diff options
| -rw-r--r-- | Documentation/cgroups.txt | 526 | ||||
| -rw-r--r-- | include/linux/cgroup.h | 214 | ||||
| -rw-r--r-- | include/linux/cgroup_subsys.h | 10 | ||||
| -rw-r--r-- | include/linux/magic.h | 1 | ||||
| -rw-r--r-- | include/linux/sched.h | 34 | ||||
| -rw-r--r-- | init/Kconfig | 8 | ||||
| -rw-r--r-- | init/main.c | 3 | ||||
| -rw-r--r-- | kernel/Makefile | 1 | ||||
| -rw-r--r-- | kernel/cgroup.c | 1198 |
9 files changed, 1994 insertions, 1 deletions
diff --git a/Documentation/cgroups.txt b/Documentation/cgroups.txt new file mode 100644 index 0000000..4717887 --- /dev/null +++ b/Documentation/cgroups.txt @@ -0,0 +1,526 @@ + CGROUPS + ------- + +Written by Paul Menage <menage@google.com> based on Documentation/cpusets.txt + +Original copyright statements from cpusets.txt: +Portions Copyright (C) 2004 BULL SA. +Portions Copyright (c) 2004-2006 Silicon Graphics, Inc. +Modified by Paul Jackson <pj@sgi.com> +Modified by Christoph Lameter <clameter@sgi.com> + +CONTENTS: +========= + +1. Control Groups + 1.1 What are cgroups ? + 1.2 Why are cgroups needed ? + 1.3 How are cgroups implemented ? + 1.4 What does notify_on_release do ? + 1.5 How do I use cgroups ? +2. Usage Examples and Syntax + 2.1 Basic Usage + 2.2 Attaching processes +3. Kernel API + 3.1 Overview + 3.2 Synchronization + 3.3 Subsystem API +4. Questions + +1. Control Groups +========== + +1.1 What are cgroups ? +---------------------- + +Control Groups provide a mechanism for aggregating/partitioning sets of +tasks, and all their future children, into hierarchical groups with +specialized behaviour. + +Definitions: + +A *cgroup* associates a set of tasks with a set of parameters for one +or more subsystems. + +A *subsystem* is a module that makes use of the task grouping +facilities provided by cgroups to treat groups of tasks in +particular ways. A subsystem is typically a "resource controller" that +schedules a resource or applies per-cgroup limits, but it may be +anything that wants to act on a group of processes, e.g. a +virtualization subsystem. + +A *hierarchy* is a set of cgroups arranged in a tree, such that +every task in the system is in exactly one of the cgroups in the +hierarchy, and a set of subsystems; each subsystem has system-specific +state attached to each cgroup in the hierarchy. Each hierarchy has +an instance of the cgroup virtual filesystem associated with it. + +At any one time there may be multiple active hierachies of task +cgroups. Each hierarchy is a partition of all tasks in the system. + +User level code may create and destroy cgroups by name in an +instance of the cgroup virtual file system, specify and query to +which cgroup a task is assigned, and list the task pids assigned to +a cgroup. Those creations and assignments only affect the hierarchy +associated with that instance of the cgroup file system. + +On their own, the only use for cgroups is for simple job +tracking. The intention is that other subsystems hook into the generic +cgroup support to provide new attributes for cgroups, such as +accounting/limiting the resources which processes in a cgroup can +access. For example, cpusets (see Documentation/cpusets.txt) allows +you to associate a set of CPUs and a set of memory nodes with the +tasks in each cgroup. + +1.2 Why are cgroups needed ? +---------------------------- + +There are multiple efforts to provide process aggregations in the +Linux kernel, mainly for resource tracking purposes. Such efforts +include cpusets, CKRM/ResGroups, UserBeanCounters, and virtual server +namespaces. These all require the basic notion of a +grouping/partitioning of processes, with newly forked processes ending +in the same group (cgroup) as their parent process. + +The kernel cgroup patch provides the minimum essential kernel +mechanisms required to efficiently implement such groups. It has +minimal impact on the system fast paths, and provides hooks for +specific subsystems such as cpusets to provide additional behaviour as +desired. + +Multiple hierarchy support is provided