linux-kernel - Re: [PATCH] fsnotify: add error handling for kmem_cache

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Message-ID: <20180612144916.5vuqy3v6nrtcxksh@quack2.suse.cz>
Date:   Tue, 12 Jun 2018 16:49:16 +0200
From:   Jan Kara <jack@...e.cz>
To:     Zhouyang Jia <jiazhouyang09@...il.com>
Cc:     Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fsnotify: add error handling for kmem_cache_create

On Tue 12-06-18 12:16:04, Zhouyang Jia wrote:
> When kmem_cache_create fails, the lack of error-handling code may
> cause unexpected results.
> 
> This patch adds error-handling code after calling kmem_cache_create.
> 
> Signed-off-by: Zhouyang Jia <jiazhouyang09@...il.com>
> ---
>  fs/notify/dnotify/dnotify.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/fs/notify/dnotify/dnotify.c b/fs/notify/dnotify/dnotify.c
> index 63a1ca4..216b411 100644
> --- a/fs/notify/dnotify/dnotify.c
> +++ b/fs/notify/dnotify/dnotify.c
> @@ -387,6 +387,9 @@ static int __init dnotify_init(void)
>  	dnotify_struct_cache = KMEM_CACHE(dnotify_struct, SLAB_PANIC);
>  	dnotify_mark_cache = KMEM_CACHE(dnotify_mark, SLAB_PANIC);
>  
> +	if (!dnotify_struct_cache || !dnotify_mark_cache)
> +		return -ENOMEM;
> +

Caches are allocated with SLAB_PANIC - i.e., we panic the system if caches
cannot be created. And that's intended since something is really wrong with
the system in that case. So this check is pointless.

								Honza

>  	dnotify_group = fsnotify_alloc_group(&dnotify_fsnotify_ops);
>  	if (IS_ERR(dnotify_group))
>  		panic("unable to allocate fsnotify group for dnotify\n");
> -- 
> 2.7.4
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR