linux-kernel - Re: [PATCH -next] fs: fix fs/fs-writeback.c build error

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Date:	Sat, 07 Jan 2012 10:17:05 -0800
From:	Randy Dunlap <rdunlap@...otime.net>
To:	Wu Fengguang <fengguang.wu@...el.com>
CC:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH -next] fs: fix fs/fs-writeback.c build error

On 01/07/2012 05:30 AM, Wu Fengguang wrote:
> On Fri, Jan 06, 2012 at 03:01:09PM -0800, Linus Torvalds wrote:
>> On Thu, Jan 5, 2012 at 4:18 PM, Randy Dunlap <rdunlap@...otime.net> wrote:
>>>
>>> In linux-next, fs/fs-writeback.c no longer #includes <linux/buffer_head.h>,
>>> which #included <linux/pagemap.h>, so add that latter header file to
>>> <linux/writeback.h> to fix the build error:
>>>
>>> fs/fs-writeback.c:510:11: error: 'PAGE_CACHE_SHIFT' undeclared (first use in this function)
>>
>> I would actually suggest:
>>
>>  - move the whole MIN_WRITEBACK_PAGES #define from the header file to
>> fs/writeback.c
> 
> Done.
> 
>> (why expose such a random #define to outside users that
>> have nothing to do with it?)
>  
> Yeah, there were some early patches that reference MIN_WRITEBACK_PAGES
> from other files, which are dropped later..
> 
>>  - make sure that fs/fs-writeback.c has that pagemap.h #include.
> 
> Done. (otherwise it won't compile)
> 
>> There's no reason why <linux/writeback.h> should include filemap.h per
>> se, and there is no reason why it should expose some internal chunking
>> #define to anybody else.
> 
> Good point. I'll queue this patch to writeback-for-next:
> 
> Subject: writeback: move MIN_WRITEBACK_PAGES to fs-writeback.c
> Date: Sat Jan 07 20:41:55 CST 2012
> 
> Fix compile error
> 
>  fs/fs-writeback.c:515:33: error: ‘PAGE_CACHE_SHIFT’ undeclared (first use in this function)
> 
> Reported-by: Randy Dunlap <rdunlap@...otime.net>
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>

Acked-by: Randy Dunlap <rdunlap@...otime.net>

Thanks.

> ---
>  fs/fs-writeback.c         |    6 ++++++
>  include/linux/writeback.h |    5 -----
>  2 files changed, 6 insertions(+), 5 deletions(-)
> 
> --- next.orig/fs/fs-writeback.c	2012-01-07 21:01:34.552000061 +0800
> +++ next/fs/fs-writeback.c	2012-01-07 21:22:45.504000051 +0800
> @@ -20,6 +20,7 @@
>  #include <linux/sched.h>
>  #include <linux/fs.h>
>  #include <linux/mm.h>
> +#include <linux/pagemap.h>
>  #include <linux/kthread.h>
>  #include <linux/freezer.h>
>  #include <linux/writeback.h>
> @@ -29,6 +30,11 @@
>  #include "internal.h"
>  
>  /*
> + * 4MB minimal write chunk size
> + */
> +#define MIN_WRITEBACK_PAGES	(4096UL >> (PAGE_CACHE_SHIFT - 10))
> +
> +/*
>   * Passed into wb_writeback(), essentially a subset of writeback_control
>   */
>  struct wb_writeback_work {
> --- next.orig/include/linux/writeback.h	2012-01-07 21:01:34.544000059 +0800
> +++ next/include/linux/writeback.h	2012-01-07 21:13:09.008000026 +0800
> @@ -25,11 +25,6 @@ DECLARE_PER_CPU(int, dirty_throttle_leak
>  #define DIRTY_SCOPE		8
>  #define DIRTY_FULL_SCOPE	(DIRTY_SCOPE / 2)
>  
> -/*
> - * 4MB minimal write chunk size
> - */
> -#define MIN_WRITEBACK_PAGES	(4096UL >> (PAGE_CACHE_SHIFT - 10))
> -
>  struct backing_dev_info;
>  
>  /*


-- 
~Randy
*** Remember to use Documentation/SubmitChecklist when testing your code ***
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