to allow for situations where +the division of tasks into cgroups is distinctly different for +different subsystems - having parallel hierarchies allows each +hierarchy to be a natural division of tasks, without having to handle +complex combinations of tasks that would be present if several +unrelated subsystems needed to be forced into the same tree of +cgroups. + +At one extreme, each resource controller or subsystem could be in a +separate hierarchy; at the other extreme, all subsystems +would be attached to the same hierarchy. + +As an example of a scenario (originally proposed by vatsa@in.ibm.com) +that can benefit from multiple hierarchies, consider a large +university server with various users - students, professors, system +tasks etc. The resource planning for this server could be along the +following lines: + + CPU : Top cpuset + / \ + CPUSet1 CPUSet2 + | | + (Profs) (Students) + + In addition (system tasks) are attached to topcpuset (so + that they can run anywhere) with a limit of 20% + + Memory : Professors (50%), students (30%), system (20%) + + Disk : Prof (50%), students (30%), system (20%) + + Network : WWW browsing (20%), Network File System (60%), others (20%) + / \ + Prof (15%) students (5%) + +Browsers like firefox/lynx go into the WWW network class, while (k)nfsd go +into NFS network class. + +At the same time firefox/lynx will share an appropriate CPU/Memory class +depending on who launched it (prof/student). + +With the ability to classify tasks differently for different resources +(by putting those resource subsystems in different hierarchies) then +the admin can easily set up a script which receives exec notifications +and depending on who is launching the browser he can + + # echo browser_pid > /mnt/<restype>/<userclass>/tasks + +With only a single hierarchy, he now would potentially have to create +a separate cgroup for every browser launched and associate it with +approp network and other resource class. This may lead to +proliferation of such cgroups. + +Also lets say that the administrator would like to give enhanced network +access temporarily to a student's browser (since it is night and the user +wants to do online gaming :) OR give one of the students simulation +apps enhanced CPU power, + +With ability to write pids directly to resource classes, its just a +matter of : + + # echo pid > /mnt/network/<new_class>/tasks + (after some time) + # echo pid > /mnt/network/<orig_class>/tasks + +Without this ability, he would have to split the cgroup into +multiple separate ones and then associate the new cgroups with the +new resource classes. + + + +1.3 How are cgroups implemented ? +--------------------------------- + +Control Groups extends the kernel as follows: + + - Each task in the system has a reference-counted pointer to a + css_set. + + - A css_set contains a set of reference-counted pointers to + cgroup_subsys_state objects, one for each cgroup subsystem + registered in the system. There is no direct link from a task to + the cgroup of which it's a member in each hierarchy, but this + can be determined by following pointers through the + cgroup_subsys_state objects. This is because accessing the + subsystem state is something that's expected to happen frequently + and in performance-critical code, whereas operations that require a + task's actual cgroup assignments (in particular, moving between + cgroups) are less common. + + - A cgroup hierarchy filesystem can be mounted for browsing and + manipulation from user space. + + - You can list all the tasks (by pid) attached to any cgroup. + +The implementation of cgroups requires a few, simple hooks +into the rest of the kernel, none in performance critical paths: + + - in init/main.c, to initialize the root cgroups and initial + css_set at system boot. + + - in fork and exit, to attach and detach a task from its css_set. + +In addition a new file system, of type "cgroup" may be mounted, to +enable browsing and modifying the cgroups presently known to the +kernel. When mounting a cgroup