Re: [PATCH 08/14] nfsd: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

Chuck Lever
2024-06-09T15:43:55Z

On Sun, Jun 09, 2024 at 10:27:20AM +0200, Julia Lawall wrote:
> Since SLOB was removed, 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.
>
> // <smpl>
> @r@
> expression e;
> local idexpression e2;
> identifier cb,f;
> position p;
> @@
>
> (
> call_rcu(...,e2)
> |
> call_rcu(&e->f,cb@p)
> )
>
> @r1@
> type T;
> identifier x,r.cb;
> @@
>
> cb(...) {
> (
> kmem_cache_free(...);
> |
> T x = ...;
> kmem_cache_free(...,x);
> |
> T x;
> x = ...;
> kmem_cache_free(...,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;
> position r.p;
> @@
>
> - call_rcu(&e->f,cb@p)
> + kfree_rcu(e,f)
>
> @r1a depends on !s@
> type T;
> identifier x,r.cb;
> @@
>
> - cb(...) {
> (
> - kmem_cache_free(...);
> |
> - T x = ...;
> - kmem_cache_free(...,x);
> |
> - T x;
> - x = ...;
> - kmem_cache_free(...,x);
> )
> - }
> // </smpl>
>
> Signed-off-by: Julia Lawall <Julia.Lawall@inria.fr>
> Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
> Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
>
> ---
> fs/nfsd/nfs4state.c | 9 +--------
> 1 file changed, 1 insertion(+), 8 deletions(-)
>
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index a20c2c9d7d45..eba5083504c7 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -571,13 +571,6 @@ opaque_hashval(const void *ptr, int nbytes)
> return x;
> }
>
> -static void nfsd4_free_file_rcu(struct rcu_head *rcu)
> -{
> - struct nfs4_file *fp = container_of(rcu, struct nfs4_file, fi_rcu);
> -
> - kmem_cache_free(file_slab, fp);
> -}
> -
> void
> put_nfs4_file(struct nfs4_file *fi)
> {
> @@ -585,7 +578,7 @@ put_nfs4_file(struct nfs4_file *fi)
> nfsd4_file_hash_remove(fi);
> WARN_ON_ONCE(!list_empty(&fi->fi_clnt_odstate));
> WARN_ON_ONCE(!list_empty(&fi->fi_delegations));
> - call_rcu(&fi->fi_rcu, nfsd4_free_file_rcu);
> + kfree_rcu(fi, fi_rcu);
> }
> }
>
>

Acked-by: Chuck Lever <chuck.lever@oracle.com>

--
Chuck Lever