| /* |
| * kernel/cgroup.c |
| * |
| * Generic process-grouping system. |
| * |
| * Based originally on the cpuset system, extracted by Paul Menage |
| * Copyright (C) 2006 Google, Inc |
| * |
| * Copyright notices from the original cpuset code: |
| * -------------------------------------------------- |
| * Copyright (C) 2003 BULL SA. |
| * Copyright (C) 2004-2006 Silicon Graphics, Inc. |
| * |
| * Portions derived from Patrick Mochel's sysfs code. |
| * sysfs is Copyright (c) 2001-3 Patrick Mochel |
| * |
| * 2003-10-10 Written by Simon Derr. |
| * 2003-10-22 Updates by Stephen Hemminger. |
| * 2004 May-July Rework by Paul Jackson. |
| * --------------------------------------------------- |
| * |
| * This file is subject to the terms and conditions of the GNU General Public |
| * License. See the file COPYING in the main directory of the Linux |
| * distribution for more details. |
| */ |
| |
| #include <linux/cgroup.h> |
| #include <linux/errno.h> |
| #include <linux/fs.h> |
| #include <linux/kernel.h> |
| #include <linux/list.h> |
| #include <linux/mm.h> |
| #include <linux/mutex.h> |
| #include <linux/mount.h> |
| #include <linux/pagemap.h> |
| #include <linux/rcupdate.h> |
| #include <linux/sched.h> |
| #include <linux/seq_file.h> |
| #include <linux/slab.h> |
| #include <linux/magic.h> |
| #include <linux/spinlock.h> |
| #include <linux/string.h> |
| #include <linux/sort.h> |
| #include <asm/atomic.h> |
| |
| /* Generate an array of cgroup subsystem pointers */ |
| #define SUBSYS(_x) &_x ## _subsys, |
| |
| static struct cgroup_subsys *subsys[] = { |
| #include <linux/cgroup_subsys.h> |
| }; |
| |
| /* |
| * A cgroupfs_root represents the root of a cgroup hierarchy, |
| * and may be associated with a superblock to form an active |
| * hierarchy |
| */ |
| struct cgroupfs_root { |
| struct super_block *sb; |
| |
| /* |
| * The bitmask of subsystems intended to be attached to this |
| * hierarchy |
| */ |
| unsigned long subsys_bits; |
| |
| /* The bitmask of subsystems currently attached to this hierarchy */ |
| unsigned long actual_subsys_bits; |
| |
| /* A list running through the attached subsystems */ |
| struct list_head subsys_list; |
| |
| /* The root cgroup for this hierarchy */ |
| struct cgroup top_cgroup; |
| |
| /* Tracks how many cgroups are currently defined in hierarchy.*/ |
| int number_of_cgroups; |
| |
| /* A list running through the mounted hierarchies */ |
| struct list_head root_list; |
| |
| /* Hierarchy-specific flags */ |
| unsigned long flags; |
| }; |
| |
| |
| /* |
| * The "rootnode" hierarchy is the "dummy hierarchy", reserved for the |
| * subsystems that are otherwise unattached - it never has more than a |
| * single cgroup, and all tasks are part of that cgroup. |
| */ |
| static struct cgroupfs_root rootnode; |
| |
| /* The list of hierarchy roots */ |
| |
| static LIST_HEAD(roots); |
| |
| /* dummytop is a shorthand for the dummy hierarchy's top cgroup */ |
| #define dummytop (&rootnode.top_cgroup) |
| |
| /* This flag indicates whether tasks in the fork and exit paths should |
| * take callback_mutex and check for fork/exit handlers to call. This |
| * avoids us having to do extra work in the fork/exit path if none of the |
| * subsystems need to be called. |
| */ |
| static int need_forkexit_callback; |
| |
| /* bits in struct cgroup flags field */ |
| enum { |
| CONT_REMOVED, |
| }; |
| |
| /* convenient tests for these bits */ |
| inline int cgroup_is_removed(const struct cgroup *cont) |
| { |
| return test_bit(CONT_REMOVED, &cont->flags); |
| } |
| |
| /* bits in struct cgroupfs_root flags field */ |
| enum { |
| ROOT_NOPREFIX, /* mounted subsystems have no named prefix */ |
| }; |
| |
| /* |
| * for_each_subsys() allows you to iterate on each subsystem attached to |
| * an active hierarchy |
| */ |
| #define for_each_subsys(_root, _ss) \ |
| list_for_each_entry(_ss, &_root->subsys_list, sibling) |
| |
| /* for_each_root() allows you to iterate across the active hierarchies */ |
| #define for_each_root(_root) \ |
| list_for_each_entry(_root, &roots, root_list) |
| |
| /* Each task_struct has an embedded css_set, so the get/put |
| * operation simply takes a reference count on all the cgroups |
| * referenced by subsystems in this css_set. This can end up |
| * multiple-counting some cgroups, but that's OK - the ref-count is |
| * just a busy/not-busy indicator; ensuring that we only count each |
| * cgroup once would require taking a global lock to ensure that no |
| * subsystems moved between hierarchies while we were doing so. |
| * |
| * Possible TODO: decide at boot time based on the number of |
| * registered subsystems and the number of CPUs or NUMA nodes whether |
| * it's better for performance to ref-count every subsystem, or to |
| * take a global lock and only add one ref count to each hierarchy. |
| */ |
| static void get_css_set(struct css_set *cg) |
| { |
| int i; |
| for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) |
| atomic_inc(&cg->subsys[i]->cgroup->count); |
| } |
| |
| static void put_css_set(struct css_set *cg) |
| { |
| int i; |
| for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) |
| atomic_dec(&cg->subsys[i]->cgroup->count); |
| } |
| |
| /* |
| * There is one global cgroup mutex. We also require taking |
| * task_lock() when dereferencing a task's cgroup subsys pointers. |
| * See "The task_lock() exception", at the end of this comment. |
| * |
| * A task must hold cgroup_mutex to modify cgroups. |
| * |
| * Any task can increment and decrement the count field without lock. |
| * So in general, code holding cgroup_mutex can't rely on the count |
| * field not changing. However, if the count goes to zero, then only |
| * attach_task() can increment it again. Because a count of zero |
| * means that no tasks are currently attached, therefore there is no |
| * way a task attached to that cgroup can fork (the other way to |
| * increment the count). So code holding cgroup_mutex can safely |
| * assume that if the count is zero, it will stay zero. Similarly, if |
| * a task holds cgroup_mutex on a cgroup with zero count, it |
| * knows that the cgroup won't be removed, as cgroup_rmdir() |
| * needs that mutex. |
| * |
| * The cgroup_common_file_write handler for operations that modify |
| * the cgroup hierarchy holds cgroup_mutex across the entire operation, |
| * single threading all such cgroup modifications across the system. |
| * |
| * The fork and exit callbacks cgroup_fork() and cgroup_exit(), don't |
| * (usually) take cgroup_mutex. These are the two most performance |
