diff options
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 2805 |
1 files changed, 2805 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c new file mode 100644 index 00000000000..5987dccdb2a --- /dev/null +++ b/kernel/cgroup.c @@ -0,0 +1,2805 @@ +/* + * 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/proc_fs.h> +#include <linux/rcupdate.h> +#include <linux/sched.h> +#include <linux/backing-dev.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 <linux/kmod.h> +#include <linux/delayacct.h> +#include <linux/cgroupstats.h> + +#include <asm/atomic.h> + +static DEFINE_MUTEX(cgroup_mutex); + +/* 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 path to use for release notifications. No locking + * between setting and use - so if userspace updates this + * while child cgroups exist, you could miss a + * notification. We ensure that it's always a valid + * NUL-terminated string */ + char release_agent_path[PATH_MAX]; +}; + + +/* + * 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); +static int root_count; + +/* 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 { + /* Control Group is dead */ + CGRP_REMOVED, + /* Control Group has previously had a child cgroup or a task, + * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set) */ + CGRP_RELEASABLE, + /* Control Group requires release notifications to userspace */ + CGRP_NOTIFY_ON_RELEASE, +}; + +/* convenient tests for these bits */ +inline int cgroup_is_removed(const struct cgroup *cgrp) +{ + return test_bit(CGRP_REMOVED, &cgrp->flags); +} + +/* bits in struct cgroupfs_root flags field */ +enum { + ROOT_NOPREFIX, /* mounted subsystems have no named prefix */ +}; + +inline int cgroup_is_releasable(const struct cgroup *cgrp) +{ + const int bits = + (1 << CGRP_RELEASABLE) | + (1 << CGRP_NOTIFY_ON_RELEASE); + return (cgrp->flags & bits) == bits; +} + +inline int notify_on_release(const struct cgroup *cgrp) +{ + return test_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); +} + +/* + * 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) + +/* the list of cgroups eligible for automatic release. Protected by + * release_list_lock */ +static LIST_HEAD(release_list); +static DEFINE_SPINLOCK(release_list_lock); +static void cgroup_release_agent(struct work_struct *work); +static DECLARE_WORK(release_agent_work, cgroup_release_agent); +static void check_for_release(struct cgroup *cgrp); + +/* Link structure for associating css_set objects with cgroups */ +struct cg_cgroup_link { + /* + * List running through cg_cgroup_links associated with a + * cgroup, anchored on cgroup->css_sets + */ + struct list_head cgrp_link_list; + /* + * List running through cg_cgroup_links pointing at a + * single css_set object, anchored on css_set->cg_links + */ + struct list_head cg_link_list; + struct css_set *cg; +}; + +/* The default css_set - used by init and its children prior to any + * hierarchies being mounted. It contains a pointer to the root state + * for each subsystem. Also used to anchor the list of css_sets. Not + * reference-counted, to improve performance when child cgroups + * haven't been created. + */ + +static struct css_set init_css_set; +static struct cg_cgroup_link init_css_set_link; + +/* css_set_lock protects the list of css_set objects, and the + * chain of tasks off each css_set. Nests outside task->alloc_lock + * due to cgroup_iter_start() */ +static DEFINE_RWLOCK(css_set_lock); +static int css_set_count; + +/* We don't maintain the lists running through each css_set to its + * task until after the first call to cgroup_iter_start(). This + * reduces the fork()/exit() overhead for people who have cgroups + * compiled into their kernel but not actually in use */ +static int use_task_css_set_links; + +/* When we create or destroy a css_set, the operation simply + * takes/releases 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. + */ + +/* + * unlink a css_set from the list and free it + */ +static void unlink_css_set(struct css_set *cg) +{ + write_lock(&css_set_lock); + list_del(&cg->list); + css_set_count--; + while (!list_empty(&cg->cg_links)) { + struct cg_cgroup_link *link; + link = list_entry(cg->cg_links.next, + struct cg_cgroup_link, cg_link_list); + list_del(&link->cg_link_list); + list_del(&link->cgrp_link_list); + kfree(link); + } + write_unlock(&css_set_lock); +} + +static void __release_css_set(struct kref *k, int taskexit) +{ + int i; + struct css_set *cg = container_of(k, struct css_set, ref); + + unlink_css_set(cg); + + rcu_read_lock(); + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup *cgrp = cg->subsys[i]->cgroup; + if (atomic_dec_and_test(&cgrp->count) && + notify_on_release(cgrp)) { + if (taskexit) + set_bit(CGRP_RELEASABLE, &cgrp->flags); + check_for_release(cgrp); + } + } + rcu_read_unlock(); + kfree(cg); +} + +static void release_css_set(struct kref *k) +{ + __release_css_set(k, 0); +} + +static void release_css_set_taskexit(struct kref *k) +{ + __release_css_set(k, 1); +} + +/* + * refcounted get/put for css_set objects + */ +static inline void get_css_set(struct css_set *cg) +{ + kref_get(&cg->ref); +} + +static inline void put_css_set(struct css_set *cg) +{ + kref_put(&cg->ref, release_css_set); +} + +static inline void put_css_set_taskexit(struct css_set *cg) +{ + kref_put(&cg->ref, release_css_set_taskexit); +} + +/* + * find_existing_css_set() is a helper for + * find_css_set(), and checks to see whether an existing + * css_set is suitable. This currently walks a linked-list for + * simplicity; a later patch will