cgroup: Convert cgroup_hierarchy to XArray

Signed-off-by: Matthew Wilcox <willy@infradead.org>

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 11b52b76ff6a89c22c2a1fd41a1598ae34cbde33..d732910f5e2dbbf1364e27f9b3067e8af3a27868 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -47,7 +47,7 @@
 #include <linux/percpu-rwsem.h>
 #include <linux/string.h>
 #include <linux/hashtable.h>
-#include <linux/idr.h>
+#include <linux/xarray.h>
 #include <linux/kthread.h>
 #include <linux/atomic.h>
 #include <linux/cpuset.h>
@@ -174,8 +174,9 @@ static u16 cgrp_dfl_threaded_ss_mask;
 LIST_HEAD(cgroup_roots);
 static int cgroup_root_count;
 
-/* hierarchy ID allocation and mapping, protected by cgroup_mutex */
-static DEFINE_IDR(cgroup_hierarchy_idr);
+/* hierarchy ID allocation and mapping */
+static DEFINE_XARRAY_ALLOC(cgroup_hierarchy);
+static u32 cgroup_hierarchy_next;
 
 /*
  * Assign a monotonically increasing serial number to csses.  It guarantees
@@ -1251,23 +1252,13 @@ struct cgroup_root *cgroup_root_from_kf(struct kernfs_root *kf_root)
 
 static int cgroup_init_root_id(struct cgroup_root *root)
 {
-       int id;
-
-       lockdep_assert_held(&cgroup_mutex);
-
-       id = idr_alloc_cyclic(&cgroup_hierarchy_idr, root, 0, 0, GFP_KERNEL);
-       if (id < 0)
-               return id;
-
-       root->hierarchy_id = id;
-       return 0;
+       return xa_alloc_cyclic(&cgroup_hierarchy, &root->hierarchy_id,
+                       root, xa_limit_32b, &cgroup_hierarchy_next, GFP_KERNEL);
 }
 
 static void cgroup_exit_root_id(struct cgroup_root *root)
 {
-       lockdep_assert_held(&cgroup_mutex);
-
-       idr_remove(&cgroup_hierarchy_idr, root->hierarchy_id);
+       xa_erase(&cgroup_hierarchy, root->hierarchy_id);
 }
 
 void cgroup_free_root(struct cgroup_root *root)
@@ -1980,7 +1971,7 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask)
                goto cancel_ref;
 
        ret = cgroup_init_root_id(root);
-       if (ret)
+       if (ret < 0)
                goto cancel_ref;
 
        kf_sops = root == &cgrp_dfl_root ?
@@ -2288,13 +2279,13 @@ int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
 {
        struct cgroup_root *root;
        struct cgroup *cgrp;
-       int hierarchy_id = 1;
+       unsigned long hierarchy_id = 1;
        int ret;
 
-       mutex_lock(&cgroup_mutex);
        spin_lock_irq(&css_set_lock);
 
-       root = idr_get_next(&cgroup_hierarchy_idr, &hierarchy_id);
+       xa_lock(&cgroup_hierarchy);
+       root = xa_find(&cgroup_hierarchy, &hierarchy_id, ULONG_MAX, XA_PRESENT);
 
        if (root) {
                cgrp = task_cgroup_from_root(task, root);
@@ -2304,8 +2295,8 @@ int task_cgroup_path(struct task_struct *task, char *buf, size_t buflen)
                ret = strlcpy(buf, "/", buflen);
        }
 
+       xa_unlock(&cgroup_hierarchy);
        spin_unlock_irq(&css_set_lock);
-       mutex_unlock(&cgroup_mutex);
        return ret;
 }
 EXPORT_SYMBOL_GPL(task_cgroup_path);