* [PATCH v3 1/2] nvme-multipath: apply delayed_removal_secs changes to a pending removal
2026-11-15 2:15 [PATCH v3 0/2] nvme-multipath: requeue work fixes Qiliang Yuan
@ 2026-11-15 2:15 ` Qiliang Yuan
2026-11-15 2:15 ` [PATCH v3 2/2] nvme-multipath: don't wait for a grace period in nvme_mpath_set_live() Qiliang Yuan
1 sibling, 0 replies; 3+ messages in thread
From: Qiliang Yuan @ 2026-11-15 2:15 UTC (permalink / raw)
To: Keith Busch, Jens Axboe, Christoph Hellwig, Sagi Grimberg,
Nilay Shroff, Hannes Reinecke
Cc: linux-nvme, linux-kernel, Qiliang Yuan
With delayed_removal_secs set, removing the last path of a namespace
head doesn't delete the head right away. nvme_mpath_remove_disk()
queues remove_work with the configured delay, and bios submitted in the
meantime wait on head->requeue_list in case a path comes back.
A write to delayed_removal_secs only takes effect for removals that
start later. A removal that is already pending keeps the old delay, so
clearing the attribute leaves the queued bios waiting until that delay
expires instead of failing them, and lowering or raising it doesn't
move the pending removal either.
Requeue a pending remove_work with the new delay when the attribute is
written. Cancel it first so that the module reference taken for it
carries over, as nvme_init_ns_head() does when a path comes back.
With delayed_removal_secs set and no path left, the attribute is
changed two seconds later and the head is removed after (mean of two
runs, min-max in parentheses):
delay (s) before (ms) after (ms) change
30 -> 0 26510 (26053-26967) 8 (8-8) -99.97%
30 -> 5 27994 (27457-28531) 6194 (5589-6798) -78%
10 -> 30 8131 (8086-8176) 29802 (29522-30082) +267%
A direct read queued before the 30 -> 0 write fails after:
before (ms) after (ms) change
26466 (26017-26915) 4 (4-4) -99.98%
Fixes: 62188639ec160 ("nvme-multipath: introduce delayed removal of the multipath head node")
Suggested-by: Nilay Shroff <nilay@linux.ibm.com>
Signed-off-by: Qiliang Yuan <qiliang.yuan@linux.dev>
---
drivers/nvme/host/multipath.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index ae8059366b57d..35278b9c4de60 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -1242,6 +1242,9 @@ static ssize_t delayed_removal_secs_store(struct device *dev,
mutex_lock(&head->subsys->lock);
head->delayed_removal_secs = sec;
assign_bit(NVME_NSHEAD_QUEUE_IF_NO_PATH, &head->flags, sec);
+ /* Apply the new delay to a removal that is already pending */
+ if (cancel_delayed_work(&head->remove_work))
+ queue_delayed_work(nvme_wq, &head->remove_work, sec * HZ);
mutex_unlock(&head->subsys->lock);
/*
* Ensure that update to NVME_NSHEAD_QUEUE_IF_NO_PATH is seen
--
2.43.0
^ permalink raw reply [flat|nested] 3+ messages in thread* [PATCH v3 2/2] nvme-multipath: don't wait for a grace period in nvme_mpath_set_live()
2026-11-15 2:15 [PATCH v3 0/2] nvme-multipath: requeue work fixes Qiliang Yuan
2026-11-15 2:15 ` [PATCH v3 1/2] nvme-multipath: apply delayed_removal_secs changes to a pending removal Qiliang Yuan
@ 2026-11-15 2:15 ` Qiliang Yuan
1 sibling, 0 replies; 3+ messages in thread
From: Qiliang Yuan @ 2026-11-15 2:15 UTC (permalink / raw)
To: Keith Busch, Jens Axboe, Christoph Hellwig, Sagi Grimberg,
Nilay Shroff, Hannes Reinecke
Cc: linux-nvme, linux-kernel, Qiliang Yuan, Hannes Reinecke
When a path goes live, nvme_mpath_set_live() waits for an SRCU grace
period of the namespace head before kicking the requeue work, so that
bios which found no usable path are on the requeue list by the time it
runs.
