netdev - [RFC PATCH bpf-next 03/10] bpf: Call bpf_map_init_from

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Message-Id: <20220921170002.29557-4-laoar.shao@gmail.com>
Date:   Wed, 21 Sep 2022 16:59:55 +0000
From:   Yafang Shao <laoar.shao@...il.com>
To:     ast@...nel.org, daniel@...earbox.net, andrii@...nel.org,
        kafai@...com, songliubraving@...com, yhs@...com,
        john.fastabend@...il.com, kpsingh@...nel.org, sdf@...gle.com,
        haoluo@...gle.com, jolsa@...nel.org, hannes@...xchg.org,
        mhocko@...nel.org, roman.gushchin@...ux.dev, shakeelb@...gle.com,
        songmuchun@...edance.com, akpm@...ux-foundation.org, tj@...nel.org,
        lizefan.x@...edance.com
Cc:     cgroups@...r.kernel.org, netdev@...r.kernel.org,
        bpf@...r.kernel.org, linux-mm@...ck.org,
        Yafang Shao <laoar.shao@...il.com>
Subject: [RFC PATCH bpf-next 03/10] bpf: Call bpf_map_init_from_attr() immediately after map creation

In order to make all other map related memory allocations been allocated
after memcg is saved in the map, we should save the memcg immediately
after map creation. But the map is created in bpf_map_area_alloc(),
within which we can't get the related bpf_map (except with a pointer
casting which may be error prone), so we can do it in
bpf_map_init_from_attr(), which is used by all bpf maps.

bpf_map_init_from_attr() is executed immediately after
bpf_map_area_alloc() for almost all bpf maps except bpf_struct_ops,
devmap and hashmap, so this patch changes these three maps.

In the future we will change the return type of bpf_map_init_from_attr()
from void to int for error cases, so put it immediately after
bpf_map_area_alloc() will make it eary to handle the error case.

Signed-off-by: Yafang Shao <laoar.shao@...il.com>
---
 kernel/bpf/bpf_struct_ops.c | 2 +-
 kernel/bpf/devmap.c         | 5 ++---
 kernel/bpf/hashtab.c        | 4 ++--
 3 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 84b2d9d..36f24f8 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -624,6 +624,7 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 
 	st_map->st_ops = st_ops;
 	map = &st_map->map;
+	bpf_map_init_from_attr(map, attr);
 
 	st_map->uvalue = bpf_map_area_alloc(vt->size, NUMA_NO_NODE);
 	st_map->links =
@@ -637,7 +638,6 @@ static struct bpf_map *bpf_struct_ops_map_alloc(union bpf_attr *attr)
 
 	mutex_init(&st_map->lock);
 	set_vm_flush_reset_perms(st_map->image);
-	bpf_map_init_from_attr(map, attr);
 
 	return map;
 }
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index f9a87dc..20decc7 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -127,9 +127,6 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
 	 */
 	attr->map_flags |= BPF_F_RDONLY_PROG;
 
-
-	bpf_map_init_from_attr(&dtab->map, attr);
-
 	if (attr->map_type == BPF_MAP_TYPE_DEVMAP_HASH) {
 		dtab->n_buckets = roundup_pow_of_two(dtab->map.max_entries);
 
@@ -167,6 +164,8 @@ static struct bpf_map *dev_map_alloc(union bpf_attr *attr)
 	if (!dtab)
 		return ERR_PTR(-ENOMEM);
 
+	bpf_map_init_from_attr(&dtab->map, attr);
+
 	err = dev_map_init_map(dtab, attr);
 	if (err) {
 		bpf_map_area_free(dtab);
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
index 86aec20..6c0e4eb 100644
--- a/kernel/bpf/hashtab.c
+++ b/kernel/bpf/hashtab.c
@@ -514,10 +514,10 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
 	if (!htab)
 		return ERR_PTR(-ENOMEM);
 
-	lockdep_register_key(&htab->lockdep_key);
-
 	bpf_map_init_from_attr(&htab->map, attr);
 
+	lockdep_register_key(&htab->lockdep_key);
+
 	if (percpu_lru) {
 		/* ensure each CPU's lru list has >=1 elements.
 		 * since we are at it, make each lru list has the same
-- 
1.8.3.1