[PATCH 03/14] KVM: PPC: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

Julia Lawall
2024-06-09T08:28:03Z

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>

---
arch/powerpc/kvm/book3s_mmu_hpte.c | 8 +-------
1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_mmu_hpte.c b/arch/powerpc/kvm/book3s_mmu_hpte.c
index ce79ac33e8d3..d904e13e069b 100644
--- a/arch/powerpc/kvm/book3s_mmu_hpte.c
+++ b/arch/powerpc/kvm/book3s_mmu_hpte.c
@@ -92,12 +92,6 @@ void kvmppc_mmu_hpte_cache_map(struct kvm_vcpu *vcpu, struct hpte_cache *pte)
spin_unlock(&vcpu3s->mmu_lock);
}

-static void free_pte_rcu(struct rcu_head *head)
-{
- struct hpte_cache *pte = container_of(head, struct hpte_cache, rcu_head);
- kmem_cache_free(hpte_cache, pte);
-}
-
static void invalidate_pte(struct kvm_vcpu *vcpu, struct hpte_cache *pte)
{
struct kvmppc_vcpu_book3s *vcpu3s = to_book3s(vcpu);
@@ -126,7 +120,7 @@ static void invalidate_pte(struct kvm_vcpu *vcpu, struct hpte_cache *pte)

spin_unlock(&vcpu3s->mmu_lock);

- call_rcu(&pte->rcu_head, free_pte_rcu);
+ kfree_rcu(pte, rcu_head);
}

static void kvmppc_mmu_pte_flush_all(struct kvm_vcpu *vcpu)