hierarchy, you may specify a +comma-separated list of subsystems to mount as the filesystem mount +options. By default, mounting the cgroup filesystem attempts to +mount a hierarchy containing all registered subsystems. + +If an active hierarchy with exactly the same set of subsystems already +exists, it will be reused for the new mount. If no existing hierarchy +matches, and any of the requested subsystems are in use in an existing +hierarchy, the mount will fail with -EBUSY. Otherwise, a new hierarchy +is activated, associated with the requested subsystems. + +It's not currently possible to bind a new subsystem to an active +cgroup hierarchy, or to unbind a subsystem from an active cgroup +hierarchy. This may be possible in future, but is fraught with nasty +error-recovery issues. + +When a cgroup filesystem is unmounted, if there are any +child cgroups created below the top-level cgroup, that hierarchy +will remain active even though unmounted; if there are no +child cgroups then the hierarchy will be deactivated. + +No new system calls are added for cgroups - all support for +querying and modifying cgroups is via this cgroup file system. + +Each task under /proc has an added file named 'cgroup' displaying, +for each active hierarchy, the subsystem names and the cgroup name +as the path relative to the root of the cgroup file system. + +Each cgroup is represented by a directory in the cgroup file system +containing the following files describing that cgroup: + + - tasks: list of tasks (by pid) attached to that cgroup + - notify_on_release flag: run /sbin/cgroup_release_agent on exit? + +Other subsystems such as cpusets may add additional files in each +cgroup dir + +New cgroups are created using the mkdir system call or shell +command. The properties of a cgroup, such as its flags, are +modified by writing to the appropriate file in that cgroups +directory, as listed above. + +The named hierarchical structure of nested cgroups allows partitioning +a large system into nested, dynamically changeable, "soft-partitions". + +The attachment of each task, automatically inherited at fork by any +children of that task, to a cgroup allows organizing the work load +on a system into related sets of tasks. A task may be re-attached to +any other cgroup, if allowed by the permissions on the necessary +cgroup file system directories. + +When a task is moved from one cgroup to another, it gets a new +css_set pointer - if there's an already existing css_set with the +desired collection of cgroups then that group is reused, else a new +css_set is allocated. Note that the current implementation uses a +linear search to locate an appropriate existing css_set, so isn't +very efficient. A future version will use a hash table for better +performance. + +The use of a Linux virtual file system (vfs) to represent the +cgroup hierarchy provides for a familiar permission and name space +for cgroups, with a minimum of additional kernel code. + +1.4 What does notify_on_release do ? +------------------------------------ + +*** notify_on_release is disabled in the current patch set. It will be +*** reactivated in a future patch in a less-intrusive manner + +If the notify_on_release flag is enabled (1) in a cgroup, then +whenever the last task in the cgroup leaves (exits or attaches to +some other cgroup) and the last child cgroup of that cgroup +is removed, then the kernel runs the command specified by the contents +of the "release_agent" file in that hierarchy's root directory, +supplying the pathname (relative to the mount point of the cgroup +file system) of the abandoned cgroup. This enables automatic +removal of abandoned cgroups. The default value of +notify_on_release in the root cgroup at system boot is disabled +(0). The default value of other cgroups at creation is the current +value of their parents notify_on_release setting. The default value of +a cgroup hierarchy's release_agent path is empty. + +1.5 How do I use cgroups ? +-------------------------- + +To start a new job that is to be