Subject: Re: [PATCH] jfs: clear PAGECACHE_TAG_DIRTY for no-write pages
From: Peter Zijlstra <peterz@infradead.org>
To: Fengguang Wu <wfg@mail.ustc.edu.cn>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       shaggy@austin.ibm.com, jfs-discussion@lists.sourceforge.net,
       Nick Piggin <nickpiggin@yahoo.com.au>
In-Reply-To: <E1J8AC5-0002BE-RP@localhost>
References: <E1J8AC5-0002BE-RP@localhost>
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Date: Fri, 28 Dec 2007 12:33:46 +0100
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On Fri, 2007-12-28 at 16:03 +0800, Fengguang Wu wrote:
> Andrew,
> 
> This patch fixed the 'pdflush stuck in D state' bug
>         http://bugzilla.kernel.org/show_bug.cgi?id=9291
> and should be pushed to mainline ASAP.
> ---
> 
> When JFS decides to drop a dirty metapage, it simply clears the META_dirty bit
> and leave alone the PG_dirty and PAGECACHE_TAG_DIRTY bits.
> 
> When such no-write page goes to metapage_writepage(), the `relic'
> PAGECACHE_TAG_DIRTY tag should be cleared, to prevent pdflush from
> repeatedly trying to sync them.
> 
> Also, avoid the redirty when a bio submission is planned.
> 
> Tested-by: Markus Rehbach <Markus.Rehbach@gmx.de>
> Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn> 
> ---

> +++ b/fs/jfs/jfs_metapage.c

> @@ -449,9 +450,15 @@ static int metapage_writepage(struct page *page, struct writeback_control *wbc)
>  			goto dump_bio;
>  
>  		submit_bio(WRITE, bio);
> -	}
> -	if (redirty)
> +	} else if (redirty) {
>  		redirty_page_for_writepage(wbc, page);
> +	} else {
> +		write_lock_irq(&mapping->tree_lock);
> +		radix_tree_tag_clear(&mapping->page_tree,
> +				page_index(page),
> +				PAGECACHE_TAG_DIRTY);
> +		write_unlock_irq(&mapping->tree_lock);
> +	}

I'm not liking this open-coded tag_clear, although I currently fail to
come up with a nice solution.

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