FAILED: patch "[PATCH] nvme: unregister when pr_register() is given a zero new key" failed to apply to 6.6-stable tree

[Sasha Levin <sashal@kernel.org>]

The patch below does not apply to the 6.6-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y
git checkout FETCH_HEAD
git cherry-pick -x a9d431124fb2e58215daf0299d6fcf47bbc2d6b1
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<stable@vger.kernel.org>' --in-reply-to '20261109201154-failed-6.6-a9d431124fb2@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..'

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From a9d431124fb2e58215daf0299d6fcf47bbc2d6b1 Mon Sep 17 00:00:00 2001
From: Daejun Park <daejun7.park@samsung.com>
Date: Thu, 29 Oct 2026 09:51:24 +0900
Subject: [PATCH] nvme: unregister when pr_register() is given a zero new key

The block layer PR API defines a zero new_key in pr_register() as
unregistering old_key. nvme_pr_register() sends Replace Reservation
Key with a zero NRKEY instead. The host stays registered with key 0,
and its next registration with another key fails with Reservation
Conflict.

The pNFS SCSI layout client unregisters this way at umount. A later
mount cannot register and sends all I/O through the metadata server.

Send Unregister Reservation Key when new_key is zero.

Fixes: 1d277a637a71 ("NVMe: Add persistent reservation ops")
Cc: stable@vger.kernel.org
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Daejun Park <daejun7.park@samsung.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
---
 drivers/nvme/host/pr.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/nvme/host/pr.c b/drivers/nvme/host/pr.c
index fe7dbe2648158..d8b6ac4d83bb9 100644
--- a/drivers/nvme/host/pr.c
+++ b/drivers/nvme/host/pr.c
@@ -128,8 +128,12 @@ static int nvme_pr_register(struct block_device *bdev, u64 old_key, u64 new_key,
 	data.crkey = cpu_to_le64(old_key);
 	data.nrkey = cpu_to_le64(new_key);
 
-	cdw10 = old_key ? NVME_PR_REGISTER_ACT_REPLACE :
-		NVME_PR_REGISTER_ACT_REG;
+	if (!new_key)
+		cdw10 = NVME_PR_REGISTER_ACT_UNREG;
+	else if (old_key)
+		cdw10 = NVME_PR_REGISTER_ACT_REPLACE;
+	else
+		cdw10 = NVME_PR_REGISTER_ACT_REG;
 	cdw10 |= (flags & PR_FL_IGNORE_KEY) ? NVME_PR_IGNORE_KEY : 0;
 	cdw10 |= NVME_PR_CPTPL_PERSIST;
 
-- 
2.53.0