linux-kernel - Re: [PATCH] mm: no need to check return value of debugfs

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Message-ID: <20190122153102.GJ4087@dhcp22.suse.cz>
Date:   Tue, 22 Jan 2019 16:31:02 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-kernel@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        David Rientjes <rientjes@...gle.com>,
        Laura Abbott <labbott@...hat.com>, linux-mm@...ck.org
Subject: Re: [PATCH] mm: no need to check return value of debugfs_create
 functions

On Tue 22-01-19 16:21:13, Greg KH wrote:
[...]
> diff --git a/mm/memblock.c b/mm/memblock.c
> index 022d4cbb3618..18ee657fb918 100644
> --- a/mm/memblock.c
> +++ b/mm/memblock.c
> @@ -1998,8 +1998,7 @@ DEFINE_SHOW_ATTRIBUTE(memblock_debug);
>  static int __init memblock_init_debugfs(void)
>  {
>  	struct dentry *root = debugfs_create_dir("memblock", NULL);
> -	if (!root)
> -		return -ENXIO;
> +
>  	debugfs_create_file("memory", 0444, root,
>  			    &memblock.memory, &memblock_debug_fops);
>  	debugfs_create_file("reserved", 0444, root,

I haven't really read the whole patch but this has just hit my eyes. Is
this a correct behavior?

Documentations says:
 * @parent: a pointer to the parent dentry for this file.  This should be a
 *          directory dentry if set.  If this parameter is NULL, then the
 *          file will be created in the root of the debugfs filesystem.

so in case of failure we would get those debugfs files outside of their
intended scope. I believe it is much more correct to simply not create
anything, no?
-- 
Michal Hocko
SUSE Labs