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>

arch/x86/mm/highmem_32.c

@@ -9,6 +9,7 @@ void *kmap(struct page *page)
 		return page_address(page);
 	return kmap_high(page);
 }
+EXPORT_SYMBOL(kmap);
 
 void kunmap(struct page *page)
 {
@@ -18,6 +19,7 @@ void kunmap(struct page *page)
 		return;
 	kunmap_high(page);
 }
+EXPORT_SYMBOL(kunmap);
 
 /*
  * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
@@ -27,10 +29,10 @@ void kunmap(struct page *page)
  * However when holding an atomic kmap it is not legal to sleep, so atomic
  * kmaps are appropriate for short, tight code paths only.
  */
-void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
+void *kmap_atomic_prot(struct page *page, pgprot_t prot)
 {
-	enum fixed_addresses idx;
 	unsigned long vaddr;
+	int idx, type;
 
 	/* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
 	pagefault_disable();
@@ -38,8 +40,7 @@ void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
 	if (!PageHighMem(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);
 	BUG_ON(!pte_none(*(kmap_pte-idx)));
@@ -47,44 +48,56 @@ void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
 
 	return (void *)vaddr;
 }
+EXPORT_SYMBOL(kmap_atomic_prot);
 
-void *kmap_atomic(struct page *page, enum km_type type)
+void *__kmap_atomic(struct page *page)
 {
-	return kmap_atomic_prot(page, type, kmap_prot);
-}
-
-void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
-{
-	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-	enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
-
-	/*
-	 * Force other mappings to Oops if they'll try to access this pte
-	 * without first remap it.  Keeping stale mappings around is a bad idea
-	 * also, in case the page changes cacheability attributes or becomes
-	 * a protected page in a hypervisor.
-	 */
-	if (vaddr == __fix_to_virt(FIX_KMAP_BEGIN+idx))
-		kpte_clear_flush(kmap_pte-idx, vaddr);
-	else {
-#ifdef CONFIG_DEBUG_HIGHMEM
-		BUG_ON(vaddr < PAGE_OFFSET);
-		BUG_ON(vaddr >= (unsigned long)high_memory);
-#endif
-	}
-
-	pagefault_enable();
+	return kmap_atomic_prot(page, kmap_prot);
 }
+EXPORT_SYMBOL(__kmap_atomic);
 
 /*
  * This is the same as kmap_atomic() but can map memory that doesn't
  * have a struct page associated with it.
  */
-void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
+void *kmap_atomic_pfn(unsigned long pfn)
 {
-	return kmap_atomic_prot_pfn(pfn, type, kmap_prot);
+	return kmap_atomic_prot_pfn(pfn, kmap_prot);
 }
-EXPORT_SYMBOL_GPL(kmap_atomic_pfn); /* temporarily in use by i915 GEM until vmap */
+EXPORT_SYMBOL_GPL(kmap_atomic_pfn);
+
+void __kunmap_atomic(void *kvaddr)
+{
+	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
+
+	if (vaddr >= __fix_to_virt(FIX_KMAP_END) &&
+	    vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
+		int idx, type;
+
+		type = kmap_atomic_idx_pop();
+		idx = type + KM_TYPE_NR * smp_processor_id();
+
+#ifdef CONFIG_DEBUG_HIGHMEM
+		WARN_ON_ONCE(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
+#endif
+		/*
+		 * Force other mappings to Oops if they'll try to access this
+		 * pte without first remap it.  Keeping stale mappings around
+		 * is a bad idea also, in case the page changes cacheability
+		 * attributes or becomes a protected page in a hypervisor.
+		 */
+		kpte_clear_flush(kmap_pte-idx, vaddr);
+	}
+#ifdef CONFIG_DEBUG_HIGHMEM
+	else {
+		BUG_ON(vaddr < PAGE_OFFSET);
+		BUG_ON(vaddr >= (unsigned long)high_memory);
+	}
+#endif
+
+	pagefault_enable();
+}
+EXPORT_SYMBOL(__kunmap_atomic);
 
 struct page *kmap_atomic_to_page(void *ptr)
 {
@@ -98,12 +111,6 @@ struct page *kmap_atomic_to_page(void *ptr)
 	pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
 	return pte_page(*pte);
 }
-
-EXPORT_SYMBOL(kmap);
-EXPORT_SYMBOL(kunmap);
-EXPORT_SYMBOL(kmap_atomic);
-EXPORT_SYMBOL(kunmap_atomic_notypecheck);
-EXPORT_SYMBOL(kmap_atomic_prot);
 EXPORT_SYMBOL(kmap_atomic_to_page);
 
 void __init set_highmem_pages_init(void)