linux-kernel - Re: [PATCH -tip v3 3/3] locking/pvqspinlock: Robustify init_qspinlock

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Date:	Wed, 20 Apr 2016 16:06:51 -0400
From:	Waiman Long <waiman.long@....com>
To:	Davidlohr Bueso <dave@...olabs.net>
CC:	"mingo@...nel.org" <mingo@...nel.org>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Davidlohr Bueso <dbueso@...e.de>
Subject: Re: [PATCH -tip v3 3/3] locking/pvqspinlock: Robustify init_qspinlock_stat()

On 04/20/2016 12:17 AM, Davidlohr Bueso wrote:
> locking/pvqspinlock: Robustify init_qspinlock_stat()
>
> Specifically around the debugfs file creation calls,
> I have no idea if they could ever possibly fail, but
> this is core code (debug aside) so lets at least
> check the return value and inform anything fishy.
>
> Signed-off-by: Davidlohr Bueso <dbueso@...e.de>
> ---
> kernel/locking/qspinlock_stat.h | 22 ++++++++++++++--------
> 1 file changed, 14 insertions(+), 8 deletions(-)
>
> diff --git a/kernel/locking/qspinlock_stat.h 
> b/kernel/locking/qspinlock_stat.h
> index 72722334237a..22e025309845 100644
> --- a/kernel/locking/qspinlock_stat.h
> +++ b/kernel/locking/qspinlock_stat.h
> @@ -212,10 +212,8 @@ static int __init init_qspinlock_stat(void)
>     struct dentry *d_qstat = debugfs_create_dir("qlockstat", NULL);
>     int i;
>
> -    if (!d_qstat) {
> -        pr_warn("Could not create 'qlockstat' debugfs directory\n");
> -        return 0;
> -    }
> +    if (!d_qstat)
> +        goto out;
>
>     /*
>      * Create the debugfs files
> @@ -225,12 +223,20 @@ static int __init init_qspinlock_stat(void)
>      * performance.
>      */
>     for (i = 0; i < qstat_num; i++)
> -        debugfs_create_file(qstat_names[i], 0400, d_qstat,
> -                   (void *)(long)i, &fops_qstat);
> +        if (!debugfs_create_file(qstat_names[i], 0400, d_qstat,
> +                     (void *)(long)i, &fops_qstat))
> +            goto fail_undo;
> +
> +    if (!debugfs_create_file(qstat_names[qstat_reset_cnts], 0200, 
> d_qstat,
> +                 (void *)(long)qstat_reset_cnts, &fops_qstat))
> +        goto fail_undo;
>
> -    debugfs_create_file(qstat_names[qstat_reset_cnts], 0200, d_qstat,
> -               (void *)(long)qstat_reset_cnts, &fops_qstat);
>     return 0;
> +fail_undo:
> +    debugfs_remove_recursive(d_qstat);
> +out:
> +    pr_warn("Could not create 'qlockstat' debugfs entries\n");
> +    return -ENOMEM;
> }
> fs_initcall(init_qspinlock_stat);
>

Reviewed-by: Waiman Long <Waiman.Long@....com>