On Mon, 12 Feb 2024 at 14:04, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
>
> This works because the internals of virtio_fs_cleanup_dax(), "kill_dax()
> and put_dax()", know how to handle a NULL @dax_dev. It is still early
> days with the "cleanup" helpers, but I wonder if anyone else cares that
> the DEFINE_FREE() above does not check for NULL?
Well, the main reason for DEFINE_FREE() to check for NULL is not
correctness, but code generation. See the comment about kfree() in
<linux/cleanup.h>:
* NOTE: the DEFINE_FREE()'s @free expression includes a NULL test even though
* kfree() is fine to be called with a NULL value. This is on purpose. This way
* the compiler sees the end of our alloc_obj() function as [...]
with the full explanation there.
Now, whether the code wants to actually use the cleanup() helpers for
a single use-case is debatable.
But yes, if it does, I suspect it should use !IS_ERR_OR_NULL(ptr).
Linus