contained within a cgroup, using +the "cpuset" cgroup subsystem, the steps are something like: + + 1) mkdir /dev/cgroup + 2) mount -t cgroup -ocpuset cpuset /dev/cgroup + 3) Create the new cgroup by doing mkdir's and write's (or echo's) in + the /dev/cgroup virtual file system. + 4) Start a task that will be the "founding father" of the new job. + 5) Attach that task to the new cgroup by writing its pid to the + /dev/cgroup tasks file for that cgroup. + 6) fork, exec or clone the job tasks from this founding father task. + +For example, the following sequence of commands will setup a cgroup +named "Charlie", containing just CPUs 2 and 3, and Memory Node 1, +and then start a subshell 'sh' in that cgroup: + + mount -t cgroup cpuset -ocpuset /dev/cgroup + cd /dev/cgroup + mkdir Charlie + cd Charlie + /bin/echo 2-3 > cpus + /bin/echo 1 > mems + /bin/echo $$ > tasks + sh + # The subshell 'sh' is now running in cgroup Charlie + # The next line should display '/Charlie' + cat /proc/self/cgroup + +2. Usage Examples and Syntax +============================ + +2.1 Basic Usage +--------------- + +Creating, modifying, using the cgroups can be done through the cgroup +virtual filesystem. + +To mount a cgroup hierarchy will all available subsystems, type: +# mount -t cgroup xxx /dev/cgroup + +The "xxx" is not interpreted by the cgroup code, but will appear in +/proc/mounts so may be any useful identifying string that you like. + +To mount a cgroup hierarchy with just the cpuset and numtasks +subsystems, type: +# mount -t cgroup -o cpuset,numtasks hier1 /dev/cgroup + +To change the set of subsystems bound to a mounted hierarchy, just +remount with different options: + +# mount -o remount,cpuset,ns /dev/cgroup + +Note that changing the set of subsystems is currently only supported +when the hierarchy consists of a single (root) cgroup. Supporting +the ability to arbitrarily bind/unbind subsystems from an existing +cgroup hierarchy is intended to be implemented in the future. + +Then under /dev/cgroup you can find a tree that corresponds to the +tree of the cgroups in the system. For instance, /dev/cgroup +is the cgroup that holds the whole system. + +If you want to create a new cgroup under /dev/cgroup: +# cd /dev/cgroup +# mkdir my_cgroup + +Now you want to do something with this cgroup. +# cd my_cgroup + +In this directory you can find several files: +# ls +notify_on_release release_agent tasks +(plus whatever files are added by the attached subsystems) + +Now attach your shell to this cgroup: +# /bin/echo $$ > tasks + +You can also create cgroups inside your cgroup by using mkdir in this +directory. +# mkdir my_sub_cs + +To remove a cgroup, just use rmdir: +# rmdir my_sub_cs + +This will fail if the cgroup is in use (has cgroups inside, or +has processes attached, or is held alive by other subsystem-specific +reference). + +2.2 Attaching processes +----------------------- + +# /bin/echo PID > tasks + +Note that it is PID, not PIDs. You can only attach ONE task at a time. +If you have several tasks to attach, you have to do it one after another: + +# /bin/echo PID1 > tasks +# /bin/echo PID2 > tasks + ... +# /bin/echo PIDn > tasks + +3. Kernel API +============= + +3.1 Overview +------------ + +Each kernel subsystem that wants to hook into the generic cgroup +system needs to create a cgroup_subsys object. This contains +various methods, which are callbacks from the cgroup system, along +with a subsystem id which will be assigned by the cgroup system. + +Other fields in the cgroup_subsys object include: + +- subsys_id: a unique array index for the subsystem, indicating which + entry in cgroup->subsys[] this subsystem should be + managing. Initialized by cgroup_register_subsys(); prior to this + it should be initialized to -1 + +- hierarchy: an index indicating which hierarchy, if any, this + subsystem is currently attached to. If this is -1, then the + subsystem is not attached to any hierarchy, and all tasks should be + considered to be members of the subsystem's top_cgroup. It should + be