Commit 092d00ea authored by Thomas Gleixner's avatar Thomas Gleixner
Browse files

cleanup: Provide retain_and_null_ptr() 



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_and_null_ptr(), which NULLs the cleanup
pointer. That makes it easy to analyze and reason about.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarJonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: default avatarJames Bottomley <James.Bottomley@HansenPartnership.com>
Link: https://lore.kernel.org/all/20250319105506.083538907@linutronix.de
parent 0af2f6be

include/linux/cleanup.h

+19 −0
Original line number Diff line number Diff line
@@ -216,6 +216,25 @@ const volatile void * __must_check_fn(const volatile void *val) 


#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_and_null_ptr(f);

 *	return ret;

 *

 * After retain_and_null_ptr(f) the variable f is NULL and cannot be

 * dereferenced anymore.

 */

#define retain_and_null_ptr(p)		((void)__get_and_null(p, NULL))



/*

 * DEFINE_CLASS(name, type, exit, init, init_args...):