drivers: cacheinfo: use __free attribute instead of of_node_put()

Introduce the __free attribute for scope-based resource management.
Resources allocated with __free are automatically released at the end of
the scope. This enhancement aims to mitigate memory management issues
associated with forgetting to release resources by utilizing __free
instead of of_node_put().

To introduce this feature, some modifications to the code structure were
necessary. The original pattern:
```
prev = np;
while(...) {
  [...]
  np = of_find_next_cache_node(np);
  of_node_put(prev);
  prev = np;
  [...]
}
```
has been updated to:
```
while(...) {
  [...]
  struct device_node __free(device_node) *prev = np;
  np =  of_find_next_cache_node(np)
  [...]
}
```
With this change, the previous node is automatically cleaned up at the end
of each iteration, allowing the elimination of all of_node_put() calls and
some goto statements.

Suggested-by: Julia Lawall <julia.lawall@inria.fr>
Signed-off-by: Vincenzo Mezzela <vincenzo.mezzela@gmail.com>
Link: https://lore.kernel.org/r/20240719151335.869145-1-vincenzo.mezzela@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
index 23b8cba4a2a3b87c34ff7e7b30f25784eab7e4dd..7a7609298e18bdc1fbf703c0284da4a8656e33e1 100644 (file)
--- a/drivers/base/cacheinfo.c
+++ b/drivers/base/cacheinfo.c
@@ -202,29 +202,24 @@ static void cache_of_set_props(struct cacheinfo *this_leaf,
 
 static int cache_setup_of_node(unsigned int cpu)
 {
-       struct device_node *np, *prev;
        struct cacheinfo *this_leaf;
        unsigned int index = 0;
 
-       np = of_cpu_device_node_get(cpu);
+       struct device_node *np __free(device_node) = of_cpu_device_node_get(cpu);
        if (!np) {
                pr_err("Failed to find cpu%d device node\n", cpu);
                return -ENOENT;
        }
 
        if (!of_check_cache_nodes(np)) {
-               of_node_put(np);
                return -ENOENT;
        }
 
-       prev = np;
-
        while (index < cache_leaves(cpu)) {
                this_leaf = per_cpu_cacheinfo_idx(cpu, index);
                if (this_leaf->level != 1) {
+                       struct device_node *prev __free(device_node) = np;
                        np = of_find_next_cache_node(np);
-                       of_node_put(prev);
-                       prev = np;
                        if (!np)
                                break;
                }
@@ -233,8 +228,6 @@ static int cache_setup_of_node(unsigned int cpu)
                index++;
        }
 
-       of_node_put(np);
-
        if (index != cache_leaves(cpu)) /* not all OF nodes populated */
                return -ENOENT;
 
@@ -243,17 +236,14 @@ static int cache_setup_of_node(unsigned int cpu)
 
 static bool of_check_cache_nodes(struct device_node *np)
 {
-       struct device_node *next;
-
        if (of_property_present(np, "cache-size")   ||
            of_property_present(np, "i-cache-size") ||
            of_property_present(np, "d-cache-size") ||
            of_property_present(np, "cache-unified"))
                return true;
 
-       next = of_find_next_cache_node(np);
+       struct device_node *next __free(device_node) = of_find_next_cache_node(np);
        if (next) {
-               of_node_put(next);
                return true;
        }
 
@@ -287,12 +277,10 @@ static int of_count_cache_leaves(struct device_node *np)
 int init_of_cache_level(unsigned int cpu)
 {
        struct cpu_cacheinfo *this_cpu_ci = get_cpu_cacheinfo(cpu);
-       struct device_node *np = of_cpu_device_node_get(cpu);
-       struct device_node *prev = NULL;
+       struct device_node *np __free(device_node) = of_cpu_device_node_get(cpu);
        unsigned int levels = 0, leaves, level;
 
        if (!of_check_cache_nodes(np)) {
-               of_node_put(np);
                return -ENOENT;
        }
 
@@ -300,30 +288,27 @@ int init_of_cache_level(unsigned int cpu)
        if (leaves > 0)
                levels = 1;
 
-       prev = np;
-       while ((np = of_find_next_cache_node(np))) {
-               of_node_put(prev);
-               prev = np;
+       while (1) {
+               struct device_node *prev __free(device_node) = np;
+               np = of_find_next_cache_node(np);
+               if (!np)
+                       break;
+
                if (!of_device_is_compatible(np, "cache"))
-                       goto err_out;
+                       return -EINVAL;
                if (of_property_read_u32(np, "cache-level", &level))
-                       goto err_out;
+                       return -EINVAL;
                if (level <= levels)
-                       goto err_out;
+                       return -EINVAL;
 
                leaves += of_count_cache_leaves(np);
                levels = level;
        }
 
-       of_node_put(np);
        this_cpu_ci->num_levels = levels;
        this_cpu_ci->num_leaves = leaves;
 
        return 0;
-
-err_out:
-       of_node_put(np);
-       return -EINVAL;
 }
 
 #else