linux-kernel - Re: [PATCH] do not limit locked memory when RLIMIT_MEMLOCK is RLIM

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Message-Id: <20070710094114.86db9e84.kamezawa.hiroyu@jp.fujitsu.com>
Date:	Tue, 10 Jul 2007 09:41:14 +0900
From:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Herbert van den Bergh <Herbert.van.den.Bergh@...cle.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org,
	Dave McCracken <dave.mccracken@...cle.com>,
	Chris Mason <chris.mason@...cle.com>
Subject: Re: [PATCH] do not limit locked memory when RLIMIT_MEMLOCK is
 RLIM_INFINITY

On Mon, 09 Jul 2007 17:26:24 -0700
Herbert van den Bergh <Herbert.van.den.Bergh@...cle.com> wrote:

> 
> This patch fixes a bug in mm/mlock.c on 32-bit architectures that prevents
> a user from locking more than 4GB of shared memory, or allocating more
> than 4GB of shared memory in hugepages, when rlim[RLIMIT_MEMLOCK] is
> set to RLIM_INFINITY.
> 
just curious...why a resouce which can be used longer than a process's
lifetime is limited by RLIMIT ?

Thanks,
-Kame


> Signed-off-by: Herbert van den Bergh <herbert.van.den.bergh@...cle.com>
> Acked-by: Chris Mason <chris.mason@...cle.com>
> 
> --- linux-2.6.22/mm/mlock.c.orig    2007-07-09 10:19:31.000000000 -0700
> +++ linux-2.6.22/mm/mlock.c    2007-07-09 10:19:19.000000000 -0700
> @@ -244,9 +244,12 @@ int user_shm_lock(size_t size, struct us
>  
>      locked = (size + PAGE_SIZE - 1) >> PAGE_SHIFT;
>      lock_limit = current->signal->rlim[RLIMIT_MEMLOCK].rlim_cur;
> +    if (lock_limit == RLIM_INFINITY)
> +        allowed = 1;
>      lock_limit >>= PAGE_SHIFT;
>      spin_lock(&shmlock_user_lock);
> -    if (locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
> +    if (!allowed &&
> +        locked + user->locked_shm > lock_limit && !capable(CAP_IPC_LOCK))
>          goto out;
>      get_uid(user);
>      user->locked_shm += locked;
> 
> -
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