| * critical pieces of code here. The exception occurs on cgroup_exit(), |
| * when a task in a notify_on_release cgroup exits. Then cgroup_mutex |
| * is taken, and if the cgroup count is zero, a usermode call made |
| * to /sbin/cgroup_release_agent with the name of the cgroup (path |
| * relative to the root of cgroup file system) as the argument. |
| * |
| * A cgroup can only be deleted if both its 'count' of using tasks |
| * is zero, and its list of 'children' cgroups is empty. Since all |
| * tasks in the system use _some_ cgroup, and since there is always at |
| * least one task in the system (init, pid == 1), therefore, top_cgroup |
| * always has either children cgroups and/or using tasks. So we don't |
| * need a special hack to ensure that top_cgroup cannot be deleted. |
| * |
| * The task_lock() exception |
| * |
| * The need for this exception arises from the action of |
| * attach_task(), which overwrites one tasks cgroup pointer with |
| * another. It does so using cgroup_mutexe, however there are |
| * several performance critical places that need to reference |
| * task->cgroup without the expense of grabbing a system global |
| * mutex. Therefore except as noted below, when dereferencing or, as |
| * in attach_task(), modifying a task'ss cgroup pointer we use |
| * task_lock(), which acts on a spinlock (task->alloc_lock) already in |
| * the task_struct routinely used for such matters. |
| * |
| * P.S. One more locking exception. RCU is used to guard the |
| * update of a tasks cgroup pointer by attach_task() |
| */ |
| |
| static DEFINE_MUTEX(cgroup_mutex); |
| |
| /** |
| * cgroup_lock - lock out any changes to cgroup structures |
| * |
| */ |
| |
| void cgroup_lock(void) |
| { |
| mutex_lock(&cgroup_mutex); |
| } |
| |
| /** |
| * cgroup_unlock - release lock on cgroup changes |
| * |
| * Undo the lock taken in a previous cgroup_lock() call. |
| */ |
| |
| void cgroup_unlock(void) |
| { |
| mutex_unlock(&cgroup_mutex); |
| } |
| |
| /* |
| * A couple of forward declarations required, due to cyclic reference loop: |
| * cgroup_mkdir -> cgroup_create -> cgroup_populate_dir -> |
| * cgroup_add_file -> cgroup_create_file -> cgroup_dir_inode_operations |
| * -> cgroup_mkdir. |
| */ |
| |
| static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode); |
| static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry); |
| static int cgroup_populate_dir(struct cgroup *cont); |
| static struct inode_operations cgroup_dir_inode_operations; |
| |
| static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb) |
| { |
| struct inode *inode = new_inode(sb); |
| static struct backing_dev_info cgroup_backing_dev_info = { |
| .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK, |
| }; |
| |
| if (inode) { |
| inode->i_mode = mode; |
| inode->i_uid = current->fsuid; |
| inode->i_gid = current->fsgid; |
| inode->i_blocks = 0; |
| inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME; |
| inode->i_mapping->backing_dev_info = &cgroup_backing_dev_info; |
| } |
| return inode; |
| } |
| |
| static void cgroup_diput(struct dentry *dentry, struct inode *inode) |
| { |
| /* is dentry a directory ? if so, kfree() associated cgroup */ |
| if (S_ISDIR(inode->i_mode)) { |
| struct cgroup *cont = dentry->d_fsdata; |
| BUG_ON(!(cgroup_is_removed(cont))); |
| kfree(cont); |
| } |
| iput(inode); |
| } |
| |
| static void remove_dir(struct dentry *d) |
| { |
| struct dentry *parent = dget(d->d_parent); |
| |
| d_delete(d); |
| simple_rmdir(parent->d_inode, d); |
| dput(parent); |
| } |
| |
| static void cgroup_clear_directory(struct dentry *dentry) |
| { |
| struct list_head *node; |
| |
| BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex)); |
| spin_lock(&dcache_lock); |
| node = dentry->d_subdirs.next; |
| while (node != &dentry->d_subdirs) { |
| struct dentry *d = list_entry(node, struct dentry, d_u.d_child); |
| list_del_init(node); |
| if (d->d_inode) { |
| /* This should never be called on a cgroup |
| * directory with child cgroups */ |
| BUG_ON(d->d_inode->i_mode & S_IFDIR); |
| d = dget_locked(d); |
| spin_unlock(&dcache_lock); |
| d_delete(d); |
| simple_unlink(dentry->d_inode, d); |
| dput(d); |
| spin_lock(&dcache_lock); |
| } |
| node = dentry->d_subdirs.next; |
| } |
| spin_unlock(&dcache_lock); |
| } |
| |
| /* |
| * NOTE : the dentry must have been dget()'ed |
| */ |
| static void cgroup_d_remove_dir(struct dentry *dentry) |
| { |
| cgroup_clear_directory(dentry); |
| |
| spin_lock(&dcache_lock); |
| list_del_init(&dentry->d_u.d_child); |
| spin_unlock(&dcache_lock); |
| remove_dir(dentry); |
| } |
| |
| static int rebind_subsystems(struct cgroupfs_root *root, |
| unsigned long final_bits) |
| { |
| unsigned long added_bits, removed_bits; |
| struct cgroup *cont = &root->top_cgroup; |
| int i; |
| |
| removed_bits = root->actual_subsys_bits & ~final_bits; |
| added_bits = final_bits & ~root->actual_subsys_bits; |
| /* Check that any added subsystems are currently free */ |
| for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { |
| unsigned long long bit = 1ull << i; |
| struct cgroup_subsys *ss = subsys[i]; |
| if (!(bit & added_bits)) |
| continue; |
| if (ss->root != &rootnode) { |
| /* Subsystem isn't free */ |
| return -EBUSY; |
| } |
| } |
| |
| /* Currently we don't handle adding/removing subsystems when |
| * any child cgroups exist. This is theoretically supportable |
| * but involves complex error handling, so it's being left until |
| * later */ |
| if (!list_empty(&cont->children)) |
| return -EBUSY; |
| |
| /* Process each subsystem */ |
| for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { |
| struct cgroup_subsys *ss = subsys[i]; |
| unsigned long bit = 1UL << i; |
| if (bit & added_bits) { |
| /* We're binding this subsystem to this hierarchy */ |
| BUG_ON(cont->subsys[i]); |
| BUG_ON(!dummytop->subsys[i]); |
| BUG_ON(dummytop->subsys[i]->cgroup != dummytop); |
| cont->subsys[i] = dummytop->subsys[i]; |
| cont->subsys[i]->cgroup = cont; |
| list_add(&ss->sibling, &root->subsys_list); |
| rcu_assign_pointer(ss->root, root); |
| if (ss->bind) |
| ss->bind(ss, cont); |
| |
| } else if (bit & removed_bits) { |
| /* We're removing this subsystem */ |
| BUG_ON(cont->subsys[i] != dummytop->subsys[i]); |
| BUG_ON(cont->subsys[i]->cgroup != cont); |
| if (ss->bind) |
| ss->bind(ss, dummytop); |
| dummytop->subsys[i]->cgroup = dummytop; |
| cont->subsys[i] = NULL; |
| rcu_assign_pointer(subsys[i]->root, &rootnode); |
| list_del(&ss->sibling); |
| } else if (bit & final_bits) { |