The ANA work calls nvme_mpath_set_live() for every namespace that
becomes optimized or non-optimized, one after another, so an ANA change
waits for one grace period per namespace.
Start the grace period with start_poll_synchronize_srcu() instead and
have nvme_requeue_work() wait for it only if it has not completed yet.
Take the cookie under head->lock, so that concurrent callers store
their cookies in order and the requeue work never sees an older one.
The grace periods of all namespaces then run in parallel, and requeue
work kicked for other reasons finds the cookie completed and does not
wait.
Flipping an ANA group from inaccessible to optimized ten times on each
of two boots over nvme-tcp loopback, nvme_read_ana_log() takes (median,
min-max in parentheses):
namespaces before (ms) after (ms) change
256 52.0 (35.4-74.7) 8.7 (2.5-19.6) -83%
1024 154.3 (123.9-193.8) 43.1 (18.2-58.3) -72%
Signed-off-by: Qiliang Yuan <qiliang.yuan@linux.dev>
Reviewed-by: Hannes Reinecke <hare@kernel.org>
Reviewed-by: Nilay Shroff <nilay@linux.ibm.com>
---
drivers/nvme/host/multipath.c | 15 ++++++++++++++-
drivers/nvme/host/nvme.h | 1 +
2 files changed, 15 insertions(+), 1 deletion(-)
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 35278b9c4de60..971bd14e46803 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -712,6 +712,11 @@ static void nvme_requeue_work(struct work_struct *work)
container_of(work, struct nvme_ns_head, requeue_work);
struct bio *bio, *next;
+ /* Let bios that found no usable path reach the requeue list first. */
+ if (!poll_state_synchronize_srcu(&head->srcu,
+ READ_ONCE(head->requeue_srcu_cookie)))
+ synchronize_srcu(&head->srcu);
+
spin_lock_irq(&head->requeue_lock);
next = bio_list_get(&head->requeue_list);
spin_unlock_irq(&head->requeue_lock);
@@ -767,6 +772,7 @@ int nvme_mpath_alloc_disk(struct nvme_ctrl *ctrl, struct nvme_ns_head *head)
mutex_init(&head->lock);
spin_lock_init(&head->requeue_lock);
INIT_WORK(&head->requeue_work, nvme_requeue_work);
+ head->requeue_srcu_cookie = get_completed_synchronize_srcu();
INIT_WORK(&head->partition_scan_work, nvme_partition_scan_work);
INIT_DELAYED_WORK(&head->remove_work, nvme_remove_head_work);
@@ -849,9 +855,16 @@ static void nvme_mpath_set_live(struct nvme_ns *ns)
__nvme_find_path(head, node);
srcu_read_unlock(&head->srcu, srcu_idx);
}
+ /*
+ * Have nvme_requeue_work() wait for the grace period instead of
+ * blocking here, so that namespaces going live together, e.g. on
+ * an ANA change, do not wait for one grace period each. Start it
+ * under head->lock so that the newest cookie is stored last.
+ */
+ WRITE_ONCE(head->requeue_srcu_cookie,
+ start_poll_synchronize_srcu(&head->srcu));
mutex_unlock(&head->lock);
- synchronize_srcu(&head->srcu);
nvme_mpath_revalidate_zones(head);
kblockd_schedule_work(&head->requeue_work);
}
diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
index 8833a463f1c84..3fff9b394b1cd 100644
--- a/drivers/nvme/host/nvme.h
+++ b/drivers/nvme/host/nvme.h
@@ -587,6 +587,7 @@ struct nvme_ns_head {
__guarded_by(&requeue_lock);
spinlock_t requeue_lock;
struct work_struct requeue_work;
+ unsigned long requeue_srcu_cookie;
struct work_struct partition_scan_work;
struct mutex lock;
unsigned long flags;
--
2.43.0
^ permalink raw reply [flat|nested] 3+ messages in thread