initialized to -1. + +- name: should be initialized to a unique subsystem name prior to + calling cgroup_register_subsystem. Should be no longer than + MAX_CGROUP_TYPE_NAMELEN + +Each cgroup object created by the system has an array of pointers, +indexed by subsystem id; this pointer is entirely managed by the +subsystem; the generic cgroup code will never touch this pointer. + +3.2 Synchronization +------------------- + +There is a global mutex, cgroup_mutex, used by the cgroup +system. This should be taken by anything that wants to modify a +cgroup. It may also be taken to prevent cgroups from being +modified, but more specific locks may be more appropriate in that +situation. + +See kernel/cgroup.c for more details. + +Subsystems can take/release the cgroup_mutex via the functions +cgroup_lock()/cgroup_unlock(), and can +take/release the callback_mutex via the functions +cgroup_lock()/cgroup_unlock(). + +Accessing a task's cgroup pointer may be done in the following ways: +- while holding cgroup_mutex +- while holding the task's alloc_lock (via task_lock()) +- inside an rcu_read_lock() section via rcu_dereference() + +3.3 Subsystem API +-------------------------- + +Each subsystem should: + +- add an entry in linux/cgroup_subsys.h +- define a cgroup_subsys object called <name>_subsys + +Each subsystem may export the following methods. The only mandatory +methods are create/destroy. Any others that are null are presumed to +be successful no-ops. + +struct cgroup_subsys_state *create(struct cgroup *cont) +LL=cgroup_mutex + +Called to create a subsystem state object for a cgroup. The +subsystem should allocate its subsystem state object for the passed +cgroup, returning a pointer to the new object on success or a +negative error code. On success, the subsystem pointer should point to +a structure of type cgroup_subsys_state (typically embedded in a +larger subsystem-specific object), which will be initialized by the +cgroup system. Note that this will be called at initialization to +create the root subsystem state for this subsystem; this case can be +identified by the passed cgroup object having a NULL parent (since +it's the root of the hierarchy) and may be an appropriate place for +initialization code. + +void destroy(struct cgroup *cont) +LL=cgroup_mutex + +The cgroup system is about to destroy the passed cgroup; the +subsystem should do any necessary cleanup + +int can_attach(struct cgroup_subsys *ss, struct cgroup *cont, + struct task_struct *task) +LL=cgroup_mutex + +Called prior to moving a task into a cgroup; if the subsystem +returns an error, this will abort the attach operation. If a NULL +task is passed, then a successful result indicates that *any* +unspecified task can be moved into the cgroup. Note that this isn't +called on a fork. If this method returns 0 (success) then this should +remain valid while the caller holds cgroup_mutex. + +void attach(struct cgroup_subsys *ss, struct cgroup *cont, + struct cgroup *old_cont, struct task_struct *task) +LL=cgroup_mutex + + +Called after the task has been attached to the cgroup, to allow any +post-attachment activity that requires memory allocations or blocking. + +void fork(struct cgroup_subsy *ss, struct task_struct *task) +LL=callback_mutex, maybe read_lock(tasklist_lock) + +Called when a task is forked into a cgroup. Also called during +registration for all existing tasks. + +void exit(struct cgroup_subsys *ss, struct task_struct *task) +LL=callback_mutex + +Called during task exit + +int populate(struct cgroup_subsys *ss, struct cgroup *cont) +LL=none + +Called after creation of a cgroup to allow a subsystem to populate +the cgroup directory with file entries. The subsystem should make +calls to cgroup_add_file() with objects of type cftype (see +include/linux/cgroup.h for details). Note that although this +method can return an error code, the error code is currently not +always handled well. + +void bind(struct cgroup_subsys *ss, struct cgroup *root) +LL=callback_mutex + +Called when a cgroup subsystem is