| /* Subsystem state should already exist */ |
| BUG_ON(!cont->subsys[i]); |
| } else { |
| /* Subsystem state shouldn't exist */ |
| BUG_ON(cont->subsys[i]); |
| } |
| } |
| root->subsys_bits = root->actual_subsys_bits = final_bits; |
| synchronize_rcu(); |
| |
| return 0; |
| } |
| |
| static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs) |
| { |
| struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info; |
| struct cgroup_subsys *ss; |
| |
| mutex_lock(&cgroup_mutex); |
| for_each_subsys(root, ss) |
| seq_printf(seq, ",%s", ss->name); |
| if (test_bit(ROOT_NOPREFIX, &root->flags)) |
| seq_puts(seq, ",noprefix"); |
| mutex_unlock(&cgroup_mutex); |
| return 0; |
| } |
| |
| struct cgroup_sb_opts { |
| unsigned long subsys_bits; |
| unsigned long flags; |
| }; |
| |
| /* Convert a hierarchy specifier into a bitmask of subsystems and |
| * flags. */ |
| static int parse_cgroupfs_options(char *data, |
| struct cgroup_sb_opts *opts) |
| { |
| char *token, *o = data ?: "all"; |
| |
| opts->subsys_bits = 0; |
| opts->flags = 0; |
| |
| while ((token = strsep(&o, ",")) != NULL) { |
| if (!*token) |
| return -EINVAL; |
| if (!strcmp(token, "all")) { |
| opts->subsys_bits = (1 << CGROUP_SUBSYS_COUNT) - 1; |
| } else if (!strcmp(token, "noprefix")) { |
| set_bit(ROOT_NOPREFIX, &opts->flags); |
| } else { |
| struct cgroup_subsys *ss; |
| int i; |
| for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { |
| ss = subsys[i]; |
| if (!strcmp(token, ss->name)) { |
| set_bit(i, &opts->subsys_bits); |
| break; |
| } |
| } |
| if (i == CGROUP_SUBSYS_COUNT) |
| return -ENOENT; |
| } |
| } |
| |
| /* We can't have an empty hierarchy */ |
| if (!opts->subsys_bits) |
| return -EINVAL; |
| |
| return 0; |
| } |
| |
| static int cgroup_remount(struct super_block *sb, int *flags, char *data) |
| { |
| int ret = 0; |
| struct cgroupfs_root *root = sb->s_fs_info; |
| struct cgroup *cont = &root->top_cgroup; |
| struct cgroup_sb_opts opts; |
| |
| mutex_lock(&cont->dentry->d_inode->i_mutex); |
| mutex_lock(&cgroup_mutex); |
| |
| /* See what subsystems are wanted */ |
| ret = parse_cgroupfs_options(data, &opts); |
| if (ret) |
| goto out_unlock; |
| |
| /* Don't allow flags to change at remount */ |
| if (opts.flags != root->flags) { |
| ret = -EINVAL; |
| goto out_unlock; |
| } |
| |
| ret = rebind_subsystems(root, opts.subsys_bits); |
| |
| /* (re)populate subsystem files */ |
| if (!ret) |
| cgroup_populate_dir(cont); |
| |
| out_unlock: |
| mutex_unlock(&cgroup_mutex); |
| mutex_unlock(&cont->dentry->d_inode->i_mutex); |
| return ret; |
| } |
| |
| static struct super_operations cgroup_ops = { |
| .statfs = simple_statfs, |
| .drop_inode = generic_delete_inode, |
| .show_options = cgroup_show_options, |
| .remount_fs = cgroup_remount, |
| }; |
| |
| static void init_cgroup_root(struct cgroupfs_root *root) |
| { |
| struct cgroup *cont = &root->top_cgroup; |
| INIT_LIST_HEAD(&root->subsys_list); |
| INIT_LIST_HEAD(&root->root_list); |
| root->number_of_cgroups = 1; |
| cont->root = root; |
| cont->top_cgroup = cont; |
| INIT_LIST_HEAD(&cont->sibling); |
| INIT_LIST_HEAD(&cont->children); |
| } |
| |
| static int cgroup_test_super(struct super_block *sb, void *data) |
| { |
| struct cgroupfs_root *new = data; |
| struct cgroupfs_root *root = sb->s_fs_info; |
| |
| /* First check subsystems */ |
| if (new->subsys_bits != root->subsys_bits) |
| return 0; |
| |
| /* Next check flags */ |
| if (new->flags != root->flags) |
| return 0; |
| |
| return 1; |
| } |
| |
| static int cgroup_set_super(struct super_block *sb, void *data) |
| { |
| int ret; |
| struct cgroupfs_root *root = data; |
| |
| ret = set_anon_super(sb, NULL); |
| if (ret) |
| return ret; |
| |
| sb->s_fs_info = root; |
| root->sb = sb; |
| |
| sb->s_blocksize = PAGE_CACHE_SIZE; |
| sb->s_blocksize_bits = PAGE_CACHE_SHIFT; |
| sb->s_magic = CGROUP_SUPER_MAGIC; |
| sb->s_op = &cgroup_ops; |
| |
| return 0; |
| } |
| |
| static int cgroup_get_rootdir(struct super_block *sb) |
| { |
| struct inode *inode = |
| cgroup_new_inode(S_IFDIR | S_IRUGO | S_IXUGO | S_IWUSR, sb); |
| struct dentry *dentry; |
| |
| if (!inode) |
| return -ENOMEM; |
| |
| inode->i_op = &simple_dir_inode_operations; |
| inode->i_fop = &simple_dir_operations; |
| inode->i_op = &cgroup_dir_inode_operations; |
| /* directories start off with i_nlink == 2 (for "." entry) */ |
| inc_nlink(inode); |
| dentry = d_alloc_root(inode); |
| if (!dentry) { |
| iput(inode); |
| return -ENOMEM; |
| } |
| sb->s_root = dentry; |
| return 0; |
| } |
| |
| static int cgroup_get_sb(struct file_system_type *fs_type, |
| int flags, const char *unused_dev_name, |
| void *data, struct vfsmount *mnt) |
| { |
| struct cgroup_sb_opts opts; |
| int ret = 0; |
| struct super_block *sb; |
| struct cgroupfs_root *root; |
| |
| /* First find the desired set of subsystems */ |
| ret = parse_cgroupfs_options(data, &opts); |
| if (ret) |
| return ret; |
| |
| root = kzalloc(sizeof(*root), GFP_KERNEL); |
| if (!root) |
| return -ENOMEM; |
| |
| init_cgroup_root(root); |
| root->subsys_bits = opts.subsys_bits; |
| root->flags = opts.flags; |
| |
| sb = sget(fs_type, cgroup_test_super, cgroup_set_super, root); |
| |
| if (IS_ERR(sb)) { |
| kfree(root); |
| return PTR_ERR(sb); |
| } |
| |
| if (sb->s_fs_info != root) { |
| /* Reusing an existing superblock */ |
| BUG_ON(sb->s_root == NULL); |
| kfree(root); |
| root = NULL; |
| } else { |
| /* New superblock */ |
| struct cgroup *cont = &root->top_cgroup; |
| |
| BUG_ON(sb->s_root != NULL); |
| |
| ret = cgroup_get_rootdir(sb); |
| if (ret) |
| goto drop_new_super; |
| |
| mutex_lock(&cgroup_mutex); |
| |
| ret = rebind_subsystems(root, root->subsys_bits); |
| if (ret == -EBUSY) { |
| mutex_unlock(&cgroup_mutex); |
| goto drop_new_super; |
| } |
| |
| /* EBUSY should be the only error here */ |
| BUG_ON(ret); |
| |
| list_add(&root->root_list, &roots); |
| |
| sb->s_root->d_fsdata = &root->top_cgroup; |
| root->top_cgroup.dentry = sb->s_root; |
| |
| BUG_ON(!list_empty(&cont->sibling)); |
| BUG_ON(!list_empty(&cont->children)); |
| BUG_ON(root->number_of_cgroups != 1); |
| |
| /* |
| * I believe that it's safe to nest i_mutex inside |
| * cgroup_mutex in this case, since no-one else can |
| * be accessing this directory yet. But we still need |
| * to teach lockdep that this is the case - currently |
| * a cgroupfs remount triggers a lockdep warning |
| */ |
| mutex_lock(&cont->dentry->d_inode->i_mutex); |
| cgroup_populate_dir(cont); |
| mutex_unlock(&cont->dentry->d_inode->i_mutex); |
