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Subject[PATCH 05/13] cgroup: factor out cgroup_setup_root() from cgroup_mount()
Date
Factor out new root initialization into cgroup_setup_root() from
cgroup_mount(). This makes it easier to follow and will ease kernfs
conversion.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
kernel/cgroup.c | 211 ++++++++++++++++++++++++++++++--------------------------
1 file changed, 113 insertions(+), 98 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index d88393c..8a9548c 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1453,17 +1453,126 @@ static int cgroup_get_rootdir(struct super_block *sb)
return 0;
}

+static int cgroup_setup_root(struct cgroupfs_root *root)
+{
+ LIST_HEAD(tmp_links);
+ struct super_block *sb = root->sb;
+ struct cgroup *root_cgrp = &root->top_cgroup;
+ struct cgroupfs_root *existing_root;
+ struct css_set *cset;
+ struct inode *inode;
+ const struct cred *cred;
+ int i, ret;
+
+ lockdep_assert_held(&cgroup_tree_mutex);
+ lockdep_assert_held(&cgroup_mutex);
+ BUG_ON(sb->s_root != NULL);
+
+ mutex_unlock(&cgroup_mutex);
+ mutex_unlock(&cgroup_tree_mutex);
+
+ ret = cgroup_get_rootdir(sb);
+ if (ret) {
+ mutex_lock(&cgroup_tree_mutex);
+ mutex_lock(&cgroup_mutex);
+ return ret;
+ }
+ inode = sb->s_root->d_inode;
+
+ mutex_lock(&inode->i_mutex);
+ mutex_lock(&cgroup_tree_mutex);
+ mutex_lock(&cgroup_mutex);
+
+ ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL);
+ if (ret < 0)
+ goto out_unlock;
+ root_cgrp->id = ret;
+
+ /* check for name clashes with existing mounts */
+ ret = -EBUSY;
+ if (strlen(root->name))
+ for_each_active_root(existing_root)
+ if (!strcmp(existing_root->name, root->name))
+ goto out_unlock;
+
+ /*
+ * We're accessing css_set_count without locking css_set_lock here,
+ * but that's OK - it can only be increased by someone holding
+ * cgroup_lock, and that's us. The worst that can happen is that we
+ * have some link structures left over
+ */
+ ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
+ if (ret)
+ goto out_unlock;
+
+ /* ID 0 is reserved for dummy root, 1 for unified hierarchy */
+ ret = cgroup_init_root_id(root, 2, 0);
+ if (ret)
+ goto out_unlock;
+
+ sb->s_root->d_fsdata = root_cgrp;
+ root_cgrp->dentry = sb->s_root;
+
+ /*
+ * We're inside get_sb() and will call lookup_one_len() to create
+ * the root files, which doesn't work if SELinux is in use. The
+ * following cred dancing somehow works around it. See 2ce9738ba
+ * ("cgroupfs: use init_cred when populating new cgroupfs mount")
+ * for more details.
+ */
+ cred = override_creds(&init_cred);
+
+ ret = cgroup_addrm_files(root_cgrp, cgroup_base_files, true);
+ if (ret)
+ goto rm_base_files;
+
+ ret = rebind_subsystems(root, root->subsys_mask, 0);
+ if (ret)
+ goto rm_base_files;
+
+ revert_creds(cred);
+
+ /*
+ * There must be no failure case after here, since rebinding takes
+ * care of subsystems' refcounts, which are explicitly dropped in
+ * the failure exit path.
+ */
+ list_add(&root->root_list, &cgroup_roots);
+ cgroup_root_count++;
+
+ /*
+ * Link the top cgroup in this hierarchy into all the css_set
+ * objects.
+ */
+ write_lock(&css_set_lock);
+ hash_for_each(css_set_table, i, cset, hlist)
+ link_css_set(&tmp_links, cset, root_cgrp);
+ write_unlock(&css_set_lock);
+
+ BUG_ON(!list_empty(&root_cgrp->children));
+ BUG_ON(root->number_of_cgroups != 1);
+
+ ret = 0;
+ goto out_unlock;
+
+rm_base_files:
+ cgroup_addrm_files(&root->top_cgroup, cgroup_base_files, false);
+ revert_creds(cred);
+ cgroup_exit_root_id(root);
+out_unlock:
+ mutex_unlock(&inode->i_mutex);
+ free_cgrp_cset_links(&tmp_links);
+ return ret;
+}
+
static struct dentry *cgroup_mount(struct file_system_type *fs_type,
int flags, const char *unused_dev_name,
void *data)
{
- LIST_HEAD(tmp_links);
struct super_block *sb = NULL;
- struct inode *inode = NULL;
struct cgroupfs_root *root = NULL;
struct cgroup_sb_opts opts;
struct cgroupfs_root *new_root;
- const struct cred *cred;
int ret;

