Re: [PATCH net] Revert "defer call to mem_cgroup_sk_alloc()"
On Fri, 2018-02-02 at 19:04 +, Roman Gushchin wrote: > On Fri, Feb 02, 2018 at 10:39:04AM -0800, Eric Dumazet wrote: > > On Fri, 2018-02-02 at 18:06 +, Roman Gushchin wrote: > > > > > > Idk, how even we can hit it? And if so, what scary will happen? > > > > > > If you prefer to have it there, I definitely can return it, > > > but I see no profit so far. > > > > I was simply curious this was not mentioned in the changelog. > > > > A revert is normally a true revert, modulo the changes needed by > > conflicts and possible changes. > > > > I personally do not care of this BUG_ON(), I had not put it in the > > first place. > > Technically it's not a true revert, but you're totally right. > Let me add a note to the commit description. > > Are you ok with the rest? Sure ! Thanks.
Re: [PATCH net] Revert "defer call to mem_cgroup_sk_alloc()"
On Fri, Feb 02, 2018 at 10:39:04AM -0800, Eric Dumazet wrote: > On Fri, 2018-02-02 at 18:06 +, Roman Gushchin wrote: > > > > Idk, how even we can hit it? And if so, what scary will happen? > > > > If you prefer to have it there, I definitely can return it, > > but I see no profit so far. > > I was simply curious this was not mentioned in the changelog. > > A revert is normally a true revert, modulo the changes needed by > conflicts and possible changes. > > I personally do not care of this BUG_ON(), I had not put it in the > first place. Technically it's not a true revert, but you're totally right. Let me add a note to the commit description. Are you ok with the rest? Thanks!
Re: [PATCH net] Revert "defer call to mem_cgroup_sk_alloc()"
On Fri, 2018-02-02 at 18:06 +, Roman Gushchin wrote: > > Idk, how even we can hit it? And if so, what scary will happen? > > If you prefer to have it there, I definitely can return it, > but I see no profit so far. I was simply curious this was not mentioned in the changelog. A revert is normally a true revert, modulo the changes needed by conflicts and possible changes. I personally do not care of this BUG_ON(), I had not put it in the first place. Thanks.
Re: [PATCH net] Revert "defer call to mem_cgroup_sk_alloc()"
On Fri, Feb 02, 2018 at 09:59:27AM -0800, Eric Dumazet wrote:
> On Fri, 2018-02-02 at 16:57 +, Roman Gushchin wrote:
> > This patch effectively reverts commit 9f1c2674b328 ("net: memcontrol:
> > defer call to mem_cgroup_sk_alloc()").
> >
> > Moving mem_cgroup_sk_alloc() to the inet_csk_accept() completely breaks
> > memcg socket memory accounting, as packets received before memcg
> > pointer initialization are not accounted and are causing refcounting
> > underflow on socket release.
> >
> > Actually the free-after-use problem was fixed by
> > commit c0576e397508 ("net: call cgroup_sk_alloc() earlier in
> > sk_clone_lock()") for the cgroup pointer.
> >
> > So, let's revert it and call mem_cgroup_sk_alloc() just before
> > cgroup_sk_alloc(). This is safe, as we hold a reference to the socket
> > we're cloning, and it holds a reference to the memcg.
> >
> > Signed-off-by: Roman Gushchin
> > Cc: Eric Dumazet
> > Cc: David S. Miller
> > Cc: Johannes Weiner
> > Cc: Tejun Heo
> > ---
> > mm/memcontrol.c | 14 ++
> > net/core/sock.c | 5 +
> > net/ipv4/inet_connection_sock.c | 1 -
> > 3 files changed, 15 insertions(+), 5 deletions(-)
> >
> > diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> > index 0ae2dc3a1748..0937f2c52c7d 100644
> > --- a/mm/memcontrol.c
> > +++ b/mm/memcontrol.c
> > @@ -5747,6 +5747,20 @@ void mem_cgroup_sk_alloc(struct sock *sk)
> > if (!mem_cgroup_sockets_enabled)
> > return;
> >
> > + /*
> > +* Socket cloning can throw us here with sk_memcg already
> > +* filled. It won't however, necessarily happen from
> > +* process context. So the test for root memcg given
> > +* the current task's memcg won't help us in this case.
> > +*
> > +* Respecting the original socket's memcg is a better
> > +* decision in this case.
> > +*/
> > + if (sk->sk_memcg) {
>
> Original commit had a BUG_ON(mem_cgroup_is_root(sk->sk_memcg));
>
> I presume it is no longer useful ?
Idk, how even we can hit it? And if so, what scary will happen?
If you prefer to have it there, I definitely can return it,
but I see no profit so far.
Thanks!
Re: [PATCH net] Revert "defer call to mem_cgroup_sk_alloc()"
On Fri, 2018-02-02 at 16:57 +, Roman Gushchin wrote:
> This patch effectively reverts commit 9f1c2674b328 ("net: memcontrol:
> defer call to mem_cgroup_sk_alloc()").
>
> Moving mem_cgroup_sk_alloc() to the inet_csk_accept() completely breaks
> memcg socket memory accounting, as packets received before memcg
> pointer initialization are not accounted and are causing refcounting
> underflow on socket release.
>
> Actually the free-after-use problem was fixed by
> commit c0576e397508 ("net: call cgroup_sk_alloc() earlier in
> sk_clone_lock()") for the cgroup pointer.
>
> So, let's revert it and call mem_cgroup_sk_alloc() just before
> cgroup_sk_alloc(). This is safe, as we hold a reference to the socket
> we're cloning, and it holds a reference to the memcg.
>
> Signed-off-by: Roman Gushchin
> Cc: Eric Dumazet
> Cc: David S. Miller
> Cc: Johannes Weiner
> Cc: Tejun Heo
> ---
> mm/memcontrol.c | 14 ++
> net/core/sock.c | 5 +
> net/ipv4/inet_connection_sock.c | 1 -
> 3 files changed, 15 insertions(+), 5 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 0ae2dc3a1748..0937f2c52c7d 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5747,6 +5747,20 @@ void mem_cgroup_sk_alloc(struct sock *sk)
> if (!mem_cgroup_sockets_enabled)
> return;
>
> + /*
> + * Socket cloning can throw us here with sk_memcg already
> + * filled. It won't however, necessarily happen from
> + * process context. So the test for root memcg given
> + * the current task's memcg won't help us in this case.
> + *
> + * Respecting the original socket's memcg is a better
> + * decision in this case.
> + */
> + if (sk->sk_memcg) {
Original commit had a BUG_ON(mem_cgroup_is_root(sk->sk_memcg));
I presume it is no longer useful ?
Thanks
> + css_get(>sk_memcg->css);
> + return;
> + }
> +
> rcu_read_lock();
