io_uring: add abstraction around apoll cache

In preparation for adding limits, and one more user, abstract out the
core bits of the allocation+free cache.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 41 insertions, 0 deletions

diff --git a/io_uring/alloc_cache.h b/io_uring/alloc_cache.h
new file mode 100644
index 000000000000..98f2374c37c7
--- /dev/null
+++ b/io_uring/alloc_cache.h
@@ -0,0 +1,41 @@
+#ifndef IOU_ALLOC_CACHE_H
+#define IOU_ALLOC_CACHE_H
+
+struct io_cache_entry {
+	struct hlist_node	node;
+};
+
+static inline void io_alloc_cache_put(struct io_alloc_cache *cache,
+				      struct io_cache_entry *entry)
+{
+	hlist_add_head(&entry->node, &cache->list);
+}
+
+static inline struct io_cache_entry *io_alloc_cache_get(struct io_alloc_cache *cache)
+{
+	if (!hlist_empty(&cache->list)) {
+		struct hlist_node *node = cache->list.first;
+
+		hlist_del(node);
+		return container_of(node, struct io_cache_entry, node);
+	}
+
+	return NULL;
+}
+
+static inline void io_alloc_cache_init(struct io_alloc_cache *cache)
+{
+	INIT_HLIST_HEAD(&cache->list);
+}
+
+static inline void io_alloc_cache_free(struct io_alloc_cache *cache,
+					void (*free)(struct io_cache_entry *))
+{
+	while (!hlist_empty(&cache->list)) {
+		struct hlist_node *node = cache->list.first;
+
+		hlist_del(node);
+		free(container_of(node, struct io_cache_entry, node));
+	}
+}
+#endif