cgroup: use new hashtable implementation
Li Zefan [Thu, 10 Jan 2013 03:49:27 +0000 (11:49 +0800)]
Switch cgroup to use the new hashtable implementation. No functional changes.

Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>

kernel/cgroup.c

index 6643f70..54b3908 100644 (file)
@@ -52,7 +52,7 @@
 #include <linux/module.h>
 #include <linux/delayacct.h>
 #include <linux/cgroupstats.h>
-#include <linux/hash.h>
+#include <linux/hashtable.h>
 #include <linux/namei.h>
 #include <linux/pid_namespace.h>
 #include <linux/idr.h>
@@ -376,22 +376,18 @@ static int css_set_count;
  * account cgroups in empty hierarchies.
  */
 #define CSS_SET_HASH_BITS      7
-#define CSS_SET_TABLE_SIZE     (1 << CSS_SET_HASH_BITS)
-static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
+static DEFINE_HASHTABLE(css_set_table, CSS_SET_HASH_BITS);
 
-static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
+static unsigned long css_set_hash(struct cgroup_subsys_state *css[])
 {
        int i;
-       int index;
-       unsigned long tmp = 0UL;
+       unsigned long key = 0UL;
 
        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
-               tmp += (unsigned long)css[i];
-       tmp = (tmp >> 16) ^ tmp;
+               key += (unsigned long)css[i];
+       key = (key >> 16) ^ key;
 
-       index = hash_long(tmp, CSS_SET_HASH_BITS);
-
-       return &css_set_table[index];
+       return key;
 }
 
 /* We don't maintain the lists running through each css_set to its
@@ -418,7 +414,7 @@ static void __put_css_set(struct css_set *cg, int taskexit)
        }
 
        /* This css_set is dead. unlink it and release cgroup refcounts */
-       hlist_del(&cg->hlist);
+       hash_del(&cg->hlist);
        css_set_count--;
 
        list_for_each_entry_safe(link, saved_link, &cg->cg_links,
@@ -550,9 +546,9 @@ static struct css_set *find_existing_css_set(
 {
        int i;
        struct cgroupfs_root *root = cgrp->root;
-       struct hlist_head *hhead;
        struct hlist_node *node;
        struct css_set *cg;
+       unsigned long key;
 
        /*
         * Build the set of subsystem state objects that we want to see in the
@@ -572,8 +568,8 @@ static struct css_set *find_existing_css_set(
                }
        }
 
-       hhead = css_set_hash(template);
-       hlist_for_each_entry(cg, node, hhead, hlist) {
+       key = css_set_hash(template);
+       hash_for_each_possible(css_set_table, cg, node, hlist, key) {
                if (!compare_css_sets(cg, oldcg, cgrp, template))
                        continue;
 
@@ -657,8 +653,8 @@ static struct css_set *find_css_set(
 
        struct list_head tmp_cg_links;
 
-       struct hlist_head *hhead;
        struct cg_cgroup_link *link;
+       unsigned long key;
 
        /* First see if we already have a cgroup group that matches
         * the desired set */
@@ -704,8 +700,8 @@ static struct css_set *find_css_set(
        css_set_count++;
 
        /* Add this cgroup group to the hash table */
-       hhead = css_set_hash(res->subsys);
-       hlist_add_head(&res->hlist, hhead);
+       key = css_set_hash(res->subsys);
+       hash_add(css_set_table, &res->hlist, key);
 
        write_unlock(&css_set_lock);
 
@@ -1597,6 +1593,8 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
                struct cgroupfs_root *existing_root;
                const struct cred *cred;
                int i;
+               struct hlist_node *node;
+               struct css_set *cg;
 
                BUG_ON(sb->s_root != NULL);
 
