Re: [patch V4 01/14] cleanup: Provide retain_ptr()

James Bottomley
2025-03-19T20:15:38Z

On Wed, 2025-03-19 at 11:56 +0100, Thomas Gleixner wrote:
> 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@linutronix.de>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> ---
> V4: Cast to void so can't be used as return_ptr() replacement - James

Reviewed-by: James Bottomley <James.Bottomley@HansenPartnership.com>