[PATCH] nvme: don't call blk_mq_{,un}quiesce_tagset when ctrl->tagset is NULL

[Christoph Hellwig]

The NVMe drivers support a mode where no tagset is allocated for the I/O
queues and only the admin queue is usable.  In that case ctrl->tagset is
NULL and we must not call the block per-tagset quiesce helpers that
dereference it.

Fixes: 98d81f0df70c ("nvme: use blk_mq_[un]quiesce_tagset")
Reported-by: Gerd Bayer <gbayer at linux.ibm.com>
Signed-off-by: Christoph Hellwig <hch at lst.de>
---

It turns out we have a bunch of other quiesce calls that can happen when
only the admin queue is live.  So bring back the original quick fix to
check for the tagset pointer in the quiesce helpers.

 drivers/nvme/host/core.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 3195ae17df309..fd2e26cb7a688 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -5215,6 +5215,8 @@ EXPORT_SYMBOL_GPL(nvme_start_freeze);
 
 void nvme_quiesce_io_queues(struct nvme_ctrl *ctrl)
 {
+	if (!ctrl->tagset)
+		return;
 	if (!test_and_set_bit(NVME_CTRL_STOPPED, &ctrl->flags))
 		blk_mq_quiesce_tagset(ctrl->tagset);
 	else
@@ -5224,6 +5226,8 @@ EXPORT_SYMBOL_GPL(nvme_quiesce_io_queues);
 
 void nvme_unquiesce_io_queues(struct nvme_ctrl *ctrl)
 {
+	if (!ctrl->tagset)
+		return;
 	if (test_and_clear_bit(NVME_CTRL_STOPPED, &ctrl->flags))
 		blk_mq_unquiesce_tagset(ctrl->tagset);
 }
-- 
2.30.2