irq/affinity: Fix extra vecs calculation

This fixes a math error calculating the extra_vecs. The error assumed
only 1 cpu per vector, but the value needs to account for the actual
number of cpus per vector in order to get the correct remainder for
extra CPU assignment.

Fixes: 7bf8222b9bd0 ("irq/affinity: Fix CPU spread for unbalanced nodes")
Reported-by: Xiaolong Ye <xiaolong.ye@intel.com>
Signed-off-by: Keith Busch <keith.busch@intel.com>
Link: http://lkml.kernel.org/r/1492104492-19943-1-git-send-email-keith.busch@intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index dc529116f7e6ce2b4025926254d253c765a86f71..d052947fe78507ac80bbe58a09cc612bca7bab73 100644 (file)
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -108,7 +108,7 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
                vecs_to_assign = min(vecs_per_node, ncpus);
 
                /* Account for rounding errors */
-               extra_vecs = ncpus - vecs_to_assign;
+               extra_vecs = ncpus - vecs_to_assign * (ncpus / vecs_to_assign);
 
                for (v = 0; curvec < last_affv && v < vecs_to_assign;
                     curvec++, v++) {