mm: stack based kmap_atomic()

Keep the current interface but ignore the KM_type and use a stack based
approach.

The advantage is that we get rid of crappy code like:

	#define __KM_PTE			\
		(in_nmi() ? KM_NMI_PTE : 	\
		 in_irq() ? KM_IRQ_PTE :	\
		 KM_PTE0)

and in general can stop worrying about what context we're in and what kmap
slots might be appropriate for that.

The downside is that FRV kmap_atomic() gets more expensive.

For now we use a CPP trick suggested by Andrew:

  #define kmap_atomic(page, args...) __kmap_atomic(page)

to avoid having to touch all kmap_atomic() users in a single patch.

[ not compiled on:
  - mn10300: the arch doesn't actually build with highmem to begin with ]

[akpm@linux-foundation.org: coding-style fixes]
[akpm@linux-foundation.org: fix up drivers/gpu/drm/i915/intel_overlay.c]
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Chris Metcalf <cmetcalf@tilera.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: David Miller <davem@davemloft.net>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Dave Airlie <airlied@linux.ie>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 26 insertions, 16 deletions

diff --git a/arch/mn10300/include/asm/highmem.h b/arch/mn10300/include/asm/highmem.h
index b0b187a..f577ba2 100644
--- a/arch/mn10300/include/asm/highmem.h
+++ b/arch/mn10300/include/asm/highmem.h
@@ -70,15 +70,16 @@ static inline void kunmap(struct page *page)
  * be used in IRQ contexts, so in some (very limited) cases we need
  * it.
  */
-static inline unsigned long kmap_atomic(struct page *page, enum km_type type)
+static inline unsigned long __kmap_atomic(struct page *page)
 {
-	enum fixed_addresses idx;
 	unsigned long vaddr;
+	int idx, type;
 
+	pagefault_disable();
 	if (page < highmem_start_page)
 		return page_address(page);
 
-	debug_kmap_atomic(type);
+	type = kmap_atomic_idx_push();
 	idx = type + KM_TYPE_NR * smp_processor_id();
 	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 #if HIGHMEM_DEBUG
@@ -91,26 +92,35 @@ static inline unsigned long kmap_atomic(struct page *page, enum km_type type)
 	return vaddr;
 }
 
-static inline void kunmap_atomic_notypecheck(unsigned long vaddr, enum km_type type)
+static inline void __kunmap_atomic(unsigned long vaddr)
 {
-#if HIGHMEM_DEBUG
-	enum fixed_addresses idx = type + KM_TYPE_NR * smp_processor_id();
+	int type;
 
-	if (vaddr < FIXADDR_START) /* FIXME */
+	if (vaddr < FIXADDR_START) { /* FIXME */
+		pagefault_enable();
 		return;
+	}
 
-	if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx))
-		BUG();
+	type = kmap_atomic_idx_pop();
 
-	/*
-	 * force other mappings to Oops if they'll try to access
-	 * this pte without first remap it
-	 */
-	pte_clear(kmap_pte - idx);
-	__flush_tlb_one(vaddr);
+#if HIGHMEM_DEBUG
+	{
+		unsigned int idx;
+		idx = type + KM_TYPE_NR * smp_processor_id();
+
+		if (vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx))
+			BUG();
+
+		/*
+		 * force other mappings to Oops if they'll try to access
+		 * this pte without first remap it
+		 */
+		pte_clear(kmap_pte - idx);
+		__flush_tlb_one(vaddr);
+	}
 #endif
+	pagefault_enable();
 }
-
 #endif /* __KERNEL__ */
 
 #endif /* _ASM_HIGHMEM_H */