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Subject[PATCH 4.19 083/131] nvme-multipath: fix deadlock between ana_work and scan_work
Date
From: Anton Eidelman <anton@lightbitslabs.com>

[ Upstream commit 489dd102a2c7c94d783a35f9412eb085b8da1aa4 ]

When scan_work calls nvme_mpath_add_disk() this holds ana_lock
and invokes nvme_parse_ana_log(), which may issue IO
in device_add_disk() and hang waiting for an accessible path.
While nvme_mpath_set_live() only called when nvme_state_is_live(),
a transition may cause NVME_SC_ANA_TRANSITION and requeue the IO.

In order to recover and complete the IO ana_work on the same ctrl
should be able to update the path state and remove NVME_NS_ANA_PENDING.

The deadlock occurs because scan_work keeps holding ana_lock,
so ana_work hangs [1].

Fix:
Now nvme_mpath_add_disk() uses nvme_parse_ana_log() to obtain a copy
of the ANA group desc, and then calls nvme_update_ns_ana_state() without
holding ana_lock.

[1]:
kernel: Workqueue: nvme-wq nvme_scan_work [nvme_core]
kernel: Call Trace:
kernel: __schedule+0x2b9/0x6c0
kernel: schedule+0x42/0xb0
kernel: io_schedule+0x16/0x40
kernel: do_read_cache_page+0x438/0x830
kernel: read_cache_page+0x12/0x20
kernel: read_dev_sector+0x27/0xc0
kernel: read_lba+0xc1/0x220
kernel: efi_partition+0x1e6/0x708
kernel: check_partition+0x154/0x244
kernel: rescan_partitions+0xae/0x280
kernel: __blkdev_get+0x40f/0x560
kernel: blkdev_get+0x3d/0x140
kernel: __device_add_disk+0x388/0x480
kernel: device_add_disk+0x13/0x20
kernel: nvme_mpath_set_live+0x119/0x140 [nvme_core]
kernel: nvme_update_ns_ana_state+0x5c/0x60 [nvme_core]
kernel: nvme_set_ns_ana_state+0x1e/0x30 [nvme_core]
kernel: nvme_parse_ana_log+0xa1/0x180 [nvme_core]
kernel: nvme_mpath_add_disk+0x47/0x90 [nvme_core]
kernel: nvme_validate_ns+0x396/0x940 [nvme_core]
kernel: nvme_scan_work+0x24f/0x380 [nvme_core]
kernel: process_one_work+0x1db/0x380
kernel: worker_thread+0x249/0x400
kernel: kthread+0x104/0x140

kernel: Workqueue: nvme-wq nvme_ana_work [nvme_core]
kernel: Call Trace:
kernel: __schedule+0x2b9/0x6c0
kernel: schedule+0x42/0xb0
kernel: schedule_preempt_disabled+0xe/0x10
kernel: __mutex_lock.isra.0+0x182/0x4f0
kernel: ? __switch_to_asm+0x34/0x70
kernel: ? select_task_rq_fair+0x1aa/0x5c0
kernel: ? kvm_sched_clock_read+0x11/0x20
kernel: ? sched_clock+0x9/0x10
kernel: __mutex_lock_slowpath+0x13/0x20
kernel: mutex_lock+0x2e/0x40
kernel: nvme_read_ana_log+0x3a/0x100 [nvme_core]
kernel: nvme_ana_work+0x15/0x20 [nvme_core]
kernel: process_one_work+0x1db/0x380
kernel: worker_thread+0x4d/0x400
kernel: kthread+0x104/0x140
kernel: ? process_one_work+0x380/0x380
kernel: ? kthread_park+0x80/0x80
kernel: ret_from_fork+0x35/0x40

Fixes: 0d0b660f214d ("nvme: add ANA support")
Signed-off-by: Anton Eidelman <anton@lightbitslabs.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/nvme/host/multipath.c | 24 ++++++++++++++++--------
1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 6f584a9515f42..3ad6183c5e6b4 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -496,26 +496,34 @@ static ssize_t ana_state_show(struct device *dev, struct device_attribute *attr,
}
DEVICE_ATTR_RO(ana_state);

-static int nvme_set_ns_ana_state(struct nvme_ctrl *ctrl,
+static int nvme_lookup_ana_group_desc(struct nvme_ctrl *ctrl,
struct nvme_ana_group_desc *desc, void *data)
{
- struct nvme_ns *ns = data;
+ struct nvme_ana_group_desc *dst = data;

- if (ns->ana_grpid == le32_to_cpu(desc->grpid)) {
- nvme_update_ns_ana_state(desc, ns);
- return -ENXIO; /* just break out of the loop */
- }
+ if (desc->grpid != dst->grpid)
+ return 0;

- return 0;
+ *dst = *desc;
+ return -ENXIO; /* just break out of the loop */
}

void nvme_mpath_add_disk(struct nvme_ns *ns, struct nvme_id_ns *id)
{
if (nvme_ctrl_use_ana(ns->ctrl)) {
+ struct nvme_ana_group_desc desc = {
+ .grpid = id->anagrpid,
+ .state = 0,
+ };
+
mutex_lock(&ns->ctrl->ana_lock);
ns->ana_grpid = le32_to_cpu(id->anagrpid);
- nvme_parse_ana_log(ns->ctrl, ns, nvme_set_ns_ana_state);
+ nvme_parse_ana_log(ns->ctrl, &desc, nvme_lookup_ana_group_desc);
mutex_unlock(&ns->ctrl->ana_lock);
+ if (desc.state) {
+ /* found the group desc: update */
+ nvme_update_ns_ana_state(&desc, ns);
+ }
} else {
mutex_lock(&ns->head->lock);
ns->ana_state = NVME_ANA_OPTIMIZED;
--
2.25.1
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