linux-kernel - [PATCH AUTOSEL for 4.9 026/156] blk-mq: Fix tagset reinit in the presence of cpu hot-unplug

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Date:   Thu, 7 Dec 2017 15:49:00 +0000
From:   alexander.levin@...izon.com
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Sagi Grimberg <sagi@...mberg.me>, Jens Axboe <axboe@...com>,
        alexander.levin@...izon.com
Subject: [PATCH AUTOSEL for 4.9 026/156] blk-mq: Fix tagset reinit in the
 presence of cpu hot-unplug

From: Sagi Grimberg <sagi@...mberg.me>

[ 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@...hat.com>
Signed-off-by: Sagi Grimberg <sagi@...mberg.me>
Signed-off-by: Jens Axboe <axboe@...com>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 block/blk-mq-tag.c | 3 +++
 1 file changed, 3 insertions(+)

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;
-- 
2.11.0