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Subject[PATCH AUTOSEL 5.2 16/44] nvme: fix controller removal race with scan work
Date
From: Sagi Grimberg <sagi@grimberg.me>

[ Upstream commit 0157ec8dad3c8fc9bc9790f76e0831ffdaf2e7f0 ]

With multipath enabled, nvme_scan_work() can read from the device
(through nvme_mpath_add_disk()) and hang [1]. However, with fabrics,
once ctrl->state is set to NVME_CTRL_DELETING, the reads will hang
(see nvmf_check_ready()) and the mpath stack device make_request
will block if head->list is not empty. However, when the head->list
consistst of only DELETING/DEAD controllers, we should actually not
block, but rather fail immediately.

In addition, before we go ahead and remove the namespaces, make sure
to clear the current path and kick the requeue list so that the
request will fast fail upon requeuing.

[1]:
--
INFO: task kworker/u4:3:166 blocked for more than 120 seconds.
Not tainted 5.2.0-rc6-vmlocalyes-00005-g808c8c2dc0cf #316
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:3 D 0 166 2 0x80004000
Workqueue: nvme-wq nvme_scan_work
Call Trace:
__schedule+0x851/0x1400
schedule+0x99/0x210
io_schedule+0x21/0x70
do_read_cache_page+0xa57/0x1330
read_cache_page+0x4a/0x70
read_dev_sector+0xbf/0x380
amiga_partition+0xc4/0x1230
check_partition+0x30f/0x630
rescan_partitions+0x19a/0x980
__blkdev_get+0x85a/0x12f0
blkdev_get+0x2a5/0x790
__device_add_disk+0xe25/0x1250
device_add_disk+0x13/0x20
nvme_mpath_set_live+0x172/0x2b0
nvme_update_ns_ana_state+0x130/0x180
nvme_set_ns_ana_state+0x9a/0xb0
nvme_parse_ana_log+0x1c3/0x4a0
nvme_mpath_add_disk+0x157/0x290
nvme_validate_ns+0x1017/0x1bd0
nvme_scan_work+0x44d/0x6a0
process_one_work+0x7d7/0x1240
worker_thread+0x8e/0xff0
kthread+0x2c3/0x3b0
ret_from_fork+0x35/0x40

INFO: task kworker/u4:1:1034 blocked for more than 120 seconds.
Not tainted 5.2.0-rc6-vmlocalyes-00005-g808c8c2dc0cf #316
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/u4:1 D 0 1034 2 0x80004000
Workqueue: nvme-delete-wq nvme_delete_ctrl_work
Call Trace:
__schedule+0x851/0x1400
schedule+0x99/0x210
schedule_timeout+0x390/0x830
wait_for_completion+0x1a7/0x310
__flush_work+0x241/0x5d0
flush_work+0x10/0x20
nvme_remove_namespaces+0x85/0x3d0
nvme_do_delete_ctrl+0xb4/0x1e0
nvme_delete_ctrl_work+0x15/0x20
process_one_work+0x7d7/0x1240
worker_thread+0x8e/0xff0
kthread+0x2c3/0x3b0
ret_from_fork+0x35/0x40
--

Reported-by: Logan Gunthorpe <logang@deltatee.com>
Tested-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/nvme/host/core.c | 7 ++++++
drivers/nvme/host/multipath.c | 46 ++++++++++++++++++++++++++++++-----
drivers/nvme/host/nvme.h | 9 +++++--
3 files changed, 54 insertions(+), 8 deletions(-)

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index 05301b94e2fa0..601509b3251ae 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c
@@ -3529,6 +3529,13 @@ void nvme_remove_namespaces(struct nvme_ctrl *ctrl)
struct nvme_ns *ns, *next;
LIST_HEAD(ns_list);

+ /*
+ * make sure to requeue I/O to all namespaces as these
+ * might result from the scan itself and must complete
+ * for the scan_work to make progress
+ */
+ nvme_mpath_clear_ctrl_paths(ctrl);
+
/* prevent racing with ns scanning */
flush_work(&ctrl->scan_work);

diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index dafb9e4aa1237..747c0d4f9ff5b 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -134,18 +134,34 @@ static const char *nvme_ana_state_names[] = {
[NVME_ANA_CHANGE] = "change",
};

