X-Git-Url: http://ftp.safe.ca/?a=blobdiff_plain;f=kernel%2Fcgroup.c;h=48348dde6d814ea52270edee180c3db89da5d0c4;hb=b3199c025d1646e25e7d1d640dd605db251dccf8;hp=6ba857bec71ba5caeea419975037ef22d9ae8841;hpb=ddbcc7e8e50aefe467c01cac3dec71f118cd8ac2;p=safe%2Fjmp%2Flinux-2.6 diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 6ba857b..48348dd 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1,6 +1,4 @@ /* - * kernel/cgroup.c - * * Generic process-grouping system. * * Based originally on the cpuset system, extracted by Paul Menage @@ -33,16 +31,26 @@ #include #include #include +#include #include #include +#include #include #include #include #include #include +#include +#include +#include +#include +#include +#include #include +static DEFINE_MUTEX(cgroup_mutex); + /* Generate an array of cgroup subsystem pointers */ #define SUBSYS(_x) &_x ## _subsys, @@ -81,6 +89,9 @@ struct cgroupfs_root { /* Hierarchy-specific flags */ unsigned long flags; + + /* The path to use for release notifications. */ + char release_agent_path[PATH_MAX]; }; @@ -94,26 +105,23 @@ 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. + * 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, -}; +static int need_forkexit_callback __read_mostly; +static int need_mm_owner_callback __read_mostly; /* convenient tests for these bits */ -inline int cgroup_is_removed(const struct cgroup *cont) +inline int cgroup_is_removed(const struct cgroup *cgrp) { - return test_bit(CONT_REMOVED, &cont->flags); + return test_bit(CGRP_REMOVED, &cgrp->flags); } /* bits in struct cgroupfs_root flags field */ @@ -121,6 +129,19 @@ enum { ROOT_NOPREFIX, /* mounted subsystems have no named prefix */ }; +static int cgroup_is_releasable(const struct cgroup *cgrp) +{ + const int bits = + (1 << CGRP_RELEASABLE) | + (1 << CGRP_NOTIFY_ON_RELEASE); + return (cgrp->flags & bits) == bits; +} + +static 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 @@ -132,6 +153,332 @@ list_for_each_entry(_ss, &_root->subsys_list, sibling) #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; + +/* hash table for cgroup groups. This improves the performance to + * find an existing css_set */ +#define CSS_SET_HASH_BITS 7 +#define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS) +static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE]; + +static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[]) +{ + int i; + int index; + unsigned long tmp = 0UL; + + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) + tmp += (unsigned long)css[i]; + tmp = (tmp >> 16) ^ tmp; + + index = hash_long(tmp, CSS_SET_HASH_BITS); + + return &css_set_table[index]; +} + +/* 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 __read_mostly; + +/* 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) +{ + struct cg_cgroup_link *link; + struct cg_cgroup_link *saved_link; + + hlist_del(&cg->hlist); + css_set_count--; + + list_for_each_entry_safe(link, saved_link, &cg->cg_links, + cg_link_list) { + list_del(&link->cg_link_list); + list_del(&link->cgrp_link_list); + kfree(link); + } +} + +static void __put_css_set(struct css_set *cg, int taskexit) +{ + int i; + /* + * Ensure that the refcount doesn't hit zero while any readers + * can see it. Similar to atomic_dec_and_lock(), but for an + * rwlock + */ + if (atomic_add_unless(&cg->refcount, -1, 1)) + return; + write_lock(&css_set_lock); + if (!atomic_dec_and_test(&cg->refcount)) { + write_unlock(&css_set_lock); + return; + } + unlink_css_set(cg); + write_unlock(&css_set_lock); + + 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); +} + +/* + * refcounted get/put for css_set objects + */ +static inline void get_css_set(struct css_set *cg) +{ + atomic_inc(&cg->refcount); +} + +static inline void put_css_set(struct css_set *cg) +{ + __put_css_set(cg, 0); +} + +static inline void put_css_set_taskexit(struct css_set *cg) +{ + __put_css_set(cg, 1); +} + +/* + * find_existing_css_set() is a helper for + * find_css_set(), and checks to see whether an existing + * css_set is suitable. + * + * 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 hlist_head *hhead; + struct hlist_node *node; + struct css_set *cg; + + /* 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 & (1UL << 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]; + } + } + + hhead = css_set_hash(template); + hlist_for_each_entry(cg, node, hhead, hlist) { + if (!memcmp(template, cg->subsys, sizeof(cg->subsys))) { + /* All subsystems matched */ + return cg; + } + } + + /* No existing cgroup group matched */ + return NULL; +} + +static void free_cg_links(struct list_head *tmp) +{ + struct cg_cgroup_link *link; + struct cg_cgroup_link *saved_link; + + list_for_each_entry_safe(link, saved_link, tmp, cgrp_link_list) { + list_del(&link->cgrp_link_list); + kfree(link); + } +} + +/* + * 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) { + free_cg_links(tmp); + return -ENOMEM; + } + list_add(&link->cgrp_link_list, tmp); + } + return 0; +} + +/* + * 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; + + struct hlist_head *hhead; + + /* First see if we already have a cgroup group that matches + * the desired set */ + read_lock(&css_set_lock); + res = find_existing_css_set(oldcg, cgrp, template); + if (res) + get_css_set(res); + read_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; + } + + atomic_set(&res->refcount, 1); + INIT_LIST_HEAD(&res->cg_links); + INIT_LIST_HEAD(&res->tasks); + INIT_HLIST_NODE(&res->hlist); + + /* 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)); + + css_set_count++; + + /* Add this cgroup group to the hash table */ + hhead = css_set_hash(res->subsys); + hlist_add_head(&res->hlist, hhead); + + 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. @@ -142,7 +489,7 @@ list_for_each_entry(_root, &roots, root_list) * 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 + * cgroup_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 @@ -151,17 +498,13 @@ list_for_each_entry(_root, &roots, root_list) * 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. + * to the 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 @@ -173,26 +516,23 @@ list_for_each_entry(_root, &roots, root_list) * 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 + * cgroup_attach_task(), which overwrites one tasks cgroup pointer with + * another. It does so using cgroup_mutex, 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 + * in cgroup_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() + * update of a tasks cgroup pointer by cgroup_attach_task() */ -static DEFINE_MUTEX(cgroup_mutex); - /** * cgroup_lock - lock out any changes to cgroup structures * */ - void cgroup_lock(void) { mutex_lock(&cgroup_mutex); @@ -203,7 +543,6 @@ void cgroup_lock(void) * * Undo the lock taken in a previous cgroup_lock() call. */ - void cgroup_unlock(void) { mutex_unlock(&cgroup_mutex); @@ -218,20 +557,22 @@ void cgroup_unlock(void) 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 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_AND_WRITEBACK, +}; 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_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; @@ -239,13 +580,51 @@ static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb) return inode; } +/* + * Call subsys's pre_destroy handler. + * This is called before css refcnt check. + */ +static void cgroup_call_pre_destroy(struct cgroup *cgrp) +{ + struct cgroup_subsys *ss; + for_each_subsys(cgrp->root, ss) + if (ss->pre_destroy && cgrp->subsys[ss->subsys_id]) + ss->pre_destroy(ss, cgrp); + return; +} + 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); + struct cgroup *cgrp = dentry->d_fsdata; + struct cgroup_subsys *ss; + 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(); + + mutex_lock(&cgroup_mutex); + /* + * Release the subsystem state objects. + */ + for_each_subsys(cgrp->root, ss) { + if (cgrp->subsys[ss->subsys_id]) + ss->destroy(ss, cgrp); + } + + cgrp->root->number_of_cgroups--; + mutex_unlock(&cgroup_mutex); + + /* Drop the active superblock reference that we took when we + * created the cgroup */ + deactivate_super(cgrp->root->sb); + + kfree(cgrp); } iput(inode); } @@ -302,14 +681,14 @@ static int rebind_subsystems(struct cgroupfs_root *root, unsigned long final_bits) { unsigned long added_bits, removed_bits; - struct cgroup *cont = &root->top_cgroup; + 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; + unsigned long bit = 1UL << i; struct cgroup_subsys *ss = subsys[i]; if (!(bit & added_bits)) continue; @@ -323,7 +702,7 @@ static int rebind_subsystems(struct cgroupfs_root *root, * 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)) + if (root->number_of_cgroups > 1) return -EBUSY; /* Process each subsystem */ @@ -332,32 +711,32 @@ static int rebind_subsystems(struct cgroupfs_root *root, unsigned long bit = 1UL << i; if (bit & added_bits) { /* We're binding this subsystem to this hierarchy */ - BUG_ON(cont->subsys[i]); + BUG_ON(cgrp->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; + 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, cont); + ss->bind(ss, cgrp); } 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); + 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; - cont->subsys[i] = NULL; + 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(!cont->subsys[i]); + BUG_ON(!cgrp->subsys[i]); } else { /* Subsystem state shouldn't exist */ - BUG_ON(cont->subsys[i]); + BUG_ON(cgrp->subsys[i]); } } root->subsys_bits = root->actual_subsys_bits = final_bits; @@ -376,6 +755,8 @@ static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs) 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; } @@ -383,6 +764,7 @@ static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs) struct cgroup_sb_opts { unsigned long subsys_bits; unsigned long flags; + char *release_agent; }; /* Convert a hierarchy specifier into a bitmask of subsystems and @@ -394,21 +776,39 @@ static int parse_cgroupfs_options(char *data, 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; + /* Add all non-disabled subsystems */ + int i; + opts->subsys_bits = 0; + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + if (!ss->disabled) + opts->subsys_bits |= 1ul << i; + } } 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); + if (!ss->disabled) + set_bit(i, &opts->subsys_bits); break; } } @@ -428,10 +828,10 @@ 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 *cgrp = &root->top_cgroup; struct cgroup_sb_opts opts; - mutex_lock(&cont->dentry->d_inode->i_mutex); + mutex_lock(&cgrp->dentry->d_inode->i_mutex); mutex_lock(&cgroup_mutex); /* See what subsystems are wanted */ @@ -449,11 +849,15 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data) /* (re)populate subsystem files */ if (!ret) - cgroup_populate_dir(cont); + 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(&cont->dentry->d_inode->i_mutex); + mutex_unlock(&cgrp->dentry->d_inode->i_mutex); return ret; } @@ -464,16 +868,23 @@ static struct super_operations cgroup_ops = { .remount_fs = cgroup_remount, }; +static void init_cgroup_housekeeping(struct cgroup *cgrp) +{ + INIT_LIST_HEAD(&cgrp->sibling); + INIT_LIST_HEAD(&cgrp->children); + INIT_LIST_HEAD(&cgrp->css_sets); + INIT_LIST_HEAD(&cgrp->release_list); + init_rwsem(&cgrp->pids_mutex); +} static void init_cgroup_root(struct cgroupfs_root *root) { - struct cgroup *cont = &root->top_cgroup; + struct cgroup *cgrp = &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); + cgrp->root = root; + cgrp->top_cgroup = cgrp; + init_cgroup_housekeeping(cgrp); } static int cgroup_test_super(struct super_block *sb, void *data) @@ -521,7 +932,6 @@ static int cgroup_get_rootdir(struct super_block *sb) 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) */ @@ -543,19 +953,30 @@ static int cgroup_get_sb(struct file_system_type *fs_type, int ret = 0; struct super_block *sb; struct cgroupfs_root *root; + struct list_head tmp_cg_links; /* First find the desired set of subsystems */ ret = parse_cgroupfs_options(data, &opts); - if (ret) + if (ret) { + if (opts.release_agent) + kfree(opts.release_agent); return ret; + } root = kzalloc(sizeof(*root), GFP_KERNEL); - if (!root) + if (!root) { + if (opts.release_agent) + kfree(opts.release_agent); 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); @@ -571,49 +992,89 @@ static int cgroup_get_sb(struct file_system_type *fs_type, root = NULL; } else { /* New superblock */ - struct cgroup *cont = &root->top_cgroup; + struct cgroup *cgrp = &root->top_cgroup; + struct inode *inode; + int i; 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); - goto drop_new_super; + mutex_unlock(&inode->i_mutex); + goto