Messages in this thread | | | Date | Thu, 26 Nov 2015 12:37:08 +0100 | Subject | Re: block-rbd: One function call less in rbd_dev_probe_parent() after error detection | From | Ilya Dryomov <> |
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On Thu, Nov 26, 2015 at 8:54 AM, SF Markus Elfring <elfring@users.sourceforge.net> wrote: >>> I interpreted the eventual passing of a null pointer to the rbd_dev_destroy() >>> function as an indication for further source code adjustments. >> >> If all error paths could be adjusted so that NULL pointers are never passed in, >> destroy functions wouldn't need to have a NULL check, would they? > > How do you think about to clarify corresponding implementation details a bit more? > > * Why was the function "rbd_dev_probe_parent" implemented in the way > that it relies on a sanity check in the function "rbd_dev_destroy" then?
Because it's not a bad thing? What's wrong with an init to NULL, a possible assignment, in this case from rbd_dev_create(), and an unconditional rbd_dev_destroy()?
The NULL check in rbd_dev_destroy() is not a sanity check, it's a feature. It's not there to "fixup" callers that pass NULL - it's there because it is _expected_ that some callers will pass NULL.
> * How are the chances to restructure the source code a bit (like changing a few > jump labels) so that it should also work without an extra function call > during error handling there?
As I said in my reply to Dan, the problem with rbd_dev_probe_parent() is the calling code which expects it to call unparent if ->parent_spec. This makes it stand out and confuses people, but can't be fixed without refactoring a bunch of other code.
The extra function call is *not* a problem.
Thanks,
Ilya
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