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-rw-r--r--block/blk-iocost.c9
1 files changed, 8 insertions, 1 deletions
diff --git a/block/blk-iocost.c b/block/blk-iocost.c
index a5b37cc65b17..769b64394298 100644
--- a/block/blk-iocost.c
+++ b/block/blk-iocost.c
@@ -2311,7 +2311,14 @@ static void ioc_timer_fn(struct timer_list *timer)
hwm = current_hweight_max(iocg);
new_hwi = hweight_after_donation(iocg, old_hwi, hwm,
usage, &now);
- if (new_hwi < hwm) {
+ /*
+ * Donation calculation assumes hweight_after_donation
+ * to be positive, a condition that a donor w/ hwa < 2
+ * can't meet. Don't bother with donation if hwa is
+ * below 2. It's not gonna make a meaningful difference
+ * anyway.
+ */
+ if (new_hwi < hwm && hwa >= 2) {
iocg->hweight_donating = hwa;
iocg->hweight_after_donation = new_hwi;
list_add(&iocg->surplus_list, &surpluses);