free_cg_links; } /* 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; - BUG_ON(!list_empty(&cont->sibling)); - BUG_ON(!list_empty(&cont->children)); + /* Link the top cgroup in this hierarchy into all + * the css_set objects */ + write_lock(&css_set_lock); + for (i = 0; i < CSS_SET_TABLE_SIZE; i++) { + struct hlist_head *hhead = &css_set_table[i]; + struct hlist_node *node; + struct css_set *cg; + + hlist_for_each_entry(cg, node, hhead, hlist) { + struct cg_cgroup_link *link; + + 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); + } + } + 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); - /* - * 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); + cgroup_populate_dir(cgrp); + mutex_unlock(&inode->i_mutex); mutex_unlock(&cgroup_mutex); } return simple_set_mnt(mnt, sb); + free_cg_links: + free_cg_links(&tmp_cg_links); drop_new_super: up_write(&sb->s_umount); deactivate_super(sb); @@ -622,14 +1083,16 @@ static int cgroup_get_sb(struct file_system_type *fs_type, static void cgroup_kill_sb(struct super_block *sb) { struct cgroupfs_root *root = sb->s_fs_info; - struct cgroup *cont = &root->top_cgroup; + struct cgroup *cgrp = &root->top_cgroup; int ret; + struct cg_cgroup_link *link; + struct cg_cgroup_link *saved_link; BUG_ON(!root); BUG_ON(root->number_of_cgroups != 1); - BUG_ON(!list_empty(&cont->children)); - BUG_ON(!list_empty(&cont->sibling)); + BUG_ON(!list_empty(&cgrp->children)); + BUG_ON(!list_empty(&cgrp->sibling)); mutex_lock(&cgroup_mutex); @@ -638,8 +1101,24 @@ static void cgroup_kill_sb(struct super_block *sb) { /* Shouldn't be able to fail ... */ BUG_ON(ret); - if (!list_empty(&root->root_list)) + /* + * Release all the links from css_sets to this hierarchy's + * root cgroup + */ + write_lock(&css_set_lock); + + list_for_each_entry_safe(link, saved_link, &cgrp->css_sets, + 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); @@ -652,7 +1131,7 @@ static struct file_system_type cgroup_fs_type = { .kill_sb = cgroup_kill_sb, }; -static inline struct cgroup *__d_cont(struct dentry *dentry) +static inline struct cgroup *__d_cgrp(struct dentry *dentry) { return dentry->d_fsdata; } @@ -662,15 +1141,20 @@ static inline struct cftype *__d_cft(struct dentry *dentry) return dentry->d_fsdata; } -/* - * Called with cgroup_mutex held. Writes path of cgroup into buf. +/** + * cgroup_path - generate the path of a cgroup + * @cgrp: the cgroup in question + * @buf: the buffer to write the path into + * @buflen: the length of the buffer + * + * 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) +int cgroup_path(const struct cgroup *cgrp, char *buf, int buflen) { char *start; - if (cont == dummytop) { + if (cgrp == dummytop) { /* * Inactive subsystems have no dentry for their root * cgroup @@ -683,14 +1167,14 @@ int cgroup_path(const struct cgroup *cont, char *buf, int buflen) *--start = '\0'; for (;;) { - int len = cont->dentry->d_name.len; + int len = cgrp->dentry->d_name.len; if ((start -= len) < buf) return -ENAMETOOLONG; - memcpy(start, cont->dentry->d_name.name, len); - cont = cont->parent; - if (!cont) + memcpy(start, cgrp->dentry->d_name.name, len); + cgrp = cgrp->parent; + if (!cgrp) break; - if (!cont->parent) + if (!cgrp->parent) continue; if (--start < buf) return -ENAMETOOLONG; @@ -700,80 +1184,405 @@ int cgroup_path(const struct cgroup *cont, char *buf, int buflen) return 0; } -/* The various types of files and directories in a cgroup file system */ - -enum cgroup_filetype { - FILE_ROOT, - FILE_DIR, - FILE_TASKLIST, -}; +/* + * Return the first subsystem attached to a cgroup's hierarchy, and + * its subsystem id. + */ -static ssize_t cgroup_file_write(struct file *file, const char __user *buf, - size_t nbytes, loff_t *ppos) +static void get_first_subsys(const struct cgroup *cgrp, + struct cgroup_subsys_state **css, int *subsys_id) { - 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); + 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; } -static ssize_t cgroup_read_uint(struct cgroup *cont, struct cftype *cft, - struct file *file, - char __user *buf, size_t nbytes, - loff_t *ppos) +/** + * cgroup_attach_task - attach task 'tsk' to cgroup 'cgrp' + * @cgrp: the cgroup the task is attaching to + * @tsk: the task to be attached + * + * Call holding cgroup_mutex. May take task_lock of + * the task 'tsk' during call. + */ +int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) { - char tmp[64]; - u64 val = cft->read_uint(cont, cft); - int len = sprintf(tmp, "%llu\n", (unsigned long long) val); + 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; - return simple_read_from_buffer(buf, nbytes, ppos, tmp, len); -} + get_first_subsys(cgrp, NULL, &subsys_id); -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); + /* Nothing to do if the task is already in that cgroup */ + oldcgrp = task_cgroup(tsk, subsys_id); + if (cgrp == oldcgrp) + return 0; - if (!cft) - return -ENODEV; + for_each_subsys(root, ss) { + if (ss->can_attach) { + retval = ss->can_attach(ss, cgrp, tsk); + if (retval) + return retval; + } + } - 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; + /* + * 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; } -static int cgroup_file_open(struct inode *inode, struct file *file) +/* + * Attach task with pid 'pid' to cgroup 'cgrp'. Call with cgroup_mutex + * held. May take task_lock of task + */ +static int attach_task_by_pid(struct cgroup *cgrp, u64 pid) { - int err; - struct cftype *cft; + struct task_struct *tsk; + const struct cred *cred = current_cred(), *tcred; + int ret; - err = generic_file_open(inode, file); - if (err) - return err; + if (pid) { + rcu_read_lock(); + tsk = find_task_by_vpid(pid); + if (!tsk || tsk->flags & PF_EXITING) { + rcu_read_unlock(); + return -ESRCH; + } - cft = __d_cft(file->f_dentry); - if (!cft) - return -ENODEV; - if (cft->open) - err = cft->open(inode, file); - else - err = 0; + tcred = __task_cred(tsk); + if (cred->euid && + cred->euid != tcred->uid && + cred->euid != tcred->suid) { + rcu_read_unlock(); + return -EACCES; + } + get_task_struct(tsk); + rcu_read_unlock(); + } else { + tsk = current; + get_task_struct(tsk); + } - return err; + ret = cgroup_attach_task(cgrp, tsk); + put_task_struct(tsk); + return ret; } -static int cgroup_file_release(struct inode *inode, struct file *file) +static