| mutex_unlock(&cgroup_mutex); |
| } |
| |
| return simple_set_mnt(mnt, sb); |
| |
| drop_new_super: |
| up_write(&sb->s_umount); |
| deactivate_super(sb); |
| return ret; |
| } |
| |
| static void cgroup_kill_sb(struct super_block *sb) { |
| struct cgroupfs_root *root = sb->s_fs_info; |
| struct cgroup *cont = &root->top_cgroup; |
| int ret; |
| |
| BUG_ON(!root); |
| |
| BUG_ON(root->number_of_cgroups != 1); |
| BUG_ON(!list_empty(&cont->children)); |
| BUG_ON(!list_empty(&cont->sibling)); |
| |
| mutex_lock(&cgroup_mutex); |
| |
| /* Rebind all subsystems back to the default hierarchy */ |
| ret = rebind_subsystems(root, 0); |
| /* Shouldn't be able to fail ... */ |
| BUG_ON(ret); |
| |
| if (!list_empty(&root->root_list)) |
| list_del(&root->root_list); |
| mutex_unlock(&cgroup_mutex); |
| |
| kfree(root); |
| kill_litter_super(sb); |
| } |
| |
| static struct file_system_type cgroup_fs_type = { |
| .name = "cgroup", |
| .get_sb = cgroup_get_sb, |
| .kill_sb = cgroup_kill_sb, |
| }; |
| |
| static inline struct cgroup *__d_cont(struct dentry *dentry) |
| { |
| return dentry->d_fsdata; |
| } |
| |
| static inline struct cftype *__d_cft(struct dentry *dentry) |
| { |
| return dentry->d_fsdata; |
| } |
| |
| /* |
| * Called with cgroup_mutex held. Writes path of cgroup into buf. |
| * Returns 0 on success, -errno on error. |
| */ |
| int cgroup_path(const struct cgroup *cont, char *buf, int buflen) |
| { |
| char *start; |
| |
| if (cont == dummytop) { |
| /* |
| * Inactive subsystems have no dentry for their root |
| * cgroup |
| */ |
| strcpy(buf, "/"); |
| return 0; |
| } |
| |
| start = buf + buflen; |
| |
| *--start = '\0'; |
| for (;;) { |
| int len = cont->dentry->d_name.len; |
| if ((start -= len) < buf) |
| return -ENAMETOOLONG; |
| memcpy(start, cont->dentry->d_name.name, len); |
| cont = cont->parent; |
| if (!cont) |
| break; |
| if (!cont->parent) |
| continue; |
| if (--start < buf) |
| return -ENAMETOOLONG; |
| *start = '/'; |
| } |
| memmove(buf, start, buf + buflen - start); |
| return 0; |
| } |
| |
| /* |
| * Return the first subsystem attached to a cgroup's hierarchy, and |
| * its subsystem id. |
| */ |
| |
| static void get_first_subsys(const struct cgroup *cont, |
| struct cgroup_subsys_state **css, int *subsys_id) |
| { |
| const struct cgroupfs_root *root = cont->root; |
| const struct cgroup_subsys *test_ss; |
| BUG_ON(list_empty(&root->subsys_list)); |
| test_ss = list_entry(root->subsys_list.next, |
| struct cgroup_subsys, sibling); |
| if (css) { |
| *css = cont->subsys[test_ss->subsys_id]; |
| BUG_ON(!*css); |
| } |
| if (subsys_id) |
| *subsys_id = test_ss->subsys_id; |
| } |
| |
| /* |
| * Attach task 'tsk' to cgroup 'cont' |
| * |
| * Call holding cgroup_mutex. May take task_lock of |
| * the task 'pid' during call. |
| */ |
| static int attach_task(struct cgroup *cont, struct task_struct *tsk) |
| { |
| int retval = 0; |
| struct cgroup_subsys *ss; |
| struct cgroup *oldcont; |
| struct css_set *cg = &tsk->cgroups; |
| struct cgroupfs_root *root = cont->root; |
| int i; |
| int subsys_id; |
| |
| get_first_subsys(cont, NULL, &subsys_id); |
| |
| /* Nothing to do if the task is already in that cgroup */ |
| oldcont = task_cgroup(tsk, subsys_id); |
| if (cont == oldcont) |
| return 0; |
| |
| for_each_subsys(root, ss) { |
| if (ss->can_attach) { |
| retval = ss->can_attach(ss, cont, tsk); |
| if (retval) { |
| return retval; |
| } |
| } |
| } |
| |
| task_lock(tsk); |
| if (tsk->flags & PF_EXITING) { |
| task_unlock(tsk); |
| return -ESRCH; |
| } |
| /* Update the css_set pointers for the subsystems in this |
| * hierarchy */ |
| for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { |
| if (root->subsys_bits & (1ull << i)) { |
| /* Subsystem is in this hierarchy. So we want |
| * the subsystem state from the new |
| * cgroup. Transfer the refcount from the |
| * old to the new */ |
| atomic_inc(&cont->count); |
| atomic_dec(&cg->subsys[i]->cgroup->count); |
| rcu_assign_pointer(cg->subsys[i], cont->subsys[i]); |
| } |
| } |
| task_unlock(tsk); |
| |
| for_each_subsys(root, ss) { |
| if (ss->attach) { |
| ss->attach(ss, cont, oldcont, tsk); |
| } |
| } |
| |
| synchronize_rcu(); |
| return 0; |
| } |
| |
| /* |
| * Attach task with pid 'pid' to cgroup 'cont'. Call with |
| * cgroup_mutex, may take task_lock of task |
| */ |
| static int attach_task_by_pid(struct cgroup *cont, char *pidbuf) |
| { |
| pid_t pid; |
| struct task_struct *tsk; |
| int ret; |
| |
| if (sscanf(pidbuf, "%d", &pid) != 1) |
| return -EIO; |
| |
| if (pid) { |
| rcu_read_lock(); |
| tsk = find_task_by_pid(pid); |
| if (!tsk || tsk->flags & PF_EXITING) { |
| rcu_read_unlock(); |
| return -ESRCH; |
| } |
| get_task_struct(tsk); |
| rcu_read_unlock(); |
| |
| if ((current->euid) && (current->euid != tsk->uid) |
| && (current->euid != tsk->suid)) { |
| put_task_struct(tsk); |
| return -EACCES; |
| } |
| } else { |
| tsk = current; |
| get_task_struct(tsk); |
| } |
| |
| ret = attach_task(cont, tsk); |
| put_task_struct(tsk); |
| return ret; |
| } |
| |
| /* The various types of files and directories in a cgroup file system */ |
| |
| enum cgroup_filetype { |
| FILE_ROOT, |
| FILE_DIR, |
| FILE_TASKLIST, |
| }; |
| |
| static ssize_t cgroup_write_uint(struct cgroup *cont, struct cftype *cft, |
| struct file *file, |
| const char __user *userbuf, |
| size_t nbytes, loff_t *unused_ppos) |
| { |
| char buffer[64]; |
| int retval = 0; |
| u64 val; |
| char *end; |
| |
| if (!nbytes) |
| return -EINVAL; |
| if (nbytes >= sizeof(buffer)) |
| return -E2BIG; |
| if (copy_from_user(buffer, userbuf, nbytes)) |
| return -EFAULT; |
| |
| buffer[nbytes] = 0; /* nul-terminate */ |
| |
| /* strip newline if necessary */ |
| if (nbytes && (buffer[nbytes-1] == '\n')) |
| buffer[nbytes-1] = 0; |
| val = simple_strtoull(buffer, &end, 0); |
| if (*end) |
| return -EINVAL; |
| |
| /* Pass to subsystem */ |
| retval = cft->write_uint(cont, cft, val); |
| if (!retval) |
| retval = nbytes; |
| return retval; |
| } |
| |
| static ssize_t cgroup_common_file_write(struct cgroup *cont, |
| struct cftype *cft, |
| struct file *file, |
| const char __user *userbuf, |
| size_t nbytes, loff_t *unused_ppos) |
| { |
| enum cgroup_filetype type = cft->private; |
| char *buffer; |
| int retval = 0; |
| |
| if (nbytes >= PATH_MAX) |
| return -E2BIG; |
| |
| /* +1 for nul-terminator */ |
| buffer = kmalloc(nbytes + 1, GFP_KERNEL); |
| if (buffer == NULL) |
| return -ENOMEM; |
| |
| if (copy_from_user(buffer, userbuf, nbytes)) { |
| retval = -EFAULT; |
| goto out1; |
