[Suspend2][ 03/10] [Suspend2] Atomic copy get_next_bit_on routine.

[Nigel Cunningham <nigel@suspend2.net>]

This routine is used find the next bit in a bitmap that is on. It is used
during the atomic restore of highmem pages.

Signed-off-by: Nigel Cunningham <nigel@suspend2.net>

 kernel/power/atomic_copy.c |   60 ++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 60 insertions(+), 0 deletions(-)

diff --git a/kernel/power/atomic_copy.c b/kernel/power/atomic_copy.c
index 07b418c..6d1bc68 100644
--- a/kernel/power/atomic_copy.c
+++ b/kernel/power/atomic_copy.c
@@ -75,3 +75,63 @@ static void suspend_init_nosave_zone_tab
 	}
 }
 
+/**
+ * __suspend_get_next_bit_on: Atomic-copy safe location of next bit on in a bitmap.
+ * 
+ * @bitmap:	The bitmap we are traversing.
+ * @zone_num:	Which zone we are in.
+ * @counter:	The current pfn.
+ *
+ * A version of __get_next_bit_on that can be used when doing the atomic
+ * copy. While doing it, we can't rely on the zone information being in
+ * a constant location.
+ **/
+static unsigned long __suspend_get_next_bit_on(dyn_pageflags_t bitmap,
+		int *zone_num, long counter)
+{
+	unsigned long *ul_ptr = NULL;
+	int reset_ul_ptr = 1;
+	BUG_ON(*zone_num == num_zones);
+
+	if (counter == -1) {
+		*zone_num = 0;
+
+		/* 
+		 * Test the end because the start can validly
+		 * be zero.
+		 */
+		while (!zone_nosave[*zone_num].end_pfn)
+			(*zone_num)++;
+		counter = zone_nosave[*zone_num].start_pfn - 1;
+	}
+
+	do {
+		counter++;
+		if (counter > zone_nosave[*zone_num].end_pfn) {
+			(*zone_num)++;
+			while (!zone_nosave[*zone_num].end_pfn &&
+					*zone_num < num_zones)
+				(*zone_num)++;
+			
+			if (*zone_num == num_zones)
+				return -1;
+			counter = zone_nosave[*zone_num].start_pfn;
+			reset_ul_ptr = 1;
+		} else
+			if (!(counter & BIT_NUM_MASK))
+				reset_ul_ptr = 1;
+
+		if (reset_ul_ptr) {
+			reset_ul_ptr = 0;
+			ul_ptr = PAGE_UL_PTR(bitmap, *zone_num,
+				(counter - zone_nosave[*zone_num].start_pfn));
+			if (!*ul_ptr) {
+				counter += BIT_NUM_MASK - 1;
+				continue;
+			}
+		}
+	} while(!test_bit(PAGEBIT(counter), ul_ptr));
+
+	return counter;
+}
+

--
Nigel Cunningham		nigel at suspend2 dot net