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From:   Vishal Verma <vishal.l.verma@intel.com>
Date:   Tue, 12 Dec 2023 12:08:31 -0700
Subject: [PATCH v4 2/3] dax/bus: Introduce guard(device) for
 device_{lock,unlock} flows
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Message-Id: <20231212-vv-dax_abi-v4-2-1351758f0c92@intel.com>
References: <20231212-vv-dax_abi-v4-0-1351758f0c92@intel.com>
In-Reply-To: <20231212-vv-dax_abi-v4-0-1351758f0c92@intel.com>
To:     Dan Williams <dan.j.williams@intel.com>,
        Vishal Verma <vishal.l.verma@intel.com>,
        Dave Jiang <dave.jiang@intel.com>
Cc:     linux-kernel@vger.kernel.org, nvdimm@lists.linux.dev,
        linux-cxl@vger.kernel.org, David Hildenbrand <david@redhat.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Huang Ying <ying.huang@intel.com>,
        Joao Martins <joao.m.martins@oracle.com>
Precedence: bulk

Introduce a guard(device) macro to lock a 'struct device', and unlock it
automatically when going out of scope using Scope Based Resource
Management semantics. A lot of the sysfs attribute writes in
drivers/dax/bus.c benefit from a cleanup using these, so change these
where applicable.

Cc: Joao Martins <joao.m.martins@oracle.com>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
---
 include/linux/device.h |   2 +
 drivers/dax/bus.c      | 109 +++++++++++++++++++------------------------------
 2 files changed, 44 insertions(+), 67 deletions(-)

diff --git a/include/linux/device.h b/include/linux/device.h
index d7a72a8749ea..a83efd9ae949 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -1131,6 +1131,8 @@ void set_secondary_fwnode(struct device *dev, struct fwnode_handle *fwnode);
 void device_set_of_node_from_dev(struct device *dev, const struct device *dev2);
 void device_set_node(struct device *dev, struct fwnode_handle *fwnode);
 
+DEFINE_GUARD(device, struct device *, device_lock(_T), device_unlock(_T))
+
 static inline int dev_num_vf(struct device *dev)
 {
 	if (dev->bus && dev->bus->num_vf)
diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 1ff1ab5fa105..ce1356ac6dc2 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -296,9 +296,8 @@ static ssize_t available_size_show(struct device *dev,
 	struct dax_region *dax_region = dev_get_drvdata(dev);
 	unsigned long long size;
 
-	device_lock(dev);
+	guard(device)(dev);
 	size = dax_region_avail_size(dax_region);
-	device_unlock(dev);
 
 	return sprintf(buf, "%llu\n", size);
 }
@@ -314,10 +313,9 @@ static ssize_t seed_show(struct device *dev,
 	if (is_static(dax_region))
 		return -EINVAL;
 
-	device_lock(dev);
+	guard(device)(dev);
 	seed = dax_region->seed;
 	rc = sprintf(buf, "%s\n", seed ? dev_name(seed) : "");
-	device_unlock(dev);
 
 	return rc;
 }
@@ -333,10 +331,9 @@ static ssize_t create_show(struct device *dev,
 	if (is_static(dax_region))
 		return -EINVAL;
 
-	device_lock(dev);
+	guard(device)(dev);
 	youngest = dax_region->youngest;
 	rc = sprintf(buf, "%s\n", youngest ? dev_name(youngest) : "");
-	device_unlock(dev);
 
 	return rc;
 }
@@ -345,7 +342,14 @@ static ssize_t create_store(struct device *dev, struct device_attribute *attr,
 		const char *buf, size_t len)
 {
 	struct dax_region *dax_region = dev_get_drvdata(dev);
+	struct dev_dax_data data = {
+		.dax_region = dax_region,
+		.size = 0,
+		.id = -1,
+		.memmap_on_memory = false,
+	};
 	unsigned long long avail;
+	struct dev_dax *dev_dax;
 	ssize_t rc;
 	int val;
 
@@ -358,38 +362,26 @@ static ssize_t create_store(struct device *dev, struct device_attribute *attr,
 	if (val != 1)
 		return -EINVAL;
 
-	device_lock(dev);
+	guard(device)(dev);
 	avail = dax_region_avail_size(dax_region);
 	if (avail == 0)
-		rc = -ENOSPC;
-	else {
-		struct dev_dax_data data = {
-			.dax_region = dax_region,
-			.size = 0,
-			.id = -1,
-			.memmap_on_memory = false,
-		};
-		struct dev_dax *dev_dax = devm_create_dev_dax(&data);
+		return -ENOSPC;
 