| } |
| buffer[nbytes] = 0; /* nul-terminate */ |
| |
| mutex_lock(&cgroup_mutex); |
| |
| if (cgroup_is_removed(cont)) { |
| retval = -ENODEV; |
| goto out2; |
| } |
| |
| switch (type) { |
| case FILE_TASKLIST: |
| retval = attach_task_by_pid(cont, buffer); |
| break; |
| default: |
| retval = -EINVAL; |
| goto out2; |
| } |
| |
| if (retval == 0) |
| retval = nbytes; |
| out2: |
| mutex_unlock(&cgroup_mutex); |
| out1: |
| kfree(buffer); |
| return retval; |
| } |
| |
| static ssize_t cgroup_file_write(struct file *file, const char __user *buf, |
| size_t nbytes, loff_t *ppos) |
| { |
| struct cftype *cft = __d_cft(file->f_dentry); |
| struct cgroup *cont = __d_cont(file->f_dentry->d_parent); |
| |
| if (!cft) |
| return -ENODEV; |
| if (cft->write) |
| return cft->write(cont, cft, file, buf, nbytes, ppos); |
| if (cft->write_uint) |
| return cgroup_write_uint(cont, cft, file, buf, nbytes, ppos); |
| return -EINVAL; |
| } |
| |
| static ssize_t cgroup_read_uint(struct cgroup *cont, struct cftype *cft, |
| struct file *file, |
| char __user *buf, size_t nbytes, |
| loff_t *ppos) |
| { |
| char tmp[64]; |
| u64 val = cft->read_uint(cont, cft); |
| int len = sprintf(tmp, "%llu\n", (unsigned long long) val); |
| |
| return simple_read_from_buffer(buf, nbytes, ppos, tmp, len); |
| } |
| |
| static ssize_t cgroup_file_read(struct file *file, char __user *buf, |
| size_t nbytes, loff_t *ppos) |
| { |
| struct cftype *cft = __d_cft(file->f_dentry); |
| struct cgroup *cont = __d_cont(file->f_dentry->d_parent); |
| |
| if (!cft) |
| return -ENODEV; |
| |
| if (cft->read) |
| return cft->read(cont, cft, file, buf, nbytes, ppos); |
| if (cft->read_uint) |
| return cgroup_read_uint(cont, cft, file, buf, nbytes, ppos); |
| return -EINVAL; |
| } |
| |
| static int cgroup_file_open(struct inode *inode, struct file *file) |
| { |
| int err; |
| struct cftype *cft; |
| |
| err = generic_file_open(inode, file); |
| if (err) |
| return err; |
| |
| cft = __d_cft(file->f_dentry); |
| if (!cft) |
| return -ENODEV; |
| if (cft->open) |
| err = cft->open(inode, file); |
| else |
| err = 0; |
| |
| return err; |
| } |
| |
| static int cgroup_file_release(struct inode *inode, struct file *file) |
| { |
| struct cftype *cft = __d_cft(file->f_dentry); |
| if (cft->release) |
| return cft->release(inode, file); |
| return 0; |
| } |
| |
| /* |
| * cgroup_rename - Only allow simple rename of directories in place. |
| */ |
| static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry, |
| struct inode *new_dir, struct dentry *new_dentry) |
| { |
| if (!S_ISDIR(old_dentry->d_inode->i_mode)) |
| return -ENOTDIR; |
| if (new_dentry->d_inode) |
| return -EEXIST; |
| if (old_dir != new_dir) |
| return -EIO; |
| return simple_rename(old_dir, old_dentry, new_dir, new_dentry); |
| } |
| |
| static struct file_operations cgroup_file_operations = { |
| .read = cgroup_file_read, |
| .write = cgroup_file_write, |
| .llseek = generic_file_llseek, |
| .open = cgroup_file_open, |
| .release = cgroup_file_release, |
| }; |
| |
| static struct inode_operations cgroup_dir_inode_operations = { |
| .lookup = simple_lookup, |
| .mkdir = cgroup_mkdir, |
| .rmdir = cgroup_rmdir, |
| .rename = cgroup_rename, |
| }; |
| |
| static int cgroup_create_file(struct dentry *dentry, int mode, |
| struct super_block *sb) |
| { |
| static struct dentry_operations cgroup_dops = { |
| .d_iput = cgroup_diput, |
| }; |
| |
| struct inode *inode; |
| |
| if (!dentry) |
| return -ENOENT; |
| if (dentry->d_inode) |
| return -EEXIST; |
| |
| inode = cgroup_new_inode(mode, sb); |
| if (!inode) |
| return -ENOMEM; |
| |
| if (S_ISDIR(mode)) { |
| inode->i_op = &cgroup_dir_inode_operations; |
| inode->i_fop = &simple_dir_operations; |
| |
| /* start off with i_nlink == 2 (for "." entry) */ |
| inc_nlink(inode); |
| |
| /* start with the directory inode held, so that we can |
| * populate it without racing with another mkdir */ |
| mutex_lock(&inode->i_mutex); |
| } else if (S_ISREG(mode)) { |
| inode->i_size = 0; |
| inode->i_fop = &cgroup_file_operations; |
| } |
| dentry->d_op = &cgroup_dops; |
| d_instantiate(dentry, inode); |
| dget(dentry); /* Extra count - pin the dentry in core */ |
| return 0; |
| } |
| |
| /* |
| * cgroup_create_dir - create a directory for an object. |
| * cont: the cgroup we create the directory for. |
| * It must have a valid ->parent field |
| * And we are going to fill its ->dentry field. |
| * dentry: dentry of the new container |
| * mode: mode to set on new directory. |
| */ |
| static int cgroup_create_dir(struct cgroup *cont, struct dentry *dentry, |
| int mode) |
| { |
| struct dentry *parent; |
| int error = 0; |
| |
| parent = cont->parent->dentry; |
| error = cgroup_create_file(dentry, S_IFDIR | mode, cont->root->sb); |
| if (!error) { |
| dentry->d_fsdata = cont; |
| inc_nlink(parent->d_inode); |
| cont->dentry = dentry; |
| dget(dentry); |
| } |
| dput(dentry); |
| |
| return error; |
| } |
| |
| int cgroup_add_file(struct cgroup *cont, |
| struct cgroup_subsys *subsys, |
| const struct cftype *cft) |
| { |
| struct dentry *dir = cont->dentry; |
| struct dentry *dentry; |
| int error; |
| |
| char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 }; |
| if (subsys && !test_bit(ROOT_NOPREFIX, &cont->root->flags)) { |
| strcpy(name, subsys->name); |
| strcat(name, "."); |
| } |
| strcat(name, cft->name); |
| BUG_ON(!mutex_is_locked(&dir->d_inode->i_mutex)); |
| dentry = lookup_one_len(name, dir, strlen(name)); |
| if (!IS_ERR(dentry)) { |
| error = cgroup_create_file(dentry, 0644 | S_IFREG, |
| cont->root->sb); |
| if (!error) |
| dentry->d_fsdata = (void *)cft; |
| dput(dentry); |
| } else |
| error = PTR_ERR(dentry); |
| return error; |
| } |
| |
| int cgroup_add_files(struct cgroup *cont, |
| struct cgroup_subsys *subsys, |
| const struct cftype cft[], |
| int count) |
| { |
| int i, err; |
| for (i = 0; i < count; i++) { |
| err = cgroup_add_file(cont, subsys, &cft[i]); |
| if (err) |
| return err; |
| } |
| return 0; |
| } |
| |
| /* Count the number of tasks in a cgroup. Could be made more |
| * time-efficient but less space-efficient with more linked lists |
| * running through each cgroup and the css_set structures that |
| * referenced it. Must be called with tasklist_lock held for read or |
| * write or in an rcu critical section. |
| */ |
| int __cgroup_task_count(const struct cgroup *cont) |
| { |
| int count = 0; |
| struct task_struct *g, *p; |
| struct cgroup_subsys_state *css; |
| int subsys_id; |
| |
| get_first_subsys(cont, &css, &subsys_id); |
