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Date: Wed, 25 Jan 2017 09:24:26 +0900
From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Dan Streetman <ddstreet@ieee.org>
Cc: Linux-MM <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Seth Jennings <sjenning@redhat.com>, Michal Hocko <mhocko@kernel.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
        Minchan Kim <minchan@kernel.org>, linux-kernel@vger.kernel.org,
        Dan Streetman <dan.streetman@canonical.com>
Subject: Re: [PATCH 2/3] zswap: allow initialization at boot without pool
Message-ID: <20170125002426.GA2234@jagdpanzerIV.localdomain>
References: <20170124200259.16191-1-ddstreet@ieee.org>
 <20170124200259.16191-3-ddstreet@ieee.org>
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just a note,

On (01/24/17 15:02), Dan Streetman wrote:
[..]
> @@ -692,6 +702,15 @@ static int __zswap_param_set(const char *val, const struct kernel_param *kp,
>  		 */
>  		list_add_tail_rcu(&pool->list, &zswap_pools);
>  		put_pool = pool;
> +	} else if (!zswap_has_pool) {
> +		/* if initial pool creation failed, and this pool creation also
> +		 * failed, maybe both compressor and zpool params were bad.
> +		 * Allow changing this param, so pool creation will succeed
> +		 * when the other param is changed. We already verified this
> +		 * param is ok in the zpool_has_pool() or crypto_has_comp()
> +		 * checks above.
> +		 */
> +		ret = param_set_charp(s, kp);
>  	}
>  
>  	spin_unlock(&zswap_pools_lock);

looks like there still GFP_KERNEL allocation from atomic section:
param_set_charp()->kmalloc_parameter()->kmalloc(GFP_KERNEL), under
`zswap_pools_lock'.

	-ss