use for_each_possible_cpu for reservation slots

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

compile-tested.

Index: 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;
	}

Ted, I don't see this in the git tree yet.

Yea? Nay? Comments?

Thanks,
-Eric