@@ -1650,14 +1648,8 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
                /* Link the top cgroup in this hierarchy into all
                 * the css_set objects */
                write_lock(&css_set_lock);
-               for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
-                       struct hlist_head *hhead = &css_set_table[i];
-                       struct hlist_node *node;
-                       struct css_set *cg;
-
-                       hlist_for_each_entry(cg, node, hhead, hlist)
-                               link_css_set(&tmp_cg_links, cg, root_cgrp);
-               }
+               hash_for_each(css_set_table, i, node, cg, hlist)
+                       link_css_set(&tmp_cg_links, cg, root_cgrp);
                write_unlock(&css_set_lock);
 
                free_cg_links(&tmp_cg_links);
@@ -4464,6 +4456,9 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
 {
        struct cgroup_subsys_state *css;
        int i, ret;
+       struct hlist_node *node, *tmp;
+       struct css_set *cg;
+       unsigned long key;
 
        /* check name and function validity */
        if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
@@ -4529,23 +4524,17 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
         * this is all done under the css_set_lock.
         */
        write_lock(&css_set_lock);
-       for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
-               struct css_set *cg;
-               struct hlist_node *node, *tmp;
-               struct hlist_head *bucket = &css_set_table[i], *new_bucket;
-
-               hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
-                       /* skip entries that we already rehashed */
-                       if (cg->subsys[ss->subsys_id])
-                               continue;
-                       /* remove existing entry */
-                       hlist_del(&cg->hlist);
-                       /* set new value */
-                       cg->subsys[ss->subsys_id] = css;
-                       /* recompute hash and restore entry */
-                       new_bucket = css_set_hash(cg->subsys);
-                       hlist_add_head(&cg->hlist, new_bucket);
-               }
+       hash_for_each_safe(css_set_table, i, node, tmp, cg, hlist) {
+               /* skip entries that we already rehashed */
+               if (cg->subsys[ss->subsys_id])
+                       continue;
+               /* remove existing entry */
+               hash_del(&cg->hlist);
+               /* set new value */
+               cg->subsys[ss->subsys_id] = css;
+               /* recompute hash and restore entry */
+               key = css_set_hash(cg->subsys);
+               hash_add(css_set_table, node, key);
        }
        write_unlock(&css_set_lock);
 
@@ -4577,7 +4566,6 @@ EXPORT_SYMBOL_GPL(cgroup_load_subsys);
 void cgroup_unload_subsys(struct cgroup_subsys *ss)
 {
        struct cg_cgroup_link *link;
-       struct hlist_head *hhead;
 
        BUG_ON(ss->module == NULL);
 
@@ -4611,11 +4599,12 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
        write_lock(&css_set_lock);
        list_for_each_entry(link, &dummytop->css_sets, cgrp_link_list) {
                struct css_set *cg = link->cg;
+               unsigned long key;
 
-               hlist_del(&cg->hlist);
+               hash_del(&cg->hlist);
                cg->subsys[ss->subsys_id] = NULL;
-               hhead = css_set_hash(cg->subsys);
-               hlist_add_head(&cg->hlist, hhead);
+               key = css_set_hash(cg->subsys);
+               hash_add(css_set_table, &cg->hlist, key);
        }
        write_unlock(&css_set_lock);
 
@@ -4657,9 +4646,6 @@ int __init cgroup_init_early(void)
        list_add(&init_css_set_link.cg_link_list,
                 &init_css_set.cg_links);
 
-       for (i = 0; i < CSS_SET_TABLE_SIZE; i++)
-               INIT_HLIST_HEAD(&css_set_table[i]);
-
        for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
                struct cgroup_subsys *ss = subsys[i];
 
@@ -4693,7 +4679,7 @@ int __init cgroup_init(void)
 {
        int err;
        int i;
-       struct hlist_head *hhead;
+       unsigned long key;
 
        err = bdi_init(&cgroup_backing_dev_info);
        if (err)
@@ -4712,8 +4698,8 @@ int __init cgroup_init(void)
        }
 
        /* Add init_css_set to the hash table */
-       hhead = css_set_hash(init_css_set.subsys);
-       hlist_add_head(&init_css_set.hlist, hhead);
+       key = css_set_hash(init_css_set.subsys);
+       hash_add(css_set_table, &init_css_set.hlist, key);
        BUG_ON(!init_root_id(&rootnode));
 
        cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj);