Messages in this thread | | | Subject | Re: [PATCH v1 3/3] net: simplify sk_page_frag | From | Paolo Abeni <> | Date | Fri, 09 Dec 2022 17:44:54 +0100 |
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On Mon, 2022-11-21 at 08:35 -0500, Benjamin Coddington wrote: > Now that in-kernel socket users that may recurse during reclaim have benn > converted to sk_use_task_frag = false, we can have sk_page_frag() simply > check that value. > > Signed-off-by: Benjamin Coddington <bcodding@redhat.com> > --- > include/net/sock.h | 9 ++------- > 1 file changed, 2 insertions(+), 7 deletions(-) > > diff --git a/include/net/sock.h b/include/net/sock.h > index ffba9e95470d..fac24c6ee30d 100644 > --- a/include/net/sock.h > +++ b/include/net/sock.h > @@ -2539,19 +2539,14 @@ static inline void sk_stream_moderate_sndbuf(struct sock *sk) > * Both direct reclaim and page faults can nest inside other > * socket operations and end up recursing into sk_page_frag() > * while it's already in use: explicitly avoid task page_frag > - * usage if the caller is potentially doing any of them. > - * This assumes that page fault handlers use the GFP_NOFS flags or > - * explicitly disable sk_use_task_frag. > + * when users disable sk_use_task_frag. > * > * Return: a per task page_frag if context allows that, > * otherwise a per socket one. > */ > static inline struct page_frag *sk_page_frag(struct sock *sk) > { > - if (sk->sk_use_task_frag && > - (sk->sk_allocation & (__GFP_DIRECT_RECLAIM | __GFP_MEMALLOC | > - __GFP_FS)) == > - (__GFP_DIRECT_RECLAIM | __GFP_FS)) > + if (sk->sk_use_task_frag) > return ¤t->task_frag; > > return &sk->sk_frag;
To make the above as safe as possible I think we should double-check the in-kernel users explicitly setting sk_allocation to GFP_ATOMIC, as that has the side effect of disabling the task_frag usage, too.
Patch 2/3 already catches some of such users, and we can safely leave alone few others, (specifically l2tp, fou and inet_ctl_sock_create()).
Even wireguard and tls looks safe IMHO.
So the only left-over should be espintcp, I suggest updating patch 2/3 clearing sk_use_task_frag even in espintcp_init_sk().
Other than that LGTM.
Cheers,
Paolo
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