linux-kernel - Re: [patch] mm: recheck lock rlim after f

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Date:	Tue, 10 Jul 2007 18:27:05 +0100 (BST)
From:	Hugh Dickins <hugh@...itas.com>
To:	Dmitry Monakhov <dmonakhov@...ru>
cc:	Jes Sorensen <jes@....com>, linux-kernel@...r.kernel.org
Subject: Re: [patch] mm: recheck lock rlim after f_op->mmap() method

On Mon, 9 Jul 2007, Dmitry Monakhov wrote:
> Some device drivers can change vm_flags in their f_op->mmap
> method. In order to be on the safe side we have to recheck
> lock rlimit. Now we have to check lock rlimit from two places,
> let's move this common code to helper functon.
> 
> Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
> ---
>  mm/mmap.c |   33 ++++++++++++++++++++++++++-------
>  1 files changed, 26 insertions(+), 7 deletions(-)

Or would this simpler patch be the right one?  I suspect the
mspec driver only says VM_LOCKED because of a deep-seated but
irrational fear that its pages might fall into reclaim.

(I'd like to take out VM_RESERVED too, but that can always happen
another, indefinitely postponed time; there are others of those.)

Hugh

--- 2.6.22/drivers/char/mspec.c	2007-04-26 04:08:32.000000000 +0100
+++ linux/drivers/char/mspec.c	2007-07-10 18:12:11.000000000 +0100
@@ -265,7 +265,7 @@ mspec_mmap(struct file *file, struct vm_
 	vdata->refcnt = ATOMIC_INIT(1);
 	vma->vm_private_data = vdata;
 
-	vma->vm_flags |= (VM_IO | VM_LOCKED | VM_RESERVED | VM_PFNMAP);
+	vma->vm_flags |= (VM_IO | VM_RESERVED | VM_PFNMAP);
 	if (vdata->type == MSPEC_FETCHOP || vdata->type == MSPEC_UNCACHED)
 		vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 	vma->vm_ops = &mspec_vm_ops;
-
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