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>

2 files changed, 17 insertions, 12 deletions

diff --git a/arch/arm/include/asm/highmem.h b/arch/arm/include/asm/highmem.h
index 5aff5812660..1fc684e70ab 100644
--- a/arch/arm/include/asm/highmem.h
+++ b/arch/arm/include/asm/highmem.h
@@ -35,9 +35,9 @@ extern void kunmap_high_l1_vipt(struct page *page, pte_t saved_pte);
 #ifdef CONFIG_HIGHMEM
 extern void *kmap(struct page *page);
 extern void kunmap(struct page *page);
-extern void *kmap_atomic(struct page *page, enum km_type type);
-extern void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type);
-extern void *kmap_atomic_pfn(unsigned long pfn, enum km_type type);
+extern void *__kmap_atomic(struct page *page);
+extern void __kunmap_atomic(void *kvaddr);
+extern void *kmap_atomic_pfn(unsigned long pfn);
 extern struct page *kmap_atomic_to_page(const void *ptr);
 #endif
 
diff --git a/arch/arm/mm/highmem.c b/arch/arm/mm/highmem.c
index 1fbdb55bfd1..c00f119babb 100644
--- a/arch/arm/mm/highmem.c
+++ b/arch/arm/mm/highmem.c
@@ -36,18 +36,17 @@ void kunmap(struct page *page)
 }
 EXPORT_SYMBOL(kunmap);
 
-void *kmap_atomic(struct page *page, enum km_type type)
+void *__kmap_atomic(struct page *page)
 {
 	unsigned int idx;
 	unsigned long vaddr;
 	void *kmap;
+	int type;
 
 	pagefault_disable();
 	if (!PageHighMem(page))
 		return page_address(page);
 
-	debug_kmap_atomic(type);
-
 #ifdef CONFIG_DEBUG_HIGHMEM
 	/*
 	 * There is no cache coherency issue when non VIVT, so force the
@@ -61,6 +60,8 @@ void *kmap_atomic(struct page *page, enum km_type type)
 	if (kmap)
 		return kmap;
 
+	type = kmap_atomic_idx_push();
+
 	idx = type + KM_TYPE_NR * smp_processor_id();
 	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 #ifdef CONFIG_DEBUG_HIGHMEM
@@ -80,14 +81,17 @@ void *kmap_atomic(struct page *page, enum km_type type)
 
 	return (void *)vaddr;
 }
-EXPORT_SYMBOL(kmap_atomic);
+EXPORT_SYMBOL(__kmap_atomic);
 
-void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
+void __kunmap_atomic(void *kvaddr)
 {
 	unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-	unsigned int idx = type + KM_TYPE_NR * smp_processor_id();
+	int idx, type;
 
 	if (kvaddr >= (void *)FIXADDR_START) {
+		type = kmap_atomic_idx_pop();
+		idx = type + KM_TYPE_NR * smp_processor_id();
+
 		if (cache_is_vivt())
 			__cpuc_flush_dcache_area((void *)vaddr, PAGE_SIZE);
 #ifdef CONFIG_DEBUG_HIGHMEM
@@ -103,15 +107,16 @@ void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
 	}
 	pagefault_enable();
 }
-EXPORT_SYMBOL(kunmap_atomic_notypecheck);
+EXPORT_SYMBOL(__kunmap_atomic);
 
-void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
+void *kmap_atomic_pfn(unsigned long pfn)
 {
-	unsigned int idx;
 	unsigned long vaddr;
+	int idx, type;
 
 	pagefault_disable();
 
+	type = kmap_atomic_idx_push();
 	idx = type + KM_TYPE_NR * smp_processor_id();
 	vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
 #ifdef CONFIG_DEBUG_HIGHMEM