linux-kernel - Re: [PATCH 1/4] inotify: Add infrastructure to account inotify limits per-namespace

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Date:	Mon, 6 Jun 2016 12:26:20 +0300
From:	Nikolay Borisov <kernel@...p.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
Cc:	john@...nmccutchan.com, eparis@...hat.com, ebiederm@...ssion.com,
	jack@...e.cz, linux-kernel@...r.kernel.org, avagin@...nvz.org,
	netdev@...r.kernel.org, operations@...eground.com
Subject: Re: [PATCH 1/4] inotify: Add infrastructure to account inotify limits
 per-namespace



On 06/06/2016 11:05 AM, Cyrill Gorcunov wrote:
> On Wed, Jun 01, 2016 at 10:52:57AM +0300, Nikolay Borisov wrote:
>> This patch adds the necessary members to user_struct. The idea behind
>> the solution is really simple - user the userns pointers as keys into
>> a hash table which holds the inotify instances/watches counts. This
>> allows to account the limits per userns rather than per real user,
>> which makes certain scenarios such as a single mapped user in a
>> container deplete the inotify resources for all other users, which
>> map to the exact same real user.
>>
>> Signed-off-by: Nikolay Borisov <kernel@...p.com>
> ...
>> +static inline unsigned long inotify_dec_return_dev(struct user_struct *user,
>> +						   void *key)
>> +{
>> +	struct inotify_state *state;
>> +	unsigned long ret;
>> +
>> +	spin_lock(&user->inotify_lock);
>> +	state = __find_inotify_state(user, key);
>> +	ret = --state->inotify_devs;
>> +	spin_unlock(&user->inotify_lock);
>> +
>> +	return ret;
>> +}
> 
> Hi Nikolay! Could you please explain why this new function is not used anywhere
> in other patches or I miss something obvious?

Hi Cyrill,

It seems this is a left-over from an earlier, internal version of this
patchset. You can disregard it. Also, given the direction that the
discussion with Eric took I think I will be redesigning the solution
entirely. Thanks for taking the time to read the code!


Nikolay