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From: Andrew Morton <akpm@linux-foundation.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-arch@vger.kernel.org,
	Andrea Arcangeli <aarcange@redhat.com>,
	Russell King <linux@arm.linux.org.uk>
Subject: Re: [PATCH] mm: Limit pgd range freeing to mm->task_size
Date: Wed, 13 Feb 2013 13:47:56 -0800	[thread overview]
Message-ID: <20130213134756.b90f8e1b.akpm@linux-foundation.org> (raw)
In-Reply-To: <1360755569-27282-1-git-send-email-catalin.marinas@arm.com>

On Wed, 13 Feb 2013 11:39:29 +0000
Catalin Marinas <catalin.marinas@arm.com> wrote:

> ARM processors with LPAE enabled use 3 levels of page tables, with an
> entry in the top level (pgd) covering 1GB of virtual space. Because of
> the branch relocation limitations on ARM, the loadable modules are
> mapped 16MB below PAGE_OFFSET, making the corresponding 1GB pgd shared
> between kernel modules and user space.
> 
> Since free_pgtables() is called with ceiling == 0, free_pgd_range() (and
> subsequently called functions) also frees the page table
> shared between user space and kernel modules (which is normally handled
> by the ARM-specific pgd_free() function).
> 
> This patch changes the ceiling argument to mm->task_size for the
> free_pgtables() and free_pgd_range() function calls. We cannot use
> TASK_SIZE since this macro may not be a run-time constant on 64-bit
> systems supporting compat applications.

I'm trying to work out why we're using 0 in there at all, rather than
->task_size.  But that's lost in the mists of time.

As you've discovered, handling of task_size and TASK_SIZE is somewhat
inconsistent across architectures and with compat tasks.  I guess we
toss it in there and see if anything breaks...

WARNING: multiple messages have this Message-ID (diff)
From: Andrew Morton <akpm@linux-foundation.org>
To: Catalin Marinas <catalin.marinas@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	linux-arch@vger.kernel.org,
	Andrea Arcangeli <aarcange@redhat.com>,
	Russell King <linux@arm.linux.org.uk>
Subject: Re: [PATCH] mm: Limit pgd range freeing to mm->task_size
Date: Wed, 13 Feb 2013 13:47:56 -0800	[thread overview]
Message-ID: <20130213134756.b90f8e1b.akpm@linux-foundation.org> (raw)
In-Reply-To: <1360755569-27282-1-git-send-email-catalin.marinas@arm.com>

On Wed, 13 Feb 2013 11:39:29 +0000
Catalin Marinas <catalin.marinas@arm.com> wrote:

> ARM processors with LPAE enabled use 3 levels of page tables, with an
> entry in the top level (pgd) covering 1GB of virtual space. Because of
> the branch relocation limitations on ARM, the loadable modules are
> mapped 16MB below PAGE_OFFSET, making the corresponding 1GB pgd shared
> between kernel modules and user space.
> 
> Since free_pgtables() is called with ceiling == 0, free_pgd_range() (and
> subsequently called functions) also frees the page table
> shared between user space and kernel modules (which is normally handled
> by the ARM-specific pgd_free() function).
> 
> This patch changes the ceiling argument to mm->task_size for the
> free_pgtables() and free_pgd_range() function calls. We cannot use
> TASK_SIZE since this macro may not be a run-time constant on 64-bit
> systems supporting compat applications.

I'm trying to work out why we're using 0 in there at all, rather than
->task_size.  But that's lost in the mists of time.

As you've discovered, handling of task_size and TASK_SIZE is somewhat
inconsistent across architectures and with compat tasks.  I guess we
toss it in there and see if anything breaks...

--
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  reply	other threads:[~2013-02-13 21:48 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-02-13 11:39 [PATCH] mm: Limit pgd range freeing to mm->task_size Catalin Marinas
2013-02-13 11:39 ` Catalin Marinas
2013-02-13 21:47 ` Andrew Morton [this message]
2013-02-13 21:47   ` Andrew Morton
2013-02-14 21:24   ` Hugh Dickins
2013-02-14 21:24     ` Hugh Dickins
2013-02-18 15:49     ` Catalin Marinas
2013-02-18 15:49       ` Catalin Marinas
  -- strict thread matches above, loose matches on Subject: below --
2012-09-25 14:52 Catalin Marinas

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