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, 4 insertions, 58 deletions

diff --git a/mm/highmem.c b/mm/highmem.c
index 7a0aa1b..781e754 100644
--- a/mm/highmem.c
+++ b/mm/highmem.c
@@ -42,6 +42,10 @@
 unsigned long totalhigh_pages __read_mostly;
 EXPORT_SYMBOL(totalhigh_pages);
 
+
+DEFINE_PER_CPU(int, __kmap_atomic_idx);
+EXPORT_PER_CPU_SYMBOL(__kmap_atomic_idx);
+
 unsigned int nr_free_highpages (void)
 {
 	pg_data_t *pgdat;
@@ -422,61 +426,3 @@ void __init page_address_init(void)
 }
 
 #endif	/* defined(CONFIG_HIGHMEM) && !defined(WANT_PAGE_VIRTUAL) */
-
-#ifdef CONFIG_DEBUG_HIGHMEM
-
-void debug_kmap_atomic(enum km_type type)
-{
-	static int warn_count = 10;
-
-	if (unlikely(warn_count < 0))
-		return;
-
-	if (unlikely(in_interrupt())) {
-		if (in_nmi()) {
-			if (type != KM_NMI && type != KM_NMI_PTE) {
-				WARN_ON(1);
-				warn_count--;
-			}
-		} else if (in_irq()) {
-			if (type != KM_IRQ0 && type != KM_IRQ1 &&
-			    type != KM_BIO_SRC_IRQ && type != KM_BIO_DST_IRQ &&
-			    type != KM_BOUNCE_READ && type != KM_IRQ_PTE) {
-				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 ||
-			type == KM_IRQ_PTE || type == KM_NMI ||
-			type == KM_NMI_PTE ) {
-		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--;
-		}
-	}
-#ifdef CONFIG_KGDB_KDB
-	if (unlikely(type == KM_KDB && atomic_read(&kgdb_active) == -1)) {
-		WARN_ON(1);
-		warn_count--;
-	}
-#endif /* CONFIG_KGDB_KDB */
-}
-
-#endif