On Fri, 15 Feb 2019 10:38:04 +0000
Vlad Buslov <vla...@mellanox.com> wrote:
> On Thu 14 Feb 2019 at 20:34, Stefano Brivio <sbri...@redhat.com> wrote:
> > On Thu, 14 Feb 2019 09:47:02 +0200
> > Vlad Buslov <vla...@mellanox.com> wrote:
> >
> >> As a preparation for using classifier spinlock instead of relying on
> >> external rtnl lock, rearrange code in fl_change. The goal is to group the
> >> code which changes classifier state in single block in order to allow
> >> following commits in this set to protect it from parallel modification with
> >> tp->lock. Data structures that require tp->lock protection are mask
> >> hashtable and filters list, and classifier handle_idr.
> >>
> >> fl_hw_replace_filter() is a sleeping function and cannot be called while
> >> holding a spinlock. In order to execute all sequence of changes to shared
> >> classifier data structures atomically, call fl_hw_replace_filter() before
> >> modifying them.
> >>
> >> Signed-off-by: Vlad Buslov <vla...@mellanox.com>
> >> Acked-by: Jiri Pirko <j...@mellanox.com>
> >> ---
> >> net/sched/cls_flower.c | 85
> >> ++++++++++++++++++++++++++------------------------
> >> 1 file changed, 44 insertions(+), 41 deletions(-)
> >>
> >> diff --git a/net/sched/cls_flower.c b/net/sched/cls_flower.c
> >> index 88d7af78ba7e..91596a6271f8 100644
> >> --- a/net/sched/cls_flower.c
> >> +++ b/net/sched/cls_flower.c
> >> @@ -1354,90 +1354,93 @@ static int fl_change(struct net *net, struct
> >> sk_buff *in_skb,
> >> if (err < 0)
> >> goto errout;
> >>
> >> - if (!handle) {
> >> - handle = 1;
> >> - err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
> >> - INT_MAX, GFP_KERNEL);
> >> - } else if (!fold) {
> >> - /* user specifies a handle and it doesn't exist */
> >> - err = idr_alloc_u32(&head->handle_idr, fnew, &handle,
> >> - handle, GFP_KERNEL);
> >> - }
> >> - if (err)
> >> - goto errout;
> >> - fnew->handle = handle;
> >> -
> >>
> >> [...]
> >>
> >> if (fold) {
> >> + fnew->handle = handle;
> >
> > I'm probably missing something, but what if fold is passed and the
> > handle isn't specified? That can still happen, right? In that case we
> > wouldn't be allocating the handle.
>
> Hi Stefano,
>
> Thank you for reviewing my code.
>
> Cls API lookups fold by handle, so this pointer can only be not NULL
> when user specified a handle and filter with such handle exists on tp.
Ah, of course. Thanks for clarifying. By the way, what tricked me here
was this check in fl_change():
if (fold && handle && fold->handle != handle)
...
which could be turned into:
if (fold && fold->handle != handle)
...
at this point.
--
Stefano
