[PATCH] Add flush_kernel_dcache_page() API

We have a problem in a lot of emulated storage in that it takes a page from
get_user_pages() and does something like

kmap_atomic(page)
modify page
kunmap_atomic(page)

However, nothing has flushed the kernel cache view of the page before the
kunmap.  We need a lightweight API to do this, so this new API would
specifically be for flushing the kernel cache view of a user page which the
kernel has modified.  The driver would need to add
flush_kernel_dcache_page(page) before the final kunmap.

Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 6 insertions, 0 deletions

diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 7bd2593dbef9..892c4ea1b425 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -13,6 +13,12 @@ static inline void flush_anon_page(struct page *page, unsigned long vmaddr)
 }
 #endif
 
+#ifndef ARCH_HAS_FLUSH_KERNEL_DCACHE_PAGE
+static inline void flush_kernel_dcache_page(struct page *page)
+{
+}
+#endif
+
 #ifdef CONFIG_HIGHMEM
 
 #include <asm/highmem.h>