[PATCH 0/5] address deadlocks in high stress ns scanning and ana updates

[PATCH 0/5] address deadlocks in high stress ns scanning and ana updates

[Sagi Grimberg]

Hey All,

The following patches addresses some deadlocks observed while performing some
stress testing of a connect/disconnect storm in addition to rapid ana path
switches concurrently (paths may transition between live<->inaccessible)
on a large number of namespaces (100+).

The test mainly triggers three main flows:
1. ongoing ns scanning, in the presence of concurrent ANA path state changes
   and controller removals (disconnect).
2. ongoing ns scanning (or ana processing) in the presence of concurrent
   controller removal (disconnect).
3. ongoing ANA processing in the presence of concurrent controller removal
   (disconnect).

What was observed is that basically when we disconnect while scan_work and/or ana_work
are running, we can easily deadlock. The main reason is that scan_work and ana_work
may both register the gendisk, triggering I/O (partition scans). Given that a
controller removal (disconnect) may also be running at the same time, I/O may
block. The issue with blocking the head->disk I/O under the locks taken by
both ana_work and scan_work, it means that no other path may update path states
and by doing so, unblock the blocking I/O.

With this patchset applied, the test is able to pass successfully without any
deadlocks.

The last patch is posted as an RFC, while it solves a real problem, we are
essentially adding state to the controller without it going via the normal
controller state, the reason is that the controller state will also affect
ongoing mpath I/O which is the original cause of the deadlock. We are open
to alternative better suggestions if such exist.

Anton Eidelman (3):
  nvme-multipath: fix deadlock between ana_work and scan_work
  nvme-multipath: fix deadlock due to head->lock
  nvme-core: fix deadlock in disconnect during scan_work and/or ana_work

Sagi Grimberg (2):
  nvme: fix possible deadlock when I/O is blocked
  nvme: don't protect ns mutation with ns->head->lock

 drivers/nvme/host/core.c      | 11 +++++++++-
 drivers/nvme/host/multipath.c | 40 +++++++++++++++++++++++------------
 drivers/nvme/host/nvme.h      |  3 +++
 3 files changed, 39 insertions(+), 15 deletions(-)

-- 
2.25.1


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[PATCH 1/5] nvme: fix possible deadlock when I/O is blocked

[Sagi Grimberg]

Revert fab7772bfbcf ("nvme-multipath: revalidate nvme_ns_head gendisk
in nvme_validate_ns")

When adding a new namespace to the head disk (via nvme_mpath_set_live)
we will see partition scan which triggers I/O on the mpath device node.
This process will usually be triggered from the scan_work which holds
the scan_lock. If I/O blocks (if we got ana change currently have only
available paths but none are accessible) this can deadlock on the head
disk bd_mutex as both partition scan I/O takes it, and head disk revalidation
takes it to check for resize (also triggered from scan_work on a different
path). See trace [1].

This is no longer needed since commit cb224c3af4df ("nvme: Convert to
use set_capacity_revalidate_and_notify") which already updates resize
info without unnecessarily revalidating the disk.

