linux-kernel - [PATCH 2/4] nvme-multipath: add the NVME_MULTIPATH

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Message-ID: <20250228032541.369804-3-jmeneghi@redhat.com>
Date: Thu, 27 Feb 2025 22:25:39 -0500
From: John Meneghini <jmeneghi@...hat.com>
To: kbusch@...nel.org,
	hch@....de,
	sagi@...mberg.me
Cc: loberman@...hat.com,
	linux-nvme@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	emilne@...hat.com,
	jmeneghi@...hat.com,
	bgurney@...hat.com
Subject: [PATCH 2/4] nvme-multipath: add the NVME_MULTIPATH_PARAM config option

The NVME_MULTIPATH_PARAM option controls the core.nvme_multipath module
parameter. When NVME_MULTIPATH_PARAM=n the multipath parameter is removed
and core nvme multipathing is enabled. When NVME_MULTIPATH_PARAM=y
the multipath parameter is added and multipath support becomes
configurable with the core.nvme_multipath parameter.

By default NVME_MULTIPATH_PARAM=y

Signed-off-by: John Meneghini <jmeneghi@...hat.com>
---
 drivers/nvme/host/Kconfig     | 15 +++++++++++++++
 drivers/nvme/host/multipath.c |  3 ++-
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/drivers/nvme/host/Kconfig b/drivers/nvme/host/Kconfig
index 91b0346ce65a..c4251504f201 100644
--- a/drivers/nvme/host/Kconfig
+++ b/drivers/nvme/host/Kconfig
@@ -28,6 +28,21 @@ config NVME_MULTIPATH
 
 	  If unsure, say Y.
 
+config NVME_MULTIPATH_PARAM
+	bool "NVMe multipath param"
+	depends on NVME_CORE && NVME_MULTIPATH
+	help
+	  This option enables configurable support for multipath access with
+	  NVMe subsystems. If this option is enabled NVMe multipath support is
+	  configured by the nvme core module parameter named "multipath". If
+	  this option is disabled the nvme core module "multipath" parameter
+	  is removed and support for NVMe multipath access can not be
+	  configured. When this option is disabled a single /dev/nvmeXnY
+	  device entry will be seen for each NVMe namespace, even if the
+	  namespace is accessible through multiple controllers.
+
+	  If unsure, say Y.
+
 config NVME_VERBOSE_ERRORS
 	bool "NVMe verbose error reporting"
 	depends on NVME_CORE
diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c
index 2a7635565083..4536ad5fbb82 100644
--- a/drivers/nvme/host/multipath.c
+++ b/drivers/nvme/host/multipath.c
@@ -10,10 +10,11 @@
 #include "nvme.h"
 
 bool multipath = true;
+#ifdef NVME_MULTIPATH_PARAM
 module_param(multipath, bool, 0444);
 MODULE_PARM_DESC(multipath,
 	"turn on native support for multiple controllers per subsystem");
-
+#endif
 static const char *nvme_iopolicy_names[] = {
 	[NVME_IOPOLICY_NUMA]	= "numa",
 	[NVME_IOPOLICY_RR]	= "round-robin",
-- 
2.48.1