int cgroup_tasks_write(struct cgroup *cgrp, struct cftype *cft, u64 pid) { - struct cftype *cft = __d_cft(file->f_dentry); - if (cft->release) + int ret; + if (!cgroup_lock_live_group(cgrp)) + return -ENODEV; + ret = attach_task_by_pid(cgrp, pid); + cgroup_unlock(); + 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_RELEASE_AGENT, +}; + +/** + * cgroup_lock_live_group - take cgroup_mutex and check that cgrp is alive. + * @cgrp: the cgroup to be checked for liveness + * + * On success, returns true; the lock should be later released with + * cgroup_unlock(). On failure returns false with no lock held. + */ +bool cgroup_lock_live_group(struct cgroup *cgrp) +{ + mutex_lock(&cgroup_mutex); + if (cgroup_is_removed(cgrp)) { + mutex_unlock(&cgroup_mutex); + return false; + } + return true; +} + +static int cgroup_release_agent_write(struct cgroup *cgrp, struct cftype *cft, + const char *buffer) +{ + BUILD_BUG_ON(sizeof(cgrp->root->release_agent_path) < PATH_MAX); + if (!cgroup_lock_live_group(cgrp)) + return -ENODEV; + strcpy(cgrp->root->release_agent_path, buffer); + cgroup_unlock(); + return 0; +} + +static int cgroup_release_agent_show(struct cgroup *cgrp, struct cftype *cft, + struct seq_file *seq) +{ + if (!cgroup_lock_live_group(cgrp)) + return -ENODEV; + seq_puts(seq, cgrp->root->release_agent_path); + seq_putc(seq, '\n'); + cgroup_unlock(); + return 0; +} + +/* A buffer size big enough for numbers or short strings */ +#define CGROUP_LOCAL_BUFFER_SIZE 64 + +static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft, + struct file *file, + const char __user *userbuf, + size_t nbytes, loff_t *unused_ppos) +{ + char buffer[CGROUP_LOCAL_BUFFER_SIZE]; + int retval = 0; + 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 */ + strstrip(buffer); + if (cft->write_u64) { + u64 val = simple_strtoull(buffer, &end, 0); + if (*end) + return -EINVAL; + retval = cft->write_u64(cgrp, cft, val); + } else { + s64 val = simple_strtoll(buffer, &end, 0); + if (*end) + return -EINVAL; + retval = cft->write_s64(cgrp, cft, val); + } + if (!retval) + retval = nbytes; + return retval; +} + +static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft, + struct file *file, + const char __user *userbuf, + size_t nbytes, loff_t *unused_ppos) +{ + char local_buffer[CGROUP_LOCAL_BUFFER_SIZE]; + int retval = 0; + size_t max_bytes = cft->max_write_len; + char *buffer = local_buffer; + + if (!max_bytes) + max_bytes = sizeof(local_buffer) - 1; + if (nbytes >= max_bytes) + return -E2BIG; + /* Allocate a dynamic buffer if we need one */ + if (nbytes >= sizeof(local_buffer)) { + buffer = kmalloc(nbytes + 1, GFP_KERNEL); + if (buffer == NULL) + return -ENOMEM; + } + if (nbytes && copy_from_user(buffer, userbuf, nbytes)) { + retval = -EFAULT; + goto out; + } + + buffer[nbytes] = 0; /* nul-terminate */ + strstrip(buffer); + retval = cft->write_string(cgrp, cft, buffer); + if (!retval) + retval = nbytes; +out: + if (buffer != local_buffer) + 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 || cgroup_is_removed(cgrp)) + return -ENODEV; + if (cft->write) + return cft->write(cgrp, cft, file, buf, nbytes, ppos); + if (cft->write_u64 || cft->write_s64) + return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos); + if (cft->write_string) + return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos); + if (cft->trigger) { + int ret = cft->trigger(cgrp, (unsigned int)cft->private); + return ret ? ret : nbytes; + } + return -EINVAL; +} + +static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft, + struct file *file, + char __user *buf, size_t nbytes, + loff_t *ppos) +{ + char tmp[CGROUP_LOCAL_BUFFER_SIZE]; + u64 val = cft->read_u64(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_read_s64(struct cgroup *cgrp, struct cftype *cft, + struct file *file, + char __user *buf, size_t nbytes, + loff_t *ppos) +{ + char tmp[CGROUP_LOCAL_BUFFER_SIZE]; + s64 val = cft->read_s64(cgrp, cft); + int len = sprintf(tmp, "%lld\n", (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 *cgrp = __d_cgrp(file->f_dentry->d_parent); + + if (!cft || cgroup_is_removed(cgrp)) + return -ENODEV; + + if (cft->read) + return cft->read(cgrp, cft, file, buf, nbytes, ppos); + if (cft->read_u64) + return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos); + if (cft->read_s64) + return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos); + return -EINVAL; +} + +/* + * seqfile ops/methods for returning structured data. Currently just + * supports string->u64 maps, but can be extended in future. + */ + +struct cgroup_seqfile_state { + struct cftype *cft; + struct cgroup *cgroup; +}; + +static int cgroup_map_add(struct cgroup_map_cb *cb, const char *key, u64 value) +{ + struct seq_file *sf = cb->state; + return seq_printf(sf, "%s %llu\n", key, (unsigned long long)value); +} + +static int cgroup_seqfile_show(struct seq_file *m, void *arg) +{ + struct cgroup_seqfile_state *state = m->private; + struct cftype *cft = state->cft; + if (cft->read_map) { + struct cgroup_map_cb cb = { + .fill = cgroup_map_add, + .state = m, + }; + return cft->read_map(state->cgroup, cft, &cb); + } + return cft->read_seq_string(state->cgroup, cft, m); +} + +static int cgroup_seqfile_release(struct inode *inode, struct file *file) +{ + struct seq_file *seq = file->private_data; + kfree(seq->private); + return single_release(inode, file); +} + +static struct file_operations cgroup_seqfile_operations = { + .read = seq_read, + .write = cgroup_file_write, + .llseek = seq_lseek, + .release = cgroup_seqfile_release, +}; + +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->read_map || cft->read_seq_string) { + struct cgroup_seqfile_state *state = + kzalloc(sizeof(*state), GFP_USER); + if (!state) + return -ENOMEM; + state->cft = cft; + state->cgroup = __d_cgrp(file->f_dentry->d_parent); + file->f_op = &cgroup_seqfile_operations; + err = single_open(file, cgroup_seqfile_show, state); + if (err < 0) + kfree(state); + } else 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; } @@ -835,7 +1644,7 @@ static int cgroup_create_file(struct dentry *dentry, int mode, /* start with the directory inode held, so that we can * populate it without racing with another mkdir */ - mutex_lock(&inode->i_mutex); + mutex_lock_nested(&inode->i_mutex, I_MUTEX_CHILD); } else if (S_ISREG(mode)) { inode->i_size = 0; inode->i_fop = &cgroup_file_operations; @@ -847,25 +1656,24 @@ static int cgroup_create_file(struct dentry *dentry, int mode, } /* - * 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. + * 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 *cont, struct dentry *dentry, +static int cgroup_create_dir(struct cgroup *cgrp, 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); + parent = cgrp->parent->dentry; + error = cgroup_create_file(dentry, S_IFDIR | mode, cgrp->root->sb); if (!error) { - dentry->d_fsdata = cont; + dentry->d_fsdata = cgrp; inc_nlink(parent->d_inode); - cont->dentry = dentry; + cgrp->dentry = dentry; dget(dentry); } dput(dentry); @@ -873,16 +1681,16 @@ static int cgroup_create_dir(struct cgroup *cont, struct dentry *dentry, return error; } -int cgroup_add_file(struct cgroup *cont, +int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys, const struct cftype *cft) { - struct dentry *dir = cont->dentry; + 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, &cont->root->flags)) { + if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) { strcpy(name, subsys->name); strcat(name, "."); } @@ -891,7 +1699,7 @@ int cgroup_add_file(struct cgroup *cont, dentry = lookup_one_len(name, dir, strlen(name)); if (!IS_ERR(dentry)) { error = cgroup_create_file(dentry, 0644 | S_IFREG, - cont->root->sb); + cgrp->root->sb); if (!error) dentry->d_fsdata = (void *)cft; dput(dentry); @@ -900,30 +1708,613 @@ int cgroup_add_file(struct cgroup *cont, return error; } -int cgroup_add_files(struct cgroup *cont, +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(cont, subsys, &cft[i]); + err = cgroup_add_file(cgrp, subsys, &cft[i]); if (err) return err; } return 0; } -static int cgroup_populate_dir(struct cgroup *cont) +/** + * cgroup_task_count - count the number of tasks in a cgroup. + * @cgrp: the cgroup in question + * + * Return the number of tasks in the cgroup. + */ +int cgroup_task_count(const struct cgroup *cgrp) +{ + int count = 0; + struct cg_cgroup_link *link; + + read_lock(&css_set_lock); + list_for_each_entry(link, &cgrp->css_sets, cgrp_link_list) { + count += atomic_read(&link->cg->refcount); + } + 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; +} + +/* + * To reduce the fork() overhead for systems that are not actually + * using their cgroups capability, we don't maintain the lists running + * through each css_set to its tasks until we see the list actually + * used - in other words after the first call to cgroup_iter_start(). + * + * The tasklist_lock is not held here, as do_each_thread() and + * while_each_thread() are protected by RCU. + */ +static void cgroup_enable_task_cg_lists(void) +{ + struct task_struct *p, *g; + write_lock(&css_set_lock); + use_task_css_set_links = 1; + do_each_thread(g, p) { + task_lock(p); + /* + * We should check if the process is exiting, otherwise + * it will race with cgroup_exit() in that the list + * entry won't be deleted though the process has exited. + */ + if (!(p->flags & PF_EXITING) && 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); +} + +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) + cgroup_enable_task_cg_lists(); + + 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); +} + +static inline int started_after_time(struct task_struct *t1, + struct timespec *time, + struct task_struct *t2) +{ + int start_diff = timespec_compare(&t1->start_time, time); + if (start_diff > 0) { + return 1; + } else if (start_diff < 0) { + return 0; + } else { + /* + * Arbitrarily, if two processes started at the same + * time, we'll say that the lower pointer value + * started first. Note that t2 may have exited by now + * so this may not be a valid pointer any longer, but + * that's fine - it still serves to distinguish + * between two tasks started (effectively) simultaneously. + */ + return t1 > t2; + } +} + +/* + * This function is a callback from heap_insert() and is used to order + * the heap. + * In this case we order the heap in descending task start time. + */ +static inline int started_after(void *p1, void *p2) +{ + struct task_struct *t1 = p1; + struct task_struct *t2 = p2; + return started_after_time(t1, &t2->start_time, t2); +} + +/** + * cgroup_scan_tasks - iterate though all the tasks in a cgroup + * @scan: struct cgroup_scanner containing arguments for the scan + * + * Arguments include pointers to callback functions test_task() and + * process_task(). + * Iterate through all the tasks in a cgroup, calling test_task() for each, + * and if it returns true, call process_task() for it also. + * The test_task pointer may be NULL, meaning always true (select all tasks). + * Effectively duplicates cgroup_iter_{start,next,end}() + * but does not lock css_set_lock for the call to process_task(). + * The struct cgroup_scanner may be embedded in any structure of the caller's + * creation. + * It is guaranteed that process_task() will act on every task that + * is a member of the cgroup for the duration of this call. This + * function may or may not call process_task() for tasks that exit + * or move to a different cgroup during the call, or are forked or + * move into the cgroup during the call. + * + * Note that test_task() may be called with locks held, and may in some + * situations be called multiple times for the same task, so it should + * be cheap. + * If the heap pointer in the struct cgroup_scanner is non-NULL, a heap has been + * pre-allocated and will be used for heap operations (and its "gt" member will + * be overwritten), else a temporary heap will be used (allocation of which + * may cause this function to fail). + */ +int cgroup_scan_tasks(struct cgroup_scanner *scan) +{ + int retval, i; + struct cgroup_iter it; + struct task_struct *p, *dropped; + /* Never dereference latest_task, since it's not refcounted */ + struct task_struct *latest_task = NULL; + struct ptr_heap tmp_heap; + struct ptr_heap *heap; + struct timespec latest_time = { 0, 0 }; + + if (scan->heap) { + /* The caller supplied our heap and pre-allocated its memory */ + heap = scan->heap; + heap->gt = &started_after; + } else { + /* We need to allocate our own heap memory */ + heap = &tmp_heap; + retval = heap_init(heap, PAGE_SIZE, GFP_KERNEL, &started_after); + if (retval) + /* cannot allocate the