[PATCH] use for_each_possible_cpu for reservation slots

[Eric Sandeen <sandeen@redhat.com>]

NR_CPUS is a config-time option that may be much more than your actual
count of runtime possible CPUs... 

compile-tested.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>

Index: linux-2.6-ext4/fs/ext4/balloc.c
===================================================================
--- linux-2.6-ext4.orig/fs/ext4/balloc.c
+++ linux-2.6-ext4/fs/ext4/balloc.c
@@ -1895,16 +1895,17 @@ void ext4_rebalance_reservation(struct e
 	__u64 chunk;
 
 	/* let's know what slots have been used */
-	for (i = 0; i < NR_CPUS; i++)
+	for_each_possible_cpu(i) {
 		if (rs[i].rs_reserved || i == smp_processor_id())
 			used_slots++;
+	}
 
 	/* chunk is a number of block every used
 	 * slot will get. make sure it isn't 0 */
 	chunk = free + used_slots - 1;
 	do_div(chunk, used_slots);
 
-	for (i = 0; i < NR_CPUS; i++) {
+	for_each_possible_cpu(i) {
 		if (free < chunk)
 			chunk = free;
 		if (rs[i].rs_reserved || i == smp_processor_id()) {
@@ -1926,7 +1927,7 @@ int ext4_reserve_global(struct super_blo
 	rs = sbi->s_reservation_slots;
 
 	/* lock all slots */
-	for (i = 0; i < NR_CPUS; i++) {
+	for_each_possible_cpu(i) {
 		spin_lock(&rs[i].rs_lock);
 		free += rs[i].rs_reserved;
 	}
@@ -1937,8 +1938,9 @@ int ext4_reserve_global(struct super_blo
 		rc = 0;
 	}
 
-	for (i = 0; i < NR_CPUS; i++)
+	for_each_possible_cpu(i) {
 		spin_unlock(&rs[i].rs_lock);
+	}
 
 	return rc;
 }
@@ -1979,12 +1981,14 @@ int ext4_reserve_init(struct super_block
 	struct ext4_reservation_slot *rs;
 	int i;
 
-	rs = kmalloc(sizeof(struct ext4_reservation_slot) * NR_CPUS, GFP_KERNEL);
+	rs = kmalloc(sizeof(struct ext4_reservation_slot) * 
+			highest_possible_processor_id()+1,
+		     GFP_KERNEL);
 	if (rs == NULL)
 		return -ENOMEM;
 	sbi->s_reservation_slots = rs;
 
-	for (i = 0; i < NR_CPUS; i++) {
+	for_each_possible_cpu(i) {
 		spin_lock_init(&rs[i].rs_lock);
 		rs[i].rs_reserved = 0;
 	}