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

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Message-ID: <CALZtONByh4VOUqNewmK77BNgKBzExBhiFwCJ9UTdhQREZ4f+ig@mail.gmail.com>
Date:   Wed, 25 Jan 2017 11:36:40 -0500
From:   Dan Streetman <ddstreet@...e.org>
To:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
Cc:     Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Seth Jennings <sjenning@...hat.com>,
        Michal Hocko <mhocko@...nel.org>,
        Minchan Kim <minchan@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        Dan Streetman <dan.streetman@...onical.com>
Subject: Re: [PATCH 2/3] zswap: allow initialization at boot without pool

On Tue, Jan 24, 2017 at 7:24 PM, Sergey Senozhatsky
<sergey.senozhatsky.work@...il.com> wrote:
>
> 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'.

thanks, it looks like the other param_set_charp above this new one has
been in the spinlock ever since i added the param callback.  I'll send
a patch.


>
>         -ss
>