From d28046fb8c435fc63f51dca30cdeb423d8ab4479 Mon Sep 17 00:00:00 2001
From: Sagi Grimberg <sagi@grimberg.me>
Date: Mon, 13 Mar 2017 16:10:11 +0200
Subject: blk-mq: Fix tagset reinit in the presence of cpu hot-unplug

[ Upstream commit 0067d4b020ea07a58540acb2c5fcd3364bf326e0 ]

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>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 block/blk-mq-tag.c | 3 +++
 1 file changed, 3 insertions(+)

(limited to 'block')

diff --git a/block/blk-mq-tag.c b/block/blk-mq-tag.c
index dcf5ce3ba4bf..4bc701b32ce2 100644
--- a/block/blk-mq-tag.c
+++ b/block/blk-mq-tag.c
@@ -311,6 +311,9 @@ 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->rqs[j])
 				continue;
-- 
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