linux-ext4 - Re: [RFC v4+ hot_track 02/19] vfs: initialize and free data structures

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Date:	Tue, 6 Nov 2012 23:24:42 +0100
From:	David Sterba <dave@...os.cz>
To:	zwu.kernel@...il.com
Cc:	linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org,
	linux-btrfs@...r.kernel.org, linux-kernel@...r.kernel.org,
	linuxram@...ux.vnet.ibm.com, viro@...iv.linux.org.uk,
	david@...morbit.com, tytso@....edu, cmm@...ibm.com,
	wuzhy@...ux.vnet.ibm.com, wenqing.lz@...bao.com
Subject: Re: [RFC v4+ hot_track 02/19] vfs: initialize and free data
 structures

On Mon, Oct 29, 2012 at 12:30:44PM +0800, zwu.kernel@...il.com wrote:
> +/* Frees the entire hot_range_tree. */
> +static void hot_inode_item_free(struct kref *kref)
> +{
> +	struct hot_comm_item *comm_item = container_of(kref,
> +			struct hot_comm_item, refs);
> +	struct hot_inode_item *he = container_of(comm_item,
> +			struct hot_inode_item, hot_inode);
> +
> +	hot_range_tree_free(he);
> +	radix_tree_delete(he->hot_inode_tree, he->i_ino);

void *radix_tree_delete(struct radix_tree_root *root, unsigned long index)

and he::i_ino is u64, this will not work when
sizeof(unsigned long) != sizeof(u64) (iirc this is a known limitation of
radix tree implementation). This will work on 64bit only, not sure if
this is intentional.

> +	kmem_cache_free(hot_inode_item_cachep, he);
> +}
> +
> +/* Frees the entire hot_inode_tree. */
> +static void hot_inode_tree_exit(struct hot_info *root)
> +{
> +	struct hot_inode_item *hi_nodes[8];
> +	u64 ino = 0;
> +	int i, n;

nitpick, put the declarations on separate lines

> +
> +	while (1) {
> +		spin_lock(&root->lock);
> +		n = radix_tree_gang_lookup(&root->hot_inode_tree,
> +					   (void **)hi_nodes, ino,
> +					   ARRAY_SIZE(hi_nodes));
> +		if (!n) {
> +			spin_unlock(&root->lock);
> +			break;
> +		}
> +
> +		ino = hi_nodes[n - 1]->i_ino + 1;
> +		for (i = 0; i < n; i++)
> +			hot_inode_item_put(hi_nodes[i]);
> +		spin_unlock(&root->lock);
> +	}
> +}
> +
>  /*
>   * Initialize kmem cache for hot_inode_item and hot_range_item.
>   */
> @@ -106,3 +197,36 @@ err:
>  	kmem_cache_destroy(hot_inode_item_cachep);
>  }
>  EXPORT_SYMBOL_GPL(hot_cache_init);
> +
> +/*
> + * Initialize the data structures for hot data tracking.
> + */
> +int hot_track_init(struct super_block *sb)
> +{
> +	struct hot_info *root;
> +	int ret = -ENOMEM;
> +
> +	root = kzalloc(sizeof(struct hot_info), GFP_NOFS);
> +	if (!root) {
> +		printk(KERN_ERR "%s: Failed to malloc memory for "
> +				"hot_info\n", __func__);
> +		return ret;

minor: you can drop the variable ret and just reurn ENOMEM here

> +	}
> +
> +	sb->s_hot_root = root;
> +	hot_inode_tree_init(root);
> +
> +	printk(KERN_INFO "VFS: Turning on hot data tracking\n");
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(hot_track_init);

david
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