From: "David S. Miller" <davem@davemloft.net>
To: akpm@osdl.org
Cc: hugh@veritas.com, wli@holomorphy.com, nickpiggin@yahoo.com.au,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] compound page: use page[1].lru
Date: Sun, 12 Feb 2006 23:05:16 -0800 (PST) [thread overview]
Message-ID: <20060212.230516.86740481.davem@davemloft.net> (raw)
In-Reply-To: <20060212181312.11392d12.akpm@osdl.org>
From: Andrew Morton <akpm@osdl.org>
Date: Sun, 12 Feb 2006 18:13:12 -0800
> We have a page which has no ->mapping, but lo, it's mmapped by userspace
> and can be MAP_SHARED between different CPUs and processes.
>
> Yes, I suspect it'll do the wrong thing in unpleasantly subtle ways.
>
> (cc's davem and runs away).
The ->mapping check is there essentially to hit user mapped pages that
would be modified by the kernel using kernel space memory accesses
other than those done by copy_user_page() and clear_user_page() (and
their brothers copy_user_highpage() and clear_user_highpage() which
just call the former directly on a non-HIGHPAGE platform like
sparc64).
Hugepages actually have no D-cache aliasing issues by definition on
sparc64 because the smallest possible hugepage size is 64K which is
larger than the D-cache aliasing factor (which is 16K).
next prev parent reply other threads:[~2006-02-13 7:05 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-02-12 19:46 Hugh Dickins
2006-02-12 19:47 ` [PATCH 2/3] compound page: default destructor Hugh Dickins
2006-02-12 19:50 ` [PATCH 3/3] compound page: no access_process_vm check Hugh Dickins
2006-02-12 21:54 ` [PATCH 1/3] compound page: use page[1].lru Andrew Morton
2006-02-13 0:57 ` Hugh Dickins
2006-02-13 2:13 ` Andrew Morton
2006-02-13 7:05 ` David S. Miller [this message]
2006-02-13 7:12 ` Andrew Morton
2006-02-13 7:59 ` David S. Miller
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