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, 27 insertions, 23 deletions

diff --git a/arch/mips/mm/highmem.c b/arch/mips/mm/highmem.c
index 6a2b1bf9ef11..1e69b1fb4b85 100644
--- a/arch/mips/mm/highmem.c
+++ b/arch/mips/mm/highmem.c
@@ -9,7 +9,7 @@ static pte_t *kmap_pte;
 
 unsigned long highstart_pfn, highend_pfn;
 
-void *__kmap(struct page *page)
+void *kmap(struct page *page)
 {
         void *addr;
 
@@ -21,16 +21,16 @@ void *__kmap(struct page *page)
 
         return addr;
 }
-EXPORT_SYMBOL(__kmap);
+EXPORT_SYMBOL(kmap);
 
-void __kunmap(struct page *page)
+void kunmap(struct page *page)
 {
         BUG_ON(in_interrupt());
         if (!PageHighMem(page))
                 return;
         kunmap_high(page);
 }
-EXPORT_SYMBOL(__kunmap);
+EXPORT_SYMBOL(kunmap);
 
 /*
  * kmap_atomic/kunmap_atomic is significantly faster than kmap/kunmap because
@@ -41,17 +41,17 @@ EXPORT_SYMBOL(__kunmap);
  * kmaps are appropriate for short, tight code paths only.
  */
 
-void *__kmap_atomic(struct page *page, enum km_type type)
+void *__kmap_atomic(struct page *page)
 {
-        enum fixed_addresses idx;
         unsigned long vaddr;
+        int idx, type;
 
         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
         pagefault_disable();
         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);
 #ifdef CONFIG_DEBUG_HIGHMEM
@@ -64,43 +64,47 @@ void *__kmap_atomic(struct page *page, enum km_type type)
 }
 EXPORT_SYMBOL(__kmap_atomic);
 
-void __kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
+void __kunmap_atomic(void *kvaddr)
 {
-#ifdef CONFIG_DEBUG_HIGHMEM
         unsigned long vaddr = (unsigned long) kvaddr & PAGE_MASK;
-        enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
+        int type;
 
         if (vaddr < FIXADDR_START) { // FIXME
                 pagefault_enable();
                 return;
         }
 
-        BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
+        type = kmap_atomic_idx_pop();
+#ifdef CONFIG_DEBUG_HIGHMEM
+        {
+                int 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
-         */
-        pte_clear(&init_mm, vaddr, kmap_pte-idx);
-        local_flush_tlb_one(vaddr);
-#endif
+                BUG_ON(vaddr != __fix_to_virt(FIX_KMAP_BEGIN + idx));
 
+                /*
+                 * force other mappings to Oops if they'll try to access
+                 * this pte without first remap it
+                 */
+                pte_clear(&init_mm, vaddr, kmap_pte-idx);
+                local_flush_tlb_one(vaddr);
+        }
+#endif
         pagefault_enable();
 }
-EXPORT_SYMBOL(__kunmap_atomic_notypecheck);
+EXPORT_SYMBOL(__kunmap_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)
 {
-        enum fixed_addresses idx;
         unsigned long vaddr;
+        int idx, type;
 
         pagefault_disable();
 
-        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);
         set_pte(kmap_pte-idx, pfn_pte(pfn, PAGE_KERNEL));
@@ -109,7 +113,7 @@ void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
         return (void*) vaddr;
 }
 
-struct page *__kmap_atomic_to_page(void *ptr)
+struct page *kmap_atomic_to_page(void *ptr)
 {
         unsigned long idx, vaddr = (unsigned long)ptr;
         pte_t *pte;