[1]:
--
kernel: INFO: task kworker/u65:9:494 blocked for more than 241 seconds.
kernel:       Tainted: G           OE     5.3.5-050305-generic #201910071830
kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kernel: kworker/u65:9   D    0   494      2 0x80004000
kernel: Workqueue: nvme-wq nvme_scan_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:  __mutex_lock_slowpath+0x13/0x20
kernel:  mutex_lock+0x2e/0x40
kernel:  revalidate_disk+0x63/0xa0
kernel:  __nvme_revalidate_disk+0xfe/0x110 [nvme_core]
kernel:  nvme_revalidate_disk+0xa4/0x160 [nvme_core]
kernel:  ? evict+0x14c/0x1b0
kernel:  revalidate_disk+0x2b/0xa0
kernel:  nvme_validate_ns+0x49/0x940 [nvme_core]
kernel:  ? blk_mq_free_request+0xd2/0x100
kernel:  ? __nvme_submit_sync_cmd+0xbe/0x1e0 [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:  ? process_one_work+0x380/0x380
kernel:  ? kthread_park+0x80/0x80
kernel:  ret_from_fork+0x1f/0x40
...
kernel: INFO: task kworker/u65:1:2630 blocked for more than 241 seconds.
kernel:       Tainted: G           OE     5.3.5-050305-generic #201910071830
kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kernel: kworker/u65:1   D    0  2630      2 0x80004000
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:  ? __switch_to_asm+0x34/0x70
kernel:  ? file_fdatawait_range+0x30/0x30
kernel:  read_cache_page+0x12/0x20
kernel:  read_dev_sector+0x27/0xc0
kernel:  read_lba+0xc1/0x220
kernel:  ? kmem_cache_alloc_trace+0x19c/0x230
kernel:  efi_partition+0x1e6/0x708
kernel:  ? vsnprintf+0x39e/0x4e0
kernel:  ? snprintf+0x49/0x60
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_update_ns_ana_state+0x60/0x60 [nvme_core]
kernel:  nvme_mpath_add_disk+0x47/0x90 [nvme_core]
kernel:  nvme_validate_ns+0x396/0x940 [nvme_core]
kernel:  ? blk_mq_free_request+0xd2/0x100
kernel:  nvme_scan_work+0x24f/0x380 [nvme_core]
kernel:  process_one_work+0x1db/0x380
kernel:  worker_thread+0x249/0x400
kernel:  kthread+0x104/0x140
kernel:  ? process_one_work+0x380/0x380
kernel:  ? kthread_park+0x80/0x80
kernel:  ret_from_fork+0x1f/0x40
--

Fixes: fab7772bfbcf ("nvme-multipath: revalidate nvme_ns_head gendisk
in nvme_validate_ns")
Signed-off-by: Anton Eidelman <anton@lightbitslabs.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/core.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 915fa2e609eb..28f4388c1337 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -1974,7 +1974,6 @@ static int __nvme_revalidate_disk(struct gendisk *disk, struct nvme_id_ns *id)
 	if (ns->head->disk) {
 		nvme_update_disk_info(ns->head->disk, ns, id);
 		blk_queue_stack_limits(ns->head->disk->queue, ns->queue);
-		revalidate_disk(ns->head->disk);
 	}
 #endif
 	return 0;
-- 
2.25.1


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[PATCH 2/5] nvme-multipath: fix deadlock between ana_work and scan_work

[Sagi Grimberg]

From: Anton Eidelman <anton@lightbitslabs.com>

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>
---
 drivers/nvme/host/multipath.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index da78e499947a..a646f9eb2e73 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -640,13 +640,13 @@ 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_get_ns_ana_state(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);
+	if (desc->grpid == dst->grpid) {
+		*dst = *desc;
 		return -ENXIO; /* just break out of the loop */
 	}
 
@@ -656,10 +656,19 @@ static int nvme_set_ns_ana_state(struct nvme_ctrl *ctrl,
 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_get_ns_ana_state);
 		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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[PATCH 3/5] nvme: don't protect ns mutation with ns->head->lock

[Sagi Grimberg]

Right now ns->head->lock is protecting namespace mutation
which is wrong and unneeded. Move it to only protect
against head mutations. While we're at it, remove unnecessary
ns->head reference as we already have head pointer.

Fixes: 0d0b660f214d ("nvme: add ANA support")
Signed-off-by: Anton Eidelman <anton@lightbitslabs.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/multipath.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index a646f9eb2e73..c8fc42e37138 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -409,11 +409,10 @@ static void nvme_mpath_set_live(struct nvme_ns *ns)
 {
 	struct nvme_ns_head *head = ns->head;
 
-	lockdep_assert_held(&ns->head->lock);
-
 	if (!head->disk)
 		return;
 