use a hash table for better + * performance + * + * oldcg: the cgroup group that we're using before the cgroup + * transition + * + * cgrp: the cgroup that we're moving into + * + * template: location in which to build the desired set of subsystem + * state objects for the new cgroup group + */ + +static struct css_set *find_existing_css_set( + struct css_set *oldcg, + struct cgroup *cgrp, + struct cgroup_subsys_state *template[]) +{ + int i; + struct cgroupfs_root *root = cgrp->root; + struct list_head *l = &init_css_set.list; + + /* Built the set of subsystem state objects that we want to + * see in the new css_set */ + 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 */ + template[i] = cgrp->subsys[i]; + } else { + /* Subsystem is not in this hierarchy, so we + * don't want to change the subsystem state */ + template[i] = oldcg->subsys[i]; + } + } + + /* Look through existing cgroup groups to find one to reuse */ + do { + struct css_set *cg = + list_entry(l, struct css_set, list); + + if (!memcmp(template, cg->subsys, sizeof(cg->subsys))) { + /* All subsystems matched */ + return cg; + } + /* Try the next cgroup group */ + l = l->next; + } while (l != &init_css_set.list); + + /* No existing cgroup group matched */ + return NULL; +} + +/* + * allocate_cg_links() allocates "count" cg_cgroup_link structures + * and chains them on tmp through their cgrp_link_list fields. Returns 0 on + * success or a negative error + */ + +static int allocate_cg_links(int count, struct list_head *tmp) +{ + struct cg_cgroup_link *link; + int i; + INIT_LIST_HEAD(tmp); + for (i = 0; i < count; i++) { + link = kmalloc(sizeof(*link), GFP_KERNEL); + if (!link) { + while (!list_empty(tmp)) { + link = list_entry(tmp->next, + struct cg_cgroup_link, + cgrp_link_list); + list_del(&link->cgrp_link_list); + kfree(link); + } + return -ENOMEM; + } + list_add(&link->cgrp_link_list, tmp); + } + return 0; +} + +static void free_cg_links(struct list_head *tmp) +{ + while (!list_empty(tmp)) { + struct cg_cgroup_link *link; + link = list_entry(tmp->next, + struct cg_cgroup_link, + cgrp_link_list); + list_del(&link->cgrp_link_list); + kfree(link); + } +} + +/* + * find_css_set() takes an existing cgroup group and a + * cgroup object, and returns a css_set object that's + * equivalent to the old group, but with the given cgroup + * substituted into the appropriate hierarchy. Must be called with + * cgroup_mutex held + */ + +static struct css_set *find_css_set( + struct css_set *oldcg, struct cgroup *cgrp) +{ + struct css_set *res; + struct cgroup_subsys_state *template[CGROUP_SUBSYS_COUNT]; + int i; + + struct list_head tmp_cg_links; + struct cg_cgroup_link *link; + + /* First see if we already have a cgroup group that matches + * the desired set */ + write_lock(&css_set_lock); + res = find_existing_css_set(oldcg, cgrp, template); + if (res) + get_css_set(res); + write_unlock(&css_set_lock); + + if (res) + return res; + + res = kmalloc(sizeof(*res), GFP_KERNEL); + if (!res) + return NULL; + + /* Allocate all the cg_cgroup_link objects that we'll need */ + if (allocate_cg_links(root_count, &tmp_cg_links) < 0) { + kfree(res); + return NULL; + } + + kref_init(&res->ref); + INIT_LIST_HEAD(&res->cg_links); + INIT_LIST_HEAD(&res->tasks); + + /* Copy the set of subsystem state objects generated in + * find_existing_css_set() */ + memcpy(res->subsys, template, sizeof(res->subsys)); + + write_lock(&css_set_lock); + /* Add reference counts and links from the new css_set. */ + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup *cgrp = res->subsys[i]->cgroup; + struct cgroup_subsys *ss = subsys[i]; + atomic_inc(&cgrp->count); + /* + * We want to add a link once per cgroup, so we + * only do it for the first subsystem in each + * hierarchy + */ + if (ss->root->subsys_list.next == &ss->sibling) { + BUG_ON(list_empty(&tmp_cg_links)); + link = list_entry(tmp_cg_links.next, + struct cg_cgroup_link, + cgrp_link_list); + list_del(&link->cgrp_link_list); + list_add(&link->cgrp_link_list, &cgrp->css_sets); + link->cg = res; + list_add(&link->cg_link_list, &res->cg_links); + } + } + if (list_empty(&rootnode.subsys_list)) { + link = list_entry(tmp_cg_links.next, + struct cg_cgroup_link, + cgrp_link_list); + list_del(&link->cgrp_link_list); + list_add(&link->cgrp_link_list, &dummytop->css_sets); + link->cg = res; + list_add(&link->cg_link_list, &res->cg_links); + } + + BUG_ON(!list_empty(&tmp_cg_links)); + + /* Link this cgroup group into the list */ + list_add(&res->list, &init_css_set.list); + css_set_count++; + INIT_LIST_HEAD(&res->tasks); + write_unlock(&css_set_lock); + + return res; +} + +/* + * 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() + */ + +/** + * 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 *cgrp); +static struct inode_operations cgroup_dir_inode_operations; +static struct file_operations proc_cgroupstats_operations; + +static struct backing_dev_info cgroup_backing_dev_info = { + .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK, +}; + +static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb) +{ + struct inode *inode = new_inode(sb); + + 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 *cgrp = dentry->d_fsdata; + BUG_ON(!