linux-kernel - [PATCH 06/14] eCryptfs: replace call_rcu by kfree_rcu for simple kmem_cache

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Date: Sun,  9 Jun 2024 10:27:18 +0200
From: Julia Lawall <Julia.Lawall@...ia.fr>
To: Tyler Hicks <code@...icks.com>
Cc: kernel-janitors@...r.kernel.org,
	ecryptfs@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	"Paul E . McKenney" <paulmck@...nel.org>,
	Vlastimil Babka <vbabka@...e.cz>
Subject: [PATCH 06/14] eCryptfs: replace call_rcu by kfree_rcu for simple kmem_cache_free callback

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@...ia.fr>
Reviewed-by: Paul E. McKenney <paulmck@...nel.org>
Reviewed-by: Vlastimil Babka <vbabka@...e.cz>

---
 fs/ecryptfs/dentry.c |    8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/fs/ecryptfs/dentry.c b/fs/ecryptfs/dentry.c
index acaa0825e9bb..49d626ff33a9 100644
--- a/fs/ecryptfs/dentry.c
+++ b/fs/ecryptfs/dentry.c
@@ -51,12 +51,6 @@ static int ecryptfs_d_revalidate(struct dentry *dentry, unsigned int flags)
 
 struct kmem_cache *ecryptfs_dentry_info_cache;
 
-static void ecryptfs_dentry_free_rcu(struct rcu_head *head)
-{
-	kmem_cache_free(ecryptfs_dentry_info_cache,
-		container_of(head, struct ecryptfs_dentry_info, rcu));
-}
-
 /**
  * ecryptfs_d_release
  * @dentry: The ecryptfs dentry
@@ -68,7 +62,7 @@ static void ecryptfs_d_release(struct dentry *dentry)
 	struct ecryptfs_dentry_info *p = dentry->d_fsdata;
 	if (p) {
 		path_put(&p->lower_path);
-		call_rcu(&p->rcu, ecryptfs_dentry_free_rcu);
+		kfree_rcu(p, rcu);
 	}
 }