cgroup_storage_type stype);
void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage);
-void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
- struct cgroup *cgroup,
- enum bpf_attach_type type);
+struct bpf_cgroup_storage *
+bpf_cgroup_storage_link(struct bpf_cgroup_storage *new_storage,
+ struct cgroup *cgroup, bool *storage_reused);
void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage);
int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux, struct bpf_map *map);
-void bpf_cgroup_storage_release(struct bpf_prog_aux *aux, struct bpf_map *map);
int bpf_percpu_cgroup_storage_copy(struct bpf_map *map, void *key, void *value);
int bpf_percpu_cgroup_storage_update(struct bpf_map *map, void *key,
@@ -383,8 +386,6 @@ static inline void bpf_cgroup_storage_set(
struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE]) {}
static inline int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux,
struct bpf_map *map) { return 0; }
-static inline void bpf_cgroup_storage_release(struct bpf_prog_aux *aux,
- struct bpf_map *map) {}
static inline struct bpf_cgroup_storage *bpf_cgroup_storage_alloc(
struct bpf_prog *prog, enum bpf_cgroup_storage_type stype) { return NULL; }
static inline void bpf_cgroup_storage_free(
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 7ac3992dacfe..b14f008ad028 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -78,7 +78,7 @@ struct bpf_lpm_trie_key {
struct bpf_cgroup_storage_key {
__u64 cgroup_inode_id; /* cgroup inode id */
- __u32 attach_type; /* program attach type */
+ __u32 attach_type; /* program attach type, unused */
};
/* BPF syscall commands, see bpf(2) man-page for details. */
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index ac53102e244a..6b1ef4a809bb 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -28,12 +28,14 @@ void cgroup_bpf_offline(struct cgroup *cgrp)
percpu_ref_kill(&cgrp->bpf.refcnt);
}
-static void bpf_cgroup_storages_free(struct bpf_cgroup_storage *storages[])
+static void bpf_cgroup_storages_free(struct bpf_cgroup_storage *storages[],
+ bool *storage_reused)
{
enum bpf_cgroup_storage_type stype;
for_each_cgroup_storage_type(stype)
- bpf_cgroup_storage_free(storages[stype]);
+ if (!storage_reused || !storage_reused[stype])
+ bpf_cgroup_storage_free(storages[stype]);
}
static int bpf_cgroup_storages_alloc(struct bpf_cgroup_storage *storages[],
@@ -45,7 +47,7 @@ static int bpf_cgroup_storages_alloc(struct bpf_cgroup_storage *storages[],
storages[stype] = bpf_cgroup_storage_alloc(prog, stype);
if (IS_ERR(storages[stype])) {
storages[stype] = NULL;
- bpf_cgroup_storages_free(storages);
+ bpf_cgroup_storages_free(storages, NULL);
return -ENOMEM;
}
}
@@ -63,21 +65,24 @@ static void bpf_cgroup_storages_assign(struct bpf_cgroup_storage *dst[],
}
static void bpf_cgroup_storages_link(struct bpf_cgroup_storage *storages[],
- struct cgroup* cgrp,
- enum bpf_attach_type attach_type)
+ struct cgroup *cgrp, bool *storage_reused)
{
enum bpf_cgroup_storage_type stype;
for_each_cgroup_storage_type(stype)
- bpf_cgroup_storage_link(storages[stype], cgrp, attach_type);
+ storages[stype] =
+ bpf_cgroup_storage_link(storages[stype], cgrp,
+ &storage_reused[stype]);
}
-static void bpf_cgroup_storages_unlink(struct bpf_cgroup_storage *storages[])
+static void bpf_cgroup_storages_unlink(struct bpf_cgroup_storage *storages[],
+ bool *storage_reused)
{
enum bpf_cgroup_storage_type stype;
for_each_cgroup_storage_type(stype)
- bpf_cgroup_storage_unlink(storages[stype]);
+ if (!storage_reused || !storage_reused[stype])
+ bpf_cgroup_storage_unlink(storages[stype]);
}
/* Called when bpf_cgroup_link is auto-detached from dying cgroup.