heap */ + return retval; + } + + again: + /* + * Scan tasks in the cgroup, using the scanner's "test_task" callback + * to determine which are of interest, and using the scanner's + * "process_task" callback to process any of them that need an update. + * Since we don't want to hold any locks during the task updates, + * gather tasks to be processed in a heap structure. + * The heap is sorted by descending task start time. + * If the statically-sized heap fills up, we overflow tasks that + * started later, and in future iterations only consider tasks that + * started after the latest task in the previous pass. This + * guarantees forward progress and that we don't miss any tasks. + */ + heap->size = 0; + cgroup_iter_start(scan->cg, &it); + while ((p = cgroup_iter_next(scan->cg, &it))) { + /* + * Only affect tasks that qualify per the caller's callback, + * if he provided one + */ + if (scan->test_task && !scan->test_task(p, scan)) + continue; + /* + * Only process tasks that started after the last task + * we processed + */ + if (!started_after_time(p, &latest_time, latest_task)) + continue; + dropped = heap_insert(heap, p); + if (dropped == NULL) { + /* + * The new task was inserted; the heap wasn't + * previously full + */ + get_task_struct(p); + } else if (dropped != p) { + /* + * The new task was inserted, and pushed out a + * different task + */ + get_task_struct(p); + put_task_struct(dropped); + } + /* + * Else the new task was newer than anything already in + * the heap and wasn't inserted + */ + } + cgroup_iter_end(scan->cg, &it); + + if (heap->size) { + for (i = 0; i < heap->size; i++) { + struct task_struct *q = heap->ptrs[i]; + if (i == 0) { + latest_time = q->start_time; + latest_task = q; + } + /* Process the task per the caller's callback */ + scan->process_task(q, scan); + put_task_struct(q); + } + /* + * If we had to process any tasks at all, scan again + * in case some of them were in the middle of forking + * children that didn't get processed. + * Not the most efficient way to do it, but it avoids + * having to take callback_mutex in the fork path + */ + goto again; + } + if (heap == &tmp_heap) + heap_free(&tmp_heap); + return 0; +} + +/* + * 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. + * + */ + +/* + * 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_vnr(tsk); + } + cgroup_iter_end(cgrp, &it); + return n; +} + +/** + * cgroupstats_build - build and fill cgroupstats + * @stats: cgroupstats to fill information into + * @dentry: A dentry entry belonging to the cgroup for which stats have + * been requested. + * + * Build and fill cgroupstats so that taskstats can export it to user + * space. + */ +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, + * and make sure it's a directory. + */ + if (dentry->d_sb->s_op != &cgroup_ops || + !S_ISDIR(dentry->d_inode->i_mode)) + 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; +} + + +/* + * seq_file methods for the "tasks" file. The seq_file position is the + * next pid to display; the seq_file iterator is a pointer to the pid + * in the cgroup->tasks_pids array. + */ + +static void *cgroup_tasks_start(struct seq_file *s, loff_t *pos) +{ + /* + * Initially we receive a position value that corresponds to + * one more than the last pid shown (or 0 on the first call or + * after a seek to the start). Use a binary-search to find the + * next pid to display, if any + */ + struct cgroup *cgrp = s->private; + int index = 0, pid = *pos; + int *iter; + + down_read(&cgrp->pids_mutex); + if (pid) { + int end = cgrp->pids_length; + + while (index < end) { + int mid = (index + end) / 2; + if (cgrp->tasks_pids[mid] == pid) { + index = mid; + break; + } else if (cgrp->tasks_pids[mid] <= pid) + index = mid + 1; + else + end = mid; + } + } + /* If we're off the end of the array, we're done */ + if (index >= cgrp->pids_length) + return NULL; + /* Update the abstract position to be the actual pid that we found */ + iter = cgrp->tasks_pids + index; + *pos = *iter; + return iter; +} + +static void cgroup_tasks_stop(struct seq_file *s, void *v) +{ + struct cgroup *cgrp = s->private; + up_read(&cgrp->pids_mutex); +} + +static void *cgroup_tasks_next(struct seq_file *s, void *v, loff_t *pos) +{ + struct cgroup *cgrp = s->private; + int *p = v; + int *end = cgrp->tasks_pids + cgrp->pids_length; + + /* + * Advance to the next pid in the array. If this goes off the + * end, we're done + */ + p++; + if (p >= end) { + return NULL; + } else { + *pos = *p; + return p; + } +} + +static int cgroup_tasks_show(struct seq_file *s, void *v) +{ + return seq_printf(s, "%d\n", *(int *)v); +} + +static struct seq_operations cgroup_tasks_seq_operations = { + .start = cgroup_tasks_start, + .stop = cgroup_tasks_stop, + .next = cgroup_tasks_next, + .show = cgroup_tasks_show, +}; + +static void release_cgroup_pid_array(struct cgroup *cgrp) +{ + down_write(&cgrp->pids_mutex); + BUG_ON(!cgrp->pids_use_count); + if (!--cgrp->pids_use_count) { + kfree(cgrp->tasks_pids); + cgrp->tasks_pids = NULL; + cgrp->pids_length = 0; + } + up_write(&cgrp->pids_mutex); +} + +static int cgroup_tasks_release(struct inode *inode, struct file *file) +{ + struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent); + + if (!(file->f_mode & FMODE_READ)) + return 0; + + release_cgroup_pid_array(cgrp); + return seq_release(inode, file); +} + +static struct file_operations cgroup_tasks_operations = { + .read = seq_read, + .llseek = seq_lseek, + .write = cgroup_file_write, + .release = cgroup_tasks_release, +}; + +/* + * Handle an open on 'tasks' file. Prepare an array containing the + * process id's of tasks currently attached to the cgroup being opened. + */ + +static int cgroup_tasks_open(struct inode *unused, struct file *file) +{ + struct cgroup *cgrp = __d_cgrp(file->f_dentry->d_parent); + pid_t *pidarray; + int npids; + int retval; + + /* Nothing to do for write-only files */ + if (!