[ARM] Resolve fuse and direct-IO failures due to missing cache flushes

fuse does not work on ARM due to cache incoherency issues - fuse wants
to use get_user_pages() to copy data from the current process into
kernel space.  However, since this accesses userspace via the kernel
mapping, the kernel mapping can be out of date wrt data written to
userspace.

This can lead to unpredictable behaviour (in the case of fuse) or data
corruption for direct-IO.

This resolves debian bug #402876

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

1 files changed, 10 insertions, 0 deletions

diff --git a/include/asm-arm/cacheflush.h b/include/asm-arm/cacheflush.h
index d51049522cd0..5f531ea03059 100644
--- a/include/asm-arm/cacheflush.h
+++ b/include/asm-arm/cacheflush.h
@@ -357,6 +357,16 @@ extern void flush_dcache_page(struct page *);
 
 extern void __flush_dcache_page(struct address_space *mapping, struct page *page);
 
+#define ARCH_HAS_FLUSH_ANON_PAGE
+static inline void flush_anon_page(struct vm_area_struct *vma,
+                         struct page *page, unsigned long vmaddr)
+{
+        extern void __flush_anon_page(struct vm_area_struct *vma,
+                                struct page *, unsigned long);
+        if (PageAnon(page))
+                __flush_anon_page(vma, page, vmaddr);
+}
+
 #define flush_dcache_mmap_lock(mapping) \
         write_lock_irq(&(mapping)->tree_lock)
 #define flush_dcache_mmap_unlock(mapping) \