Use the 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.mart...@oracle.com>
Cc: Dan Williams <dan.j.willi...@intel.com>
Signed-off-by: Vishal Verma <vishal.l.ve...@intel.com>
---
 drivers/dax/bus.c | 143 ++++++++++++++++++++++--------------------------------
 1 file changed, 59 insertions(+), 84 deletions(-)

diff --git a/drivers/dax/bus.c b/drivers/dax/bus.c
index 1ff1ab5fa105..6226de131d17 100644
--- a/drivers/dax/bus.c
+++ b/drivers/dax/bus.c
@@ -294,13 +294,10 @@ static ssize_t available_size_show(struct device *dev,
                struct device_attribute *attr, char *buf)
 {
        struct dax_region *dax_region = dev_get_drvdata(dev);
-       unsigned long long size;
 
-       device_lock(dev);
-       size = dax_region_avail_size(dax_region);
-       device_unlock(dev);
+       guard(device)(dev);
 
-       return sprintf(buf, "%llu\n", size);
+       return sprintf(buf, "%llu\n", dax_region_avail_size(dax_region));
 }
 static DEVICE_ATTR_RO(available_size);
 
@@ -309,17 +306,14 @@ static ssize_t seed_show(struct device *dev,
 {
        struct dax_region *dax_region = dev_get_drvdata(dev);
        struct device *seed;
-       ssize_t rc;
 
        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;
+       return sprintf(buf, "%s\n", seed ? dev_name(seed) : "");
 }
 static DEVICE_ATTR_RO(seed);
 
@@ -328,24 +322,28 @@ static ssize_t create_show(struct device *dev,
 {
        struct dax_region *dax_region = dev_get_drvdata(dev);
        struct device *youngest;
-       ssize_t rc;
 
        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;
+       return sprintf(buf, "%s\n", youngest ? dev_name(youngest) : "");
 }
 
 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 +356,25 @@ 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 +466,9 @@ 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 +890,8 @@ 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);
 }
@@ -1080,17 +1061,16 @@ 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);
+       if (rc)
+               return rc;
 
-       return rc == 0 ? len : rc;
+       return len;
 }
 static DEVICE_ATTR_RW(size);
 
@@ -1137,21 +1117,20 @@ static ssize_t mapping_store(struct device *dev, struct 
device_attribute *attr,
        if (rc)
                return rc;
 
-       rc = -ENXIO;
-       device_lock(dax_region->dev);
-       if (!dax_region->dev->driver) {
-               device_unlock(dax_region->dev);
-               return rc;
-       }
-       device_lock(dev);
+       guard(device)(dax_region->dev);
+       if (!dax_region->dev->driver)
+               return -ENXIO;
 
+       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);
+       if (!alloc_is_aligned(dev_dax, to_alloc))
+               return -ENXIO;
 
-       return rc == 0 ? len : rc;
+       rc = alloc_dev_dax_range(dev_dax, r.start, to_alloc);
+       if (rc)
+               return rc;
+
+       return len;
 }
 static DEVICE_ATTR_WO(mapping);
 
@@ -1196,27 +1175,23 @@ 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)
+       if (rc) {
                dev_dax->align = align_save;
-out_unlock:
-       device_unlock(dev);
-       device_unlock(dax_region->dev);
-       return rc == 0 ? len : rc;
+               return rc;
+       }
+
+       return len;
 }
 static DEVICE_ATTR_RW(align);
 

-- 
2.41.0


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