[RFC][PATCH 3/4] mm: k{,um}map_atomic() vs in_atomic()

[Peter Zijlstra]

Make kmap_atomic/kunmap_atomic denote a pagefault disabled scope. All
non trivial implementations already do this anyway.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 include/asm-mips/highmem.h |   10 ++++++++--
 include/linux/highmem.h    |    8 +++++---
 2 files changed, 13 insertions(+), 5 deletions(-)

Index: linux-2.6/include/asm-mips/highmem.h
===================================================================
--- linux-2.6.orig/include/asm-mips/highmem.h
+++ linux-2.6/include/asm-mips/highmem.h
@@ -21,6 +21,7 @@
 
 #include <linux/init.h>
 #include <linux/interrupt.h>
+#include <linux/uaccess.h>
 #include <asm/kmap_types.h>
 
 /* undef for production */
@@ -70,11 +71,16 @@ static inline void *kmap(struct page *pa
 
 static inline void *kmap_atomic(struct page *page, enum km_type type)
 {
+	pagefault_disable();
 	return page_address(page);
 }
 
-static inline void kunmap_atomic(void *kvaddr, enum km_type type) { }
-#define kmap_atomic_pfn(pfn, idx)	page_address(pfn_to_page(pfn))
+static inline void kunmap_atomic(void *kvaddr, enum km_type type)
+{
+	pagefault_enable();
+}
+
+#define kmap_atomic_pfn(pfn, idx) kmap_atomic(pfn_to_page(pfn), (idx))
 
 #define kmap_atomic_to_page(ptr) virt_to_page(ptr)
 
Index: linux-2.6/include/linux/highmem.h
===================================================================
--- linux-2.6.orig/include/linux/highmem.h
+++ linux-2.6/include/linux/highmem.h
@@ -3,6 +3,7 @@
 
 #include <linux/fs.h>
 #include <linux/mm.h>
+#include <linux/uaccess.h>
 
 #include <asm/cacheflush.h>
 
@@ -41,9 +42,10 @@ static inline void *kmap(struct page *pa
 
 #define kunmap(page) do { (void) (page); } while (0)
 
-#define kmap_atomic(page, idx)		page_address(page)
-#define kunmap_atomic(addr, idx)	do { } while (0)
-#define kmap_atomic_pfn(pfn, idx)	page_address(pfn_to_page(pfn))
+#define kmap_atomic(page, idx) \
+	({ pagefault_disable(); page_address(page); })
+#define kunmap_atomic(addr, idx)	do { pagefault_enable(); } while (0)
+#define kmap_atomic_pfn(pfn, idx)	kmap_atomic(pfn_to_page(pfn), (idx))
 #define kmap_atomic_to_page(ptr)	virt_to_page(ptr)
 #endif
 

--

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