(cgroup_is_removed(cgrp))); + /* It's possible for external users to be holding css + * reference counts on a cgroup; css_put() needs to + * be able to access the cgroup after decrementing + * the reference count in order to know if it needs to + * queue the cgroup to be handled by the release + * agent */ + synchronize_rcu(); + kfree(cgrp); + } + 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 *cgrp = &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(&cgrp->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(cgrp->subsys[i]); + BUG_ON(!dummytop->subsys[i]); + BUG_ON(dummytop->subsys[i]->cgroup != dummytop); + cgrp->subsys[i] = dummytop->subsys[i]; + cgrp->subsys[i]->cgroup = cgrp; + list_add(&ss->sibling, &root->subsys_list); + rcu_assign_pointer(ss->root, root); + if (ss->bind) + ss->bind(ss, cgrp); + + } else if (bit & removed_bits) { + /* We're removing this subsystem */ + BUG_ON(cgrp->subsys[i] != dummytop->subsys[i]); + BUG_ON(cgrp->subsys[i]->cgroup != cgrp); + if (ss->bind) + ss->bind(ss, dummytop); + dummytop->subsys[i]->cgroup = dummytop; + cgrp->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(!cgrp->subsys[i]); + } else { + /* Subsystem state shouldn't exist */ + BUG_ON(cgrp->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"); + if (strlen(root->release_agent_path)) + seq_printf(seq, ",release_agent=%s", root->release_agent_path); + mutex_unlock(&cgroup_mutex); + return 0; +} + +struct cgroup_sb_opts { + unsigned long subsys_bits; + unsigned long flags; + char *release_agent; +}; + +/* 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; + opts->release_agent = NULL; + + 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 if (!strncmp(token, "release_agent=", 14)) { + /* Specifying two release agents is forbidden */ + if (opts->release_agent) + return -EINVAL; + opts->release_agent = kzalloc(PATH_MAX, GFP_KERNEL); + if (!opts->release_agent) + return -ENOMEM; + strncpy(opts->release_agent, token + 14, PATH_MAX - 1); + opts->release_agent[PATH_MAX - 1] = 0; + } 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 *cgrp = &root->top_cgroup; + struct cgroup_sb_opts opts; + + mutex_lock(&cgrp->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(cgrp); + + if (opts.release_agent) + strcpy(root->release_agent_path, opts.release_agent); + out_unlock: + if (opts.release_agent) + kfree(opts.release_agent); + mutex_unlock(&cgroup_mutex); + mutex_unlock(&cgrp->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 *cgrp = &root->top_cgroup; + INIT_LIST_HEAD(&root->subsys_list); + INIT_LIST_HEAD(&root->root_list); + root->number_of_cgroups = 1; + cgrp->root = root; + cgrp->top_cgroup = cgrp; + INIT_LIST_HEAD(&cgrp->sibling); + INIT_LIST_HEAD(&cgrp->children); + INIT_LIST_HEAD(&cgrp->css_sets); + INIT_LIST_HEAD(&cgrp->release_list); +} + +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; + struct list_head tmp_cg_links, *l; + INIT_LIST_HEAD(&tmp_cg_links); + + /* First find the desired set of subsystems */ + ret = parse_cgroupfs_options(data, &opts); + if (ret) { + if (opts.release_agent) + kfree(opts.release_agent); + 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; + if (opts.release_agent) { + strcpy(root->release_agent_path, opts.release_agent); + kfree(opts.release_agent); + } + + 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 *cgrp = &root->top_cgroup; + struct inode *inode; + + BUG_ON(sb->s_root != NULL); + + ret = cgroup_get_rootdir(sb); + if (ret) + goto drop_new_super; + inode = sb->s_root->d_inode; + + mutex_lock(&inode->i_mutex); + mutex_lock(&cgroup_mutex); + + /* + * 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_cg_links(css_set_count, &tmp_cg_links); + if (ret) { + mutex_unlock(&cgroup_mutex); + mutex_unlock(&inode->i_mutex); + goto drop_new_super; + } + + ret = rebind_subsystems(root, root->subsys_bits); + if (ret == -EBUSY) { + mutex_unlock(&cgroup_mutex); + mutex_unlock(&inode->i_mutex); + goto drop_new_super; + } + + /* EBUSY should be the only error here */ + BUG_ON(ret); + + list_add(&root->root_list, &roots); + root_count++; + + sb->s_root->d_fsdata = &root->top_cgroup; + root->top_cgroup.dentry = sb->s_root; + + /* Link the top cgroup in this hierarchy into all + * the css_set objects */ + write_lock(&css_set_lock); + l = &init_css_set.list; + do { + struct css_set *cg; + struct cg_cgroup_link *link; + cg = list_entry(l, struct css_set, list); + BUG_ON(list_empty(&tmp_cg_links)); + link = list_entry(tmp_cg_links.next, + struct cg_cgroup_link, + cgrp_link_list); + list_del(&link->cgrp_link_list); + link->cg = cg; + list_add(&link->cgrp_link_list, + &root->top_cgroup.css_sets); + list_add(&link->cg_link_list, &cg->cg_links); + l = l->next; + } while (l != &init_css_set.list); + write_unlock(&css_set_lock); + + free_cg_links(&tmp_cg_links); + + BUG_ON(!list_empty(&cgrp->sibling)); + BUG_ON(!list_empty(&cgrp->children)); + BUG_ON(root->number_of_cgroups != 1); + + cgroup_populate_dir(cgrp); + mutex_unlock(&inode->i_mutex); + mutex_unlock(&cgroup_mutex); + } + + return simple_set_mnt(mnt, sb); + + drop_new_super: + up_write(&sb->s_umount); + deactivate_super(sb); + free_cg_links(&tmp_cg_links); + return ret; +} + +static void cgroup_kill_sb(struct super_block *sb) { + struct cgroupfs_root *root = sb->s_fs_info; + struct cgroup *cgrp = &root->top_cgroup; + int ret; + + BUG_ON(!root); + + BUG_ON(root->number_of_cgroups != 1); + BUG_ON(!list_empty(&cgrp->children)); + BUG_ON(!list_empty(&cgrp->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); + + /* + * Release all the links from css_sets to this hierarchy's + * root cgroup + */ + write_lock(&css_set_lock); + while (!list_empty(&cgrp->css_sets)) { + struct cg_cgroup_link *link; + link = list_entry(cgrp->css_sets.next, + struct cg_cgroup_link, cgrp_link_list); + list_del(&link->cg_link_list); + list_del(&link->cgrp_link_list); + kfree(link); + } + write_unlock(&css_set_lock); + + if (!list_empty(&root->root_list)) { + list_del(&root->root_list); + root_count--; + } + 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_cgrp(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 *cgrp, char *buf, int buflen) +{ + char *start; + + if (cgrp == dummytop) { + /* + * Inactive subsystems have no dentry for their root + * cgroup + */ + strcpy(buf, "/"); + return 0; + } + + start = buf + buflen; + + *--start = '\0'; + for (;;) { + int len = cgrp->dentry->d_name.len; + if ((start -= len) < buf) + return -ENAMETOOLONG; + memcpy(start, cgrp->dentry->d_name.name, len); + cgrp = cgrp->parent; + if (!cgrp) + break; + if (!cgrp->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 *cgrp, + struct cgroup_subsys_state **css, int *subsys_id) +{ + const struct cgroupfs_root *root = cgrp->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 = cgrp->subsys[test_ss->subsys_id]; + BUG_ON(!*css); + } + if (subsys_id) + *subsys_id = test_ss->subsys_id; +} + +/* + * Attach task 'tsk' to cgroup 'cgrp' + * + * Call holding cgroup_mutex. May take task_lock of + * the task 'pid' during call. + */ +static int attach_task(struct cgroup *cgrp, struct task_struct *tsk) +{ + int retval = 0; + struct cgroup_subsys *ss; + struct cgroup *oldcgrp; + struct css_set *cg = tsk->cgroups; + struct css_set *newcg; + struct cgroupfs_root *root = cgrp->root; + int subsys_id; + + get_first_subsys(cgrp, NULL, &subsys_id); + + /* Nothing to do if the task is already in that cgroup */ + oldcgrp = task_cgroup(tsk, subsys_id); + if (cgrp == oldcgrp) + return 0; + + for_each_subsys(root, ss) { + if (ss->can_attach) { + retval = ss->can_attach(ss, cgrp, tsk); + if (retval) { + return retval; + } + } + } + + /* + * Locate or allocate a new css_set for this task, + * based on its final set of cgroups + */ + newcg = find_css_set(cg, cgrp); + if (!newcg) { + return -ENOMEM; + } + + task_lock(tsk); + if (tsk->flags & PF_EXITING) { + task_unlock(tsk); + put_css_set(newcg); + return -ESRCH; + } + rcu_assign_pointer(tsk->cgroups, newcg); + task_unlock(tsk); + + /* Update the css_set linked lists if we're using them */ + write_lock(&css_set_lock); + if (!list_empty(&tsk->cg_list)) { + list_del(&tsk->cg_list); + list_add(&tsk->cg_list, &newcg->tasks); + } + write_unlock(&css_set_lock); + + for_each_subsys(root, ss) { + if (ss->attach) { + ss->attach(ss, cgrp, oldcgrp, tsk); + } + } + set_bit(CGRP_RELEASABLE, &oldcgrp->flags); + synchronize_rcu(); + put_css_set(cg); + return 0; +} + +/* + * Attach task with pid 'pid' to cgroup 'cgrp'. Call with + * cgroup_mutex, may take task_lock of task + */ +static int attach_task_by_pid(struct cgroup *cgrp, 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(cgrp, 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, + FILE_NOTIFY_ON_RELEASE, + FILE_RELEASABLE, + FILE_RELEASE_AGENT, +}; + +static ssize_t cgroup_write_uint(struct cgroup *cgrp, 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(cgrp, cft, val); + if (!retval) + retval = nbytes; + return retval; +} + +static ssize_t cgroup_common_file_write(struct cgroup *cgrp, + 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(cgrp)) { + retval = -ENODEV; + goto out2; + } + + switch (type) { + case FILE_TASKLIST: + retval = attach_task_by_pid(cgrp, buffer); + break; + case FILE_NOTIFY_ON_RELEASE: + clear_bit(CGRP_RELEASABLE, &cgrp->flags); + if (simple_strtoul(buffer, NULL, 10) != 0) + set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); + else + clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); + break; + case FILE_RELEASE_AGENT: + { + struct cgroupfs_root *root = cgrp->root; + /* Strip trailing newline */ + if (nbytes && (buffer[nbytes-1] == '\n')) { + buffer[nbytes-1] = 0; + } + if (nbytes < sizeof(root->release_agent_path)) { + /* We never write anything other than '\0' + * into the last char of release_agent_path, + * so it always remains a NUL-terminated + * string */ + strncpy(root->release_agent_path, buffer, nbytes); + root->release_agent_path[nbytes] = 0; + } else { + retval = -ENOSPC; + } + 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 *cgrp = __d_cgrp(file->f_dentry->d_parent); + + if (!cft) + return -ENODEV; + if (cft->write) + return cft->write(cgrp, cft, file, buf, nbytes, ppos); + if (cft->write_uint) + return cgroup_write_uint(cgrp, cft, file, buf, nbytes, ppos); + return -EINVAL; +} + +static ssize_t cgroup_read_uint(struct cgroup *cgrp, struct cftype *cft, + struct file *file, + char __user *buf, size_t nbytes, + loff_t *ppos) +{ + char tmp[64]; + u64 val = cft->read_uint(cgrp, 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_common_file_read(struct cgroup *cgrp, + struct cftype *cft, + struct file *file, + char __user *buf, + size_t nbytes, loff_t *ppos) +{ + enum cgroup_filetype type = cft->private; + char *page; + ssize_t retval = 0; + char *s; + + if (!