From: Christoph Lameter <clameter@engr.sgi.com>
To: Andrew Morton <akpm@osdl.org>
Cc: linux-mm@kvack.org
Subject: Re: Fix sys_migrate_pages: Move all pages when invoked from root
Date: Fri, 24 Feb 2006 17:27:18 -0800 (PST) [thread overview]
Message-ID: <Pine.LNX.4.64.0602241719290.24858@schroedinger.engr.sgi.com> (raw)
In-Reply-To: <20060224171501.1e19d34a.akpm@osdl.org>
On Fri, 24 Feb 2006, Andrew Morton wrote:
> Oh, it uses the mapcount rather than a permission check on vma->vm_file.
Right. The permissions of a file do not determine if a user is
allowed to move the pages he has from that file. If the user is the sole
proprietor of a page located in a file where he has no write access
then he should nevertheless be able to get these pages where he wants
them to be. Otherwise a processes control over its own address space would
be somewhat limited.
Ray did a lot of work to get this to work right with file permissions in
earlier years but this ended up with setting special access bits on files
to determine the migration behavior. We can still do that if there are any
volunteers that can come up with something that works nicely.
The current approach is IMHO the simplest but it also has some drawbacks.
F.e. the user may move a page in a critical file before other
processes have started using it. But at least he cannot move a page that
is mapped out of position.
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prev parent reply other threads:[~2006-02-25 1:27 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-25 0:17 Christoph Lameter
2006-02-25 0:47 ` Andrew Morton
2006-02-25 0:57 ` Christoph Lameter
2006-02-25 1:15 ` Andrew Morton
2006-02-25 1:27 ` Christoph Lameter [this message]
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