+	mutex_lock(&head->lock);
 	if (!(head->disk->flags & GENHD_FL_UP))
 		device_add_disk(&head->subsys->dev, head->disk,
 				nvme_ns_id_attr_groups);
@@ -427,8 +426,9 @@ static void nvme_mpath_set_live(struct nvme_ns *ns)
 		srcu_read_unlock(&head->srcu, srcu_idx);
 	}
 
-	synchronize_srcu(&ns->head->srcu);
-	kblockd_schedule_work(&ns->head->requeue_work);
+	synchronize_srcu(&head->srcu);
+	kblockd_schedule_work(&head->requeue_work);
+	mutex_unlock(&head->lock);
 }
 
 static int nvme_parse_ana_log(struct nvme_ctrl *ctrl, void *data,
@@ -483,14 +483,12 @@ static inline bool nvme_state_is_live(enum nvme_ana_state state)
 static void nvme_update_ns_ana_state(struct nvme_ana_group_desc *desc,
 		struct nvme_ns *ns)
 {
-	mutex_lock(&ns->head->lock);
 	ns->ana_grpid = le32_to_cpu(desc->grpid);
 	ns->ana_state = desc->state;
 	clear_bit(NVME_NS_ANA_PENDING, &ns->flags);
 
 	if (nvme_state_is_live(ns->ana_state))
 		nvme_mpath_set_live(ns);
-	mutex_unlock(&ns->head->lock);
 }
 
 static int nvme_update_ana_state(struct nvme_ctrl *ctrl,
@@ -670,10 +668,8 @@ void nvme_mpath_add_disk(struct nvme_ns *ns, struct nvme_id_ns *id)
 			nvme_update_ns_ana_state(&desc, ns);
 		}
 	} else {
-		mutex_lock(&ns->head->lock);
 		ns->ana_state = NVME_ANA_OPTIMIZED; 
 		nvme_mpath_set_live(ns);
-		mutex_unlock(&ns->head->lock);
 	}
 
 	if (bdi_cap_stable_pages_required(ns->queue->backing_dev_info)) {
-- 
2.25.1


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[PATCH 4/5] nvme-multipath: fix deadlock due to head->lock

[Sagi Grimberg]

From: Anton Eidelman <anton@lightbitslabs.com>

In the following scenario scan_work and ana_work will deadlock:

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.

Since nvme_mpath_set_live() holds ns->head->lock, an ana_work on
ANY ctrl will not be able to complete nvme_mpath_set_live()
on the same ns->head, which is required in order to update
the new accessible path and remove NVME_NS_ANA_PENDING..
Therefore IO never completes: deadlock [1].

Fix:
Move device_add_disk out of the head->lock and protect it with an
atomic test_and_set for a new NVME_NS_HEAD_HAS_DISK bit.

[1]:
kernel: INFO: task kworker/u8:2:160 blocked for more than 120 seconds.
kernel:       Tainted: G           OE     5.3.5-050305-generic #201910071830
kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kernel: kworker/u8:2    D    0   160      2 0x80004000
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:  __mutex_lock_slowpath+0x13/0x20
kernel:  mutex_lock+0x2e/0x40
kernel:  nvme_update_ns_ana_state+0x22/0x60 [nvme_core]
kernel:  nvme_update_ana_state+0xca/0xe0 [nvme_core]
kernel:  nvme_parse_ana_log+0xa1/0x180 [nvme_core]
kernel:  nvme_read_ana_log+0x76/0x100 [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:  ret_from_fork+0x35/0x40
kernel: INFO: task kworker/u8:4:439 blocked for more than 120 seconds.
kernel:       Tainted: G           OE     5.3.5-050305-generic #201910071830
kernel: "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kernel: kworker/u8:4    D    0   439      2 0x80004000
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_mpath_add_disk+0xbe/0x100 [nvme_core]
kernel:  nvme_validate_ns+0x396/0x940 [nvme_core]
kernel:  nvme_scan_work+0x256/0x390 [nvme_core]
kernel:  process_one_work+0x1db/0x380
kernel:  worker_thread+0x4d/0x400
kernel:  kthread+0x104/0x140
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>
---
 drivers/nvme/host/multipath.c | 4 ++--
 drivers/nvme/host/nvme.h      | 2 ++
 2 files changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index c8fc42e37138..505f5f43cd69 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -412,11 +412,11 @@ static void nvme_mpath_set_live(struct nvme_ns *ns)
 	if (!head->disk)
 		return;
 
