cachefiles: Implement object lifecycle funcs

Implement allocate, get, see and put functions for the cachefiles_object
struct.  The members of the struct we're going to need are also added.

Additionally, implement a lifecycle tracepoint.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
Link: https://lore.kernel.org/r/163819639457.215744.4600093239395728232.stgit@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/163906939569.143852.3594314410666551982.stgit@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/163967148857.1823006.6332962598220464364.stgit@warthog.procyon.org.uk/ # v3
Link: https://lore.kernel.org/r/164021547762.640689.8422781599594931000.stgit@warthog.procyon.org.uk/ # v4

1 files changed, 86 insertions, 0 deletions

diff --git a/fs/cachefiles/interface.c b/fs/cachefiles/interface.c
index 1793e46bd3e7..68bb7b6c4945 100644
--- a/fs/cachefiles/interface.c
+++ b/fs/cachefiles/interface.c
@@ -13,6 +13,92 @@
 #include <trace/events/fscache.h>
 #include "internal.h"
 
+static atomic_t cachefiles_object_debug_id;
+
+/*
+ * Allocate a cache object record.
+ */
+static
+struct cachefiles_object *cachefiles_alloc_object(struct fscache_cookie *cookie)
+{
+	struct fscache_volume *vcookie = cookie->volume;
+	struct cachefiles_volume *volume = vcookie->cache_priv;
+	struct cachefiles_object *object;
+
+	_enter("{%s},%x,", vcookie->key, cookie->debug_id);
+
+	object = kmem_cache_zalloc(cachefiles_object_jar, GFP_KERNEL);
+	if (!object)
+		return NULL;
+
+	refcount_set(&object->ref, 1);
+
+	spin_lock_init(&object->lock);
+	INIT_LIST_HEAD(&object->cache_link);
+	object->volume = volume;
+	object->debug_id = atomic_inc_return(&cachefiles_object_debug_id);
+	object->cookie = fscache_get_cookie(cookie, fscache_cookie_get_attach_object);
+
+	fscache_count_object(vcookie->cache);
+	trace_cachefiles_ref(object->debug_id, cookie->debug_id, 1,
+			     cachefiles_obj_new);
+	return object;
+}
+
+/*
+ * Note that an object has been seen.
+ */
+void cachefiles_see_object(struct cachefiles_object *object,
+			   enum cachefiles_obj_ref_trace why)
+{
+	trace_cachefiles_ref(object->debug_id, object->cookie->debug_id,
+			     refcount_read(&object->ref), why);
+}
+
+/*
+ * Increment the usage count on an object;
+ */
+struct cachefiles_object *cachefiles_grab_object(struct cachefiles_object *object,
+						 enum cachefiles_obj_ref_trace why)
+{
+	int r;
+
+	__refcount_inc(&object->ref, &r);
+	trace_cachefiles_ref(object->debug_id, object->cookie->debug_id, r, why);
+	return object;
+}
+
+/*
+ * dispose of a reference to an object
+ */
+void cachefiles_put_object(struct cachefiles_object *object,
+			   enum cachefiles_obj_ref_trace why)
+{
+	unsigned int object_debug_id = object->debug_id;
+	unsigned int cookie_debug_id = object->cookie->debug_id;
+	struct fscache_cache *cache;
+	bool done;
+	int r;
+
+	done = __refcount_dec_and_test(&object->ref, &r);
+	trace_cachefiles_ref(object_debug_id, cookie_debug_id, r, why);
+	if (done) {
+		_debug("- kill object OBJ%x", object_debug_id);
+
+		ASSERTCMP(object->file, ==, NULL);
+
+		kfree(object->d_name);
+
+		cache = object->volume->cache->cache;
+		fscache_put_cookie(object->cookie, fscache_cookie_put_object);
+		object->cookie = NULL;
+		kmem_cache_free(cachefiles_object_jar, object);
+		fscache_uncount_object(cache);
+	}
+
+	_leave("");
+}
+
 const struct fscache_cache_ops cachefiles_cache_ops = {
 	.name			= "cachefiles",
 	.acquire_volume		= cachefiles_acquire_volume,