[PATCH 5.15 035/132] nvme-multipath: fix hang when disk goes live over reconnect

Greg Kroah-Hartman
2022-05-23T17:33:18Z

From: Anton Eidelman <anton.eidelman@gmail.com>

[ Upstream commit a4a6f3c8f61c3cfbda4998ad94596059ad7e4332 ]

nvme_mpath_init_identify() invoked from nvme_init_identify() fetches a
fresh ANA log from the ctrl. This is essential to have an up to date
path states for both existing namespaces and for those scan_work may
discover once the ctrl is up.

This happens in the following cases:
1) A new ctrl is being connected.
2) An existing ctrl is successfully reconnected.
3) An existing ctrl is being reset.

While in (1) ctrl->namespaces is empty, (2 & 3) may have namespaces, and
nvme_read_ana_log() may call nvme_update_ns_ana_state().

This result in a hang when the ANA state of an existing namespace changes
and makes the disk live: nvme_mpath_set_live() issues IO to the namespace
through the ctrl, which does NOT have IO queues yet.

See sample hang below.

Solution:
- nvme_update_ns_ana_state() to call set_live only if ctrl is live
- nvme_read_ana_log() call from nvme_mpath_init_identify()
therefore only fetches and parses the ANA log;
any erros in this process will fail the ctrl setup as appropriate;
- a separate function nvme_mpath_update()
is called in nvme_start_ctrl();
this parses the ANA log without fetching it.
At this point the ctrl is live,
therefore, disks can be set live normally.

Sample failure:
nvme nvme0: starting error recovery
nvme nvme0: Reconnecting in 10 seconds...
block nvme0n6: no usable path - requeuing I/O
INFO: task kworker/u8:3:312 blocked for more than 122 seconds.
Tainted: G E 5.14.5-1.el7.elrepo.x86_64 #1
Workqueue: nvme-wq nvme_tcp_reconnect_ctrl_work [nvme_tcp]
Call Trace:
__schedule+0x2a2/0x7e0
schedule+0x4e/0xb0
io_schedule+0x16/0x40
wait_on_page_bit_common+0x15c/0x3e0
do_read_cache_page+0x1e0/0x410
read_cache_page+0x12/0x20
read_part_sector+0x46/0x100
read_lba+0x121/0x240
efi_partition+0x1d2/0x6a0
bdev_disk_changed.part.0+0x1df/0x430
bdev_disk_changed+0x18/0x20
blkdev_get_whole+0x77/0xe0
blkdev_get_by_dev+0xd2/0x3a0
__device_add_disk+0x1ed/0x310
device_add_disk+0x13/0x20
nvme_mpath_set_live+0x138/0x1b0 [nvme_core]
nvme_update_ns_ana_state+0x2b/0x30 [nvme_core]
nvme_update_ana_state+0xca/0xe0 [nvme_core]
nvme_parse_ana_log+0xac/0x170 [nvme_core]
nvme_read_ana_log+0x7d/0xe0 [nvme_core]
nvme_mpath_init_identify+0x105/0x150 [nvme_core]
nvme_init_identify+0x2df/0x4d0 [nvme_core]
nvme_init_ctrl_finish+0x8d/0x3b0 [nvme_core]
nvme_tcp_setup_ctrl+0x337/0x390 [nvme_tcp]
nvme_tcp_reconnect_ctrl_work+0x24/0x40 [nvme_tcp]
process_one_work+0x1bd/0x360
worker_thread+0x50/0x3d0

Signed-off-by: Anton Eidelman <anton@lightbitslabs.com>
Reviewed-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/core.c | 1 +
drivers/nvme/host/multipath.c | 25 +++++++++++++++++++++++--
drivers/nvme/host/nvme.h | 4 ++++
3 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index f2bb57615762..87877397d1ad 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -4358,6 +4358,7 @@ void nvme_start_ctrl(struct nvme_ctrl *ctrl)
if (ctrl->queue_count > 1) {
nvme_queue_scan(ctrl);
nvme_start_queues(ctrl);
+ nvme_mpath_update(ctrl);
}
}
EXPORT_SYMBOL_GPL(nvme_start_ctrl);
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index e9301b51db76..064acad505d3 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -574,8 +574,17 @@ static void nvme_update_ns_ana_state(struct nvme_ana_group_desc *desc,
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() will trigger I/O to the multipath path device
+ * and in turn to this path device. However we cannot accept this I/O
+ * if the controller is not live. This may deadlock if called from
+ * nvme_mpath_init_identify() and the ctrl will never complete
+ * initialization, preventing I/O from completing. For this case we
+ * will reprocess the ANA log page in nvme_mpath_update() once the
+ * controller is ready.
+ */
+ if (nvme_state_is_live(ns->ana_state) &&
+ ns->ctrl->state == NVME_CTRL_LIVE)
nvme_mpath_set_live(ns);
}

@@ -662,6 +671,18 @@ static void nvme_ana_work(struct work_struct *work)
nvme_read_ana_log(ctrl);
}

+void nvme_mpath_update(struct nvme_ctrl *ctrl)
+{
+ u32 nr_change_groups = 0;
+
+ if (!ctrl->ana_log_buf)
+ return;
+
+ mutex_lock(&ctrl->ana_lock);
+ nvme_parse_ana_log(ctrl, &nr_change_groups, nvme_update_ana_state);
+ mutex_unlock(&ctrl->ana_lock);
+}
+
static void nvme_anatt_timeout(struct timer_list *t)
{
struct nvme_ctrl *ctrl = from_timer(ctrl, t, anatt_timer);
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index f1e5c7564cae..72bcd7e5716e 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -776,6 +776,7 @@ void nvme_mpath_add_disk(struct nvme_ns *ns, struct nvme_id_ns *id);
void nvme_mpath_remove_disk(struct nvme_ns_head *head);
int nvme_mpath_init_identify(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id);
void nvme_mpath_init_ctrl(struct nvme_ctrl *ctrl);
+void nvme_mpath_update(struct nvme_ctrl *ctrl);
void nvme_mpath_uninit(struct nvme_ctrl *ctrl);
void nvme_mpath_stop(struct nvme_ctrl *ctrl);
bool nvme_mpath_clear_current_path(struct nvme_ns *ns);
@@ -850,6 +851,9 @@ static inline int nvme_mpath_init_identify(struct nvme_ctrl *ctrl,
"Please enable CONFIG_NVME_MULTIPATH for full support of multi-port devices.\n");
return 0;
}
+static inline void nvme_mpath_update(struct nvme_ctrl *ctrl)
+{
+}
static inline void nvme_mpath_uninit(struct nvme_ctrl *ctrl)
{
}
--
2.35.1