(file->f_mode & FMODE_READ)) + return 0; + + /* + * 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); + pidarray = kmalloc(npids * sizeof(pid_t), GFP_KERNEL); + if (!pidarray) + return -ENOMEM; + npids = pid_array_load(pidarray, npids, cgrp); + sort(pidarray, npids, sizeof(pid_t), cmppid, NULL); + + /* + * Store the array in the cgroup, freeing the old + * array if necessary + */ + down_write(&cgrp->pids_mutex); + kfree(cgrp->tasks_pids); + cgrp->tasks_pids = pidarray; + cgrp->pids_length = npids; + cgrp->pids_use_count++; + up_write(&cgrp->pids_mutex); + + file->f_op = &cgroup_tasks_operations; + + retval = seq_open(file, &cgroup_tasks_seq_operations); + if (retval) { + release_cgroup_pid_array(cgrp); + return retval; + } + ((struct seq_file *)file->private_data)->private = cgrp; + return 0; +} + +static u64 cgroup_read_notify_on_release(struct cgroup *cgrp, + struct cftype *cft) +{ + return notify_on_release(cgrp); +} + +static int cgroup_write_notify_on_release(struct cgroup *cgrp, + struct cftype *cft, + u64 val) +{ + clear_bit(CGRP_RELEASABLE, &cgrp->flags); + if (val) + set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); + else + clear_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); + return 0; +} + +/* + * for the common functions, 'private' gives the type of file + */ +static struct cftype files[] = { + { + .name = "tasks", + .open = cgroup_tasks_open, + .write_u64 = cgroup_tasks_write, + .release = cgroup_tasks_release, + .private = FILE_TASKLIST, + }, + + { + .name = "notify_on_release", + .read_u64 = cgroup_read_notify_on_release, + .write_u64 = cgroup_write_notify_on_release, + .private = FILE_NOTIFY_ON_RELEASE, + }, +}; + +static struct cftype cft_release_agent = { + .name = "release_agent", + .read_seq_string = cgroup_release_agent_show, + .write_string = cgroup_release_agent_write, + .max_write_len = PATH_MAX, + .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(cont->dentry); + 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(cont->root, ss) { - if (ss->populate && (err = ss->populate(ss, cont)) < 0) + for_each_subsys(cgrp->root, ss) { + if (ss->populate && (err = ss->populate(ss, cgrp)) < 0) return err; } @@ -932,37 +2323,36 @@ static int cgroup_populate_dir(struct cgroup *cont) static void init_cgroup_css(struct cgroup_subsys_state *css, struct cgroup_subsys *ss, - struct cgroup *cont) + struct cgroup *cgrp) { - css->cgroup = cont; + css->cgroup = cgrp; atomic_set(&css->refcnt, 0); css->flags = 0; - if (cont == dummytop) + if (cgrp == dummytop) set_bit(CSS_ROOT, &css->flags); - BUG_ON(cont->subsys[ss->subsys_id]); - cont->subsys[ss->subsys_id] = css; + 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 + * cgroup_create - create a cgroup + * @parent: cgroup that will be parent of the new cgroup + * @dentry: dentry of the new cgroup + * @mode: mode to set on new inode * - * Must be called with the mutex on the parent inode held + * 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 cgroup *cgrp; 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) + cgrp = kzalloc(sizeof(*cgrp), GFP_KERNEL); + if (!cgrp) return -ENOMEM; /* Grab a reference on the superblock so the hierarchy doesn't @@ -974,51 +2364,52 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, mutex_lock(&cgroup_mutex); - cont->flags = 0; - INIT_LIST_HEAD(&cont->sibling); - INIT_LIST_HEAD(&cont->children); + init_cgroup_housekeeping(cgrp); + + cgrp->parent = parent; + cgrp->root = parent->root; + cgrp->top_cgroup = parent->top_cgroup; - cont->parent = parent; - cont->root = parent->root; - cont->top_cgroup = parent->top_cgroup; + if (notify_on_release(parent)) + set_bit(CGRP_NOTIFY_ON_RELEASE, &cgrp->flags); for_each_subsys(root, ss) { - struct cgroup_subsys_state *css = ss->create(ss, cont); + 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, cont); + init_cgroup_css(css, ss, cgrp); } - list_add(&cont->sibling, &cont->parent->children); + list_add(&cgrp->sibling, &cgrp->parent->children); root->number_of_cgroups++; - err = cgroup_create_dir(cont, dentry, mode); + 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(&cont->dentry->d_inode->i_mutex)); + BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex)); - err = cgroup_populate_dir(cont); + err = cgroup_populate_dir(cgrp); /* If err < 0, we have a half-filled directory - oh well ;) */ mutex_unlock(&cgroup_mutex); - mutex_unlock(&cont->dentry->d_inode->i_mutex); + mutex_unlock(&cgrp->dentry->d_inode->i_mutex); return 0; err_remove: - list_del(&cont->sibling); + list_del(&cgrp->sibling); root->number_of_cgroups--; err_destroy: for_each_subsys(root, ss) { - if (cont->subsys[ss->subsys_id]) - ss->destroy(ss, cont); + if (cgrp->subsys[ss->subsys_id]) + ss->destroy(ss, cgrp); } mutex_unlock(&cgroup_mutex); @@ -1026,7 +2417,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, /* Release the reference count that we took on the superblock */ deactivate_super(sb); - kfree(cont); + kfree(cgrp); return err; } @@ -1038,79 +2429,102 @@ static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, int mode) return cgroup_create(c_parent, dentry, mode | S_IFDIR); } +static 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 *cont = dentry->d_fsdata; + struct cgroup *cgrp = 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) { + if (atomic_read(&cgrp->count) != 0) { mutex_unlock(&cgroup_mutex); return -EBUSY; } - if (!list_empty(&cont->children)) { + if (!list_empty(&cgrp->children)) { mutex_unlock(&cgroup_mutex); return -EBUSY; } + mutex_unlock(&cgroup_mutex); + + /* + * Call pre_destroy handlers of subsys. Notify subsystems + * that rmdir() request comes. + */ + cgroup_call_pre_destroy(cgrp); - parent = cont->parent; - root = cont->root; + mutex_lock(&cgroup_mutex); + parent = cgrp->parent; + root = cgrp->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) { + if (atomic_read(&cgrp->count) + || !list_empty(&cgrp->children) + || cgroup_has_css_refs(cgrp)) { 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); + 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(&cont->sibling); - spin_lock(&cont->dentry->d_lock); - d = dget(cont->dentry); - cont->dentry = NULL; + list_del(&cgrp->sibling); + spin_lock(&cgrp->dentry->d_lock); + d = dget(cgrp->dentry); 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) +static void __init 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); + + printk(KERN_INFO "Initializing cgroup subsys %s\n", ss->name); /* Create the top cgroup state for this subsystem */ ss->root = &rootnode; @@ -1119,41 +2533,50 @@ static void cgroup_init_subsys(struct cgroup_subsys *ss) 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); + /* Update the init_css_set to contain