-	mutex_lock(&head->lock);
-	if (!(head->disk->flags & GENHD_FL_UP))
+	if (!test_and_set_bit(NVME_NS_HEAD_HAS_DISK, &head->flags))
 		device_add_disk(&head->subsys->dev, head->disk,
 				nvme_ns_id_attr_groups);
 
+	mutex_lock(&head->lock);
 	if (nvme_path_is_optimized(ns)) {
 		int node, srcu_idx;
 
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index c0f4226d3299..eccafd52b055 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -365,6 +365,8 @@ struct nvme_ns_head {
 	struct work_struct	requeue_work;
 	struct mutex		lock;
 	struct nvme_ns __rcu	*current_path[];
+	unsigned long		flags;
+#define NVME_NS_HEAD_HAS_DISK	0
 #endif
 };
 
-- 
2.25.1


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[PATCH 5/5 RFC] nvme-core: fix deadlock in disconnect during scan_work and/or ana_work

[Sagi Grimberg]

From: Anton Eidelman <anton@lightbitslabs.com>

A deadlock happens in the following scenario with multipath:
1) scan_work(nvme0) detects a new nsid while nvme0
    is an optimized path to it, path nvme1 happens to be
    inaccessible.

2) Before scan_work is complete nvme0 disconnect is initiated
    nvme_delete_ctrl_sync() sets nvme0 state to NVME_CTRL_DELETING

3) scan_work(1) attempts to submit IO,
    but nvme_path_is_optimized() observes nvme0 is not LIVE.
    Since nvme1 is a possible path IO is requeued and scan_work hangs.

--
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
--

4) Delete also hangs in flush_work(ctrl->scan_work)
    from nvme_remove_namespaces().

Similiarly a deadlock with ana_work may happen: if ana_work has started
and calls nvme_mpath_set_live and device_add_disk, it will
trigger I/O. When we trigger disconnect I/O will block because
our accessible (optimized) path is disconnecting, but the alternate
path is inaccessible, so I/O blocks. Then disconnect tries to flush
the ana_work and hangs.

[  605.550896] Workqueue: nvme-wq nvme_ana_work [nvme_core]
[  605.552087] Call Trace:
[  605.552683]  __schedule+0x2b9/0x6c0
[  605.553507]  schedule+0x42/0xb0
[  605.554201]  io_schedule+0x16/0x40
[  605.555012]  do_read_cache_page+0x438/0x830
[  605.556925]  read_cache_page+0x12/0x20
[  605.557757]  read_dev_sector+0x27/0xc0
[  605.558587]  amiga_partition+0x4d/0x4c5
[  605.561278]  check_partition+0x154/0x244
[  605.562138]  rescan_partitions+0xae/0x280
[  605.563076]  __blkdev_get+0x40f/0x560
[  605.563830]  blkdev_get+0x3d/0x140
[  605.564500]  __device_add_disk+0x388/0x480
[  605.565316]  device_add_disk+0x13/0x20
[  605.566070]  nvme_mpath_set_live+0x5e/0x130 [nvme_core]
[  605.567114]  nvme_update_ns_ana_state+0x2c/0x30 [nvme_core]
[  605.568197]  nvme_update_ana_state+0xca/0xe0 [nvme_core]
[  605.569360]  nvme_parse_ana_log+0xa1/0x180 [nvme_core]
[  605.571385]  nvme_read_ana_log+0x76/0x100 [nvme_core]
[  605.572376]  nvme_ana_work+0x15/0x20 [nvme_core]
[  605.573330]  process_one_work+0x1db/0x380
[  605.574144]  worker_thread+0x4d/0x400
[  605.574896]  kthread+0x104/0x140
[  605.577205]  ret_from_fork+0x35/0x40
[  605.577955] INFO: task nvme:14044 blocked for more than 120 seconds.
[  605.579239]       Tainted: G           OE     5.3.5-050305-generic #201910071830
[  605.580712] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[  605.582320] nvme            D    0 14044  14043 0x00000000
[  605.583424] Call Trace:
[  605.583935]  __schedule+0x2b9/0x6c0
[  605.584625]  schedule+0x42/0xb0
[  605.585290]  schedule_timeout+0x203/0x2f0
[  605.588493]  wait_for_completion+0xb1/0x120
[  605.590066]  __flush_work+0x123/0x1d0
[  605.591758]  __cancel_work_timer+0x10e/0x190
[  605.593542]  cancel_work_sync+0x10/0x20
[  605.594347]  nvme_mpath_stop+0x2f/0x40 [nvme_core]
[  605.595328]  nvme_stop_ctrl+0x12/0x50 [nvme_core]
[  605.596262]  nvme_do_delete_ctrl+0x3f/0x90 [nvme_core]
[  605.597333]  nvme_sysfs_delete+0x5c/0x70 [nvme_core]
[  605.598320]  dev_attr_store+0x17/0x30

