linux-kernel - [PATCH 1/1] device-dax: avoid an unnecessary check in alloc_dev_dax

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Date:   Fri, 20 Nov 2020 17:22:51 +0800
From:   Zhen Lei <thunder.leizhen@...wei.com>
To:     Dan Williams <dan.j.williams@...el.com>,
        Vishal Verma <vishal.l.verma@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        linux-nvdimm <linux-nvdimm@...ts.01.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
CC:     Zhen Lei <thunder.leizhen@...wei.com>
Subject: [PATCH 1/1] device-dax: avoid an unnecessary check in alloc_dev_dax_range()

Swap the calling sequence of krealloc() and __request_region(), call the
latter first. In this way, the value of dev_dax->nr_range does not need to
be considered when __request_region() failed.

Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
---
 drivers/dax/bus.c | 29 ++++++++++++-----------------
 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 27513d311242..1efae11d947a 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -763,23 +763,15 @@ static int alloc_dev_dax_range(struct dev_dax *dev_dax, u64 start,
 		return 0;
 	}
 
-	ranges = krealloc(dev_dax->ranges, sizeof(*ranges)
-			* (dev_dax->nr_range + 1), GFP_KERNEL);
-	if (!ranges)
-		return -ENOMEM;
-
 	alloc = __request_region(res, start, size, dev_name(dev), 0);
-	if (!alloc) {
-		/*
-		 * If this was an empty set of ranges nothing else
-		 * will release @ranges, so do it now.
-		 */
-		if (!dev_dax->nr_range) {
-			kfree(ranges);
-			ranges = NULL;
-		}
-		dev_dax->ranges = ranges;
+	if (!alloc)
 		return -ENOMEM;
+
+	ranges = krealloc(dev_dax->ranges, sizeof(*ranges)
+			* (dev_dax->nr_range + 1), GFP_KERNEL);
+	if (!ranges) {
+		rc = -ENOMEM;
+		goto err;
 	}
 
 	for (i = 0; i < dev_dax->nr_range; i++)
@@ -808,11 +800,14 @@ static int alloc_dev_dax_range(struct dev_dax *dev_dax, u64 start,
 		dev_dbg(dev, "delete range[%d]: %pa:%pa\n", dev_dax->nr_range - 1,
 				&alloc->start, &alloc->end);
 		dev_dax->nr_range--;
-		__release_region(res, alloc->start, resource_size(alloc));
-		return rc;
+		goto err;
 	}
 
 	return 0;
+
+err:
+	__release_region(res, alloc->start, resource_size(alloc));
+	return rc;
 }
 
 static int adjust_dev_dax_range(struct dev_dax *dev_dax, struct resource *res, resource_size_t size)
-- 
2.26.0.106.g9fadedd