rebound to a different hierarchy +and root cgroup. Currently this will only involve movement between +the default hierarchy (which never has sub-cgroups) and a hierarchy +that is being created/destroyed (and hence has no sub-cgroups). + +4. Questions +============ + +Q: what's up with this '/bin/echo' ? +A: bash's builtin 'echo' command does not check calls to write() against + errors. If you use it in the cgroup file system, you won't be + able to tell whether a command succeeded or failed. + +Q: When I attach processes, only the first of the line gets really attached ! +A: We can only return one error code per call to write(). So you should also + put only ONE pid. + diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h new file mode 100644 index 0000000..60735dc --- /dev/null +++ b/include/linux/cgroup.h @@ -0,0 +1,214 @@ +#ifndef _LINUX_CGROUP_H +#define _LINUX_CGROUP_H +/* + * cgroup interface + * + * Copyright (C) 2003 BULL SA + * Copyright (C) 2004-2006 Silicon Graphics, Inc. + * + */ + +#include <linux/sched.h> +#include <linux/kref.h> +#include <linux/cpumask.h> +#include <linux/nodemask.h> +#include <linux/rcupdate.h> + +#ifdef CONFIG_CGROUPS + +struct cgroupfs_root; +struct cgroup_subsys; +struct inode; + +extern int cgroup_init_early(void); +extern int cgroup_init(void); +extern void cgroup_init_smp(void); +extern void cgroup_lock(void); +extern void cgroup_unlock(void); + +/* Per-subsystem/per-cgroup state maintained by the system. */ +struct cgroup_subsys_state { + /* The cgroup that this subsystem is attached to. Useful + * for subsystems that want to know about the cgroup + * hierarchy structure */ + struct cgroup *cgroup; + + /* State maintained by the cgroup system to allow + * subsystems to be "busy". Should be accessed via css_get() + * and css_put() */ + + atomic_t refcnt; + + unsigned long flags; +}; + +/* bits in struct cgroup_subsys_state flags field */ +enum { + CSS_ROOT, /* This CSS is the root of the subsystem */ +}; + +/* + * Call css_get() to hold a reference on the cgroup; + * + */ + +static inline void css_get(struct cgroup_subsys_state *css) +{ + /* We don't need to reference count the root state */ + if (!test_bit(CSS_ROOT, &css->flags)) + atomic_inc(&css->refcnt); +} +/* + * css_put() should be called to release a reference taken by + * css_get() + */ + +static inline void css_put(struct cgroup_subsys_state *css) +{ + if (!test_bit(CSS_ROOT, &css->flags)) + atomic_dec(&css->refcnt); +} + +struct cgroup { + unsigned long flags; /* "unsigned long" so bitops work */ + + /* count users of this cgroup. >0 means busy, but doesn't + * necessarily indicate the number of tasks in the + * cgroup */ + atomic_t count; + + /* + * We link our 'sibling' struct into our parent's 'children'. + * Our children link their 'sibling' into our 'children'. + */ + struct list_head sibling; /* my parent's children */ + struct list_head children; /* my children */ + + struct cgroup *parent; /* my parent */ + struct dentry *dentry; /* cgroup fs entry */ + + /* Private pointers for each registered subsystem */ + struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT]; + + struct cgroupfs_root *root; + struct cgroup *top_cgroup; +}; + +/* struct cftype: + * + * The files in the cgroup filesystem mostly have a very simple read/write + * handling, some common function will take care of it. Nevertheless some cases + * (read tasks) are special and therefore I define this structure for every + * kind of file. + * + * + * When reading/writing to a file: + * - the cgroup to use in file->f_dentry->d_parent->d_fsdata + * - the 'cftype' of the file is file->f_dentry->d_fsdata + */ + +#define MAX_CFTYPE_NAME 64 +struct cftype { + /* By convention, the name should begin with the name of the + * subsystem, followed by a period */ + char name[MAX_CFTYPE_NAME]; + int private; + int (*open) (struct inode *inode, struct file *file); + ssize_t (*read) (struct cgroup *cont, struct cftype *cft, + struct file *file, + char __user *buf, size_t nbytes, loff_t *ppos); + /* + * read_uint() is