Add a helper that calls flush_kernel_dcache_page before unmapping the
local mapping. flush_kernel_dcache_page is required for all pages
potentially mapped into userspace that were written to using kmap*,
so having a helper that does the right thing can be very convenient.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
include/linux/highmem-internal.h | 7 +++++++
include/linux/highmem.h | 4 ++++
2 files changed, 11 insertions(+)
diff --git a/include/linux/highmem-internal.h b/include/linux/highmem-internal.h
index 7902c7d8b55f..bd37706db147 100644
--- a/include/linux/highmem-internal.h
+++ b/include/linux/highmem-internal.h
@@ -224,4 +224,11 @@ do { \
__kunmap_local(__addr); \
} while (0)
+#define kunmap_local_dirty(__page, __addr) \
+do { \
+ if (!PageSlab(__page)) \
+ flush_kernel_dcache_page(__page); \
+ kunmap_local(__addr); \
+} while (0)
+
#endif
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 832b49b50c7b..65f548db4f2d 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -93,6 +93,10 @@ static inline void kmap_flush_unused(void);
* On HIGHMEM enabled systems mapping a highmem page has the side effect of
* disabling migration in order to keep the virtual address stable across
* preemption. No caller of kmap_local_page() can rely on this side effect.
+ *
+ * If data is written to the returned kernel mapping, the callers needs to
+ * unmap the mapping using kunmap_local_dirty(), else kunmap_local() should
+ * be used.
*/
static inline void *kmap_local_page(struct page *page);
--
2.30.2
