linux-kernel - [PATCH 4/9] dax/kmem: allow PMEM devices to bind to KMEM driver

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Message-Id: <20181022201324.EBB64302@viggo.jf.intel.com>
Date:   Mon, 22 Oct 2018 13:13:24 -0700
From:   Dave Hansen <dave.hansen@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     Dave Hansen <dave.hansen@...ux.intel.com>,
        dan.j.williams@...el.com, dave.jiang@...el.com, zwisler@...nel.org,
        vishal.l.verma@...el.com, thomas.lendacky@....com,
        akpm@...ux-foundation.org, mhocko@...e.com,
        linux-nvdimm@...ts.01.org, linux-mm@...ck.org,
        ying.huang@...el.com, fengguang.wu@...el.com
Subject: [PATCH 4/9] dax/kmem: allow PMEM devices to bind to KMEM driver


Currently, a persistent memory device's mode must be coordinated
with the driver to which it needs to bind.  To change it from the
fsdax to the device-dax driver, you first change the mode of the
device itself.

Instead of adding a new device mode, allow the PMEM mode to also
bind to the KMEM driver.

As I write this, I'm realizing that it might have just been
better to add a new device mode, rather than hijacking the PMEM
eode.  If this is the case, please speak up, NVDIMM folks.  :)

Cc: Dan Williams <dan.j.williams@...el.com>
Cc: Dave Jiang <dave.jiang@...el.com>
Cc: Ross Zwisler <zwisler@...nel.org>
Cc: Vishal Verma <vishal.l.verma@...el.com>
Cc: Tom Lendacky <thomas.lendacky@....com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Michal Hocko <mhocko@...e.com>
Cc: linux-nvdimm@...ts.01.org
Cc: linux-kernel@...r.kernel.org
Cc: linux-mm@...ck.org
Cc: Huang Ying <ying.huang@...el.com>
Cc: Fengguang Wu <fengguang.wu@...el.com>

---

 b/drivers/nvdimm/bus.c |   15 ++++++++++++++-
 1 file changed, 14 insertions(+), 1 deletion(-)

diff -puN drivers/nvdimm/bus.c~dax-kmem-try-again-2018-3-bus-match-override drivers/nvdimm/bus.c
--- a/drivers/nvdimm/bus.c~dax-kmem-try-again-2018-3-bus-match-override	2018-10-22 13:12:22.522930391 -0700
+++ b/drivers/nvdimm/bus.c	2018-10-22 13:12:22.525930391 -0700
@@ -464,11 +464,24 @@ static struct nd_device_driver nd_bus_dr
 static int nvdimm_bus_match(struct device *dev, struct device_driver *drv)
 {
 	struct nd_device_driver *nd_drv = to_nd_device_driver(drv);
+	bool match;
 
 	if (is_nvdimm_bus(dev) && nd_drv == &nd_bus_driver)
 		return true;
 
-	return !!test_bit(to_nd_device_type(dev), &nd_drv->type);
+	match = !!test_bit(to_nd_device_type(dev), &nd_drv->type);
+
+	/*
+	 * We allow PMEM devices to be bound to the KMEM driver.
+	 * Force a match if we detect a PMEM device type but
+	 * a KMEM device driver.
+	 */
+	if (!match &&
+	    (to_nd_device_type(dev) == ND_DEVICE_DAX_PMEM) &&
+	    (nd_drv->type == ND_DRIVER_DAX_KMEM))
+		match = true;
+
+	return match;
 }
 
 static ASYNC_DOMAIN_EXCLUSIVE(nd_async_domain);
_