Re: [PATCH v2 net] net: free ip_vs_dest structs when refcnt=0

[Simon Horman]

On Fri, Jan 27, 2017 at 01:21:11PM +0100, Pablo Neira Ayuso wrote:
> On Fri, Jan 27, 2017 at 09:07:38AM +0100, Simon Horman wrote:
> > On Thu, Jan 26, 2017 at 10:49:10PM +0200, Julian Anastasov wrote:
> > > 
> > >   Hello,
> > > 
> > > On Mon, 23 Jan 2017, David Windsor wrote:
> > > 
> > > > Currently, the ip_vs_dest cache frees ip_vs_dest objects when their
> > > > reference count becomes < 0.  Aside from not being semantically sound,
> > > > this is problematic for the new type refcount_t, which will be 
> > > > introduced
> > > > shortly in a separate patch. refcount_t is the new kernel type for
> > > > holding reference counts, and provides overflow protection and a
> > > > constrained interface relative to atomic_t (the type currently being
> > > > used for kernel reference counts).
> > > > 
> > > > Per Julian Anastasov: "The problem is that dest_trash currently holds
> > > > deleted dests (unlinked from RCU lists) with refcnt=0."  Changing
> > > > dest_trash to hold dest with refcnt=1 will allow us to free ip_vs_dest
> > > > structs when their refcnt=0, in ip_vs_dest_put_and_free().
> > > > 
> > > > Signed-off-by: David Windsor 
> > > 
> > >   Thanks! I tested the first version and this one
> > > just adds the needed changes in comments, so
> > > 
> > > Signed-off-by: Julian Anastasov 
> > > 
> > >   Simon and Pablo, this is more appropriate for
> > > ipvs-next/nf-next. Please apply!
> > 
> > Pablo, would you mind taking this one directly into nf-next?
> > 
> > Signed-off-by: Simon Horman 
> 
> Sure, no problem. I'll take it. Thanks!

Thanks!
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Re: [PATCH v2 net] net: free ip_vs_dest structs when refcnt=0

[Simon Horman]

On Thu, Jan 26, 2017 at 10:49:10PM +0200, Julian Anastasov wrote:
> 
>   Hello,
> 
> On Mon, 23 Jan 2017, David Windsor wrote:
> 
> > Currently, the ip_vs_dest cache frees ip_vs_dest objects when their
> > reference count becomes < 0.  Aside from not being semantically sound,
> > this is problematic for the new type refcount_t, which will be introduced
> > shortly in a separate patch. refcount_t is the new kernel type for
> > holding reference counts, and provides overflow protection and a
> > constrained interface relative to atomic_t (the type currently being
> > used for kernel reference counts).
> > 
> > Per Julian Anastasov: "The problem is that dest_trash currently holds
> > deleted dests (unlinked from RCU lists) with refcnt=0."  Changing
> > dest_trash to hold dest with refcnt=1 will allow us to free ip_vs_dest
> > structs when their refcnt=0, in ip_vs_dest_put_and_free().
> > 
> > Signed-off-by: David Windsor 
> 
>   Thanks! I tested the first version and this one
> just adds the needed changes in comments, so
> 
> Signed-off-by: Julian Anastasov 
> 
>   Simon and Pablo, this is more appropriate for
> ipvs-next/nf-next. Please apply!

Pablo, would you mind taking this one directly into nf-next?

