diff options
Diffstat (limited to 'kernel/cgroup.c')
| -rw-r--r-- | kernel/cgroup.c | 1198 |
1 files changed, 1198 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c new file mode 100644 index 0000000..6ba857b --- /dev/null +++ b/kernel/cgroup.c @@ -0,0 +1,1198 @@ +/* + * 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 <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) + +/* + * 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; +} + +/* 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_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 -EINVAL; + + return cft->write(cont, cft, file, buf, nbytes, ppos); +} + +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; +} + +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); + + 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; +} |
