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>
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index c07222e..575f3ad 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -144,7 +144,14 @@
* 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,