From fa3ca07e96185aa1496b405472399a2a2a336a17 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Sun, 14 Apr 2013 11:36:56 -0700 Subject: [PATCH] cgroup: refactor hierarchy_id handling We're planning to converting hierarchy_ida to an idr and use it to look up hierarchy from its id. As we want the mapping to happen atomically with cgroupfs_root registration, this patch refactors hierarchy_id init / exit so that ida operations happen inside cgroup_[root_]mutex. * s/init_root_id()/cgroup_init_root_id()/ and make it return 0 or -errno like a normal function. * Move hierarchy_id initialization from cgroup_root_from_opts() into cgroup_mount() block where the root is confirmed to be used and being registered while holding both mutexes. * Split cgroup_drop_id() into cgroup_exit_root_id() and cgroup_free_root(), so that ID release can happen before dropping the mutexes in cgroup_kill_sb(). The latter expects hierarchy_id to be exited before being invoked. Signed-off-by: Tejun Heo Acked-by: Li Zefan --- kernel/cgroup.c | 56 +++++++++++++++++++++++++++++++++++--------------------- 1 file changed, 35 insertions(+), 21 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 2a99262..dbc84f7 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1426,13 +1426,13 @@ static void init_cgroup_root(struct cgroupfs_root *root) list_add_tail(&cgrp->allcg_node, &root->allcg_list); } -static bool init_root_id(struct cgroupfs_root *root) +static int cgroup_init_root_id(struct cgroupfs_root *root) { - int ret = 0; + int ret; do { if (!ida_pre_get(&hierarchy_ida, GFP_KERNEL)) - return false; + return -ENOMEM; spin_lock(&hierarchy_id_lock); /* Try to allocate the next unused ID */ ret = ida_get_new_above(&hierarchy_ida, next_hierarchy_id, @@ -1448,7 +1448,18 @@ static bool init_root_id(struct cgroupfs_root *root) } spin_unlock(&hierarchy_id_lock); } while (ret); - return true; + return 0; +} + +static void cgroup_exit_root_id(struct cgroupfs_root *root) +{ + if (root->hierarchy_id) { + spin_lock(&hierarchy_id_lock); + ida_remove(&hierarchy_ida, root->hierarchy_id); + spin_unlock(&hierarchy_id_lock); + + root->hierarchy_id = 0; + } } static int cgroup_test_super(struct super_block *sb, void *data) @@ -1482,10 +1493,6 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts) if (!root) return ERR_PTR(-ENOMEM); - if (!init_root_id(root)) { - kfree(root); - return ERR_PTR(-ENOMEM); - } init_cgroup_root(root); root->subsys_mask = opts->subsys_mask; @@ -1500,17 +1507,15 @@ static struct cgroupfs_root *cgroup_root_from_opts(struct cgroup_sb_opts *opts) return root; } -static void cgroup_drop_root(struct cgroupfs_root *root) +static void cgroup_free_root(struct cgroupfs_root *root) { - if (!root) - return; + if (root) { + /* hierarhcy ID shoulid already have been released */ + WARN_ON_ONCE(root->hierarchy_id); - BUG_ON(!root->hierarchy_id); - spin_lock(&hierarchy_id_lock); - ida_remove(&hierarchy_ida, root->hierarchy_id); - spin_unlock(&hierarchy_id_lock); - ida_destroy(&root->cgroup_ida); - kfree(root); + ida_destroy(&root->cgroup_ida); + kfree(root); + } } static int cgroup_set_super(struct super_block *sb, void *data) @@ -1597,7 +1602,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, sb = sget(fs_type, cgroup_test_super, cgroup_set_super, 0, &opts); if (IS_ERR(sb)) { ret = PTR_ERR(sb); - cgroup_drop_root(opts.new_root); + cgroup_free_root(opts.new_root); goto drop_modules; } @@ -1641,6 +1646,10 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, if (ret) goto unlock_drop; + ret = cgroup_init_root_id(root); + if (ret) + goto unlock_drop; + ret = rebind_subsystems(root, root->subsys_mask); if (ret == -EBUSY) { free_cg_links(&tmp_cg_links); @@ -1684,7 +1693,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, * We re-used an existing hierarchy - the new root (if * any) is not needed */ - cgroup_drop_root(opts.new_root); + cgroup_free_root(opts.new_root); if (((root->flags | opts.flags) & CGRP_ROOT_SANE_BEHAVIOR) && root->flags != opts.flags) { @@ -1702,6 +1711,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, return dget(sb->s_root); unlock_drop: + cgroup_exit_root_id(root); mutex_unlock(&cgroup_root_mutex); mutex_unlock(&cgroup_mutex); mutex_unlock(&inode->i_mutex); @@ -1754,13 +1764,15 @@ static void cgroup_kill_sb(struct super_block *sb) { root_count--; } + cgroup_exit_root_id(root); + mutex_unlock(&cgroup_root_mutex); mutex_unlock(&cgroup_mutex); simple_xattrs_free(&cgrp->xattrs); kill_litter_super(sb); - cgroup_drop_root(root); + cgroup_free_root(root); } static struct file_system_type cgroup_fs_type = { @@ -4642,7 +4654,9 @@ int __init cgroup_init(void) /* Add init_css_set to the hash table */ key = css_set_hash(init_css_set.subsys); hash_add(css_set_table, &init_css_set.hlist, key); - BUG_ON(!init_root_id(&rootnode)); + + /* allocate id for the dummy hierarchy */ + BUG_ON(cgroup_init_root_id(&rootnode)); cgroup_kobj = kobject_create_and_add("cgroup", fs_kobj); if (!cgroup_kobj) { -- 2.7.4