| do_each_thread(g, p) { |
| if (task_subsys_state(p, subsys_id) == css) |
| count ++; |
| } while_each_thread(g, p); |
| return count; |
| } |
| |
| /* |
| * Stuff for reading the 'tasks' file. |
| * |
| * Reading this file can return large amounts of data if a cgroup has |
| * *lots* of attached tasks. So it may need several calls to read(), |
| * but we cannot guarantee that the information we produce is correct |
| * unless we produce it entirely atomically. |
| * |
| * Upon tasks file open(), a struct ctr_struct is allocated, that |
| * will have a pointer to an array (also allocated here). The struct |
| * ctr_struct * is stored in file->private_data. Its resources will |
| * be freed by release() when the file is closed. The array is used |
| * to sprintf the PIDs and then used by read(). |
| */ |
| struct ctr_struct { |
| char *buf; |
| int bufsz; |
| }; |
| |
| /* |
| * Load into 'pidarray' up to 'npids' of the tasks using cgroup |
| * 'cont'. Return actual number of pids loaded. No need to |
| * task_lock(p) when reading out p->cgroup, since we're in an RCU |
| * read section, so the css_set can't go away, and is |
| * immutable after creation. |
| */ |
| static int pid_array_load(pid_t *pidarray, int npids, struct cgroup *cont) |
| { |
| int n = 0; |
| struct task_struct *g, *p; |
| struct cgroup_subsys_state *css; |
| int subsys_id; |
| |
| get_first_subsys(cont, &css, &subsys_id); |
| rcu_read_lock(); |
| do_each_thread(g, p) { |
| if (task_subsys_state(p, subsys_id) == css) { |
| pidarray[n++] = pid_nr(task_pid(p)); |
| if (unlikely(n == npids)) |
| goto array_full; |
| } |
| } while_each_thread(g, p); |
| |
| array_full: |
| rcu_read_unlock(); |
| return n; |
| } |
| |
| static int cmppid(const void *a, const void *b) |
| { |
| return *(pid_t *)a - *(pid_t *)b; |
| } |
| |
| /* |
| * Convert array 'a' of 'npids' pid_t's to a string of newline separated |
| * decimal pids in 'buf'. Don't write more than 'sz' chars, but return |
| * count 'cnt' of how many chars would be written if buf were large enough. |
| */ |
| static int pid_array_to_buf(char *buf, int sz, pid_t *a, int npids) |
| { |
| int cnt = 0; |
| int i; |
| |
| for (i = 0; i < npids; i++) |
| cnt += snprintf(buf + cnt, max(sz - cnt, 0), "%d\n", a[i]); |
| return cnt; |
| } |
| |
| /* |
| * Handle an open on 'tasks' file. Prepare a buffer listing the |
| * process id's of tasks currently attached to the cgroup being opened. |
| * |
| * Does not require any specific cgroup mutexes, and does not take any. |
| */ |
| static int cgroup_tasks_open(struct inode *unused, struct file *file) |
| { |
| struct cgroup *cont = __d_cont(file->f_dentry->d_parent); |
| struct ctr_struct *ctr; |
| pid_t *pidarray; |
| int npids; |
| char c; |
| |
| if (!(file->f_mode & FMODE_READ)) |
| return 0; |
| |
| ctr = kmalloc(sizeof(*ctr), GFP_KERNEL); |
| if (!ctr) |
| goto err0; |
| |
| /* |
| * If cgroup gets more users after we read count, we won't have |
| * enough space - tough. This race is indistinguishable to the |
| * caller from the case that the additional cgroup users didn't |
| * show up until sometime later on. |
| */ |
| npids = cgroup_task_count(cont); |
| if (npids) { |
| pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL); |
| if (!pidarray) |
| goto err1; |
| |
| npids = pid_array_load(pidarray, npids, cont); |
| sort(pidarray, npids, sizeof(pid_t), cmppid, NULL); |
| |
| /* Call pid_array_to_buf() twice, first just to get bufsz */ |
| ctr->bufsz = pid_array_to_buf(&c, sizeof(c), pidarray, npids) + 1; |
| ctr->buf = kmalloc(ctr->bufsz, GFP_KERNEL); |
| if (!ctr->buf) |
| goto err2; |
| ctr->bufsz = pid_array_to_buf(ctr->buf, ctr->bufsz, pidarray, npids); |
| |
| kfree(pidarray); |
| } else { |
| ctr->buf = 0; |
| ctr->bufsz = 0; |
| } |
| file->private_data = ctr; |
| return 0; |
| |
| err2: |
| kfree(pidarray); |
| err1: |
| kfree(ctr); |
| err0: |
| return -ENOMEM; |
| } |
| |
| static ssize_t cgroup_tasks_read(struct cgroup *cont, |
| struct cftype *cft, |
| struct file *file, char __user *buf, |
| size_t nbytes, loff_t *ppos) |
| { |
| struct ctr_struct *ctr = file->private_data; |
| |
| return simple_read_from_buffer(buf, nbytes, ppos, ctr->buf, ctr->bufsz); |
| } |
| |
| static int cgroup_tasks_release(struct inode *unused_inode, |
| struct file *file) |
| { |
| struct ctr_struct *ctr; |
| |
| if (file->f_mode & FMODE_READ) { |
| ctr = file->private_data; |
| kfree(ctr->buf); |
| kfree(ctr); |
| } |
| return 0; |
| } |
| |
| /* |
| * for the common functions, 'private' gives the type of file |
| */ |
| static struct cftype cft_tasks = { |
| .name = "tasks", |
| .open = cgroup_tasks_open, |
| .read = cgroup_tasks_read, |
| .write = cgroup_common_file_write, |
| .release = cgroup_tasks_release, |
| .private = FILE_TASKLIST, |
| }; |
| |
| static int cgroup_populate_dir(struct cgroup *cont) |
| { |
| int err; |
| struct cgroup_subsys *ss; |
| |
| /* First clear out any existing files */ |
| cgroup_clear_directory(cont->dentry); |
| |
| err = cgroup_add_file(cont, NULL, &cft_tasks); |
| if (err < 0) |
| return err; |
| |
| for_each_subsys(cont->root, ss) { |
| if (ss->populate && (err = ss->populate(ss, cont)) < 0) |
| return err; |
| } |
| |
| return 0; |
| } |
| |
| static void init_cgroup_css(struct cgroup_subsys_state *css, |
| struct cgroup_subsys *ss, |
| struct cgroup *cont) |
| { |
| css->cgroup = cont; |
| atomic_set(&css->refcnt, 0); |
| css->flags = 0; |
| if (cont == dummytop) |
| set_bit(CSS_ROOT, &css->flags); |
| BUG_ON(cont->subsys[ss->subsys_id]); |
| cont->subsys[ss->subsys_id] = css; |
| } |
| |
| /* |
| * cgroup_create - create a cgroup |
| * parent: cgroup that will be parent of the new cgroup. |
| * name: name of the new cgroup. Will be strcpy'ed. |
| * mode: mode to set on new inode |
| * |
| * Must be called with the mutex on the parent inode held |
| */ |
| |
| static long cgroup_create(struct cgroup *parent, struct dentry *dentry, |
| int mode) |
| { |
| struct cgroup *cont; |
| struct cgroupfs_root *root = parent->root; |
| int err = 0; |
| struct cgroup_subsys *ss; |
| struct super_block *sb = root->sb; |
| |
| cont = kzalloc(sizeof(*cont), GFP_KERNEL); |
| if (!cont) |
| return -ENOMEM; |
| |
| /* Grab a reference on the superblock so the hierarchy doesn't |
| * get deleted on unmount if there are child cgroups. This |
| * can be done outside cgroup_mutex, since the sb can't |
| * disappear while someone has an open control file on the |
| * fs */ |
| atomic_inc(&sb->s_active); |
| |
| mutex_lock(&cgroup_mutex); |
| |
