From: Sagi Grimberg <sagi@grimberg.me>
Date: Mon, 13 Mar 2017 14:10:11 +0000 (+0200)
Subject: blk-mq: Fix tagset reinit in the presence of cpu hot-unplug
X-Git-Tag: v4.11-rc3~24^2~2
X-Git-Url: https://asedeno.scripts.mit.edu/gitweb/?a=commitdiff_plain;h=0067d4b020ea07a58540acb2c5fcd3364bf326e0;p=linux.git

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>
---

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;