Re: [PATCH 02/11] kernfs: use idr instead of ida to manage inode number

From	Tejun Heo <tj@kernel.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH 02/11] kernfs: use idr instead of ida to manage inode number
Date	2017-06-12 20:20 +0200
Message-ID	<tRC6u-5IS-5@gated-at.bofh.it> (permalink)
References	<tO2LT-6Ey-3@gated-at.bofh.it> <tO2LT-6Ey-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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Hello,

On Fri, Jun 02, 2017 at 02:53:55PM -0700, Shaohua Li wrote:
> @@ -630,7 +633,11 @@ static struct kernfs_node *__kernfs_new_node(struct kernfs_root *root,
>  	if (!kn)
>  		goto err_out1;
>  
> -	ret = ida_simple_get(&root->ino_ida, 1, 0, GFP_KERNEL);
> +	idr_preload(GFP_KERNEL);
> +	spin_lock(&kernfs_idr_lock);
> +	ret = idr_alloc(&root->ino_idr, kn, 1, 0, GFP_ATOMIC);
> +	spin_unlock(&kernfs_idr_lock);
> +	idr_preload_end();

So, this ends up populating the idr w/ a kn which isn't fully
initialized yet, which can lead to bugs which are difficult to hunt
down as we're gonna allow kn's to be looked up through ino / gen.  We
probably should allocate with NULL here and populate the actual
pointer with idr_replace() after the kn is fully initialized / online.

Thanks.

-- 
tejun

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Re: [PATCH 02/11] kernfs: use idr instead of ida to manage inode  number Tejun Heo <tj@kernel.org> - 2017-06-12 20:20 +0200

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