linux-kernel - Re: [PATCH 2/3] zswap: allow initialization at boot without pool

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Date:   Wed, 25 Jan 2017 09:24:26 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Dan Streetman <ddstreet@...e.org>
Cc:     Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Seth Jennings <sjenning@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Minchan Kim <minchan@...nel.org>, linux-kernel@...r.kernel.org,
        Dan Streetman <dan.streetman@...onical.com>
Subject: Re: [PATCH 2/3] zswap: allow initialization at boot without pool


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