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Date: Sun, 18 Jun 2006 19:04:22 -0700
From: Andrew Morton <akpm@osdl.org>
To: Neil Brown <neilb@suse.de>
Cc: dgc@sgi.com, jblunck@suse.de, linux-kernel@vger.kernel.org,
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Subject: Re: [patch 0/5] [PATCH,RFC] vfs: per-superblock unused dentries
 list (2nd version)
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On Mon, 19 Jun 2006 11:21:04 +1000
Neil Brown <neilb@suse.de> wrote:

> static void prune_dcache(int count, struct super_block *sb)
> +static void prune_dcache(int count, struct list_head *list)
>  {
> +	int have_list = list != NULL;
> +	struct list_head alt_head;
>  	spin_lock(&dcache_lock);
> +	if (list == NULL) {
> +		/* use the dentry_unused list */
> +		list_add(&alt_head, &dentry_unused);
> +		list_del_init(&dentry_unused);
> +		list = &alt_head;
> +	}

This will make dentry_unused appear to be empty.

>  	for (; count ; count--) {
>  		struct dentry *dentry;
>  		struct list_head *tmp;
> @@ -405,23 +417,11 @@ static void prune_dcache(int count, stru
>  
>  		cond_resched_lock(&dcache_lock);

And then it makes that apparent-emptiness globally visible.

Won't this cause concurrent unmounting or memory shrinking to malfunction?