Signed-off-by: Simon Horman 

> 
> > ---
> >  include/net/ip_vs.h| 2 +-
> >  net/netfilter/ipvs/ip_vs_ctl.c | 8 +++-
> >  2 files changed, 4 insertions(+), 6 deletions(-)
> > 
> > diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
> > index cd6018a..a3e78ad 100644
> > --- a/include/net/ip_vs.h
> > +++ b/include/net/ip_vs.h
> > @@ -1421,7 +1421,7 @@ static inline void ip_vs_dest_put(struct ip_vs_dest 
> > *dest)
> >  
> >  static inline void ip_vs_dest_put_and_free(struct ip_vs_dest *dest)
> >  {
> > -   if (atomic_dec_return(>refcnt) < 0)
> > +   if (atomic_dec_and_test(>refcnt))
> > kfree(dest);
> >  }
> >  
> > diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> > index 55e0169..5fc4836 100644
> > --- a/net/netfilter/ipvs/ip_vs_ctl.c
> > +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> > @@ -711,7 +711,6 @@ ip_vs_trash_get_dest(struct ip_vs_service *svc, int 
> > dest_af,
> >   dest->vport == svc->port))) {
> > /* HIT */
> > list_del(>t_list);
> > -   ip_vs_dest_hold(dest);
> > goto out;
> > }
> > }
> > @@ -741,7 +740,7 @@ static void ip_vs_dest_free(struct ip_vs_dest *dest)
> >   *  When the ip_vs_control_clearup is activated by ipvs module exit,
> >   *  the service tables must have been flushed and all the connections
> >   *  are expired, and the refcnt of each destination in the trash must
> > - *  be 0, so we simply release them here.
> > + *  be 1, so we simply release them here.
> >   */
> >  static void ip_vs_trash_cleanup(struct netns_ipvs *ipvs)
> >  {
> > @@ -1080,11 +1079,10 @@ static void __ip_vs_del_dest(struct netns_ipvs 
> > *ipvs, struct ip_vs_dest *dest,
> > if (list_empty(>dest_trash) && !cleanup)
> > mod_timer(>dest_trash_timer,
> >   jiffies + (IP_VS_DEST_TRASH_PERIOD >> 1));
> > -   /* dest lives in trash without reference */
> > +   /* dest lives in trash with reference */
> > list_add(>t_list, >dest_trash);
> > dest->idle_start = 0;
> > spin_unlock_bh(>dest_trash_lock);
> > -   ip_vs_dest_put(dest);
> >  }
> >  
> >  
> > @@ -1160,7 +1158,7 @@ static void ip_vs_dest_trash_expire(unsigned long 
> > data)
> >  
> > spin_lock(>dest_trash_lock);
> > list_for_each_entry_safe(dest, next, >dest_trash, t_list) {
> > -   if (atomic_read(>refcnt) > 0)
> > +   if (atomic_read(>refcnt) > 1)
> > continue;
> > if (dest->idle_start) {
> > if (time_before(now, dest->idle_start +
> > -- 
> > 2.7.4
> 
> Regards
> 
> --
> Julian Anastasov 
> 
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Re: [PATCH v2 net] net: free ip_vs_dest structs when refcnt=0

[Julian Anastasov]

Hello,

On Mon, 23 Jan 2017, David Windsor wrote:

> Currently, the ip_vs_dest cache frees ip_vs_dest objects when their
> reference count becomes < 0.  Aside from not being semantically sound,
> this is problematic for the new type refcount_t, which will be introduced
> shortly in a separate patch. refcount_t is the new kernel type for
> holding reference counts, and provides overflow protection and a
> constrained interface relative to atomic_t (the type currently being
> used for kernel reference counts).
> 
> Per Julian Anastasov: "The problem is that dest_trash currently holds
> deleted dests (unlinked from RCU lists) with refcnt=0."  Changing
> dest_trash to hold dest with refcnt=1 will allow us to free ip_vs_dest
> structs when their refcnt=0, in ip_vs_dest_put_and_free().
> 
> Signed-off-by: David Windsor 

Thanks! I tested the first version and this one
just adds the needed changes in comments, so

Signed-off-by: Julian Anastasov 

Simon and Pablo, this is more appropriate for
ipvs-next/nf-next. Please apply!

> ---
>  include/net/ip_vs.h| 2 +-
>  net/netfilter/ipvs/ip_vs_ctl.c | 8 +++-
>  2 files changed, 4 insertions(+), 6 deletions(-)
> 
> diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
> index cd6018a..a3e78ad 100644
> --- a/include/net/ip_vs.h
> +++ b/include/net/ip_vs.h
> @@ -1421,7 +1421,7 @@ static inline void ip_vs_dest_put(struct ip_vs_dest 
> *dest)
>  
>  static inline void ip_vs_dest_put_and_free(struct ip_vs_dest *dest)
>  {
> - if (atomic_dec_return(>refcnt) < 0)
> + if (atomic_dec_and_test(>refcnt))
>   kfree(dest);
>  }
>  
> diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
> index 55e0169..5fc4836 100644
> --- a/net/netfilter/ipvs/ip_vs_ctl.c
> +++ b/net/netfilter/ipvs/ip_vs_ctl.c
> @@ -711,7 +711,6 @@ ip_vs_trash_get_dest(struct ip_vs_service *svc, int 
> dest_af,
> dest->vport == svc->port))) {
>   /* HIT */
>   list_del(>t_list);
> - ip_vs_dest_hold(dest);
>   goto out;
>   }
>   }
> @@ -741,7 +740,7 @@ static void ip_vs_dest_free(struct ip_vs_dest *dest)
>   *  When the ip_vs_control_clearup is activated by ipvs module exit,
>   *  the service tables must have been flushed and all the connections
>   *  are expired, and the refcnt of each destination in the trash must
> - *  be 0, so we simply release them here.
> + *  be 1, so we simply release them here.
>   */
>  static void ip_vs_trash_cleanup(struct netns_ipvs *ipvs)
>  {
> @@ -1080,11 +1079,10 @@ static void __ip_vs_del_dest(struct netns_ipvs *ipvs, 
> struct ip_vs_dest *dest,
>   if (list_empty(>dest_trash) && !cleanup)
>   mod_timer(>dest_trash_timer,
> jiffies + (IP_VS_DEST_TRASH_PERIOD >> 1));
> - /* dest lives in trash without reference */
> + /* dest lives in trash with reference */
>   list_add(>t_list, >dest_trash);
>   dest->idle_start = 0;
>   spin_unlock_bh(>dest_trash_lock);
> - ip_vs_dest_put(dest);
>  }
>  
>  
> @@ -1160,7 +1158,7 @@ static void ip_vs_dest_trash_expire(unsigned long data)
>  
>   spin_lock(>dest_trash_lock);
>   list_for_each_entry_safe(dest, next, >dest_trash, t_list) {
> - if (atomic_read(>refcnt) > 0)
> + if (atomic_read(>refcnt) > 1)
>   continue;
>   if (dest->idle_start) {
>   if (time_before(now, dest->idle_start +
> -- 
> 2.7.4