(page = (char *)__get_free_page(GFP_KERNEL))) + return -ENOMEM; + + s = page; + + switch (type) { + case FILE_RELEASE_AGENT: + { + struct cgroupfs_root *root; + size_t n; + mutex_lock(&cgroup_mutex); + root = cgrp->root; + n = strnlen(root->release_agent_path, + sizeof(root->release_agent_path)); + n = min(n, (size_t) PAGE_SIZE); + strncpy(s, root->release_agent_path, n); + mutex_unlock(&cgroup_mutex); + s += n; + break; + } + default: + retval = -EINVAL; + goto out; + } + *s++ = '\n'; + + retval = simple_read_from_buffer(buf, nbytes, ppos, page, s - page); +out: + free_page((unsigned long)page); + return retval; +} + +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 *cgrp = __d_cgrp(file->f_dentry->d_parent); + + if (!cft) + return -ENODEV; + + if (cft->read) + return cft->read(cgrp, cft, file, buf, nbytes, ppos); + if (cft->read_uint) + return cgroup_read_uint(cgrp, 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_nested(&inode->i_mutex, I_MUTEX_CHILD); + } 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. + * cgrp: 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 cgroup + * mode: mode to set on new directory. + */ +static int cgroup_create_dir(struct cgroup *cgrp, struct dentry *dentry, + int mode) +{ + struct dentry *parent; + int error = 0; + + parent = cgrp->parent->dentry; + error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb); + if (!error) { + dentry->d_fsdata = cgrp; + inc_nlink(parent->d_inode); + cgrp->dentry = dentry; + dget(dentry); + } + dput(dentry); + + return error; +} + +int cgroup_add_file(struct cgroup *cgrp, + struct cgroup_subsys *subsys, + const struct cftype *cft) +{ + struct dentry *dir = cgrp->dentry; + struct dentry *dentry; + int error; + + char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 }; + if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->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, + cgrp->root->sb); + if (!error) + dentry->d_fsdata = (void *)cft; + dput(dentry); + } else + error = PTR_ERR(dentry); + return error; +} + +int cgroup_add_files(struct cgroup *cgrp, + struct cgroup_subsys *subsys, + const struct cftype cft[], + int count) +{ + int i, err; + for (i = 0; i < count; i++) { + err = cgroup_add_file(cgrp, subsys, &cft[i]); + if (err) + return err; + } + return 0; +} + +/* Count the number of tasks in a cgroup. */ + +int cgroup_task_count(const struct cgroup *cgrp) +{ + int count = 0; + struct list_head *l; + + read_lock(&css_set_lock); + l = cgrp->css_sets.next; + while (l != &cgrp->css_sets) { + struct cg_cgroup_link *link = + list_entry(l, struct cg_cgroup_link, cgrp_link_list); + count += atomic_read(&link->cg->ref.refcount); + l = l->next; + } + read_unlock(&css_set_lock); + return count; +} + +/* + * Advance a list_head iterator. The iterator should be positioned at + * the start of a css_set + */ +static void cgroup_advance_iter(struct cgroup *cgrp, + struct cgroup_iter *it) +{ + struct list_head *l = it->cg_link; + struct cg_cgroup_link *link; + struct css_set *cg; + + /* Advance to the next non-empty css_set */ + do { + l = l->next; + if (l == &cgrp->css_sets) { + it->cg_link = NULL; + return; + } + link = list_entry(l, struct cg_cgroup_link, cgrp_link_list); + cg = link->cg; + } while (list_empty(&cg->tasks)); + it->cg_link = l; + it->task = cg->tasks.next; +} + +void cgroup_iter_start(struct cgroup *cgrp, struct cgroup_iter *it) +{ + /* + * The first time anyone tries to iterate across a cgroup, + * we need to enable the list linking each css_set to its + * tasks, and fix up all existing tasks. + */ + if (!use_task_css_set_links) { + struct task_struct *p, *g; + write_lock(&css_set_lock); + use_task_css_set_links = 1; + do_each_thread(g, p) { + task_lock(p); + if (list_empty(&p->cg_list)) + list_add(&p->cg_list, &p->cgroups->tasks); + task_unlock(p); + } while_each_thread(g, p); + write_unlock(&css_set_lock); + } + read_lock(&css_set_lock); + it->cg_link = &cgrp->css_sets; + cgroup_advance_iter(cgrp, it); +} + +struct task_struct *cgroup_iter_next(struct cgroup *cgrp, + struct cgroup_iter *it) +{ + struct task_struct *res; + struct list_head *l = it->task; + + /* If the iterator cg is NULL, we have no tasks */ + if (!it->cg_link) + return NULL; + res = list_entry(l, struct task_struct, cg_list); + /* Advance iterator to find next entry */ + l = l->next; + if (l == &res->cgroups->tasks) { + /* We reached the end of this task list - move on to + * the next cg_cgroup_link */ + cgroup_advance_iter(cgrp, it); + } else { + it->task = l; + } + return res; +} + +void cgroup_iter_end(struct cgroup *cgrp, struct cgroup_iter *it) +{ + read_unlock(&css_set_lock); +} + +/* + * 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 + * 'cgrp'. 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 *cgrp) +{ + int n = 0; + struct cgroup_iter it; + struct task_struct *tsk; + cgroup_iter_start(cgrp, &it); + while ((tsk = cgroup_iter_next(cgrp, &it))) { + if (unlikely(n == npids)) + break; + pidarray[n++] = task_pid_nr(tsk); + } + cgroup_iter_end(cgrp, &it); + return n; +} + +/** + * Build and fill cgroupstats so that taskstats can export it to user + * space. + * + * @stats: cgroupstats to fill information into + * @dentry: A dentry entry belonging to the cgroup for which stats have + * been requested. + */ +int cgroupstats_build(struct cgroupstats *stats, struct dentry *dentry) +{ + int ret = -EINVAL; + struct cgroup *cgrp; + struct cgroup_iter it; + struct task_struct *tsk; + /* + * Validate dentry by checking the superblock operations + */ + if (dentry->d_sb->s_op != &cgroup_ops) + goto err; + + ret = 0; + cgrp = dentry->d_fsdata; + rcu_read_lock(); + + cgroup_iter_start(cgrp, &it); + while ((tsk = cgroup_iter_next(cgrp, &it))) { + switch (tsk->state) { + case TASK_RUNNING: + stats->nr_running++; + break; + case TASK_INTERRUPTIBLE: + stats->nr_sleeping++; + break; + case TASK_UNINTERRUPTIBLE: + stats->nr_uninterruptible++; + break; + case TASK_STOPPED: + stats->nr_stopped++; + break; + default: + if (delayacct_is_task_waiting_on_io(tsk)) + stats->nr_io_wait++; + break; + } + } + cgroup_iter_end(cgrp, &it); + + rcu_read_unlock(); +err: + return