@@ -101,22 +106,23 @@ static void cgroup_bpf_release(struct work_struct *work)
struct cgroup *p, *cgrp = container_of(work, struct cgroup,
bpf.release_work);
struct bpf_prog_array *old_array;
+ struct list_head *storages = &cgrp->bpf.storages;
+ struct bpf_cgroup_storage *storage, *stmp;
+
unsigned int type;
mutex_lock(&cgroup_mutex);
for (type = 0; type < ARRAY_SIZE(cgrp->bpf.progs); type++) {
struct list_head *progs = &cgrp->bpf.progs[type];
- struct bpf_prog_list *pl, *tmp;
+ struct bpf_prog_list *pl, *pltmp;
- list_for_each_entry_safe(pl, tmp, progs, node) {
+ list_for_each_entry_safe(pl, pltmp, progs, node) {
list_del(&pl->node);
if (pl->prog)
bpf_prog_put(pl->prog);
if (pl->link)
bpf_cgroup_link_auto_detach(pl->link);
- bpf_cgroup_storages_unlink(pl->storage);
- bpf_cgroup_storages_free(pl->storage);
kfree(pl);
static_branch_dec(&cgroup_bpf_enabled_key);
}
@@ -126,6 +132,11 @@ static void cgroup_bpf_release(struct work_struct *work)
bpf_prog_array_free(old_array);
}
+ list_for_each_entry_safe(storage, stmp, storages, list_cg) {
+ bpf_cgroup_storage_unlink(storage);
+ bpf_cgroup_storage_free(storage);
+ }
+
mutex_unlock(&cgroup_mutex);
for (p = cgroup_parent(cgrp); p; p = cgroup_parent(p))
@@ -290,6 +301,8 @@ int cgroup_bpf_inherit(struct cgroup *cgrp)
for (i = 0; i < NR; i++)
INIT_LIST_HEAD(&cgrp->bpf.progs[i]);
+ INIT_LIST_HEAD(&cgrp->bpf.storages);
+
for (i = 0; i < NR; i++)
if (compute_effective_progs(cgrp, i, &arrays[i]))
goto cleanup;
@@ -422,7 +435,7 @@ int __cgroup_bpf_attach(struct cgroup *cgrp,
struct list_head *progs = &cgrp->bpf.progs[type];
struct bpf_prog *old_prog = NULL;
struct bpf_cgroup_storage *storage[MAX_BPF_CGROUP_STORAGE_TYPE] = {};
- struct bpf_cgroup_storage *old_storage[MAX_BPF_CGROUP_STORAGE_TYPE] = {};
+ bool storage_reused[MAX_BPF_CGROUP_STORAGE_TYPE];
struct bpf_prog_list *pl;
int err;
@@ -455,22 +468,22 @@ int __cgroup_bpf_attach(struct cgroup *cgrp,
if (IS_ERR(pl))
return PTR_ERR(pl);
- if (bpf_cgroup_storages_alloc(storage, prog ? : link->link.prog))
- return -ENOMEM;
-
if (pl) {
old_prog = pl->prog;
- bpf_cgroup_storages_unlink(pl->storage);
- bpf_cgroup_storages_assign(old_storage, pl->storage);
} else {
pl = kmalloc(sizeof(*pl), GFP_KERNEL);
- if (!pl) {
- bpf_cgroup_storages_free(storage);
+ if (!pl)
return -ENOMEM;
- }
+
list_add_tail(&pl->node, progs);
}
+ err = bpf_cgroup_storages_alloc(storage, prog ? : link->link.prog);
+ if (err)
+ goto cleanup;
+
+ bpf_cgroup_storages_link(storage, cgrp, storage_reused);
+
pl->prog = prog;
pl->link = link;
bpf_cgroup_storages_assign(pl->storage, storage);
@@ -478,24 +491,24 @@ int __cgroup_bpf_attach(struct cgroup *cgrp,
err = update_effective_progs(cgrp, type);
if (err)
- goto cleanup;
+ goto cleanup_unlink;
- bpf_cgroup_storages_free(old_storage);
if (old_prog)
bpf_prog_put(old_prog);
else
static_branch_inc(&cgroup_bpf_enabled_key);
- bpf_cgroup_storages_link(pl->storage, cgrp, type);
return 0;
+cleanup_unlink:
+ bpf_cgroup_storages_unlink(storage, storage_reused);
+
cleanup:
+ bpf_cgroup_storages_free(storage, storage_reused);
+
if (old_prog) {
pl->prog = old_prog;
pl->link = NULL;
}
- bpf_cgroup_storages_free(pl->storage);
- bpf_cgroup_storages_assign(pl->storage, old_storage);
- bpf_cgroup_storages_link(pl->storage, cgrp, type);
if (!old_prog) {
list_del(&pl->node);
kfree(pl);
@@ -679,8 +692,6 @@ int __cgroup_bpf_detach(struct cgroup *cgrp, struct bpf_prog *prog,
/* now can actually delete it from this cgroup list */
list_del(&pl->node);
- bpf_cgroup_storages_unlink(pl->storage);
- bpf_cgroup_storages_free(pl->storage);
kfree(pl);
if (list_empty(progs))
/* last program was detached, reset flags to zero */
diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 9df4cc9a2907..f367fe7422ea 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -2042,24 +2042,12 @@ int bpf_prog_array_copy_info(struct bpf_prog_array *array,
: 0;
}
-static void bpf_free_cgroup_storage(struct bpf_prog_aux *aux)
-{
- enum bpf_cgroup_storage_type stype;
-
- for_each_cgroup_storage_type(stype) {
- if (!aux->cgroup_storage[stype])
- continue;
- bpf_cgroup_storage_release(aux, aux->cgroup_storage[stype]);
- }
-}
-
void __bpf_free_used_maps(struct bpf_prog_aux *aux,
struct bpf_map **used_maps, u32 len)
{
struct bpf_map *map;
u32 i;
- bpf_free_cgroup_storage(aux);
for (i = 0; i < len; i++) {
map = used_maps[i];
if (map->ops->map_poke_untrack)
diff --git a/kernel/bpf/local_storage.c b/kernel/bpf/local_storage.c
index 51bd5a8cb01b..78ffe69ff1d8 100644
--- a/kernel/bpf/local_storage.c
+++ b/kernel/bpf/local_storage.c
@@ -9,6 +9,8 @@
#include <linux/slab.h>
#include <uapi/linux/btf.h>
+#include "../cgroup/cgroup-internal.h"
+
DEFINE_PER_CPU(struct bpf_cgroup_storage*, bpf_cgroup_storage[MAX_BPF_CGROUP_STORAGE_TYPE]);
#ifdef CONFIG_CGROUP_BPF
@@ -20,7 +22,6 @@ struct bpf_cgroup_storage_map {
struct bpf_map map;
spinlock_t lock;
- struct bpf_prog_aux *aux;
struct rb_root root;
struct list_head list;
};
@@ -38,10 +39,6 @@ static int bpf_cgroup_storage_key_cmp(
return -1;
else if (key1->cgroup_inode_id > key2->cgroup_inode_id)
return 1;
- else if (key1->attach_type < key2->attach_type)
- return -1;
- else if (key1->attach_type > key2->attach_type)
- return 1;
return 0;
}
@@ -81,8 +78,9 @@ static struct bpf_cgroup_storage *cgroup_storage_lookup(
return NULL;
}
-static int cgroup_storage_insert(struct bpf_cgroup_storage_map *map,
- struct bpf_cgroup_storage *storage)
+static struct bpf_cgroup_storage *
+cgroup_storage_lookup_insert(struct bpf_cgroup_storage_map *map,
+ struct bpf_cgroup_storage *storage)
{
struct rb_root *root = &map->root;
struct rb_node **new = &(root->rb_node), *parent = NULL;
@@ -101,14 +99,15 @@ static int cgroup_storage_insert(struct bpf_cgroup_storage_map *map,
new = &((*new)->rb_right);
break;
default:
- return -EEXIST;
+ bpf_cgroup_storage_free(storage);
+ return this;
}
}
rb_link_node(&storage->node, parent, new);
rb_insert_color(&storage->node, root);
- return 0;
+ return NULL;
}
static void *cgroup_storage_lookup_elem(struct bpf_map *_map, void *_key)
@@ -131,10 +130,7 @@ static int cgroup_storage_update_elem(struct bpf_map *map, void *_key,
struct bpf_cgroup_storage *storage;
struct bpf_storage_buffer *new;
- if (unlikely(flags & ~(BPF_F_LOCK | BPF_EXIST | BPF_NOEXIST)))
- return -EINVAL;
-
- if (unlikely(flags & BPF_NOEXIST))
+ if (unlikely(flags & ~(BPF_F_LOCK | BPF_EXIST)))
return -EINVAL;
if (unlikely((flags & BPF_F_LOCK) &&
@@ -250,16 +246,15 @@ static int cgroup_storage_get_next_key(struct bpf_map *_map, void *_key,
if (!storage)
goto enoent;
- storage = list_next_entry(storage, list);
+ storage = list_next_entry(storage, list_map);
if (!storage)
goto enoent;
} else {
storage = list_first_entry(&map->list,
- struct bpf_cgroup_storage, list);
+ struct bpf_cgroup_storage, list_map);
}
spin_unlock_bh(&map->lock);
- next->attach_type = storage->key.attach_type;
next->cgroup_inode_id = storage->key.cgroup_inode_id;
