In cases where an allocation is consumed by another function, the
allocation needs to be retained on success or freed on failure. The code
pattern is usually:
struct foo *f = kzalloc(sizeof(*f), GFP_KERNEL);
struct bar *b;
,,,
// Initialize f
...
if (ret)
goto free;
...
bar = bar_create(f);
if (!bar) {
ret = -ENOMEM;
goto free;
}
...
return 0;
free:
kfree(f);
return ret;
This prevents using __free(kfree) on @f because there is no canonical way
to tell the cleanup code that the allocation should not be freed.
Abusing no_free_ptr() by force ignoring the return value is not really a
sensible option either.
Provide an explicit macro retain_ptr(), which NULLs the cleanup
pointer. That makes it easy to analyze and reason about.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
include/linux/cleanup.h | 17 +++++++++++++++++
1 file changed, 17 insertions(+)
--- a/include/linux/cleanup.h
+++ b/include/linux/cleanup.h
@@ -216,6 +216,23 @@ const volatile void * __must_check_fn(co
#define return_ptr(p) return no_free_ptr(p)
+/*
+ * Only for situations where an allocation is handed in to another function
+ * and consumed by that function on success.
+ *
+ * struct foo *f __free(kfree) = kzalloc(sizeof(*f), GFP_KERNEL);
+ *
+ * setup(f);
+ * if (some_condition)
+ * return -EINVAL;
+ * ....
+ * ret = bar(f);
+ * if (!ret)
+ * retain_ptr(f);
+ * return ret;
+ */
+#define retain_ptr(p) \
+ __get_and_null(p, NULL)
/*
* DEFINE_CLASS(name, type, exit, init, init_args...):
