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Date:   Wed, 19 Aug 2020 10:05:02 +0800
From:   Zhen Lei <>
To:     Oliver O'Halloran <>,
        Dan Williams <>,
        Vishal Verma <>,
        "Dave Jiang" <>,
        Ira Weiny <>,
        Markus Elfring <>,
        linux-nvdimm <>,
        linux-kernel <>
CC:     Zhen Lei <>
Subject: [PATCH v2 3/4] libnvdimm/bus: simplify walk_to_nvdimm_bus()

I first want to move dev_WARN_ONCE() after "if (dev)" branch, but further
I find the "if (dev)" can only be true when is_nvdimm_bus(dev) successed.

No functional change. In fact, the compiler can optimize it correctly. I
run "size drivers/nvdimm/bus.o" and find nothing has changed. So it's
just source code level optimization, make us can read it faster.

Signed-off-by: Zhen Lei <>
 drivers/nvdimm/bus.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/nvdimm/bus.c b/drivers/nvdimm/bus.c
index 955265656b96c73..1d89114cb6ab93e 100644
--- a/drivers/nvdimm/bus.c
+++ b/drivers/nvdimm/bus.c
@@ -316,10 +316,9 @@ struct nvdimm_bus *walk_to_nvdimm_bus(struct device *nd_dev)
 	for (dev = nd_dev; dev; dev = dev->parent)
 		if (is_nvdimm_bus(dev))
-			break;
-	dev_WARN_ONCE(nd_dev, !dev, "invalid dev, not on nd bus\n");
-	if (dev)
-		return to_nvdimm_bus(dev);
+			return to_nvdimm_bus(dev);
+	dev_WARN_ONCE(nd_dev, 1, "invalid dev, not on nd bus\n");
 	return NULL;

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