-		if (IS_ERR(dev_dax))
-			rc = PTR_ERR(dev_dax);
-		else {
-			/*
-			 * In support of crafting multiple new devices
-			 * simultaneously multiple seeds can be created,
-			 * but only the first one that has not been
-			 * successfully bound is tracked as the region
-			 * seed.
-			 */
-			if (!dax_region->seed)
-				dax_region->seed = &dev_dax->dev;
-			dax_region->youngest = &dev_dax->dev;
-			rc = len;
-		}
-	}
-	device_unlock(dev);
+	dev_dax = devm_create_dev_dax(&data);
+	if (IS_ERR(dev_dax))
+		return PTR_ERR(dev_dax);
 
-	return rc;
+	/*
+	 * In support of crafting multiple new devices
+	 * simultaneously multiple seeds can be created,
+	 * but only the first one that has not been
+	 * successfully bound is tracked as the region
+	 * seed.
+	 */
+	if (!dax_region->seed)
+		dax_region->seed = &dev_dax->dev;
+	dax_region->youngest = &dev_dax->dev;
+	return len;
 }
 static DEVICE_ATTR_RW(create);
 
@@ -481,12 +473,9 @@ static int __free_dev_dax_id(struct dev_dax *dev_dax)
 static int free_dev_dax_id(struct dev_dax *dev_dax)
 {
 	struct device *dev = &dev_dax->dev;
-	int rc;
 
-	device_lock(dev);
-	rc = __free_dev_dax_id(dev_dax);
-	device_unlock(dev);
-	return rc;
+	guard(device)(dev);
+	return __free_dev_dax_id(dev_dax);
 }
 
 static int alloc_dev_dax_id(struct dev_dax *dev_dax)
@@ -908,9 +897,8 @@ static ssize_t size_show(struct device *dev,
 	struct dev_dax *dev_dax = to_dev_dax(dev);
 	unsigned long long size;
 
-	device_lock(dev);
+	guard(device)(dev);
 	size = dev_dax_size(dev_dax);
-	device_unlock(dev);
 
 	return sprintf(buf, "%llu\n", size);
 }
@@ -1080,15 +1068,12 @@ static ssize_t size_store(struct device *dev, struct device_attribute *attr,
 		return -EINVAL;
 	}
 
-	device_lock(dax_region->dev);
-	if (!dax_region->dev->driver) {
-		device_unlock(dax_region->dev);
+	guard(device)(dax_region->dev);
+	if (!dax_region->dev->driver)
 		return -ENXIO;
-	}
-	device_lock(dev);
+
+	guard(device)(dev);
 	rc = dev_dax_resize(dax_region, dev_dax, val);
-	device_unlock(dev);
-	device_unlock(dax_region->dev);
 
 	return rc == 0 ? len : rc;
 }
@@ -1138,18 +1123,14 @@ static ssize_t mapping_store(struct device *dev, struct device_attribute *attr,
 		return rc;
 
 	rc = -ENXIO;
-	device_lock(dax_region->dev);
-	if (!dax_region->dev->driver) {
-		device_unlock(dax_region->dev);
+	guard(device)(dax_region->dev);
+	if (!dax_region->dev->driver)
 		return rc;
-	}
-	device_lock(dev);
 
+	guard(device)(dev);
 	to_alloc = range_len(&r);
 	if (alloc_is_aligned(dev_dax, to_alloc))
 		rc = alloc_dev_dax_range(dev_dax, r.start, to_alloc);
-	device_unlock(dev);
-	device_unlock(dax_region->dev);
 
 	return rc == 0 ? len : rc;
 }
@@ -1196,26 +1177,20 @@ static ssize_t align_store(struct device *dev, struct device_attribute *attr,
 	if (!dax_align_valid(val))
 		return -EINVAL;
 
-	device_lock(dax_region->dev);
-	if (!dax_region->dev->driver) {
-		device_unlock(dax_region->dev);
+	guard(device)(dax_region->dev);
+	if (!dax_region->dev->driver)
 		return -ENXIO;
-	}
 
-	device_lock(dev);
-	if (dev->driver) {
-		rc = -EBUSY;
-		goto out_unlock;
-	}
+	guard(device)(dev);
+	if (dev->driver)
+		return -EBUSY;
 
 	align_save = dev_dax->align;
 	dev_dax->align = val;
 	rc = dev_dax_validate_align(dev_dax);
 	if (rc)
 		dev_dax->align = align_save;
-out_unlock:
-	device_unlock(dev);
-	device_unlock(dax_region->dev);
+
 	return rc == 0 ? len : rc;
 }
 static DEVICE_ATTR_RW(align);

-- 
2.41.0