Re: [PATCH] Btrfs: add support for asserts

[Jeff Mahoney <jeffm@suse.com>]

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On 8/27/13 5:21 PM, Eric Sandeen wrote:
> On 8/27/13 4:07 PM, Jeff Mahoney wrote:
>> On 8/27/13 4:56 PM, Josef Bacik wrote:
>>> On Tue, Aug 27, 2013 at 03:28:24PM -0400, Jeff Mahoney wrote:
>>>> On 8/26/13 4:56 PM, Josef Bacik wrote:
>>>>> One of the complaints we get a lot is how many BUG_ON()'s we have.  So to help
>>>>> with this I'm introducing a kconfig option to enable/disable a new ASSERT()
>>>>> mechanism much like what XFS does.  This will allow us developers to still get
>>>>> our nice panics but allow users/distros to compile them out.  With this we can
>>>>> go through and convert any BUG_ON()'s that we have to catch actual programming
>>>>> mistakes to the new ASSERT() and then fix everybody else to return errors.  This
>>>>> will also allow developers to leave sanity checks in their new code to make sure
>>>>> we don't trip over problems while testing stuff and vetting new features.
>>>>> Thanks,
>>>>
>>>> I don't think the complaint is so much about the number of BUG_ONs, but
>>>> that there's no distinction between something that is supposed to be
>>>> impossible and something that is improbable. The BUG_ONs to keep code
>>>> correctness are good and are littered all over the kernel with positive
>>>> results. The BUG_ONs that are there in place of real error handling
>>>> served their purpose and need to be replaced.
>>>>
>>>> So, I don't know if it's a net win to compile the "good" BUG_ONs out of
>>>> the code. Especially if a user runs into something strange yet familiar
>>>> and the first response is "oh, huh, can you rebuild with asserts enabled?"
>>>>
>>>
>>> Either I provide an option for it or distros do it themselves, this cuts out the
>>> middle man.  I'd really rather they just be on all the time since they aren't
>>> things we should hit anyway, but at least this way people have a choice.
> 
>> Ok. With my distro hat on, I can tell you I'll be leaving them on. :)
> 
>> -Jeff
> 
> XFS also has XFS_WARN as a config option, which keeps all the assertions
> in place, but printk's & backtraces w/o the icky BUG().  That might be
> good to add as well, and perhaps best for a shipping distro (vs. a developer
> debugging who might want to drop a core file when the assert trips).

Isn't that the distinction between BUG_ON and WARN_ON? If it's worth a
BUG_ON, things should be bad enough (or could result in being bad
enough) that we want to bail out.

-Jeff

-- 
Jeff Mahoney
SUSE Labs


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