| cont->flags = 0; |
| INIT_LIST_HEAD(&cont->sibling); |
| INIT_LIST_HEAD(&cont->children); |
| |
| cont->parent = parent; |
| cont->root = parent->root; |
| cont->top_cgroup = parent->top_cgroup; |
| |
| for_each_subsys(root, ss) { |
| struct cgroup_subsys_state *css = ss->create(ss, cont); |
| if (IS_ERR(css)) { |
| err = PTR_ERR(css); |
| goto err_destroy; |
| } |
| init_cgroup_css(css, ss, cont); |
| } |
| |
| list_add(&cont->sibling, &cont->parent->children); |
| root->number_of_cgroups++; |
| |
| err = cgroup_create_dir(cont, dentry, mode); |
| if (err < 0) |
| goto err_remove; |
| |
| /* The cgroup directory was pre-locked for us */ |
| BUG_ON(!mutex_is_locked(&cont->dentry->d_inode->i_mutex)); |
| |
| err = cgroup_populate_dir(cont); |
| /* If err < 0, we have a half-filled directory - oh well ;) */ |
| |
| mutex_unlock(&cgroup_mutex); |
| mutex_unlock(&cont->dentry->d_inode->i_mutex); |
| |
| return 0; |
| |
| err_remove: |
| |
| list_del(&cont->sibling); |
| root->number_of_cgroups--; |
| |
| err_destroy: |
| |
| for_each_subsys(root, ss) { |
| if (cont->subsys[ss->subsys_id]) |
| ss->destroy(ss, cont); |
| } |
| |
| mutex_unlock(&cgroup_mutex); |
| |
| /* Release the reference count that we took on the superblock */ |
| deactivate_super(sb); |
| |
| kfree(cont); |
| return err; |
| } |
| |
| static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode) |
| { |
| struct cgroup *c_parent = dentry->d_parent->d_fsdata; |
| |
| /* the vfs holds inode->i_mutex already */ |
| return cgroup_create(c_parent, dentry, mode | S_IFDIR); |
| } |
| |
| static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry) |
| { |
| struct cgroup *cont = dentry->d_fsdata; |
| struct dentry *d; |
| struct cgroup *parent; |
| struct cgroup_subsys *ss; |
| struct super_block *sb; |
| struct cgroupfs_root *root; |
| int css_busy = 0; |
| |
| /* the vfs holds both inode->i_mutex already */ |
| |
| mutex_lock(&cgroup_mutex); |
| if (atomic_read(&cont->count) != 0) { |
| mutex_unlock(&cgroup_mutex); |
| return -EBUSY; |
| } |
| if (!list_empty(&cont->children)) { |
| mutex_unlock(&cgroup_mutex); |
| return -EBUSY; |
| } |
| |
| parent = cont->parent; |
| root = cont->root; |
| sb = root->sb; |
| |
| /* Check the reference count on each subsystem. Since we |
| * already established that there are no tasks in the |
| * cgroup, if the css refcount is also 0, then there should |
| * be no outstanding references, so the subsystem is safe to |
| * destroy */ |
| for_each_subsys(root, ss) { |
| struct cgroup_subsys_state *css; |
| css = cont->subsys[ss->subsys_id]; |
| if (atomic_read(&css->refcnt)) { |
| css_busy = 1; |
| break; |
| } |
| } |
| if (css_busy) { |
| mutex_unlock(&cgroup_mutex); |
| return -EBUSY; |
| } |
| |
| for_each_subsys(root, ss) { |
| if (cont->subsys[ss->subsys_id]) |
| ss->destroy(ss, cont); |
| } |
| |
| set_bit(CONT_REMOVED, &cont->flags); |
| /* delete my sibling from parent->children */ |
| list_del(&cont->sibling); |
| spin_lock(&cont->dentry->d_lock); |
| d = dget(cont->dentry); |
| cont->dentry = NULL; |
| spin_unlock(&d->d_lock); |
| |
| cgroup_d_remove_dir(d); |
| dput(d); |
| root->number_of_cgroups--; |
| |
| mutex_unlock(&cgroup_mutex); |
| /* Drop the active superblock reference that we took when we |
| * created the cgroup */ |
| deactivate_super(sb); |
| return 0; |
| } |
| |
| static void cgroup_init_subsys(struct cgroup_subsys *ss) |
| { |
| struct task_struct *g, *p; |
| struct cgroup_subsys_state *css; |
| printk(KERN_ERR "Initializing cgroup subsys %s\n", ss->name); |
| |
| /* Create the top cgroup state for this subsystem */ |
| ss->root = &rootnode; |
| css = ss->create(ss, dummytop); |
| /* We don't handle early failures gracefully */ |
| BUG_ON(IS_ERR(css)); |
| init_cgroup_css(css, ss, dummytop); |
| |
| /* Update all tasks to contain a subsys pointer to this state |
| * - since the subsystem is newly registered, all tasks are in |
| * the subsystem's top cgroup. */ |
| |
| /* If this subsystem requested that it be notified with fork |
| * events, we should send it one now for every process in the |
| * system */ |
| |
| read_lock(&tasklist_lock); |
| init_task.cgroups.subsys[ss->subsys_id] = css; |
| if (ss->fork) |
| ss->fork(ss, &init_task); |
| |
| do_each_thread(g, p) { |
| printk(KERN_INFO "Setting task %p css to %p (%d)\n", css, p, p->pid); |
| p->cgroups.subsys[ss->subsys_id] = css; |
| if (ss->fork) |
| ss->fork(ss, p); |
| } while_each_thread(g, p); |
| read_unlock(&tasklist_lock); |
| |
| need_forkexit_callback |= ss->fork || ss->exit; |
| |
| ss->active = 1; |
| } |
| |
| /** |
| * cgroup_init_early - initialize cgroups at system boot, and |
| * initialize any subsystems that request early init. |
| */ |
| int __init cgroup_init_early(void) |
| { |
| int i; |
| init_cgroup_root(&rootnode); |
| list_add(&rootnode.root_list, &roots); |
| |
| for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { |
| struct cgroup_subsys *ss = subsys[i]; |
| |
| BUG_ON(!ss->name); |
| BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN); |
| BUG_ON(!ss->create); |
| BUG_ON(!ss->destroy); |
| if (ss->subsys_id != i) { |
| printk(KERN_ERR "Subsys %s id == %d\n", |
| ss->name, ss->subsys_id); |
| BUG(); |
| } |
| |
| if (ss->early_init) |
| cgroup_init_subsys(ss); |
| } |
| return 0; |
| } |
| |
| /** |
| * cgroup_init - register cgroup filesystem and /proc file, and |
| * initialize any subsystems that didn't request early init. |
| */ |
| int __init cgroup_init(void) |
| { |
| int err; |
| int i; |
| |
| for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { |
| struct cgroup_subsys *ss = subsys[i]; |
| if (!ss->early_init) |
| cgroup_init_subsys(ss); |
| } |
| |
| err = register_filesystem(&cgroup_fs_type); |
| if (err < 0) |
| goto out; |
| |
| out: |
| return err; |
| } |
| |
| /** |
| * cgroup_fork - attach newly forked task to its parents cgroup. |
| * @tsk: pointer to task_struct of forking parent process. |
| * |
| * Description: A task inherits its parent's cgroup at fork(). |
| * |
| * A pointer to the shared css_set was automatically copied in |
| * fork.c by dup_task_struct(). However, we ignore that copy, since |
| * it was not made under the protection of RCU or cgroup_mutex, so |
| * might no longer be a valid cgroup pointer. attach_task() might |
| * have already changed current->cgroup, allowing the previously |
| * referenced cgroup to be removed and freed. |
| * |
| * At the point that cgroup_fork() is called, 'current' is the parent |
| * task, and the passed argument 'child' points to the child task. |
