linux-kernel - Re: [PATCH RESEND v1 02/16] vfs: add init and cleanup functions

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Date:	Thu, 10 Jan 2013 01:48:31 +0100
From:	David Sterba <dsterba@...e.cz>
To:	zwu.kernel@...il.com
Cc:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	viro@...iv.linux.org.uk, david@...morbit.com,
	darrick.wong@...cle.com, andi@...stfloor.org, hch@...radead.org,
	linuxram@...ux.vnet.ibm.com, wuzhy@...ux.vnet.ibm.com
Subject: Re: [PATCH RESEND v1 02/16] vfs: add init and cleanup functions

On Thu, Dec 20, 2012 at 10:43:21PM +0800, zwu.kernel@...il.com wrote:
> From: Zhi Yong Wu <wuzhy@...ux.vnet.ibm.com>
> --- a/fs/hot_tracking.c
> +++ b/fs/hot_tracking.c
> @@ -107,3 +189,38 @@ 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;
> +	}
> +
> +	hot_inode_tree_init(root);

This function is supposed to be called from the filesystem init, please
add a sanity check that would catch multiple initialization attempts.

> +
> +	sb->s_hot_root = root;
> +
> +	printk(KERN_INFO "VFS: Turning on hot data tracking\n");
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_GPL(hot_track_init);
> +
> +void hot_track_exit(struct super_block *sb)
> +{
> +	struct hot_info *root = sb->s_hot_root;

another sanity check to catch the opposite.

Why? The option is parsed and enabled from the filesystems, due to
unexpected bugs eg with remounting or incorrectly handled error paths,
vfs layer should IMHO rather warn than crash.

> +
> +	hot_inode_tree_exit(root);
> +	sb->s_hot_root = NULL;
> +	kfree(root);
> +}
> +EXPORT_SYMBOL_GPL(hot_track_exit);


david
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