cgroup: Convert css_idr to XArray

Remove the internal wrappers as the XArray behaves exactly how the
cgroup code wishes the IDR did.

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

diff --git a/include/linux/cgroup-defs.h b/include/linux/cgroup-defs.h
index 341d062905bec6f31e453251bed29ee528fd23f5..c17fa7b658da6ddd6cac126bc3c6af1f9acaf348 100644 (file)
--- a/include/linux/cgroup-defs.h
+++ b/include/linux/cgroup-defs.h
@@ -10,7 +10,7 @@
 
 #include <linux/limits.h>
 #include <linux/list.h>
-#include <linux/idr.h>
+#include <linux/xarray.h>
 #include <linux/wait.h>
 #include <linux/mutex.h>
 #include <linux/rcupdate.h>
@@ -700,8 +700,8 @@ struct cgroup_subsys {
        /* link to parent, protected by cgroup_lock() */
        struct cgroup_root *root;
 
-       /* idr for css->id */
-       struct idr css_idr;
+       /* xarray for css->id */
+       struct xarray css_xa;
 
        /*
         * List of cftypes.  Each entry is the first entry of an array

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index bc9c8fd63d8d21f13ac848eeeac3397527d4ac05..11b52b76ff6a89c22c2a1fd41a1598ae34cbde33 100644 (file)
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -89,12 +89,6 @@ DEFINE_SPINLOCK(trace_cgroup_path_lock);
 char trace_cgroup_path[TRACE_CGROUP_PATH_LEN];
 bool cgroup_debug __read_mostly;
 
-/*
- * Protects css_idr so that IDs can be released without
- * grabbing cgroup_mutex.
- */
-static DEFINE_SPINLOCK(cgroup_idr_lock);
-
 /*
  * Protects cgroup_file->kn for !self csses.  It synchronizes notifications
  * against file removal/re-creation across css hiding.
@@ -300,37 +294,6 @@ bool cgroup_on_dfl(const struct cgroup *cgrp)
        return cgrp->root == &cgrp_dfl_root;
 }
 
-/* IDR wrappers which synchronize using cgroup_idr_lock */
-static int cgroup_idr_alloc(struct idr *idr, void *ptr, int start, int end,
-                           gfp_t gfp_mask)
-{
-       int ret;
-
-       idr_preload(gfp_mask);
-       spin_lock_bh(&cgroup_idr_lock);
-       ret = idr_alloc(idr, ptr, start, end, gfp_mask & ~__GFP_DIRECT_RECLAIM);
-       spin_unlock_bh(&cgroup_idr_lock);
-       idr_preload_end();
-       return ret;
-}
-
-static void *cgroup_idr_replace(struct idr *idr, void *ptr, int id)
-{
-       void *ret;
-
-       spin_lock_bh(&cgroup_idr_lock);
-       ret = idr_replace(idr, ptr, id);
-       spin_unlock_bh(&cgroup_idr_lock);
-       return ret;
-}
-
-static void cgroup_idr_remove(struct idr *idr, int id)
-{
-       spin_lock_bh(&cgroup_idr_lock);
-       idr_remove(idr, id);
-       spin_unlock_bh(&cgroup_idr_lock);
-}
-
 static bool cgroup_has_tasks(struct cgroup *cgrp)
 {
        return cgrp->nr_populated_csets;
@@ -4961,7 +4924,7 @@ static void css_free_rwork_fn(struct work_struct *work)
                int id = css->id;
 
                ss->css_free(css);
-               cgroup_idr_remove(&ss->css_idr, id);
+               xa_erase_bh(&ss->css_xa, id);
                cgroup_put(cgrp);
 
                if (parent)
@@ -5015,7 +4978,7 @@ static void css_release_work_fn(struct work_struct *work)
                        list_del_rcu(&css->rstat_css_node);
                }
 
-               cgroup_idr_replace(&ss->css_idr, NULL, css->id);
+               xa_store_bh(&ss->css_xa, css->id, NULL, 0);
                if (ss->css_released)
                        ss->css_released(css);
        } else {
@@ -5162,14 +5125,15 @@ static struct cgroup_subsys_state *css_create(struct cgroup *cgrp,
        if (err)
                goto err_free_css;
 
-       err = cgroup_idr_alloc(&ss->css_idr, NULL, 2, 0, GFP_KERNEL);
+       err = xa_alloc_bh(&ss->css_xa, &css->id, NULL, xa_limit_31b,
+                       GFP_KERNEL);
        if (err < 0)
                goto err_free_css;
-       css->id = err;
+       BUG_ON(css->id < 2);
 
        /* @css is ready to be brought online now, make it visible */
        list_add_tail_rcu(&css->sibling, &parent_css->children);
-       cgroup_idr_replace(&ss->css_idr, css, css->id);
+       xa_store_bh(&ss->css_xa, css->id, css, 0);
 
        err = online_css(css);
        if (err)
@@ -5609,7 +5573,7 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
 
        mutex_lock(&cgroup_mutex);
 
-       idr_init(&ss->css_idr);
+       xa_init_flags(&ss->css_xa, XA_FLAGS_ALLOC1 | XA_FLAGS_LOCK_BH);
        INIT_LIST_HEAD(&ss->cfts);
 
        /* Create the root cgroup state for this subsystem */
@@ -5624,13 +5588,12 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss, bool early)
         * percpu_ref during early init.  Disable refcnting.
         */
        css->flags |= CSS_NO_REF;
+       css->id = 1;
 
-       if (early) {
+       if (!early) {
                /* allocation can't be done safely during early init */
-               css->id = 1;
-       } else {
-               css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2, GFP_KERNEL);
-               BUG_ON(css->id < 0);
+               void *old = xa_store_bh(&ss->css_xa, 1, css, GFP_KERNEL);
+               BUG_ON(old);
        }
 
        /* Update the init_css_set to contain a subsys
@@ -5736,9 +5699,8 @@ int __init cgroup_init(void)
                        struct cgroup_subsys_state *css =
                                init_css_set.subsys[ss->id];
 
-                       css->id = cgroup_idr_alloc(&ss->css_idr, css, 1, 2,
-                                                  GFP_KERNEL);
-                       BUG_ON(css->id < 0);
+                       void *p = xa_store_bh(&ss->css_xa, 1, css, GFP_KERNEL);
+                       BUG_ON(p != NULL);
                } else {
                        cgroup_init_subsys(ss, false);
                }
@@ -6211,7 +6173,7 @@ struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry,
 struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss)
 {
        WARN_ON_ONCE(!rcu_read_lock_held());
-       return idr_find(&ss->css_idr, id);
+       return xa_load(&ss->css_xa, id);
 }
 
 /**