| */ |
| void cgroup_fork(struct task_struct *child) |
| { |
| rcu_read_lock(); |
| child->cgroups = rcu_dereference(current->cgroups); |
| get_css_set(&child->cgroups); |
| rcu_read_unlock(); |
| } |
| |
| /** |
| * cgroup_fork_callbacks - called on a new task very soon before |
| * adding it to the tasklist. No need to take any locks since no-one |
| * can be operating on this task |
| */ |
| void cgroup_fork_callbacks(struct task_struct *child) |
| { |
| if (need_forkexit_callback) { |
| int i; |
| for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { |
| struct cgroup_subsys *ss = subsys[i]; |
| if (ss->fork) |
| ss->fork(ss, child); |
| } |
| } |
| } |
| |
| /** |
| * cgroup_exit - detach cgroup from exiting task |
| * @tsk: pointer to task_struct of exiting process |
| * |
| * Description: Detach cgroup from @tsk and release it. |
| * |
| * Note that cgroups marked notify_on_release force every task in |
| * them to take the global cgroup_mutex mutex when exiting. |
| * This could impact scaling on very large systems. Be reluctant to |
| * use notify_on_release cgroups where very high task exit scaling |
| * is required on large systems. |
| * |
| * the_top_cgroup_hack: |
| * |
| * Set the exiting tasks cgroup to the root cgroup (top_cgroup). |
| * |
| * We call cgroup_exit() while the task is still competent to |
| * handle notify_on_release(), then leave the task attached to the |
| * root cgroup in each hierarchy for the remainder of its exit. |
| * |
| * To do this properly, we would increment the reference count on |
| * top_cgroup, and near the very end of the kernel/exit.c do_exit() |
| * code we would add a second cgroup function call, to drop that |
| * reference. This would just create an unnecessary hot spot on |
| * the top_cgroup reference count, to no avail. |
| * |
| * Normally, holding a reference to a cgroup without bumping its |
| * count is unsafe. The cgroup could go away, or someone could |
| * attach us to a different cgroup, decrementing the count on |
| * the first cgroup that we never incremented. But in this case, |
| * top_cgroup isn't going away, and either task has PF_EXITING set, |
| * which wards off any attach_task() attempts, or task is a failed |
| * fork, never visible to attach_task. |
| * |
| */ |
| void cgroup_exit(struct task_struct *tsk, int run_callbacks) |
| { |
| int i; |
| |
| if (run_callbacks && need_forkexit_callback) { |
| for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { |
| struct cgroup_subsys *ss = subsys[i]; |
| if (ss->exit) |
| ss->exit(ss, tsk); |
| } |
| } |
| /* Reassign the task to the init_css_set. */ |
| task_lock(tsk); |
| put_css_set(&tsk->cgroups); |
| tsk->cgroups = init_task.cgroups; |
| task_unlock(tsk); |
| } |
| |
| /** |
| * cgroup_clone - duplicate the current cgroup in the hierarchy |
| * that the given subsystem is attached to, and move this task into |
| * the new child |
| */ |
| int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys) |
| { |
| struct dentry *dentry; |
| int ret = 0; |
| char nodename[MAX_CGROUP_TYPE_NAMELEN]; |
| struct cgroup *parent, *child; |
| struct inode *inode; |
| struct css_set *cg; |
| struct cgroupfs_root *root; |
| struct cgroup_subsys *ss; |
| |
| /* We shouldn't be called by an unregistered subsystem */ |
| BUG_ON(!subsys->active); |
| |
| /* First figure out what hierarchy and cgroup we're dealing |
| * with, and pin them so we can drop cgroup_mutex */ |
| mutex_lock(&cgroup_mutex); |
| again: |
| root = subsys->root; |
| if (root == &rootnode) { |
| printk(KERN_INFO |
| "Not cloning cgroup for unused subsystem %s\n", |
| subsys->name); |
| mutex_unlock(&cgroup_mutex); |
| return 0; |
| } |
| cg = &tsk->cgroups; |
| parent = task_cgroup(tsk, subsys->subsys_id); |
| |
| snprintf(nodename, MAX_CGROUP_TYPE_NAMELEN, "node_%d", tsk->pid); |
| |
| /* Pin the hierarchy */ |
| atomic_inc(&parent->root->sb->s_active); |
| |
| mutex_unlock(&cgroup_mutex); |
| |
| /* Now do the VFS work to create a cgroup */ |
| inode = parent->dentry->d_inode; |
| |
| /* Hold the parent directory mutex across this operation to |
| * stop anyone else deleting the new cgroup */ |
| mutex_lock(&inode->i_mutex); |
| dentry = lookup_one_len(nodename, parent->dentry, strlen(nodename)); |
| if (IS_ERR(dentry)) { |
| printk(KERN_INFO |
| "Couldn't allocate dentry for %s: %ld\n", nodename, |
| PTR_ERR(dentry)); |
| ret = PTR_ERR(dentry); |
| goto out_release; |
| } |
| |
| /* Create the cgroup directory, which also creates the cgroup */ |
| ret = vfs_mkdir(inode, dentry, S_IFDIR | 0755); |
| child = __d_cont(dentry); |
| dput(dentry); |
| if (ret) { |
| printk(KERN_INFO |
| "Failed to create cgroup %s: %d\n", nodename, |
| ret); |
| goto out_release; |
| } |
| |
| if (!child) { |
| printk(KERN_INFO |
| "Couldn't find new cgroup %s\n", nodename); |
| ret = -ENOMEM; |
| goto out_release; |
| } |
| |
| /* The cgroup now exists. Retake cgroup_mutex and check |
| * that we're still in the same state that we thought we |
| * were. */ |
| mutex_lock(&cgroup_mutex); |
| if ((root != subsys->root) || |
| (parent != task_cgroup(tsk, subsys->subsys_id))) { |
| /* Aargh, we raced ... */ |
| mutex_unlock(&inode->i_mutex); |
| |
| deactivate_super(parent->root->sb); |
| /* The cgroup is still accessible in the VFS, but |
| * we're not going to try to rmdir() it at this |
| * point. */ |
| printk(KERN_INFO |
| "Race in cgroup_clone() - leaking cgroup %s\n", |
| nodename); |
| goto again; |
| } |
| |
| /* do any required auto-setup */ |
| for_each_subsys(root, ss) { |
| if (ss->post_clone) |
| ss->post_clone(ss, child); |
| } |
| |
| /* All seems fine. Finish by moving the task into the new cgroup */ |
| ret = attach_task(child, tsk); |
| mutex_unlock(&cgroup_mutex); |
| |
| out_release: |
| mutex_unlock(&inode->i_mutex); |
| deactivate_super(parent->root->sb); |
| return ret; |
| } |
| |
| /* |
| * See if "cont" is a descendant of the current task's cgroup in |
| * the appropriate hierarchy |
| * |
| * If we are sending in dummytop, then presumably we are creating |
| * the top cgroup in the subsystem. |
| * |
| * Called only by the ns (nsproxy) cgroup. |
| */ |
| int cgroup_is_descendant(const struct cgroup *cont) |
| { |
| int ret; |
| struct cgroup *target; |
| int subsys_id; |
| |
| if (cont == dummytop) |
| return 1; |
| |
| get_first_subsys(cont, NULL, &subsys_id); |
| target = task_cgroup(current, subsys_id); |
| while (cont != target && cont!= cont->top_cgroup) |
| cont = cont->parent; |
| ret = (cont == target); |
| return ret; |
| } |