linux-kernel - RE: [PATCH v2] staging: zcache: fix possible sleep under lock

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Message-ID: <77df3157-6d98-4b86-857e-aa1d6d95f834@default>
Date:	Tue, 23 Aug 2011 08:18:25 -0700 (PDT)
From:	Dan Magenheimer <dan.magenheimer@...cle.com>
To:	Seth Jennings <sjenning@...ux.vnet.ibm.com>, gregkh@...e.de
Cc:	ascardo@...oscopio.com, rdunlap@...otime.net,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: RE: [PATCH v2] staging: zcache: fix possible sleep under lock

> From: Seth Jennings [mailto:sjenning@...ux.vnet.ibm.com]
> Sent: Monday, August 22, 2011 1:31 PM
> To: gregkh@...e.de
> Cc: ascardo@...oscopio.com; Dan Magenheimer; sjenning@...ux.vnet.ibm.com; rdunlap@...otime.net;
> devel@...verdev.osuosl.org; linux-kernel@...r.kernel.org
> Subject: [PATCH v2] staging: zcache: fix possible sleep under lock
> 
> zcache_new_pool() calls kmalloc() with GFP_KERNEL which has
> __GFP_WAIT set.  However, zcache_new_pool() gets called on
> a stack that holds the swap_lock spinlock, leading to a
> possible sleep-with-lock situation. The lock is obtained
> in enable_swap_info().
> 
> The patch replaces GFP_KERNEL with GFP_ATOMIC.
> 
> v2: replace with GFP_ATOMIC, not GFP_IOFS
> 
> Signed-off-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>

Acked-by: Dan Magenheimer <dan.magenheimer@...cle.com>

> ---
>  drivers/staging/zcache/zcache-main.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
> index 855a5bb..cdf0128 100644
> --- a/drivers/staging/zcache/zcache-main.c
> +++ b/drivers/staging/zcache/zcache-main.c
> @@ -1668,7 +1668,7 @@ static int zcache_new_pool(uint16_t cli_id, uint32_t flags)
>  	if (cli == NULL)
>  		goto out;
>  	atomic_inc(&cli->refcount);
> -	pool = kmalloc(sizeof(struct tmem_pool), GFP_KERNEL);
> +	pool = kmalloc(sizeof(struct tmem_pool), GFP_ATOMIC);
>  	if (pool == NULL) {
>  		pr_info("zcache: pool creation failed: out of memory\n");
>  		goto out;
> --
> 1.7.4.1
> 
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