[PATCH bpf-next v2 5/8] xdp: make devmap flush_list common for all map instances

Björn Töpel
2019-12-19T06:10:42Z

From: Björn Töpel <bjorn.topel@intel.com>

The devmap flush list is used to track entries that need to flushed
from via the xdp_do_flush_map() function. This list used to be
per-map, but there is really no reason for that. Instead make the
flush list global for all devmaps, which simplifies __dev_map_flush()
and dev_map_init_map().

Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
---
include/linux/bpf.h | 4 ++--
kernel/bpf/devmap.c | 35 +++++++++++++----------------------
net/core/filter.c | 2 +-
3 files changed, 16 insertions(+), 25 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index d467983e61bb..31191804ca09 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -959,7 +959,7 @@ struct sk_buff;

struct bpf_dtab_netdev *__dev_map_lookup_elem(struct bpf_map *map, u32 key);
struct bpf_dtab_netdev *__dev_map_hash_lookup_elem(struct bpf_map *map, u32 key);
-void __dev_map_flush(struct bpf_map *map);
+void __dev_map_flush(void);
int dev_map_enqueue(struct bpf_dtab_netdev *dst, struct xdp_buff *xdp,
struct net_device *dev_rx);
int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
@@ -1068,7 +1068,7 @@ static inline struct net_device *__dev_map_hash_lookup_elem(struct bpf_map *map
return NULL;
}

-static inline void __dev_map_flush(struct bpf_map *map)
+static inline void __dev_map_flush(void)
{
}

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index b7595de6a91a..da9c832fc5c8 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -75,7 +75,6 @@ struct bpf_dtab_netdev {
struct bpf_dtab {
struct bpf_map map;
struct bpf_dtab_netdev **netdev_map; /* DEVMAP type only */
- struct list_head __percpu *flush_list;
struct list_head list;

/* these are only used for DEVMAP_HASH type maps */
@@ -85,6 +84,7 @@ struct bpf_dtab {
u32 n_buckets;
};

+static DEFINE_PER_CPU(struct list_head, dev_map_flush_list);
static DEFINE_SPINLOCK(dev_map_lock);
static LIST_HEAD(dev_map_list);

@@ -109,8 +109,8 @@ static inline struct hlist_head *dev_map_index_hash(struct bpf_dtab *dtab,

static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
{
- int err, cpu;
- u64 cost;
+ u64 cost = 0;
+ int err;

/* check sanity of attributes */
if (attr->max_entries == 0 || attr->key_size != 4 ||
@@ -125,9 +125,6 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)

bpf_map_init_from_attr(&dtab->map, attr);

- /* make sure page count doesn't overflow */
- cost = (u64) sizeof(struct list_head) * num_possible_cpus();
-
if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
dtab->n_buckets = roundup_pow_of_two(dtab->map.max_entries);

@@ -143,17 +140,10 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
if (err)
return -EINVAL;

- dtab->flush_list = alloc_percpu(struct list_head);
- if (!dtab->flush_list)
- goto free_charge;
-
- for_each_possible_cpu(cpu)
- INIT_LIST_HEAD(per_cpu_ptr(dtab->flush_list, cpu));
-
if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
dtab->dev_index_head = dev_map_create_hash(dtab->n_buckets);
if (!dtab->dev_index_head)
- goto free_percpu;
+ goto free_charge;

spin_lock_init(&dtab->index_lock);
} else {
@@ -161,13 +151,11 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
sizeof(struct bpf_dtab_netdev *),
dtab->map.numa_node);
if (!dtab->netdev_map)
- goto free_percpu;
+ goto free_charge;
}

return 0;

-free_percpu:
- free_percpu(dtab->flush_list);
free_charge:
bpf_map_charge_finish(&dtab->map.memory);
return -ENOMEM;
@@ -254,7 +242,6 @@ static void dev_map_free(struct bpf_map *map)
bpf_map_area_free(dtab->netdev_map);
}

- free_percpu(dtab->flush_list);
kfree(dtab);
}

@@ -384,10 +371,9 @@ static int bq_xmit_all(struct xdp_bulk_queue *bq, u32 flags)
* net device can be torn down. On devmap tear down we ensure the flush list
* is empty before completing to ensure all flush operations have completed.
*/
-void __dev_map_flush(struct bpf_map *map)
+void __dev_map_flush(void)
{
- struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
- struct list_head *flush_list = this_cpu_ptr(dtab->flush_list);
+ struct list_head *flush_list = this_cpu_ptr(&dev_map_flush_list);
struct xdp_bulk_queue *bq, *tmp;

rcu_read_lock();
@@ -419,7 +405,7 @@ static int bq_enqueue(struct bpf_dtab_netdev *obj, struct xdp_frame *xdpf,
struct net_device *dev_rx)

{
- struct list_head *flush_list = this_cpu_ptr(obj->dtab->flush_list);
+ struct list_head *flush_list = this_cpu_ptr(&dev_map_flush_list);
struct xdp_bulk_queue *bq = this_cpu_ptr(obj->bulkq);

if (unlikely(bq->count == DEV_MAP_BULK_SIZE))
@@ -777,10 +763,15 @@ static struct notifier_block dev_map_notifier = {

static int __init dev_map_init(void)
{
+ int cpu;
+
/* Assure tracepoint shadow struct _bpf_dtab_netdev is in sync */
BUILD_BUG_ON(offsetof(struct bpf_dtab_netdev, dev) !=
offsetof(struct _bpf_dtab_netdev, dev));
register_netdevice_notifier(&dev_map_notifier);
+
+ for_each_possible_cpu(cpu)
+ INIT_LIST_HEAD(&per_cpu(dev_map_flush_list, cpu));
return 0;
}

diff --git a/net/core/filter.c b/net/core/filter.c
index c51678c473c5..b7570cb84902 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -3555,7 +3555,7 @@ void xdp_do_flush_map(void)
switch (map->map_type) {
case BPF_MAP_TYPE_DEVMAP:
case BPF_MAP_TYPE_DEVMAP_HASH:
- __dev_map_flush(map);
+ __dev_map_flush();
break;
case BPF_MAP_TYPE_CPUMAP:
__cpu_map_flush(map);
--
2.20.1