mutex_lock(&cgroup_tree_mutex);
@@ -1500,94 +1609,9 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
root = sb->s_fs_info;
BUG_ON(!root);
if (root == opts.new_root) {
- /* We used the new root structure, so this is a new hierarchy */
- struct cgroup *root_cgrp = &root->top_cgroup;
- struct cgroupfs_root *existing_root;
- int i;
- struct css_set *cset;
-
- BUG_ON(sb->s_root != NULL);
-
- mutex_unlock(&cgroup_mutex);
- mutex_unlock(&cgroup_tree_mutex);
-
- ret = cgroup_get_rootdir(sb);
+ ret = cgroup_setup_root(root);
if (ret)
goto out_unlock;
- inode = sb->s_root->d_inode;
-
- mutex_lock(&inode->i_mutex);
- mutex_lock(&cgroup_tree_mutex);
- mutex_lock(&cgroup_mutex);
-
- ret = idr_alloc(&root->cgroup_idr, root_cgrp, 0, 1, GFP_KERNEL);
- if (ret < 0)
- goto out_unlock;
- root_cgrp->id = ret;
-
- /* Check for name clashes with existing mounts */
- ret = -EBUSY;
- if (strlen(root->name))
- for_each_active_root(existing_root)
- if (!strcmp(existing_root->name, root->name))
- goto out_unlock;
-
- /*
- * We're accessing css_set_count without locking
- * css_set_lock here, but that's OK - it can only be
- * increased by someone holding cgroup_lock, and
- * that's us. The worst that can happen is that we
- * have some link structures left over
- */
- ret = allocate_cgrp_cset_links(css_set_count, &tmp_links);
- if (ret)
- goto out_unlock;
-
- /* ID 0 is reserved for dummy root, 1 for unified hierarchy */
- ret = cgroup_init_root_id(root, 2, 0);
- if (ret)
- goto out_unlock;
-
- sb->s_root->d_fsdata = root_cgrp;
- root_cgrp->dentry = sb->s_root;
-
- /*
- * We're inside get_sb() and will call lookup_one_len() to
- * create the root files, which doesn't work if SELinux is
- * in use. The following cred dancing somehow works around
- * it. See 2ce9738ba ("cgroupfs: use init_cred when
- * populating new cgroupfs mount") for more details.
- */
- cred = override_creds(&init_cred);
-
- ret = cgroup_addrm_files(root_cgrp, cgroup_base_files, true);
- if (ret)
- goto rm_base_files;
-
- ret = rebind_subsystems(root, root->subsys_mask, 0);
- if (ret)
- goto rm_base_files;
-
- revert_creds(cred);
-
- /*
- * There must be no failure case after here, since rebinding
- * takes care of subsystems' refcounts, which are explicitly
- * dropped in the failure exit path.
- */
-
- list_add(&root->root_list, &cgroup_roots);
- cgroup_root_count++;
-
- /* Link the top cgroup in this hierarchy into all
- * the css_set objects */
- write_lock(&css_set_lock);
- hash_for_each(css_set_table, i, cset, hlist)
- link_css_set(&tmp_links, cset, root_cgrp);
- write_unlock(&css_set_lock);
-
- BUG_ON(!list_empty(&root_cgrp->children));
- BUG_ON(root->number_of_cgroups != 1);
} else {
/*
* We re-used an existing hierarchy - the new root (if
@@ -1607,22 +1631,13 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
}

ret = 0;
- goto out_unlock;
-
-rm_base_files:
- cgroup_addrm_files(&root->top_cgroup, cgroup_base_files, false);
- revert_creds(cred);
- cgroup_exit_root_id(root);
out_unlock:
mutex_unlock(&cgroup_mutex);
mutex_unlock(&cgroup_tree_mutex);
- if (inode)
- mutex_unlock(&inode->i_mutex);

if (ret && !IS_ERR_OR_NULL(sb))
deactivate_locked_super(sb);

- free_cgrp_cset_links(&tmp_links);
kfree(opts.release_agent);
kfree(opts.name);

--
1.8.5.3


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