blk-mq: Fix tagset reinit in the presence of cpu hot-unplug

In case cpu was unplugged, we need to make sure not to assume
that the tags for that cpu are still allocated. so check
for null tags when reinitializing a tagset.

Reported-by: Yi Zhang <yizhan@redhat.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 3 insertions, 0 deletions

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index e48bc2c72615..9d97bfc4d465 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -295,6 +295,9 @@ int blk_mq_reinit_tagset(struct blk_mq_tag_set *set)
         for (i = 0; i < set->nr_hw_queues; i++) {
                 struct blk_mq_tags *tags = set->tags[i];
 
+                if (!tags)
+                        continue;
+
                 for (j = 0; j < tags->nr_tags; j++) {
                         if (!tags->static_rqs[j])
                                 continue;