ret; +} + +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 *cgrp = __d_cgrp(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(cgrp); + if (npids) { + pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL); + if (!pidarray) + goto err1; + + npids = pid_array_load(pidarray, npids, cgrp); + 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 *cgrp, + 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; +} + +static u64 cgroup_read_notify_on_release(struct cgroup *cgrp, + struct cftype *cft) +{ + return notify_on_release(cgrp); +} + +static u64 cgroup_read_releasable(struct cgroup *cgrp, struct cftype *cft) +{ + return test_bit(CGRP_RELEASABLE, &cgrp->flags); +} + +/* + * for the common functions, 'private' gives the type of file + */ +static struct cftype files[] = { + { + .name = "tasks", + .open = cgroup_tasks_open, + .read = cgroup_tasks_read, + .write = cgroup_common_file_write, + .release = cgroup_tasks_release, + .private = FILE_TASKLIST, + }, + + { + .name = "notify_on_release", + .read_uint = cgroup_read_notify_on_release, + .write = cgroup_common_file_write, + .private = FILE_NOTIFY_ON_RELEASE, + }, + + { + .name = "releasable", + .read_uint = cgroup_read_releasable, + .private = FILE_RELEASABLE, + } +}; + +static struct cftype cft_release_agent = { + .name = "release_agent", + .read = cgroup_common_file_read, + .write = cgroup_common_file_write, + .private = FILE_RELEASE_AGENT, +}; + +static int cgroup_populate_dir(struct cgroup *cgrp) +{ + int err; + struct cgroup_subsys *ss; + + /* First clear out any existing files */ + cgroup_clear_directory(cgrp->dentry); + + err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files)); + if (err < 0) + return err; + + if (cgrp == cgrp->top_cgroup) { + if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0) + return err; + } + + for_each_subsys(cgrp->root, ss) { + if (ss->populate && (err = ss->populate(ss, cgrp)) < 0) + return err; + } + + return 0; +} + +static void init_cgroup_css(struct cgroup_subsys_state *css, + struct cgroup_subsys *ss, + struct cgroup *cgrp) +{ + css->cgroup = cgrp; + atomic_set(&css->refcnt, 0); + css->flags = 0; + if (cgrp == dummytop) + set_bit(CSS_ROOT, &css->flags); + BUG_ON(cgrp->subsys[ss->subsys_id]); + cgrp->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 *cgrp; + struct cgroupfs_root *root = parent->root; + int err = 0; + struct cgroup_subsys *ss; + struct super_block *sb = root->sb; + + cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL); + if (!cgrp) + 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); + + cgrp->flags = 0; + INIT_LIST_HEAD(&cgrp->sibling); + INIT_LIST_HEAD(&cgrp->children); + INIT_LIST_HEAD(&cgrp->css_sets); + INIT_LIST_HEAD(&cgrp->release_list); + + cgrp->parent = parent; + cgrp->root = parent->root; + cgrp->top_cgroup = parent->top_cgroup; + + for_each_subsys(root, ss) { + struct cgroup_subsys_state *css = ss->create(ss, cgrp); + if (IS_ERR(css)) { + err = PTR_ERR(css); + goto err_destroy; + } + init_cgroup_css(css, ss, cgrp); + } + + list_add(&cgrp->sibling, &cgrp->parent->children); + root->number_of_cgroups++; + + err = cgroup_create_dir(cgrp, dentry, mode); + if (err < 0) + goto err_remove; + + /* The cgroup directory was pre-locked for us */ + BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex)); + + err = cgroup_populate_dir(cgrp); + /* If err < 0, we have a half-filled directory - oh well ;) */ + + mutex_unlock(&cgroup_mutex); + mutex_unlock(&cgrp->dentry->d_inode->i_mutex); + + return 0; + + err_remove: + + list_del(&cgrp->sibling); + root->number_of_cgroups--; + + err_destroy: + + for_each_subsys(root, ss) { + if (cgrp->subsys[ss->subsys_id]) + ss->destroy(ss, cgrp); + } + + mutex_unlock(&cgroup_mutex); + + /* Release the reference count that we took on the superblock */ + deactivate_super(sb); + + kfree(cgrp); + 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 inline int cgroup_has_css_refs(struct cgroup *cgrp) +{ + /* 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. We scan across all subsystems rather than using + * the per-hierarchy linked list of mounted subsystems since + * we can be called via check_for_release() with no + * synchronization other than RCU, and the subsystem linked + * list isn't RCU-safe */ + int i; + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + struct cgroup_subsys_state *css; + /* Skip subsystems not in this hierarchy */ + if (ss->root != cgrp->root) + continue; + css = cgrp->subsys[ss->subsys_id]; + /* When called from check_for_release() it's possible + * that by this point the cgroup has been removed + * and the css deleted. But a false-positive doesn't + * matter, since it can only happen if the cgroup + * has been deleted and hence no longer needs the + * release agent to be called anyway. */ + if (css && atomic_read(&css->refcnt)) { + return 1; + } + } + return 0; +} + +static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry) +{ + struct cgroup *cgrp = dentry->d_fsdata; + struct dentry *d; + struct cgroup *parent; + struct cgroup_subsys *ss; + struct super_block *sb; + struct cgroupfs_root *root; + + /* the vfs holds both inode->i_mutex already */ + + mutex_lock(&cgroup_mutex); + if (atomic_read(&cgrp->count) != 0) { + mutex_unlock(&cgroup_mutex); + return -EBUSY; + } + if (!list_empty(&cgrp->children)) { + mutex_unlock(&cgroup_mutex); + return -EBUSY; + } + + parent = cgrp->parent; + root = cgrp->root; + sb = root->sb; + + if (cgroup_has_css_refs(cgrp)) { + mutex_unlock(&cgroup_mutex); + return -EBUSY; + } + + for_each_subsys(root, ss) { + if (cgrp->subsys[ss->subsys_id]) + ss->destroy(ss, cgrp); + } + + spin_lock(&release_list_lock); + set_bit(CGRP_REMOVED, &cgrp->flags); + if (!list_empty(&cgrp->release_list)) + list_del(&cgrp->release_list); + spin_unlock(&release_list_lock); + /* delete my sibling from parent->children */ + list_del(&cgrp->sibling); + spin_lock(&cgrp->dentry->d_lock); + d = dget(cgrp->dentry); + cgrp->dentry = NULL; + spin_unlock(&d->d_lock); + + cgroup_d_remove_dir(d); + dput(d); + root->number_of_cgroups--; + + set_bit(CGRP_RELEASABLE, &parent->flags); + check_for_release(parent); + + 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 cgroup_subsys_state *css; + struct list_head *l; + 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 cgroup groups to contain a subsys + * pointer to this state - since the subsystem is + * newly registered, all tasks and hence all cgroup + * groups are in the subsystem's top cgroup. */ + write_lock(&css_set_lock); + l = &init_css_set.list; + do { + struct css_set *cg = + list_entry(l, struct css_set, list); + cg->subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id]; + l = l->next; + } while (l != &init_css_set.list); + write_unlock(&css_set_lock); + + /* If this subsystem requested that it be notified with fork + * events, we should send it one now for every process in the + * system */ + if (ss->fork) { + struct task_struct *g, *p; + + read_lock(&tasklist_lock); + do_each_thread(g, p) { + 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; + kref_init(&init_css_set.ref); + kref_get(&init_css_set.ref); + INIT_LIST_HEAD(&init_css_set.list); + INIT_LIST_HEAD(&init_css_set.cg_links); + INIT_LIST_HEAD(&init_css_set.tasks); + css_set_count = 1; + init_cgroup_root(&rootnode); + list_add(&rootnode.root_list, &roots); + root_count = 1; + init_task.cgroups = &init_css_set; + + init_css_set_link.cg = &init_css_set; + list_add(&init_css_set_link.cgrp_link_list, + &rootnode.top_cgroup.css_sets); + list_add(&init_css_set_link.cg_link_list, + &init_css_set.cg_links); + + 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; + struct proc_dir_entry *entry; + + err = bdi_init(&cgroup_backing_dev_info); + if (err) + return err; + + 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; + + entry = create_proc_entry("cgroups", 0, NULL); + if (entry) + entry->proc_fops = &proc_cgroupstats_operations; + +out: + if (err) + bdi_destroy(&cgroup_backing_dev_info); + + return err; +} + +/* + * proc_cgroup_show() + * - Print task's cgroup paths into seq_file, one line for each hierarchy + * - Used for /proc/<pid>/cgroup. + * - No need to task_lock(tsk) on this tsk->cgroup reference, as it + * doesn't really matter if tsk->cgroup changes after we read it, + * and we take cgroup_mutex, keeping attach_task() from changing it + * anyway. No need to check that tsk->cgroup != NULL, thanks to + * the_top_cgroup_hack in cgroup_exit(), which sets an exiting tasks + * cgroup to top_cgroup. + */ + +/* TODO: Use a proper seq_file iterator */ +static int proc_cgroup_show(struct seq_file *m, void *v) +{ + struct pid *pid; + struct task_struct *tsk; + char *buf; + int retval; + struct cgroupfs_root *root; + + retval = -ENOMEM; + buf = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!buf) + goto out; + + retval = -ESRCH; + pid = m->private; + tsk = get_pid_task(pid, PIDTYPE_PID); + if (!tsk) + goto out_free; + + retval = 0; + + mutex_lock(&cgroup_mutex); + + for_each_root(root) { + struct cgroup_subsys *ss; + struct cgroup *cgrp; + int subsys_id; + int count = 0; + + /* Skip this hierarchy if it has no active subsystems */ + if (!root->actual_subsys_bits) + continue; + for_each_subsys(root, ss) + seq_printf(m, "%s%s", count++ ? "," : "", ss->name); + seq_putc(m, ':'); + get_first_subsys(&root->top_cgroup, NULL, &subsys_id); + cgrp = task_cgroup(tsk, subsys_id); + retval = cgroup_path(cgrp, buf, PAGE_SIZE); + if (retval < 0) + goto out_unlock; + seq_puts(m, buf); + seq_putc(m, '\n'); + } + +out_unlock: + mutex_unlock(&cgroup_mutex); + put_task_struct(tsk); +out_free: + kfree(buf); +out: + return retval; +} + +static int cgroup_open(struct inode *inode, struct file *file) +{ + struct pid *pid = PROC_I(inode)->pid; + return single_open(file, proc_cgroup_show, pid); +} + +struct file_operations proc_cgroup_operations = { + .open = cgroup_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + +/* Display information about each subsystem and each hierarchy */ +static int proc_cgroupstats_show(struct seq_file *m, void *v) +{ + int i; + struct cgroupfs_root *root; + + seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\n"); + mutex_lock(&cgroup_mutex); + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + seq_printf(m, "%s\t%lu\t%d\n", + ss->name, ss->root->subsys_bits, + ss->root->number_of_cgroups); + } + mutex_unlock(&cgroup_mutex); + return 0; +} + +static int cgroupstats_open(struct inode *inode, struct file *file) +{ + return single_open(file, proc_cgroupstats_show, 0); +} + +static struct file_operations proc_cgroupstats_operations = { + .open = cgroupstats_open, + .read = seq_read, + .llseek = seq_lseek, + .release = single_release, +}; + +/** + * 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->cgroups, allowing the previously + * referenced cgroup group 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) +{ + task_lock(current); + child->cgroups = current->cgroups; + get_css_set(child->cgroups); + task_unlock(current); + INIT_LIST_HEAD(&child->cg_list); +} + +/** + * 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_post_fork - called on a new task after adding it to the + * task list. Adds the task to the list running through its css_set + * if necessary. Has to be after the task is visible on the task list + * in case we race with the first call to cgroup_iter_start() - to + * guarantee that the new task ends up on its list. */ +void cgroup_post_fork(struct task_struct *child) +{ + if (use_task_css_set_links) { + write_lock(&css_set_lock); + if (list_empty(&child->cg_list)) + list_add(&child->cg_list, &child->cgroups->tasks); + write_unlock(&css_set_lock); + } +} +/** + * 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; + struct css_set *cg; + + 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); + } + } + + /* + * Unlink from the css_set task list if necessary. + * Optimistically check cg_list before taking + * css_set_lock + */ + if (!list_empty(&tsk->cg_list)) { + write_lock(&css_set_lock); + if (!list_empty(&tsk->cg_list)) + list_del(&tsk->cg_list); + write_unlock(&css_set_lock); + } + + /* Reassign the task to the init_css_set. */ + task_lock(tsk); + cg = tsk->cgroups; + tsk->cgroups = &init_css_set; + task_unlock(tsk); + if (cg) + put_css_set_taskexit(cg); +} + +/** + * 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); + + /* Keep the cgroup alive */ + get_css_set(cg); + 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_cgrp(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); + put_css_set(cg); + + 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); + + mutex_lock(&cgroup_mutex); + put_css_set(cg); + mutex_unlock(&cgroup_mutex); + deactivate_super(parent->root->sb); + return ret; +} + +/* + * See if "cgrp" 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 *cgrp) +{ + int ret; + struct cgroup *target; + int subsys_id; + + if (cgrp == dummytop) + return 1; + + get_first_subsys(cgrp, NULL, &subsys_id); + target = task_cgroup(current, subsys_id); + while (cgrp != target && cgrp!= cgrp->top_cgroup) + cgrp = cgrp->parent; + ret = (cgrp == target); + return ret; +} + +static void check_for_release(struct cgroup *cgrp) +{ + /* All of these checks rely on RCU to keep the cgroup + * structure alive */ + if (cgroup_is_releasable(cgrp) && !atomic_read(&cgrp->count) + && list_empty(&cgrp->children) && !cgroup_has_css_refs(cgrp)) { + /* Control Group is currently removeable. If it's not + * already queued for a userspace notification, queue + * it now */ + int need_schedule_work = 0; + spin_lock(&release_list_lock); + if (!cgroup_is_removed(cgrp) && + list_empty(&cgrp->release_list)) { + list_add(&cgrp->release_list, &release_list); + need_schedule_work = 1; + } + spin_unlock(&release_list_lock); + if (need_schedule_work) + schedule_work(&release_agent_work); + } +} + +void __css_put(struct cgroup_subsys_state *css) +{ + struct cgroup *cgrp = css->cgroup; + rcu_read_lock(); + if (atomic_dec_and_test(&css->refcnt) && notify_on_release(cgrp)) { + set_bit(CGRP_RELEASABLE, &cgrp->flags); + check_for_release(cgrp); + } + rcu_read_unlock(); +} + +/* + * Notify userspace when a cgroup is released, by running the + * configured release agent with the name of the cgroup (path + * relative to the root of cgroup file system) as the argument. + * + * Most likely, this user command will try to rmdir this cgroup. + * + * This races with the possibility that some other task will be + * attached to this cgroup before it is removed, or that some other + * user task will 'mkdir' a child cgroup of this cgroup. That's ok. + * The presumed 'rmdir' will fail quietly if this cgroup is no longer + * unused, and this cgroup will be reprieved from its death sentence, + * to continue to serve a useful existence. Next time it's released, + * we will get notified again, if it still has 'notify_on_release' set. + * + * The final arg to call_usermodehelper() is UMH_WAIT_EXEC, which + * means only wait until the task is successfully execve()'d. The + * separate release agent task is forked by call_usermodehelper(), + * then control in this thread returns here, without waiting for the + * release agent task. We don't bother to wait because the caller of + * this routine has no use for the exit status of the release agent + * task, so no sense holding our caller up for that. + * + */ + +static void cgroup_release_agent(struct work_struct *work) +{ + BUG_ON(work != &release_agent_work); + mutex_lock(&cgroup_mutex); + spin_lock(&release_list_lock); + while (!list_empty(&release_list)) { + char *argv[3], *envp[3]; + int i; + char *pathbuf; + struct cgroup *cgrp = list_entry(release_list.next, + struct cgroup, + release_list); + list_del_init(&cgrp->release_list); + spin_unlock(&release_list_lock); + pathbuf = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!pathbuf) { + spin_lock(&release_list_lock); + continue; + } + + if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0) { + kfree(pathbuf); + spin_lock(&release_list_lock); + continue; + } + + i = 0; + argv[i++] = cgrp->root->release_agent_path; + argv[i++] = (char *)pathbuf; + argv[i] = NULL; + + i = 0; + /* minimal command environment */ + envp[i++] = "HOME=/"; + envp[i++] = "PATH=/sbin:/bin:/usr/sbin:/usr/bin"; + envp[i] = NULL; + + /* Drop the lock while we invoke the usermode helper, + * since the exec could involve hitting disk and hence + * be a slow process */ + mutex_unlock(&cgroup_mutex); + call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC); + kfree(pathbuf); + mutex_lock(&cgroup_mutex); + spin_lock(&release_list_lock); + } + spin_unlock(&release_list_lock); + mutex_unlock(&cgroup_mutex); +} |