Re: [PATCH net-next 3/9] bpf: pre-allocate hash map elements

[Daniel Borkmann]

On 03/07/2016 02:58 AM, Alexei Starovoitov wrote:
[...]

---
  include/linux/bpf.h      |   1 +
  include/uapi/linux/bpf.h |   3 +
  kernel/bpf/hashtab.c     | 264 ++++++++++++++++++++++++++++++++++-------------
  kernel/bpf/syscall.c     |   2 +-
  4 files changed, 196 insertions(+), 74 deletions(-)

Shouldn't all other map types (like array) need something like this as well to
reserve this for their future flags?

  if (attr->map_flags)
    return ERR_PTR(-EINVAL);

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 4b070827200d..c81efb10bbb5 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -37,6 +37,7 @@ struct bpf_map {
        u32 key_size;
        u32 value_size;
        u32 max_entries;
+       u32 map_flags;

Just naming this 'flags' doesn't work due to the anonymous struct inside that
union, right? :/

        u32 pages;
        struct user_struct *user;
        const struct bpf_map_ops *ops;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 6496f98d3d68..5eeb2ca9441e 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -101,12 +101,15 @@ enum bpf_prog_type {
  #define BPF_NOEXIST   1 /* create new element if it didn't exist */
  #define BPF_EXIST     2 /* update existing element */

+#define BPF_F_NO_PREALLOC      (1ULL << 0)

Nit: Should better be (1U << 0) as map_flags are of __u32.

  union bpf_attr {
        struct { /* anonymous struct used by BPF_MAP_CREATE command */
                __u32   map_type;       /* one of enum bpf_map_type */
                __u32   key_size;       /* size of key in bytes */
                __u32   value_size;     /* size of value in bytes */
                __u32   max_entries;    /* max number of entries in a map */
+               __u32   map_flags;      /* prealloc or not */
        };

        struct { /* anonymous struct used by BPF_MAP_*_ELEM commands */

Thanks,
Daniel