Fix: disconnect sets ctrl->abort_scan_and_ana that prevents any further
scan_work or ana_work activation and flushes them before setting the ctrl
state to NVME_CTRL_DELETING.

Fixes: 0d0b660f214d ("nvme: add ANA support")
Signed-off-by: Anton Eidelman <anton@lightbitslabs.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
---
 drivers/nvme/host/core.c      | 10 ++++++++++
 drivers/nvme/host/multipath.c |  7 +++++++
 drivers/nvme/host/nvme.h      |  1 +
 3 files changed, 18 insertions(+)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 28f4388c1337..85e7c7887ae8 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -198,6 +198,9 @@ static void nvme_delete_ctrl_sync(struct nvme_ctrl *ctrl)
 	 * since ->delete_ctrl can free the controller.
 	 */
 	nvme_get_ctrl(ctrl);
+	ctrl->abort_scan_and_ana = true;
+	flush_work(&ctrl->scan_work);
+	nvme_mpath_stop(ctrl);
 	if (nvme_change_ctrl_state(ctrl, NVME_CTRL_DELETING))
 		nvme_do_delete_ctrl(ctrl);
 	nvme_put_ctrl(ctrl);
@@ -3865,6 +3868,13 @@ static void nvme_scan_work(struct work_struct *work)
 	struct nvme_ctrl *ctrl =
 		container_of(work, struct nvme_ctrl, scan_work);
 
+	/*
+	 * Controller deletion started, we may issue I/O, block and prevent
+	 * the controller deletion process from completing
+	 */
+	if (ctrl->abort_scan_and_ana)
+		return;
+
 	/* No tagset on a live ctrl means IO queues could not created */
 	if (ctrl->state != NVME_CTRL_LIVE || !ctrl->tagset)
 		return;
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 505f5f43cd69..f20271f4a20a 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -565,6 +565,13 @@ static void nvme_ana_work(struct work_struct *work)
 {
 	struct nvme_ctrl *ctrl = container_of(work, struct nvme_ctrl, ana_work);
 
+	/*
+	 * Controller deletion started, we may issue I/O, block and prevent
+	 * the controller deletion process from completing
+	 */
+	if (ctrl->abort_scan_and_ana)
+		return;
+
 	nvme_read_ana_log(ctrl);
 }
 
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index eccafd52b055..8a22726b1945 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -264,6 +264,7 @@ struct nvme_ctrl {
 	struct work_struct fw_act_work;
 	unsigned long events;
 	bool created;
+	bool abort_scan_and_ana;
 
 #ifdef CONFIG_NVME_MULTIPATH
 	/* asymmetric namespace access: */
-- 
2.25.1


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Re: [PATCH 0/5] address deadlocks in high stress ns scanning and ana updates

[Sagi Grimberg]

Crickets...

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