netdev - Re: [PATCH 00/17] replace call_rcu by kfree_rcu for simple kmem_cache

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Message-ID: <47a98e77-8bbf-48d7-bb52-50e85a5336a0@paulmck-laptop>
Date: Sun, 13 Oct 2024 17:31:30 -0700
From: "Paul E. McKenney" <paulmck@...nel.org>
To: Julia Lawall <Julia.Lawall@...ia.fr>
Cc: linux-nfs@...r.kernel.org, kernel-janitors@...r.kernel.org,
	vbabka@...e.cz, Tom Talpey <tom@...pey.com>,
	Dai Ngo <Dai.Ngo@...cle.com>,
	Olga Kornievskaia <okorniev@...hat.com>, Neil Brown <neilb@...e.de>,
	linux-can@...r.kernel.org, bridge@...ts.linux.dev,
	b.a.t.m.a.n@...ts.open-mesh.org, linux-kernel@...r.kernel.org,
	wireguard@...ts.zx2c4.com, netdev@...r.kernel.org,
	ecryptfs@...r.kernel.org, linux-block@...r.kernel.org,
	Nicholas Piggin <npiggin@...il.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	Naveen N Rao <naveen@...nel.org>,
	Madhavan Srinivasan <maddy@...ux.ibm.com>,
	linuxppc-dev@...ts.ozlabs.org, kvm@...r.kernel.org,
	netfilter-devel@...r.kernel.org, coreteam@...filter.org
Subject: Re: [PATCH 00/17] replace call_rcu by kfree_rcu for simple
 kmem_cache_free callback

On Sun, Oct 13, 2024 at 10:16:47PM +0200, Julia Lawall wrote:
> Since SLOB was removed and since
> commit 6c6c47b063b5 ("mm, slab: call kvfree_rcu_barrier() from kmem_cache_destroy()"),
> it is not necessary to use call_rcu when the callback only performs
> kmem_cache_free. Use kfree_rcu() directly.
> 
> The changes were done using the following Coccinelle semantic patch.
> This semantic patch is designed to ignore cases where the callback
> function is used in another way.

For the series:

Acked-by: Paul E. McKenney <paulmck@...nel.org>

> // <smpl>
> #spatch --all-includes --include-headers
> 
> @r@
> expression e;
> local idexpression e2;
> identifier cb,f,g;
> position p;
> @@
> 
> (
> call_rcu(...,e2)
> |
> call_rcu(&e->f,cb@p)
> |
> call_rcu(&e->f.g,cb@p)
> )
> 
> @r1@
> type T,T1;
> identifier x,r.cb;
> @@
> 
>  cb(...) {
> (
>    kmem_cache_free(...);
> |
>    T x = ...;
>    kmem_cache_free(...,(T1)x);
> |
>    T x;
>    x = ...;
>    kmem_cache_free(...,(T1)x);
> )
>  }
> 
> @s depends on r1@
> position p != r.p;
> identifier r.cb;
> @@
> 
>  cb@p
> 
> @script:ocaml@
> cb << r.cb;
> p << s.p;
> @@
> 
> Printf.eprintf "Other use of %s at %s:%d\n" cb (List.hd p).file (List.hd p).line
> 
> @depends on r1 && !s@
> expression e;
> identifier r.cb,f,g;
> position r.p;
> @@
> 
> (
> - call_rcu(&e->f,cb@p)
> + kfree_rcu(e,f)
> |
> - call_rcu(&e->f.g,cb@p)
> + kfree_rcu(e,f.g)
> )
> 
> @r1a depends on !s@
> type T,T1;
> identifier x,r.cb;
> @@
> 
> - cb(...) {
> (
> -  kmem_cache_free(...);
> |
> -  T x = ...;
> -  kmem_cache_free(...,(T1)x);
> |
> -  T x;
> -  x = ...;
> -  kmem_cache_free(...,(T1)x);
> )
> - }
> 
> @r2 depends on !r1@
> identifier r.cb;
> @@
> 
> cb(...) {
>  ...
> }
> 
> @script:ocaml depends on !r1 && !r2@
> cb << r.cb;
> @@
> 
> Printf.eprintf "need definition for %s\n" cb
> // </smpl>
> 
> ---
> 
>  arch/powerpc/kvm/book3s_mmu_hpte.c  |    8 ------
>  block/blk-ioc.c                     |    9 ------
>  drivers/net/wireguard/allowedips.c  |    9 +-----
>  fs/ecryptfs/dentry.c                |    8 ------
>  fs/nfsd/nfs4state.c                 |    9 ------
>  kernel/time/posix-timers.c          |    9 ------
>  net/batman-adv/translation-table.c  |   47 ++----------------------------------
>  net/bridge/br_fdb.c                 |    9 ------
>  net/can/gw.c                        |   13 ++-------
>  net/ipv4/fib_trie.c                 |    8 ------
>  net/ipv4/inetpeer.c                 |    9 +-----
>  net/ipv6/ip6_fib.c                  |    9 ------
>  net/ipv6/xfrm6_tunnel.c             |    8 ------
>  net/kcm/kcmsock.c                   |   10 -------
>  net/netfilter/nf_conncount.c        |   10 -------
>  net/netfilter/nf_conntrack_expect.c |   10 -------
>  net/netfilter/xt_hashlimit.c        |    9 ------
>  17 files changed, 23 insertions(+), 171 deletions(-)