linux-kernel - Re: [PATCH] Store sysfs dirent structs in rbtree

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Date:	Thu, 24 Jun 2010 20:04:24 +0200
From:	Cornelia Huck <cornelia.huck@...ibm.com>
To:	Nathan Fontenot <nfont@...tin.ibm.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Store sysfs dirent structs in rbtree

On Wed, 23 Jun 2010 21:56:04 -0500,
Nathan Fontenot <nfont@...tin.ibm.com> wrote:

> +static void sysfs_dirent_insert(struct sysfs_dirent *sd)
> +{
> +	struct sysfs_dirent *parent_sd = sd->s_parent;
> +	struct sysfs_dirent *d;
> +	struct rb_node **p = &parent_sd->s_dir.rb_root.rb_node;
> +	struct rb_node *parent = NULL;
> +
> +	while (*p) {
> +		int cmp_val;
> +		parent = *p;
> +		d = to_sysfs_dirent(parent);
> +
> +		cmp_val = strcmp(d->s_name, sd->s_name);
> +		if (cmp_val < 0)
> +			p = &parent->rb_left;
> +		if (cmp_val > 0)
> +			p = &parent->rb_right;
> +	}
> +
> +	rb_link_node(&sd->s_dir.rb_node, parent, p);
> +	rb_insert_color(&sd->s_dir.rb_node, &parent_sd->s_dir.rb_root);
> +}

This will run into trouble if you have duplicate names in different
namespaces. You won't see it with your patch though, since...

> @@ -536,14 +572,24 @@
>  				       const void *ns,
>  				       const unsigned char *name)
>  {
> -	struct sysfs_dirent *sd;
> -
> -	for (sd = parent_sd->s_dir.children; sd; sd = sd->s_sibling) {
> -		if (ns && sd->s_ns && (sd->s_ns != ns))
> -			continue;
> -		if (!strcmp(sd->s_name, name))
> -			return sd;
> +	struct sysfs_dirent *d;
> +	struct rb_node **p = &parent_sd->s_dir.rb_root.rb_node;
> +	struct rb_node *parent = NULL;
> +
> +	while (*p) {
> +		int cmp_val;
> +		parent = *p;
> +		d = to_sysfs_dirent(parent);
> +
> +		cmp_val = strcmp(d->s_name, name);
> +		if (cmp_val == 0)
> +			return d;
> +		else if (cmp_val < 0)
> +			p = &parent->rb_left;
> +		else /* (cmp_val > 0) */
> +			p = &parent->rb_right;
>  	}
> +
>  	return NULL;
>  }

...you removed the namespace check down here.
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