Merge tag 'probes-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace

Pull probes updates from Masami Hiramatsu:
 "Cleanups:

   - kprobes: Fixes typo in kprobes samples

   - tracing/eprobes: Remove 'break' after return

  kretprobe/fprobe performance improvements:

   - lib: Introduce new `objpool`, which is a high performance lockless
     object queue. This uses per-cpu ring array to allocate/release
     objects from the pre-allocated object pool.

     Since the index of ring array is a 32bit sequential counter, we can
     retry to push/pop the object pointer from the ring without lock (as
     seq-lock does)

   - lib: Add an objpool test module to test the functionality and
     evaluate the performance under some circumstances

   - kprobes/fprobe: Improve kretprobe and rethook scalability
     performance with objpool.

     This improves both legacy kretprobe and fprobe exit handler (which
     is based on rethook) to be scalable on SMP systems. Even with
     8-threads parallel test, it shows a great scalability improvement

   - Remove unneeded freelist.h which is replaced by objpool

   - objpool: Add maintainers entry for the objpool

   - objpool: Fix to remove unused include header lines"

* tag 'probes-v6.7' of git://git.kernel.org/pub/scm/linux/kernel/git/trace/linux-trace:
  kprobes: unused header files removed
  MAINTAINERS: objpool added
  kprobes: freelist.h removed
  kprobes: kretprobe scalability improvement
  lib: objpool test module added
  lib: objpool added: ring-array based lockless MPMC
  tracing/eprobe: drop unneeded breaks
  samples: kprobes: Fixes a typo

1 files changed, 39 insertions, 51 deletions

diff --git a/kernel/trace/rethook.c b/kernel/trace/rethook.c
index 5eb9b598f4e9..6fd7d4ecbbc6 100644
--- a/kernel/trace/rethook.c
+++ b/kernel/trace/rethook.c
@@ -8,7 +8,6 @@
 #include <linux/preempt.h>
 #include <linux/rethook.h>
 #include <linux/slab.h>
-#include <linux/sort.h>
 
 /* Return hook list (shadow stack by list) */
 
@@ -36,21 +35,7 @@ void rethook_flush_task(struct task_struct *tk)
 static void rethook_free_rcu(struct rcu_head *head)
 {
 	struct rethook *rh = container_of(head, struct rethook, rcu);
-	struct rethook_node *rhn;
-	struct freelist_node *node;
-	int count = 1;
-
-	node = rh->pool.head;
-	while (node) {
-		rhn = container_of(node, struct rethook_node, freelist);
-		node = node->next;
-		kfree(rhn);
-		count++;
-	}
-
-	/* The rh->ref is the number of pooled node + 1 */
-	if (refcount_sub_and_test(count, &rh->ref))
-		kfree(rh);
+	objpool_fini(&rh->pool);
 }
 
 /**
@@ -83,54 +68,62 @@ void rethook_free(struct rethook *rh)
 	call_rcu(&rh->rcu, rethook_free_rcu);
 }
 
+static int rethook_init_node(void *nod, void *context)
+{
+	struct rethook_node *node = nod;
+
+	node->rethook = context;
+	return 0;
+}
+
+static int rethook_fini_pool(struct objpool_head *head, void *context)
+{
+	kfree(context);
+	return 0;
+}
+
 /**
  * rethook_alloc() - Allocate struct rethook.
  * @data: a data to pass the @handler when hooking the return.
- * @handler: the return hook callback function.
+ * @handler: the return hook callback function, must NOT be NULL
+ * @size: node size: rethook node and additional data
+ * @num: number of rethook nodes to be preallocated
  *
  * Allocate and initialize a new rethook with @data and @handler.
- * Return NULL if memory allocation fails or @handler is NULL.
+ * Return pointer of new rethook, or error codes for failures.
+ *
  * Note that @handler == NULL means this rethook is going to be freed.
  */
-struct rethook *rethook_alloc(void *data, rethook_handler_t handler)
+struct rethook *rethook_alloc(void *data, rethook_handler_t handler,
+			      int size, int num)
 {
-	struct rethook *rh = kzalloc(sizeof(struct rethook), GFP_KERNEL);
+	struct rethook *rh;
 
-	if (!rh || !handler) {
-		kfree(rh);
-		return NULL;
-	}
+	if (!handler || num <= 0 || size < sizeof(struct rethook_node))
+		return ERR_PTR(-EINVAL);
+
+	rh = kzalloc(sizeof(struct rethook), GFP_KERNEL);
+	if (!rh)
+		return ERR_PTR(-ENOMEM);
 
 	rh->data = data;
 	rh->handler = handler;
-	rh->pool.head = NULL;
-	refcount_set(&rh->ref, 1);
 
+	/* initialize the objpool for rethook nodes */
+	if (objpool_init(&rh->pool, num, size, GFP_KERNEL, rh,
+			 rethook_init_node, rethook_fini_pool)) {
+		kfree(rh);
+		return ERR_PTR(-ENOMEM);
+	}
 	return rh;
 }
 
-/**
- * rethook_add_node() - Add a new node to the rethook.
- * @rh: the struct rethook.
- * @node: the struct rethook_node to be added.
- *
- * Add @node to @rh. User must allocate @node (as a part of user's
- * data structure.) The @node fields are initialized in this function.
- */
-void rethook_add_node(struct rethook *rh, struct rethook_node *node)
-{
-	node->rethook = rh;
-	freelist_add(&node->freelist, &rh->pool);
-	refcount_inc(&rh->ref);
-}
-
 static void free_rethook_node_rcu(struct rcu_head *head)
 {
 	struct rethook_node *node = container_of(head, struct rethook_node, rcu);
+	struct rethook *rh = node->rethook;
 
-	if (refcount_dec_and_test(&node->rethook->ref))
-		kfree(node->rethook);
-	kfree(node);
+	objpool_drop(node, &rh->pool);
 }
 
 /**
@@ -145,7 +138,7 @@ void rethook_recycle(struct rethook_node *node)
 	lockdep_assert_preemption_disabled();
 
 	if (likely(READ_ONCE(node->rethook->handler)))
-		freelist_add(&node->freelist, &node->rethook->pool);
+		objpool_push(node, &node->rethook->pool);
 	else
 		call_rcu(&node->rcu, free_rethook_node_rcu);
 }
@@ -161,7 +154,6 @@ NOKPROBE_SYMBOL(rethook_recycle);
 struct rethook_node *rethook_try_get(struct rethook *rh)
 {
 	rethook_handler_t handler = READ_ONCE(rh->handler);
-	struct freelist_node *fn;
 
 	lockdep_assert_preemption_disabled();
 
@@ -178,11 +170,7 @@ struct rethook_node *rethook_try_get(struct rethook *rh)
 	if (unlikely(!rcu_is_watching()))
 		return NULL;
 
-	fn = freelist_try_get(&rh->pool);
-	if (!fn)
-		return NULL;
-
-	return container_of(fn, struct rethook_node, freelist);
+	return (struct rethook_node *)objpool_pop(&rh->pool);
 }
 NOKPROBE_SYMBOL(rethook_try_get);