linux-kernel - Re: [PATCH 1/2] Move kfree_call_rcu() to slab

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Date:   Thu, 4 Jan 2018 14:18:50 -0800
From:   Rao Shoaib <rao.shoaib@...cle.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Boqun Feng <boqun.feng@...il.com>, linux-kernel@...r.kernel.org,
        paulmck@...ux.vnet.ibm.com, brouer@...hat.com, linux-mm@...ck.org
Subject: Re: [PATCH 1/2] Move kfree_call_rcu() to slab_common.c



On 01/04/2018 01:46 PM, Matthew Wilcox wrote:
> On Thu, Jan 04, 2018 at 01:27:49PM -0800, Rao Shoaib wrote:
>> On 01/04/2018 12:35 PM, Rao Shoaib wrote:
>>> As far as your previous comments are concerned, only the following one
>>> has not been addressed. Can you please elaborate as I do not understand
>>> the comment. The code was expanded because the new macro expansion check
>>> fails. Based on Matthew Wilcox's comment I have reverted rcu_head_name
>>> back to rcu_head.
>> It turns out I did not remember the real reason for the change. With the
>> macro rewritten, using rcu_head as a macro argument does not work because it
>> conflicts with the name of the type 'struct rcu_head' used in the macro. I
>> have renamed the macro argument to rcu_name.
>>
>> Shoaib
>>>> +#define kfree_rcu(ptr, rcu_head_name) \
>>>> +    do { \
>>>> +        typeof(ptr) __ptr = ptr;    \
>>>> +        unsigned long __off = offsetof(typeof(*(__ptr)), \
>>>> +                              rcu_head_name); \
>>>> +        struct rcu_head *__rptr = (void *)__ptr + __off; \
>>>> +        __kfree_rcu(__rptr, __off); \
>>>> +    } while (0)
>>> why do you want to open code this?
> But why are you changing this macro at all?  If it was to avoid the
> double-mention of "ptr", then you haven't done that.
I have -- I do not get the error because ptr is being assigned only one. 
If you have a better way than let me know and I will be happy to make 
the change.

Shoaib.