genirq/affinity: Allow irq spreading from a given starting point

To support two stage irq vector spreading, it's required to add a starting
point to the spreading function. No functional change, just preparatory
work for the actual two stage change.

[ tglx: Renamed variables, tidied up the code and massaged changelog ]

Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: linux-block@vger.kernel.org
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Christoph Hellwig <hch@infradead.org>
Link: https://lkml.kernel.org/r/20180308105358.1506-4-ming.lei@redhat.com

1 files changed, 20 insertions, 15 deletions

diff --git a/kernel/irq/affinity.c b/kernel/irq/affinity.c
index a9c36904500c..213695a27ddb 100644
--- a/kernel/irq/affinity.c
+++ b/kernel/irq/affinity.c
@@ -94,17 +94,17 @@ static int get_nodes_in_cpumask(cpumask_var_t *node_to_cpumask,
         return nodes;
 }
 
-static int irq_build_affinity_masks(int nvecs, const struct irq_affinity *affd,
+static int irq_build_affinity_masks(const struct irq_affinity *affd,
+                                    int startvec, int numvecs,
                                     cpumask_var_t *node_to_cpumask,
                                     const struct cpumask *cpu_mask,
                                     struct cpumask *nmsk,
                                     struct cpumask *masks)
 {
-        int affv = nvecs - affd->pre_vectors - affd->post_vectors;
-        int last_affv = affv + affd->pre_vectors;
-        int curvec = affd->pre_vectors;
+        int n, nodes, cpus_per_vec, extra_vecs, done = 0;
+        int last_affv = affd->pre_vectors + numvecs;
+        int curvec = startvec;
         nodemask_t nodemsk = NODE_MASK_NONE;
-        int n, nodes, cpus_per_vec, extra_vecs;
 
         nodes = get_nodes_in_cpumask(node_to_cpumask, cpu_mask, &nodemsk);
 
@@ -112,12 +112,13 @@ static int irq_build_affinity_masks(int nvecs, const struct irq_affinity *affd,
          * If the number of nodes in the mask is greater than or equal the
          * number of vectors we just spread the vectors across the nodes.
          */
-        if (affv <= nodes) {
+        if (numvecs <= nodes) {
                 for_each_node_mask(n, nodemsk) {
-                        cpumask_copy(masks + curvec,
-                                     node_to_cpumask[n]);
-                        if (++curvec == last_affv)
+                        cpumask_copy(masks + curvec, node_to_cpumask[n]);
+                        if (++done == numvecs)
                                 break;
+                        if (++curvec == last_affv)
+                                curvec = affd->pre_vectors;
                 }
                 goto out;
         }
@@ -126,7 +127,7 @@ static int irq_build_affinity_masks(int nvecs, const struct irq_affinity *affd,
                 int ncpus, v, vecs_to_assign, vecs_per_node;
 
                 /* Spread the vectors per node */
-                vecs_per_node = (affv - (curvec - affd->pre_vectors)) / nodes;
+                vecs_per_node = (numvecs - (curvec - affd->pre_vectors)) / nodes;
 
                 /* Get the cpus on this node which are in the mask */
                 cpumask_and(nmsk, cpu_mask, node_to_cpumask[n]);
@@ -150,13 +151,16 @@ static int irq_build_affinity_masks(int nvecs, const struct irq_affinity *affd,
                         irq_spread_init_one(masks + curvec, nmsk, cpus_per_vec);
                 }
 
-                if (curvec >= last_affv)
+                done += v;
+                if (done >= numvecs)
                         break;
+                if (curvec >= last_affv)
+                        curvec = affd->pre_vectors;
                 --nodes;
         }
 
 out:
-        return curvec - affd->pre_vectors;
+        return done;
 }
 
 /**
@@ -169,9 +173,9 @@ out:
 struct cpumask *
 irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
 {
+        int curvec, affvecs = nvecs - affd->pre_vectors - affd->post_vectors;
         cpumask_var_t nmsk, *node_to_cpumask;
         struct cpumask *masks = NULL;
-        int curvec;
 
         /*
          * If there aren't any vectors left after applying the pre/post
@@ -198,8 +202,9 @@ irq_create_affinity_masks(int nvecs, const struct irq_affinity *affd)
         /* Stabilize the cpumasks */
         get_online_cpus();
         build_node_to_cpumask(node_to_cpumask);
-        curvec += irq_build_affinity_masks(nvecs, affd, node_to_cpumask,
-                                           cpu_possible_mask, nmsk, masks);
+        curvec += irq_build_affinity_masks(affd, curvec, affvecs,
+                                           node_to_cpumask, cpu_possible_mask,
+                                           nmsk, masks);
         put_online_cpus();
 
         /* Fill out vectors at the end that don't need affinity */