linux-kernel - Re: [PATCH 3/3] zswap: change zpool/compressor at runtime

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Message-ID: <CALZtONCquXbE-dHWQUfKL_OSO7Bk5HN+t2EZduoD11vcaiJxmQ@mail.gmail.com>
Date:	Thu, 6 Aug 2015 06:06:49 -0400
From:	Dan Streetman <ddstreet@...e.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Seth Jennings <sjennings@...iantweb.net>,
	Linux-MM <linux-mm@...ck.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 3/3] zswap: change zpool/compressor at runtime

On Wed, Aug 5, 2015 at 4:14 PM, Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Wed,  5 Aug 2015 09:46:43 -0400 Dan Streetman <ddstreet@...e.org> wrote:
>
>> Update the zpool and compressor parameters to be changeable at runtime.
>> When changed, a new pool is created with the requested zpool/compressor,
>> and added as the current pool at the front of the pool list.  Previous
>> pools remain in the list only to remove existing compressed pages from.
>> The old pool(s) are removed once they become empty.
>>
>> +/*********************************
>> +* param callbacks
>> +**********************************/
>> +
>> +static int __zswap_param_set(const char *val, const struct kernel_param *kp,
>> +                          char *type, char *compressor)
>> +{
>> +     struct zswap_pool *pool, *put_pool = NULL;
>> +     char str[kp->str->maxlen], *s;
>
> What's the upper bound on the size of this variable-sized array?

the kernel_param in this function will always be either
zswap_compressor_kparam or zswap_zpool_kparam, which are defined at
the top, and their maxlen fields are set to sizeof(their string),
which is either CRYPTO_MAX_ALG_NAME (currently 64) or 32 (arbitrary
max for zpool name).

I can also add a comment here to clarify that.

>
>> +     int ret;
>> +
>> +     strlcpy(str, val, kp->str->maxlen);
>> +     s = strim(str);
>> +
>> +     /* if this is load-time (pre-init) param setting,
>
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