Hi Pablo, > -----Original Message----- > From: Pablo Neira Ayuso [mailto:pablo@xxxxxxxxxxxxx] > Sent: Wednesday, March 29, 2017 6:44 PM > To: Gao Feng <gfree.wind@xxxxxxxxxxx> > Cc: netfilter-devel@xxxxxxxxxxxxxxx; 'Gao Feng' <fgao@xxxxxxxxxx> > Subject: Re: [PATCH nf-next v2 1/1] netfilter: helper: Remove useless rcu lock > when get expectfn > > On Wed, Mar 29, 2017 at 06:29:10PM +0800, Gao Feng wrote: > > Hi Pablo, > > > > > -----Original Message----- > > > From: Pablo Neira Ayuso [mailto:pablo@xxxxxxxxxxxxx] > > > Sent: Wednesday, March 29, 2017 6:08 PM > > > To: gfree.wind@xxxxxxxxxxx > > > Cc: netfilter-devel@xxxxxxxxxxxxxxx; Gao Feng <fgao@xxxxxxxxxx> > > > Subject: Re: [PATCH nf-next v2 1/1] netfilter: helper: Remove > > > useless rcu > > lock > > > when get expectfn > > > > > > On Wed, Mar 22, 2017 at 10:15:02AM +0800, gfree.wind@xxxxxxxxxxx > wrote: > > > > From: Gao Feng <fgao@xxxxxxxxxx> > > > > > > > > Because these two functions return the nf_ct_helper_expectfn > > > > pointer which should be protected by rcu lock. So it should makes > > > > sure the caller should hold the rcu lock, not inside these functions. > > > > > > > > Signed-off-by: Gao Feng <fgao@xxxxxxxxxx> > > > > --- > > > > v2: Shorter subject, per Pablo > > > > v1: Initial version > > > > > > > > net/netfilter/nf_conntrack_helper.c | 6 ++---- > > > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > > > > > diff --git a/net/netfilter/nf_conntrack_helper.c > > > > b/net/netfilter/nf_conntrack_helper.c > > > > index 6dc44d9..bce3d1f 100644 > > > > --- a/net/netfilter/nf_conntrack_helper.c > > > > +++ b/net/netfilter/nf_conntrack_helper.c > > > > @@ -311,38 +311,36 @@ void nf_ct_helper_expectfn_unregister(struct > > > > nf_ct_helper_expectfn *n) } > > > > EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_unregister); > > > > > > > > +/* Caller should hold the rcu lock */ > > > > struct nf_ct_helper_expectfn * > > > > nf_ct_helper_expectfn_find_by_name(const char *name) { > > > > struct nf_ct_helper_expectfn *cur; > > > > bool found = false; > > > > > > > > - rcu_read_lock(); > > > > list_for_each_entry_rcu(cur, &nf_ct_helper_expectfn_list, head) { > > > > if (!strcmp(cur->name, name)) { > > > > found = true; > > > > break; > > > > } > > > > } > > > > - rcu_read_unlock(); > > > > return found ? cur : NULL; > > > > } > > > > EXPORT_SYMBOL_GPL(nf_ct_helper_expectfn_find_by_name); > > > > > > nf_ct_helper_expectfn_find_by_name() is called from ctnetlink, via > > > ctnetlink_create_expect() and rcu read side lock is not held there. > > There are two reasons. > > 1. The rcu lock would be added in my patch " netfilter: helper: Add > > the rcu lock when call __nf_conntrack_helper_find" for nf > > https://patchwork.ozlabs.org/patch/741865/. > > If you have interdependencies between two patches like this, it's better to > make it in one single go. > > > So the ctnetlink_create_expect would hold the rcu lock after apply > > that patch. > > > > 2. Because these two functions return one pointer which needs RCU > > lock, so the caller must hold rcu lock. > > Or it still meets one error even though there is one rcu lock in these > > two functions. > > Because the memory which the returned pointer point to would be freed > > already after rcu_read_unlock. > > So the rcu lock is unnecessary in these functions. > > That's right. You're fixing up a real problem, no doubt. > > I'm just questioning that I think that if you are fixing up rcu locking, which > seems to be the case, you just do it in one single patch. > > Thanks! Ok, I would merge them into one patch. Actually I couldn't get that what modifications could be done in the nf. I learnt only bug fix could be accepted in net.git, so I assumed the nf.git did too. Best Regards Feng -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
