Subject: Re: [PATCH 1/2] Move kfree_call_rcu() to slab_common.c
To: Matthew Wilcox <willy@infradead.org>
Cc: Boqun Feng <boqun.feng@gmail.com>, linux-kernel@vger.kernel.org,
        paulmck@linux.vnet.ibm.com, brouer@redhat.com, linux-mm@kvack.org
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 <3be609d4-800e-a89e-f885-7e0f5d288862@oracle.com>
 <20180104013807.GA31392@tardis>
 <be1abd24-56c8-45bc-fecc-3f0c5b978678@oracle.com>
 <64ca3929-4044-9393-a6ca-70c0a2589a35@oracle.com>
 <20180104214658.GA20740@bombadil.infradead.org>
From: Rao Shoaib <rao.shoaib@oracle.com>
Message-ID: <3e4ea0b9-686f-7e36-d80c-8577401517e2@oracle.com>
Date: Thu, 4 Jan 2018 14:18:50 -0800
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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.