-void nvme_mpath_clear_current_path(struct nvme_ns *ns)
+bool nvme_mpath_clear_current_path(struct nvme_ns *ns)
{
struct nvme_ns_head *head = ns->head;
+ bool changed = false;
int node;

if (!head)
- return;
+ goto out;

for_each_node(node) {
- if (ns == rcu_access_pointer(head->current_path[node]))
+ if (ns == rcu_access_pointer(head->current_path[node])) {
rcu_assign_pointer(head->current_path[node], NULL);
+ changed = true;
+ }
}
+out:
+ return changed;
+}
+
+void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl)
+{
+ struct nvme_ns *ns;
+
+ mutex_lock(&ctrl->scan_lock);
+ list_for_each_entry(ns, &ctrl->namespaces, list)
+ if (nvme_mpath_clear_current_path(ns))
+ kblockd_schedule_work(&ns->head->requeue_work);
+ mutex_unlock(&ctrl->scan_lock);
}

static struct nvme_ns *__nvme_find_path(struct nvme_ns_head *head, int node)
@@ -248,6 +264,24 @@ inline struct nvme_ns *nvme_find_path(struct nvme_ns_head *head)
return ns;
}

+static bool nvme_available_path(struct nvme_ns_head *head)
+{
+ struct nvme_ns *ns;
+
+ list_for_each_entry_rcu(ns, &head->list, siblings) {
+ switch (ns->ctrl->state) {
+ case NVME_CTRL_LIVE:
+ case NVME_CTRL_RESETTING:
+ case NVME_CTRL_CONNECTING:
+ /* fallthru */
+ return true;
+ default:
+ break;
+ }
+ }
+ return false;
+}
+
static blk_qc_t nvme_ns_head_make_request(struct request_queue *q,
struct bio *bio)
{
@@ -274,14 +308,14 @@ static blk_qc_t nvme_ns_head_make_request(struct request_queue *q,
disk_devt(ns->head->disk),
bio->bi_iter.bi_sector);
ret = direct_make_request(bio);
- } else if (!list_empty_careful(&head->list)) {
- dev_warn_ratelimited(dev, "no path available - requeuing I/O\n");
+ } else if (nvme_available_path(head)) {
+ dev_warn_ratelimited(dev, "no usable path - requeuing I/O\n");

spin_lock_irq(&head->requeue_lock);
bio_list_add(&head->requeue_list, bio);
spin_unlock_irq(&head->requeue_lock);
} else {
- dev_warn_ratelimited(dev, "no path - failing I/O\n");
+ dev_warn_ratelimited(dev, "no available path - failing I/O\n");

bio->bi_status = BLK_STS_IOERR;
bio_endio(bio);
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index b8b45822f7be0..81215ca32671a 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -490,7 +490,8 @@ void nvme_mpath_remove_disk(struct nvme_ns_head *head);
int nvme_mpath_init(struct nvme_ctrl *ctrl, struct nvme_id_ctrl *id);
void nvme_mpath_uninit(struct nvme_ctrl *ctrl);
void nvme_mpath_stop(struct nvme_ctrl *ctrl);
-void nvme_mpath_clear_current_path(struct nvme_ns *ns);
+bool nvme_mpath_clear_current_path(struct nvme_ns *ns);
+void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl);
struct nvme_ns *nvme_find_path(struct nvme_ns_head *head);

static inline void nvme_mpath_check_last_path(struct nvme_ns *ns)
@@ -538,7 +539,11 @@ static inline void nvme_mpath_add_disk(struct nvme_ns *ns,
static inline void nvme_mpath_remove_disk(struct nvme_ns_head *head)
{
}
-static inline void nvme_mpath_clear_current_path(struct nvme_ns *ns)
+static inline bool nvme_mpath_clear_current_path(struct nvme_ns *ns)
+{
+ return false;
+}
+static inline void nvme_mpath_clear_ctrl_paths(struct nvme_ctrl *ctrl)
{
}
static inline void nvme_mpath_check_last_path(struct nvme_ns *ns)
--
2.20.1
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