From: firstname.lastname@example.org (Eric W. Biederman)
To: Andrew Morton <email@example.com>
Cc: Pavel Emelyanov <firstname.lastname@example.org>,
Subject: Re: [PATCH 1/7][QUOTA] Move sysctl management code under ifdef CONFIG_SYSCTL
Date: Tue, 04 Dec 2007 04:40:26 -0700 [thread overview]
Message-ID: <email@example.com> (raw)
In-Reply-To: <firstname.lastname@example.org> (Andrew Morton's message of "Tue, 4 Dec 2007 01:45:49 -0800")
Andrew Morton <email@example.com> writes:
> On Tue, 04 Dec 2007 12:31:37 +0300 Pavel Emelyanov <firstname.lastname@example.org> wrote:
>> Andrew Morton wrote:
>> > On Tue, 04 Dec 2007 11:58:30 +0300 Pavel Emelyanov <email@example.com> wrote:
>> >>>> +#ifdef CONFIG_SYSCTL
>> >>>> register_sysctl_table(sys_table);
>> >>>> +#endif
>> >>>> dquot_cachep = kmem_cache_create("dquot",
>> >>>> sizeof(struct dquot), sizeof(unsigned long) * 4,
>> >>> We should avoid the ifdefs around the register_sysctl_table() call.
>> >>> At present the !CONFIG_SYSCTL implementation of register_sysctl_table() is
>> >>> a non-inlined NULL-returning stub. All we have to do is to inline that
>> >>> then these ifdefs can go away.
>> >> What if some code checks for the return value to be not-NULL? In case
>> >> CONFIG_SYSCTL=n this code will always think, that the registration failed.
>> > The stub function should return success?
>> Well, I think yes. If some functionality is turned off, then the
>> caller should think that everything is going fine (or he should
>> explicitly removes the call to it with some other ifdef).
>> At least this is true for stubs that return the error code, not
>> the pointer. E.g. copy_semundo() always returns success if SYSVIPC
>> is off, or namespaces cloning routines act in a similar way.
>> Thus I though, that routines, that return pointers should better
>> report that everything is OK (somehow) to reduce the number of
>> "helpers" in the outer code. No?
> Dunno. Returning NULL should be OK. If anyone is dereferenceing that
> pointer with CONFIG_SYSCTL=n then they might need some attention?
We do have some current code in the network stack that fails miserably
when register_sysctl_table returns NULL, and there are explicit
checks for that.
I had forgotten about that.
I expect the right answer is to simply have code ignore the fact
that register_sysctl_xxxx returns NULL, and not error on it.
The alternative is to get fancy and have everyone check the
return code and make the return type an IS_ERR thing. That seems
a lot more trouble then it is worth.
We can probably define it as register_sysctl_xxxx always returns
a token that must be passed to unregister_sysctl, and no errors
will be reported except to dmesg. That at sounds simple sane
and supportable from where we are now.
next prev parent reply other threads:[~2007-12-04 11:41 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-30 12:58 [PATCH 0/7] Start using sysctl paths in the core kernel code Pavel Emelyanov
2007-11-30 13:02 ` [PATCH 1/7][QUOTA] Move sysctl management code under ifdef CONFIG_SYSCTL Pavel Emelyanov
2007-12-03 21:38 ` Andrew Morton
2007-12-03 23:32 ` Eric W. Biederman
2007-12-04 8:58 ` Pavel Emelyanov
2007-12-04 9:23 ` Andrew Morton
2007-12-04 9:31 ` Pavel Emelyanov
2007-12-04 9:45 ` Andrew Morton
2007-12-04 11:40 ` Eric W. Biederman [this message]
2007-12-04 11:48 ` Andrew Morton
2007-12-04 11:58 ` Pavel Emelyanov
2007-12-04 12:48 ` Eric W. Biederman
2007-11-30 13:04 ` [PATCH 2/7][QUOTA] Use sysctl paths to register tables Pavel Emelyanov
2007-11-30 13:09 ` [PATCH 3/7][SYSVIPC] Use the ctl " Pavel Emelyanov
2007-11-30 13:11 ` [PATCH 4/7][SCHED] " Pavel Emelyanov
2007-11-30 13:13 ` [PATCH 5/7][UTS] " Pavel Emelyanov
2007-11-30 13:16 ` [PATCH 6/7][MQUEUE] Move sysctl management code under ifdef CONFIG_SYSCTL Pavel Emelyanov
2007-11-30 13:18 ` [PATCH 7/7][MQUEUE] Use the ctl paths to register tables Pavel Emelyanov
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