diff mbox

[v3] blk-mq: remap queues when adding/removing hardware queues

Message ID 9753ebd0c51a9d49f110a6d0d00888170905d97a.1490993257.git.osandov@fb.com (mailing list archive)
State New, archived
Headers show

Commit Message

Omar Sandoval March 31, 2017, 8:48 p.m. UTC 
From: Omar Sandoval <osandov@fb.com>

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")
Signed-off-by: Omar Sandoval <osandov@fb.com>
---
 block/blk-mq.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

Comments

Keith Busch March 31, 2017, 9:09 p.m. UTC | #1 
On Fri, Mar 31, 2017 at 01:48:35PM -0700, Omar Sandoval wrote:
> From: Omar Sandoval <osandov@fb.com>
> 
> 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")
> Signed-off-by: Omar Sandoval <osandov@fb.com>

This looks good to me. 

Reviewed-by: Keith Busch <keith.busch@intel.com>
Christoph Hellwig April 4, 2017, 6:24 a.m. UTC | #2 
Looks fine,

Reviewed-by: Christoph Hellwig <hch@lst.de>
Sagi Grimberg April 5, 2017, 12:01 p.m. UTC | #3 
Looks good,

Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
diff mbox

Patch

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 061fc2cc88d3..dbc0f2f745e3 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2478,6 +2478,14 @@  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
@@ -2532,10 +2540,7 @@  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;
 
@@ -2627,6 +2632,7 @@  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);