Regards

--
Julian Anastasov 
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[PATCH v2 net] net: free ip_vs_dest structs when refcnt=0

[David Windsor]

Currently, the ip_vs_dest cache frees ip_vs_dest objects when their
reference count becomes < 0.  Aside from not being semantically sound,
this is problematic for the new type refcount_t, which will be introduced
shortly in a separate patch. refcount_t is the new kernel type for
holding reference counts, and provides overflow protection and a
constrained interface relative to atomic_t (the type currently being
used for kernel reference counts).

Per Julian Anastasov: "The problem is that dest_trash currently holds
deleted dests (unlinked from RCU lists) with refcnt=0."  Changing
dest_trash to hold dest with refcnt=1 will allow us to free ip_vs_dest
structs when their refcnt=0, in ip_vs_dest_put_and_free().

Signed-off-by: David Windsor 
---
 include/net/ip_vs.h| 2 +-
 net/netfilter/ipvs/ip_vs_ctl.c | 8 +++-
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/include/net/ip_vs.h b/include/net/ip_vs.h
index cd6018a..a3e78ad 100644
--- a/include/net/ip_vs.h
+++ b/include/net/ip_vs.h
@@ -1421,7 +1421,7 @@ static inline void ip_vs_dest_put(struct ip_vs_dest *dest)
 
 static inline void ip_vs_dest_put_and_free(struct ip_vs_dest *dest)
 {
-   if (atomic_dec_return(>refcnt) < 0)
+   if (atomic_dec_and_test(>refcnt))
kfree(dest);
 }
 
diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index 55e0169..5fc4836 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -711,7 +711,6 @@ ip_vs_trash_get_dest(struct ip_vs_service *svc, int dest_af,
  dest->vport == svc->port))) {
/* HIT */
list_del(>t_list);
-   ip_vs_dest_hold(dest);
goto out;
}
}
@@ -741,7 +740,7 @@ static void ip_vs_dest_free(struct ip_vs_dest *dest)
  *  When the ip_vs_control_clearup is activated by ipvs module exit,
  *  the service tables must have been flushed and all the connections
  *  are expired, and the refcnt of each destination in the trash must
- *  be 0, so we simply release them here.
+ *  be 1, so we simply release them here.
  */
 static void ip_vs_trash_cleanup(struct netns_ipvs *ipvs)
 {
@@ -1080,11 +1079,10 @@ static void __ip_vs_del_dest(struct netns_ipvs *ipvs, 
struct ip_vs_dest *dest,
if (list_empty(>dest_trash) && !cleanup)
mod_timer(>dest_trash_timer,
  jiffies + (IP_VS_DEST_TRASH_PERIOD >> 1));
-   /* dest lives in trash without reference */
+   /* dest lives in trash with reference */
list_add(>t_list, >dest_trash);
dest->idle_start = 0;
spin_unlock_bh(>dest_trash_lock);
-   ip_vs_dest_put(dest);
 }
 
 
@@ -1160,7 +1158,7 @@ static void ip_vs_dest_trash_expire(unsigned long data)
 
spin_lock(>dest_trash_lock);
list_for_each_entry_safe(dest, next, >dest_trash, t_list) {
-   if (atomic_read(>refcnt) > 0)
+   if (atomic_read(>refcnt) > 1)
continue;
if (dest->idle_start) {
if (time_before(now, dest->idle_start +
-- 
2.7.4

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