[dm-devel] dm: remove pointless comparison
Milan Broz
gmazyland at gmail.com
Tue Jan 7 17:28:15 UTC 2014
On 01/07/2014 04:52 PM, Mike Snitzer wrote:
> On Tue, Jan 07 2014 at 5:39am -0500,
> Joe Thornber <thornber at redhat.com> wrote:
>
>> On Mon, Jan 06, 2014 at 10:53:28PM -0500, Mikulas Patocka wrote:
>>> Remove pointless comparison in dm_get_from_kobject. The comparison is
>>> always true and the compiler optimizes it out anyway.
>>>gmane.linux.kernel.device-mapper.devel
>>> Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
>>>
>>> ---
>>> drivers/md/dm.c | 2 --
>>> 1 file changed, 2 deletions(-)
>>>
>>> Index: linux-3.13-rc7/drivers/md/dm.c
>>> ===================================================================
>>> --- linux-3.13-rc7.orig/drivers/md/dm.c 2014-01-07 01:28:27.000000000 +0100
>>> +++ linux-3.13-rc7/drivers/md/dm.c 2014-01-07 01:28:39.000000000 +0100
>>> @@ -2922,8 +2922,6 @@ struct mapped_device *dm_get_from_kobjec
>>> struct mapped_device *md;
>>>
>>> md = container_of(kobj, struct mapped_device, kobj);
>>> - if (&md->kobj != kobj)
>>> - return NULL;
>>
>> What were they trying to check? The compiler?
>>
>
> Milan's commit 784aae735d, and the current dm.c code, offers this
> comment above dm_get_from_kobject:
>
> /*
> * struct mapped_device should not be exported outside of dm.c
> * so use this check to verify that kobj is part of md structure
> */
>
> I'm lacking the vision to _know_ why the kobject would suddenly be
> outside of the mapped_device without us knowing via code change..
>
> The check does seem overly cautious/useless (if we remove it the above
> comment should be removed too).
Yes, please remove both :) The check doesn't make sense.
I think it is just relict of some experiments before I committed this simple
embedded sysfs kobj handling (there were always problems like the missing .release
function you are just solving in other thread).
Milan
More information about the dm-devel
mailing list