a subsys + * pointer to this state - since the subsystem is + * newly registered, all tasks and hence the + * init_css_set is in the subsystem's top cgroup. */ + init_css_set.subsys[ss->subsys_id] = dummytop->subsys[ss->subsys_id]; need_forkexit_callback |= ss->fork || ss->exit; + need_mm_owner_callback |= !!ss->mm_owner_changed; + + /* At system boot, before all subsystems have been + * registered, no tasks have been forked, so we don't + * need to invoke fork callbacks here. */ + BUG_ON(!list_empty(&init_task.tasks)); ss->active = 1; } /** - * cgroup_init_early - initialize cgroups at system boot, and - * initialize any subsystems that request early init. + * cgroup_init_early - cgroup initialization at system boot + * + * Initialize cgroups at system boot, and initialize any + * subsystems that request early init. */ int __init cgroup_init_early(void) { int i; + atomic_set(&init_css_set.refcount, 1); + INIT_LIST_HEAD(&init_css_set.cg_links); + INIT_LIST_HEAD(&init_css_set.tasks); + INIT_HLIST_NODE(&init_css_set.hlist); + 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 < CSS_SET_TABLE_SIZE; i++) + INIT_HLIST_HEAD(&css_set_table[i]); for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { struct cgroup_subsys *ss = subsys[i]; @@ -1163,7 +2586,7 @@ int __init cgroup_init_early(void) BUG_ON(!ss->create); BUG_ON(!ss->destroy); if (ss->subsys_id != i) { - printk(KERN_ERR "Subsys %s id == %d\n", + printk(KERN_ERR "cgroup: Subsys %s id == %d\n", ss->name, ss->subsys_id); BUG(); } @@ -1175,13 +2598,20 @@ int __init cgroup_init_early(void) } /** - * cgroup_init - register cgroup filesystem and /proc file, and - * initialize any subsystems that didn't request early init. + * cgroup_init - cgroup initialization + * + * 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 hlist_head *hhead; + + 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]; @@ -1189,10 +2619,565 @@ int __init cgroup_init(void) cgroup_init_subsys(ss); } + /* Add init_css_set to the hash table */ + hhead = css_set_hash(init_css_set.subsys); + hlist_add_head(&init_css_set.hlist, hhead); + err = register_filesystem(&cgroup_fs_type); if (err < 0) goto out; + proc_create("cgroups", 0, NULL, &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//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 cgroup_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; + seq_printf(m, "%lu:", root->subsys_bits); + 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; + + seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\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\t%d\n", + ss->name, ss->root->subsys_bits, + ss->root->number_of_cgroups, !ss->disabled); + } + mutex_unlock(&cgroup_mutex); + return 0; +} + +static int cgroupstats_open(struct inode *inode, struct file *file) +{ + return single_open(file, proc_cgroupstats_show, NULL); +} + +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. + * @child: 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. cgroup_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 - run fork callbacks + * @child: the new task + * + * 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); + } + } +} + +#ifdef CONFIG_MM_OWNER +/** + * cgroup_mm_owner_callbacks - run callbacks when the mm->owner changes + * @p: the new owner + * + * Called on every change to mm->owner. mm_init_owner() does not + * invoke this routine, since it assigns the mm->owner the first time + * and does not change it. + * + * The callbacks are invoked with mmap_sem held in read mode. + */ +void cgroup_mm_owner_callbacks(struct task_struct *old, struct task_struct *new) +{ + struct cgroup *oldcgrp, *newcgrp = NULL; + + if (need_mm_owner_callback) { + int i; + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + oldcgrp = task_cgroup(old, ss->subsys_id); + if (new) + newcgrp = task_cgroup(new, ss->subsys_id); + if (oldcgrp == newcgrp) + continue; + if (ss->mm_owner_changed) + ss->mm_owner_changed(ss, oldcgrp, newcgrp, new); + } + } +} +#endif /* CONFIG_MM_OWNER */ + +/** + * cgroup_post_fork - called on a new task after adding it to the task list + * @child: the task in question + * + * 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 + * @run_callback: run exit callbacks? + * + * 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 cgroup_attach_task() attempts, or task is a failed + * fork, never visible to cgroup_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 - clone the cgroup the given subsystem is attached to + * @tsk: the task to be moved + * @subsys: the given subsystem + * @nodename: the name for the new cgroup + * + * 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, + char *nodename) +{ + struct dentry *dentry; + int ret = 0; + 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) { + mutex_unlock(&cgroup_mutex); + return 0; + } + cg = tsk->cgroups; + parent = task_cgroup(tsk, subsys->subsys_id); + + /* 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 + "cgroup: 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 = cgroup_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; +} + +/** + * cgroup_is_descendant - see if @cgrp is a descendant of current task's cgrp + * @cgrp: the cgroup in question + * + * 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 = NULL, *agentbuf = NULL; + 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) + goto continue_free; + if (cgroup_path(cgrp, pathbuf, PAGE_SIZE) < 0) + goto continue_free; + agentbuf = kstrdup(cgrp->root->release_agent_path, GFP_KERNEL); + if (!agentbuf) + goto continue_free; + + i = 0; + argv[i++] = agentbuf; + argv[i++] = 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); + mutex_lock(&cgroup_mutex); + continue_free: + kfree(pathbuf); + kfree(agentbuf); + spin_lock(&release_list_lock); + } + spin_unlock(&release_list_lock); + mutex_unlock(&cgroup_mutex); +} + +static int __init cgroup_disable(char *str) +{ + int i; + char *token; + + while ((token = strsep(&str, ",")) != NULL) { + if (!*token) + continue; + + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + struct cgroup_subsys *ss = subsys[i]; + + if (!strcmp(token, ss->name)) { + ss->disabled = 1; + printk(KERN_INFO "Disabling %s control group" + " subsystem\n", ss->name); + break; + } + } + } + return 1; +} +__setup("cgroup_disable=", cgroup_disable);