linux-kernel - Re: [PATCH] remove no longer use of pdflush interface

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Message-ID: <20120604125356.GB7738@localhost>
Date:	Mon, 4 Jun 2012 20:53:56 +0800
From:	Fengguang Wu <fengguang.wu@...el.com>
To:	Wanpeng Li <liwp.linux@...il.com>
Cc:	Alexander Viro <viro@...iv.linux.org.uk>, Jan Kara <jack@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	Minchan Kim <minchan.kim@...il.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	David Howells <dhowells@...hat.com>,
	James Morris <james.l.morris@...cle.com>,
	Ingo Molnar <mingo@...e.hu>, linux-doc@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	Wanpeng Li <liwp@...ux.vnet.ibm.com>
Subject: Re: [PATCH] remove no longer use of pdflush interface

Hi Wanpeng,

On Mon, Jun 04, 2012 at 08:40:42PM +0800, Wanpeng Li wrote:
> From: Wanpeng Li <liwp@...ux.vnet.ibm.com>
> 
> remove no longer use of pdflush interface nr_pdflush_threads.

The patch looks good in itself: the nr_pdflush_threads takes no effect
for many of the recent kernels. But what's the normal process of
interface removal?  Shall we carry some warning printk for some time
first or whatever?

Thanks,
Fengguang

> Signed-off-by: Wanpeng Li <liwp@...ux.vnet.ibm.com>
> ---
>  Documentation/sysctl/vm.txt |   11 -----------
>  fs/fs-writeback.c           |    5 -----
>  include/linux/writeback.h   |    5 -----
>  kernel/sysctl.c             |    7 -------
>  4 files changed, 28 deletions(-)
> 
> diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
> index 96f0ee8..71c17d2 100644
> --- a/Documentation/sysctl/vm.txt
> +++ b/Documentation/sysctl/vm.txt
> @@ -42,7 +42,6 @@ Currently, these files are in /proc/sys/vm:
>  - mmap_min_addr
>  - nr_hugepages
>  - nr_overcommit_hugepages
> -- nr_pdflush_threads
>  - nr_trim_pages         (only if CONFIG_MMU=n)
>  - numa_zonelist_order
>  - oom_dump_tasks
> @@ -426,16 +425,6 @@ See Documentation/vm/hugetlbpage.txt
>  
>  ==============================================================
>  
> -nr_pdflush_threads
> -
> -The current number of pdflush threads.  This value is read-only.
> -The value changes according to the number of dirty pages in the system.
> -
> -When necessary, additional pdflush threads are created, one per second, up to
> -nr_pdflush_threads_max.
> -
> -==============================================================
> -
>  nr_trim_pages
>  
>  This is available only on NOMMU kernels.
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 539f36c..30ddb8a 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -52,11 +52,6 @@ struct wb_writeback_work {
>  	struct completion *done;	/* set if the caller waits */
>  };
>  
> -/*
> - * We don't actually have pdflush, but this one is exported though /proc...
> - */
> -int nr_pdflush_threads;
> -
>  /**
>   * writeback_in_progress - determine whether there is writeback in progress
>   * @bdi: the device's backing_dev_info structure.
> diff --git a/include/linux/writeback.h b/include/linux/writeback.h
> index a2b84f5..13b5df7 100644
> --- a/include/linux/writeback.h
> +++ b/include/linux/writeback.h
> @@ -193,9 +193,4 @@ void tag_pages_for_writeback(struct address_space *mapping,
>  
>  void account_page_redirty(struct page *page);
>  
> -/* pdflush.c */
> -extern int nr_pdflush_threads;	/* Global so it can be exported to sysctl
> -				   read-only. */
> -
> -
>  #endif		/* WRITEBACK_H */
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index 4ab1187..e257b61 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1095,13 +1095,6 @@ static struct ctl_table vm_table[] = {
>  		.extra1		= &zero,
>  	},
>  	{
> -		.procname	= "nr_pdflush_threads",
> -		.data		= &nr_pdflush_threads,
> -		.maxlen		= sizeof nr_pdflush_threads,
> -		.mode		= 0444 /* read-only*/,
> -		.proc_handler	= proc_dointvec,
> -	},
> -	{
>  		.procname	= "swappiness",
>  		.data		= &vm_swappiness,
>  		.maxlen		= sizeof(vm_swappiness),
> -- 
> 1.7.9.5
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