[PATCH v2 06/14] NTB: ntb_transport: Clear link state before QP cleanup

[Koichiro Den]

Cleanup leaves the transport link marked up after releasing its MWs.
A subsequent client link-up request can therefore start QP link work
before the transport has been set up again.

Clear link_is_up before cancelling QP work and releasing the MWs.
Have QP link work return if the transport went down after it was
queued.

Fixes: e26a5843f7f5 ("NTB: Split ntb_hw_intel and ntb_transport drivers")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Koichiro Den <den@xxxxxxxxxxxxx>
---
Changes in v2:
  - No changes.

Note: this is a reworked version of my earlier, withdrawn patch:
https://lore.kernel.org/r/20260717061223.2203863-1-den@xxxxxxxxxxxxx/

 drivers/ntb/ntb_transport.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/ntb/ntb_transport.c b/drivers/ntb/ntb_transport.c
index 1332d53bcfe7..8dd1770aaaf1 100644
--- a/drivers/ntb/ntb_transport.c
+++ b/drivers/ntb/ntb_transport.c
@@ -977,6 +977,8 @@ static void ntb_transport_link_cleanup(struct ntb_transport_ctx *nt)
 
 	guard(mutex)(&nt->link_event_lock);
 
+	WRITE_ONCE(nt->link_is_up, false);
+
 	qp_bitmap_alloc = nt->qp_bitmap & ~nt->qp_bitmap_free;
 
 	/* Pass along the info to any clients */
@@ -1142,7 +1144,9 @@ static void ntb_qp_link_work(struct work_struct *work)
 	struct ntb_transport_ctx *nt = qp->transport;
 	int val;
 
-	WARN_ON(!nt->link_is_up);
+	/* Pair with the link publication in ntb_transport_link_work(). */
+	if (!smp_load_acquire(&nt->link_is_up))
+		return;
 
 	val = ntb_spad_read(nt->ndev, QP_LINKS);
 
-- 
2.51.0