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ARM: 5687/1: fix an oops with highmem 

In xdr_partial_copy_from_skb() there is that sequence:

		kaddr = kmap_atomic(*ppage, KM_SKB_SUNRPC_DATA);
		[...]
		flush_dcache_page(*ppage);
		kunmap_atomic(kaddr, KM_SKB_SUNRPC_DATA);

Mixing flush_dcache_page() and kmap_atomic() is a bit odd,
especially since kunmap_atomic() must deal with cache issues
already.  OTOH the non-highmem case must use flush_dcache_page()
as kunmap_atomic() becomes a no op with no cache maintenance.

Problem is that with highmem the implementation of kmap_atomic()
doesn't set page->virtual, and page_address(page) returns 0 in
that case. Here flush_dcache_page() calls __flush_dcache_page()
which calls __cpuc_flush_dcache_page(page_address(page)) resulting
in a kernel oops.

None of the kmap_atomic() implementations uses set_page_address().
Hence we can assume page_address() is always expected to return 0 in
that case. Let's conditionally call __cpuc_flush_dcache_page() only
when the page address is non zero, and perform that test only when
highmem is configured.

Signed-off-by: Nicolas Pitre <nico@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
This commit is contained in:
Nicolas Pitre 2009-09-01 22:01:27 +01:00 committed by Russell King
parent 37d0892c5a
commit 13f96d8f4c
1 changed files with 8 additions and 1 deletions
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9
arch/arm/mm/flush.c
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@ -144,7 +144,14 @@ void __flush_dcache_page(struct address_space *mapping, struct page *page)
* page. This ensures that data in the physical page is mutually
* coherent with the kernels mapping.
*/
__cpuc_flush_dcache_page(page_address(page));
#ifdef CONFIG_HIGHMEM
/*
* kmap_atomic() doesn't set the page virtual address, and
* kunmap_atomic() takes care of cache flushing already.
*/
if (page_address(page))
#endif
__cpuc_flush_dcache_page(page_address(page));
/*
* If this is a page cache page, and we have an aliasing VIPT cache,