[PATCH bpf-next v3 1/4] bpf: export bpf_map_inc_not_zero

[Stanislav Fomichev]

Rename existing bpf_map_inc_not_zero to __bpf_map_inc_not_zero to
indicate that it's caller's responsibility to do proper locking.
Create and export bpf_map_inc_not_zero wrapper that properly
locks map_idr_lock. Will be used in the next commit to
hold a map while cloning a socket.

Cc: Martin KaFai Lau <ka...@fb.com>
Cc: Yonghong Song <y...@fb.com>
Acked-by: Yonghong Song <y...@fb.com>
Signed-off-by: Stanislav Fomichev <s...@google.com>
---
 include/linux/bpf.h  |  2 ++
 kernel/bpf/syscall.c | 16 +++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f9a506147c8a..15ae49862b82 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -647,6 +647,8 @@ void bpf_map_free_id(struct bpf_map *map, bool do_idr_lock);
 struct bpf_map *bpf_map_get_with_uref(u32 ufd);
 struct bpf_map *__bpf_map_get(struct fd f);
 struct bpf_map * __must_check bpf_map_inc(struct bpf_map *map, bool uref);
+struct bpf_map * __must_check bpf_map_inc_not_zero(struct bpf_map *map,
+                                                  bool uref);
 void bpf_map_put_with_uref(struct bpf_map *map);
 void bpf_map_put(struct bpf_map *map);
 int bpf_map_charge_memlock(struct bpf_map *map, u32 pages);
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 5d141f16f6fa..cf8052b016e7 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -683,8 +683,8 @@ struct bpf_map *bpf_map_get_with_uref(u32 ufd)
 }
 
 /* map_idr_lock should have been held */
-static struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map,
-                                           bool uref)
+static struct bpf_map *__bpf_map_inc_not_zero(struct bpf_map *map,
+                                             bool uref)
 {
        int refold;
 
@@ -704,6 +704,16 @@ static struct bpf_map *bpf_map_inc_not_zero(struct bpf_map 
*map,
        return map;
 }
 
+struct bpf_map *bpf_map_inc_not_zero(struct bpf_map *map, bool uref)
+{
+       spin_lock_bh(&map_idr_lock);
+       map = __bpf_map_inc_not_zero(map, uref);
+       spin_unlock_bh(&map_idr_lock);
+
+       return map;
+}
+EXPORT_SYMBOL_GPL(bpf_map_inc_not_zero);
+
 int __weak bpf_stackmap_copy(struct bpf_map *map, void *key, void *value)
 {
        return -ENOTSUPP;
@@ -2177,7 +2187,7 @@ static int bpf_map_get_fd_by_id(const union bpf_attr 
*attr)
        spin_lock_bh(&map_idr_lock);
        map = idr_find(&map_idr, id);
        if (map)
-               map = bpf_map_inc_not_zero(map, true);
+               map = __bpf_map_inc_not_zero(map, true);
        else
                map = ERR_PTR(-ENOENT);
        spin_unlock_bh(&map_idr_lock);
-- 
2.23.0.rc1.153.gdeed80330f-goog