[patch 30/59] Revert "[PATCH] Fix up mmap_kmem"

Chris Wright
2007-02-03T02:38:56Z

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-stable review patch. If anyone has any objections, please let us know.
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From: Linus Torvalds <torvalds@woody.linux-foundation.org>

This reverts commit 99a10a60ba9bedcf5d70ef81414d3e03816afa3f.

As per Hugh Dickins:

"Nadia Derbey has reported that mmap of /dev/kmem no longer works with
the kernel virtual address as offset, and Franck has confirmed that
his patch came from a misunderstanding of what an offset means to
/dev/kmem - whereas his patch description seems to say that he was
correcting the offset on a few plaforms, there was no such problem to
correct, and his patch was in fact changing its API on all platforms."

Suggested-by: Hugh Dickins <hugh@veritas.com>
Cc: Franck Bui-Huu <fbuihuu@gmail.com>
Cc: Nadia Derbey <Nadia.Derbey@bull.net>
Cc: Andi Kleen <ak@suse.de>
Cc: Arjan van de Ven <arjan@infradead.org>
Cc: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
drivers/char/mem.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- linux-2.6.19.2.orig/drivers/char/mem.c
+++ linux-2.6.19.2/drivers/char/mem.c
@@ -293,8 +293,8 @@ static int mmap_kmem(struct file * file,
{
unsigned long pfn;

- /* Turn a pfn offset into an absolute pfn */
- pfn = PFN_DOWN(virt_to_phys((void *)PAGE_OFFSET)) + vma->vm_pgoff;
+ /* Turn a kernel-virtual address into a physical page frame */
+ pfn = __pa((u64)vma->vm_pgoff << PAGE_SHIFT) >> PAGE_SHIFT;

/*
* RED-PEN: on some architectures there is more mapped memory

--