[v2,5/8] blk-mq: remap queues when adding/removing hardware queues

Commit Message

Omar Sandoval April 5, 2017, 6:28 p.m. UTC

From: Omar Sandoval <[e-mail]>

blk_mq_update_nr_hw_queues() used to remap hardware queues, which is the
behavior that drivers expect. However, commit 4e68a011428a changed
blk_mq_queue_reinit() to not remap queues for the case of CPU
hotplugging, inadvertently making blk_mq_update_nr_hw_queues() not remap
queues as well. This breaks, for example, NBD's multi-connection mode,
leaving the added hardware queues unused. Fix it by making
blk_mq_update_nr_hw_queues() explicitly remap the queues.

Fixes: 4e68a011428a ("blk-mq: don't redistribute hardware queues on a CPU hotplug event")
Reviewed-by: Keith Busch <[e-mail]>
Reviewed-by: Christoph Hellwig <[e-mail]>
Reviewed-by: Sagi Grimberg <[e-mail]>
Signed-off-by: Omar Sandoval <[e-mail]>
---
 block/blk-mq.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

Patch

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 53c5c6097be9..4aa3148befe1 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2484,6 +2484,14 @@  static int blk_mq_alloc_rq_maps(struct blk_mq_tag_set *set)
 	return 0;
 }
 
+static int blk_mq_update_queue_map(struct blk_mq_tag_set *set)
+{
+	if (set->ops->map_queues)
+		return set->ops->map_queues(set);
+	else
+		return blk_mq_map_queues(set);
+}
+
 /*
  * Alloc a tag set to be associated with one or more request queues.
  * May fail with EINVAL for various error conditions. May adjust the
@@ -2538,10 +2546,7 @@  int blk_mq_alloc_tag_set(struct blk_mq_tag_set *set)
 	if (!set->mq_map)
 		goto out_free_tags;
 
-	if (set->ops->map_queues)
-		ret = set->ops->map_queues(set);
-	else
-		ret = blk_mq_map_queues(set);
+	ret = blk_mq_update_queue_map(set);
 	if (ret)
 		goto out_free_mq_map;
 
@@ -2633,6 +2638,7 @@  void blk_mq_update_nr_hw_queues(struct blk_mq_tag_set *set, int nr_hw_queues)
 		blk_mq_freeze_queue(q);
 
 	set->nr_hw_queues = nr_hw_queues;
+	blk_mq_update_queue_map(set);
 	list_for_each_entry(q, &set->tag_list, tag_set_list) {
 		blk_mq_realloc_hw_ctxs(set, q);
 		blk_mq_queue_reinit(q, cpu_online_mask);