sched, block: Unify cache detection

The block layer has some code trying to determine if two CPUs share a
cache, the scheduler has a similar function. Expose the function used
by the scheduler and make the block layer use it, thereby removing the
block layers usage of CONFIG_SCHED* and topology bits.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Jens Axboe <axboe@kernel.dk>
Link: http://lkml.kernel.org/r/1327579450.2446.95.camel@twins

2 files changed, 8 insertions, 24 deletions

diff --git a/block/blk-softirq.c b/block/blk-softirq.c
index 1366a89..467c8de 100644
--- a/block/blk-softirq.c
+++ b/block/blk-softirq.c
@@ -8,6 +8,7 @@
 #include <linux/blkdev.h>
 #include <linux/interrupt.h>
 #include <linux/cpu.h>
+#include <linux/sched.h>
 
 #include "blk.h"
 
@@ -103,9 +104,10 @@ static struct notifier_block __cpuinitdata blk_cpu_notifier = {
 
 void __blk_complete_request(struct request *req)
 {
-	int ccpu, cpu, group_cpu = NR_CPUS;
+	int ccpu, cpu;
 	struct request_queue *q = req->q;
 	unsigned long flags;
+	bool shared = false;
 
 	BUG_ON(!q->softirq_done_fn);
 
@@ -117,22 +119,20 @@ void __blk_complete_request(struct request *req)
 	 */
 	if (req->cpu != -1) {
 		ccpu = req->cpu;
-		if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags)) {
-			ccpu = blk_cpu_to_group(ccpu);
-			group_cpu = blk_cpu_to_group(cpu);
-		}
+		if (!test_bit(QUEUE_FLAG_SAME_FORCE, &q->queue_flags))
+			shared = cpus_share_cache(cpu, ccpu);
 	} else
 		ccpu = cpu;
 
 	/*
-	 * If current CPU and requested CPU are in the same group, running
-	 * softirq in current CPU. One might concern this is just like
+	 * If current CPU and requested CPU share a cache, run the softirq on
+	 * the current CPU. One might concern this is just like
 	 * QUEUE_FLAG_SAME_FORCE, but actually not. blk_complete_request() is
 	 * running in interrupt handler, and currently I/O controller doesn't
 	 * support multiple interrupts, so current CPU is unique actually. This
 	 * avoids IPI sending from current CPU to the first CPU of a group.
 	 */
-	if (ccpu == cpu || ccpu == group_cpu) {
+	if (ccpu == cpu || shared) {
 		struct list_head *list;
 do_local:
 		list = &__get_cpu_var(blk_cpu_done);
diff --git a/block/blk.h b/block/blk.h
index 7efd772..df5b59a 100644
--- a/block/blk.h
+++ b/block/blk.h
@@ -164,22 +164,6 @@ static inline int queue_congestion_off_threshold(struct request_queue *q)
 	return q->nr_congestion_off;
 }
 
-static inline int blk_cpu_to_group(int cpu)
-{
-	int group = NR_CPUS;
-#ifdef CONFIG_SCHED_MC
-	const struct cpumask *mask = cpu_coregroup_mask(cpu);
-	group = cpumask_first(mask);
-#elif defined(CONFIG_SCHED_SMT)
-	group = cpumask_first(topology_thread_cpumask(cpu));
-#else
-	return cpu;
-#endif
-	if (likely(group < NR_CPUS))
-		return group;
-	return cpu;
-}
-
 /*
  * Contribute to IO statistics IFF:
  *