selftests/bpf: Add a test for objects stuck in free_by_rcu_ttracegrafted

Delete all elements of BPF_F_NO_PREALLOC hash map in one batch. The first
free_bulk() starts RCU tasks trace GP and the rest of the elements are
freed while it's in flight. Wait for call_rcu_ttrace_in_progress to clear
in bpf_mem_cache of every cpu and check that free_by_rcu_ttrace and
waiting_for_gp_ttrace lists are empty.

Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20260930095920.601738-4-alexei.starovoitov@gmail.com
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

1 files changed, 44 insertions, 0 deletions

diff --git a/io_uring/alloc_cache.c b/io_uring/alloc_cache.c
new file mode 100644
index 000000000..58423888b
--- /dev/null
+++ b/io_uring/alloc_cache.c
@@ -0,0 +1,44 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "alloc_cache.h"
+
+void io_alloc_cache_free(struct io_alloc_cache *cache,
+			 void (*free)(const void *))
+{
+	void *entry;
+
+	if (!cache->entries)
+		return;
+
+	while ((entry = io_alloc_cache_get(cache)) != NULL)
+		free(entry);
+
+	kvfree(cache->entries);
+	cache->entries = NULL;
+}
+
+/* returns false if the cache was initialized properly */
+bool io_alloc_cache_init(struct io_alloc_cache *cache,
+			 unsigned max_nr, unsigned int size,
+			 unsigned int init_bytes)
+{
+	cache->entries = kvmalloc_array(max_nr, sizeof(void *), GFP_KERNEL);
+	if (!cache->entries)
+		return true;
+
+	cache->nr_cached = 0;
+	cache->max_cached = max_nr;
+	cache->elem_size = size;
+	cache->init_clear = init_bytes;
+	return false;
+}
+
+void *io_cache_alloc_new(struct io_alloc_cache *cache, gfp_t gfp)
+{
+	void *obj;
+
+	obj = kmalloc(cache->elem_size, gfp);
+	if (obj && cache->init_clear)
+		memset(obj, 0, cache->init_clear);
+	return obj;
+}