| Message ID | 20161202011258.GC31170@avx2 |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
On Thu, Dec 1, 2016 at 5:12 PM, Alexey Dobriyan <adobriyan@gmail.com> wrote: > struct net_generic { > - unsigned int len; > - struct rcu_head rcu; > + struct { > + unsigned int len; > + struct rcu_head rcu; > + } s; > > void *ptr[0]; > }; I think you can put them in a union, since rcu is only used for kfree_rcu() where len is not needed and rcu_head doesn't need to be initialized by callers.
On Thu, Dec 1, 2016 at 9:42 PM, Cong Wang <xiyou.wangcong@gmail.com> wrote: > On Thu, Dec 1, 2016 at 5:12 PM, Alexey Dobriyan <adobriyan@gmail.com> wrote: >> struct net_generic { >> - unsigned int len; >> - struct rcu_head rcu; >> + struct { >> + unsigned int len; >> + struct rcu_head rcu; >> + } s; >> >> void *ptr[0]; >> }; > > I think you can put them in a union, since rcu is only used > for kfree_rcu() where len is not needed and rcu_head doesn't > need to be initialized by callers. Never mind, readers could be still reading ->len while we modify ->rcu. So they can't be in a union.
--- a/include/net/netns/generic.h +++ b/include/net/netns/generic.h @@ -25,8 +25,10 @@ */ struct net_generic { - unsigned int len; - struct rcu_head rcu; + struct { + unsigned int len; + struct rcu_head rcu; + } s; void *ptr[0]; }; --- a/net/core/net_namespace.c +++ b/net/core/net_namespace.c @@ -50,7 +50,7 @@ static struct net_generic *net_alloc_generic(void) ng = kzalloc(generic_size, GFP_KERNEL); if (ng) - ng->len = max_gen_ptrs; + ng->s.len = max_gen_ptrs; return ng; } @@ -64,7 +64,7 @@ static int net_assign_generic(struct net *net, unsigned int id, void *data) old_ng = rcu_dereference_protected(net->gen, lockdep_is_held(&net_mutex)); - if (old_ng->len >= id) { + if (old_ng->s.len >= id) { old_ng->ptr[id - 1] = data; return 0; } @@ -84,11 +84,11 @@ static int net_assign_generic(struct net *net, unsigned int id, void *data) * the old copy for kfree after a grace period. */ - memcpy(&ng->ptr, &old_ng->ptr, old_ng->len * sizeof(void*)); + memcpy(&ng->ptr, &old_ng->ptr, old_ng->s.len * sizeof(void*)); ng->ptr[id - 1] = data; rcu_assign_pointer(net->gen, ng); - kfree_rcu(old_ng, rcu); + kfree_rcu(old_ng, s.rcu); return 0; }
This is precursor to fixing "[id - 1]" bloat inside net_generic(). Name "s" is chosen to complement name "u" often used for dummy unions. Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com> --- include/net/netns/generic.h | 6 ++++-- net/core/net_namespace.c | 8 ++++---- 2 files changed, 8 insertions(+), 6 deletions(-)