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, 23 insertions, 62 deletions

diff --git a/arch/tile/mm/highmem.c b/arch/tile/mm/highmem.c
index 12ab137e7d4f..8ef6595e162c 100644
--- a/arch/tile/mm/highmem.c
+++ b/arch/tile/mm/highmem.c
@@ -56,50 +56,6 @@ void kunmap(struct page *page)
 }
 EXPORT_SYMBOL(kunmap);
 
-static void debug_kmap_atomic_prot(enum km_type type)
-{
-#ifdef CONFIG_DEBUG_HIGHMEM
-        static unsigned warn_count = 10;
-
-        if (unlikely(warn_count == 0))
-                return;
-
-        if (unlikely(in_interrupt())) {
-                if (in_irq()) {
-                        if (type != KM_IRQ0 && type != KM_IRQ1 &&
-                            type != KM_BIO_SRC_IRQ &&
-                            /* type != KM_BIO_DST_IRQ && */
-                            type != KM_BOUNCE_READ) {
-                                WARN_ON(1);
-                                warn_count--;
-                        }
-                } else if (!irqs_disabled()) {  /* softirq */
-                        if (type != KM_IRQ0 && type != KM_IRQ1 &&
-                            type != KM_SOFTIRQ0 && type != KM_SOFTIRQ1 &&
-                            type != KM_SKB_SUNRPC_DATA &&
-                            type != KM_SKB_DATA_SOFTIRQ &&
-                            type != KM_BOUNCE_READ) {
-                                WARN_ON(1);
-                                warn_count--;
-                        }
-                }
-        }
-
-        if (type == KM_IRQ0 || type == KM_IRQ1 || type == KM_BOUNCE_READ ||
-            type == KM_BIO_SRC_IRQ /* || type == KM_BIO_DST_IRQ */) {
-                if (!irqs_disabled()) {
-                        WARN_ON(1);
-                        warn_count--;
-                }
-        } else if (type == KM_SOFTIRQ0 || type == KM_SOFTIRQ1) {
-                if (irq_count() == 0 && !irqs_disabled()) {
-                        WARN_ON(1);
-                        warn_count--;
-                }
-        }
-#endif
-}
-
 /*
  * Describe a single atomic mapping of a page on a given cpu at a
  * given address, and allow it to be linked into a list.
@@ -240,10 +196,10 @@ void kmap_atomic_fix_kpte(struct page *page, int finished)
  * When holding an atomic kmap is 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;
         pte_t *pte;
 
         /* even !CONFIG_PREEMPT needs this, for in_atomic in do_page_fault */
@@ -255,8 +211,7 @@ void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
         if (!PageHighMem(page))
                 return page_address(page);
 
-        debug_kmap_atomic_prot(type);
-
+        type = kmap_atomic_idx_push();
         idx = type + KM_TYPE_NR*smp_processor_id();
         vaddr = __fix_to_virt(FIX_KMAP_BEGIN + idx);
         pte = kmap_get_pte(vaddr);
@@ -269,25 +224,31 @@ void *kmap_atomic_prot(struct page *page, enum km_type type, pgprot_t prot)
 }
 EXPORT_SYMBOL(kmap_atomic_prot);
 
-void *kmap_atomic(struct page *page, enum km_type type)
+void *__kmap_atomic(struct page *page)
 {
         /* PAGE_NONE is a magic value that tells us to check immutability. */
         return kmap_atomic_prot(page, type, PAGE_NONE);
 }
-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;
-        enum fixed_addresses idx = type + KM_TYPE_NR*smp_processor_id();
 
-        /*
-         * Force other mappings to Oops if they try to access this pte without
-         * first remapping it.  Keeping stale mappings around is a bad idea.
-         */
-        if (vaddr == __fix_to_virt(FIX_KMAP_BEGIN+idx)) {
+        if (vaddr >= __fix_to_virt(FIX_KMAP_END) &&
+            vaddr <= __fix_to_virt(FIX_KMAP_BEGIN)) {
                 pte_t *pte = kmap_get_pte(vaddr);
                 pte_t pteval = *pte;
+                int idx, type;
+
+                type = kmap_atomic_idx_pop();
+                idx = type + KM_TYPE_NR*smp_processor_id();
+
+                /*
+                 * Force other mappings to Oops if they try to access this pte
+                 * without first remapping it.  Keeping stale mappings around
+                 * is a bad idea.
+                 */
                 BUG_ON(!pte_present(pteval) && !pte_migrating(pteval));
                 kmap_atomic_unregister(pte_page(pteval), vaddr);
                 kpte_clear_flush(pte, vaddr);
@@ -300,19 +261,19 @@ void kunmap_atomic_notypecheck(void *kvaddr, enum km_type type)
         arch_flush_lazy_mmu_mode();
         pagefault_enable();
 }
-EXPORT_SYMBOL(kunmap_atomic_notypecheck);
+EXPORT_SYMBOL(__kunmap_atomic);
 
 /*
  * This API is supposed to allow us to map memory without a "struct page".
  * Currently we don't support this, though this may change in the future.
  */
-void *kmap_atomic_pfn(unsigned long pfn, enum km_type type)
+void *kmap_atomic_pfn(unsigned long pfn)
 {
-        return kmap_atomic(pfn_to_page(pfn), type);
+        return kmap_atomic(pfn_to_page(pfn));
 }
-void *kmap_atomic_prot_pfn(unsigned long pfn, enum km_type type, pgprot_t prot)
+void *kmap_atomic_prot_pfn(unsigned long pfn, pgprot_t prot)
 {
-        return kmap_atomic_prot(pfn_to_page(pfn), type, prot);
+        return kmap_atomic_prot(pfn_to_page(pfn), prot);
 }
 
 struct page *kmap_atomic_to_page(void *ptr)