return 0;
@@ -318,6 +313,17 @@ static struct bpf_map *cgroup_storage_map_alloc(union bpf_attr *attr)
static void cgroup_storage_map_free(struct bpf_map *_map)
{
struct bpf_cgroup_storage_map *map = map_to_storage(_map);
+ struct list_head *storages = &map->list;
+ struct bpf_cgroup_storage *storage, *stmp;
+
+ mutex_lock(&cgroup_mutex);
+
+ list_for_each_entry_safe(storage, stmp, storages, list_map) {
+ bpf_cgroup_storage_unlink(storage);
+ bpf_cgroup_storage_free(storage);
+ }
+
+ mutex_unlock(&cgroup_mutex);
WARN_ON(!RB_EMPTY_ROOT(&map->root));
WARN_ON(!list_empty(&map->list));
@@ -431,13 +437,10 @@ int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux, struct bpf_map *_map)
spin_lock_bh(&map->lock);
- if (map->aux && map->aux != aux)
- goto unlock;
if (aux->cgroup_storage[stype] &&
aux->cgroup_storage[stype] != _map)
goto unlock;
- map->aux = aux;
aux->cgroup_storage[stype] = _map;
ret = 0;
unlock:
@@ -446,20 +449,6 @@ int bpf_cgroup_storage_assign(struct bpf_prog_aux *aux, struct bpf_map *_map)
return ret;
}
-void bpf_cgroup_storage_release(struct bpf_prog_aux *aux, struct bpf_map *_map)
-{
- enum bpf_cgroup_storage_type stype = cgroup_storage_type(_map);
- struct bpf_cgroup_storage_map *map = map_to_storage(_map);
-
- spin_lock_bh(&map->lock);
- if (map->aux == aux) {
- WARN_ON(aux->cgroup_storage[stype] != _map);
- map->aux = NULL;
- aux->cgroup_storage[stype] = NULL;
- }
- spin_unlock_bh(&map->lock);
-}
-
static size_t bpf_cgroup_storage_calculate_size(struct bpf_map *map, u32 *pages)
{
size_t size;
@@ -562,24 +551,31 @@ void bpf_cgroup_storage_free(struct bpf_cgroup_storage *storage)
call_rcu(&storage->rcu, free_percpu_cgroup_storage_rcu);
}
-void bpf_cgroup_storage_link(struct bpf_cgroup_storage *storage,
- struct cgroup *cgroup,
- enum bpf_attach_type type)
+struct bpf_cgroup_storage *
+bpf_cgroup_storage_link(struct bpf_cgroup_storage *new_storage,
+ struct cgroup *cgroup, bool *storage_reused)
{
struct bpf_cgroup_storage_map *map;
+ struct bpf_cgroup_storage *old_storage;
- if (!storage)
- return;
+ if (!new_storage)
+ return NULL;
- storage->key.attach_type = type;
- storage->key.cgroup_inode_id = cgroup_id(cgroup);
+ new_storage->key.cgroup_inode_id = cgroup_id(cgroup);
- map = storage->map;
+ map = new_storage->map;
spin_lock_bh(&map->lock);
- WARN_ON(cgroup_storage_insert(map, storage));
- list_add(&storage->list, &map->list);
+ old_storage = cgroup_storage_lookup_insert(map, new_storage);
+ if (!old_storage) {
+ list_add(&new_storage->list_map, &map->list);
+ list_add(&new_storage->list_cg, &cgroup->bpf.storages);
+ }
spin_unlock_bh(&map->lock);
+
+ *storage_reused = old_storage;
+
+ return old_storage ? : new_storage;
}
void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage)
@@ -596,7 +592,8 @@ void bpf_cgroup_storage_unlink(struct bpf_cgroup_storage *storage)
root = &map->root;
rb_erase(&storage->node, root);
- list_del(&storage->list);
+ list_del(&storage->list_map);
+ list_del(&storage->list_cg);
spin_unlock_bh(&map->lock);
}
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 7ac3992dacfe..b14f008ad028 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -78,7 +78,7 @@ struct bpf_lpm_trie_key {
struct bpf_cgroup_storage_key {
__u64 cgroup_inode_id; /* cgroup inode id */
- __u32 attach_type; /* program attach type */
+ __u32 attach_type; /* program attach type, unused */
};
/* BPF syscall commands, see bpf(2) man-page for details. */
--
2.27.0