a shortcut for the common case of returning a + * single integer. Use it in place of read() + */ + u64 (*read_uint) (struct cgroup *cont, struct cftype *cft); + ssize_t (*write) (struct cgroup *cont, struct cftype *cft, + struct file *file, + const char __user *buf, size_t nbytes, loff_t *ppos); + int (*release) (struct inode *inode, struct file *file); +}; + +/* Add a new file to the given cgroup directory. Should only be + * called by subsystems from within a populate() method */ +int cgroup_add_file(struct cgroup *cont, struct cgroup_subsys *subsys, + const struct cftype *cft); + +/* Add a set of new files to the given cgroup directory. Should + * only be called by subsystems from within a populate() method */ +int cgroup_add_files(struct cgroup *cont, + struct cgroup_subsys *subsys, + const struct cftype cft[], + int count); + +int cgroup_is_removed(const struct cgroup *cont); + +int cgroup_path(const struct cgroup *cont, char *buf, int buflen); + +/* Return true if the cgroup is a descendant of the current cgroup */ +int cgroup_is_descendant(const struct cgroup *cont); + +/* Control Group subsystem type. See Documentation/cgroups.txt for details */ + +struct cgroup_subsys { + struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss, + struct cgroup *cont); + void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cont); + int (*can_attach)(struct cgroup_subsys *ss, + struct cgroup *cont, struct task_struct *tsk); + void (*attach)(struct cgroup_subsys *ss, struct cgroup *cont, + struct cgroup *old_cont, struct task_struct *tsk); + void (*fork)(struct cgroup_subsys *ss, struct task_struct *task); + void (*exit)(struct cgroup_subsys *ss, struct task_struct *task); + int (*populate)(struct cgroup_subsys *ss, + struct cgroup *cont); + void (*bind)(struct cgroup_subsys *ss, struct cgroup *root); + int subsys_id; + int active; + int early_init; +#define MAX_CGROUP_TYPE_NAMELEN 32 + const char *name; + + /* Protected by RCU */ + struct cgroupfs_root *root; + + struct list_head sibling; + + void *private; +}; + +#define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys; +#include <linux/cgroup_subsys.h> +#undef SUBSYS + +static inline struct cgroup_subsys_state *cgroup_subsys_state( + struct cgroup *cont, int subsys_id) +{ + return cont->subsys[subsys_id]; +} + +static inline struct cgroup_subsys_state *task_subsys_state( + struct task_struct *task, int subsys_id) +{ + return rcu_dereference(task->cgroups.subsys[subsys_id]); +} + +static inline struct cgroup* task_cgroup(struct task_struct *task, + int subsys_id) +{ + return task_subsys_state(task, subsys_id)->cgroup; +} + +int cgroup_path(const struct cgroup *cont, char *buf, int buflen); + +#else /* !CONFIG_CGROUPS */ + +static inline int cgroup_init_early(void) { return 0; } +static inline int cgroup_init(void) { return 0; } +static inline void cgroup_init_smp(void) {} + +static inline void cgroup_lock(void) {} +static inline void cgroup_unlock(void) {} + +#endif /* !CONFIG_CGROUPS */ + +#endif /* _LINUX_CGROUP_H */ diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h new file mode 100644 index 0000000..f8eddbb --- /dev/null +++ b/include/linux/cgroup_subsys.h @@ -0,0 +1,10 @@ +/* Add subsystem definitions of the form SUBSYS(<name>) in this + * file. Surround each one by a line of comment markers so that + * patches don't collide + */ + +/* */ + +/* */ + +/* */ diff --git a/include/linux/magic.h b/include/linux/magic.h index 722d475..1fa0c2c 100644 --- a/include/linux/magic.h +++ b/include/linux/magic.h @@ -37,6 +37,7 @@ #define SMB_SUPER_MAGIC 0x517B #define USBDEVICE_SUPER_MAGIC 0x9fa2 +#define CGROUP_SUPER_MAGIC 0x27e0eb #define FUTEXFS_SUPER_MAGIC 0xBAD1DEA #define INOTIFYFS_SUPER_MAGIC 0x2BAD1DEA diff --git a/include/linux/sched.h b/include/linux/sched.h index 10a83d8..af2ed4b 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -894,6 +894,34 @@ struct sched_entity { #endif }; +#ifdef CONFIG_CGROUPS + +#define SUBSYS(_x) _x ## _subsys_id, +enum cgroup_subsys_id { +#include <linux/cgroup_subsys.h> + CGROUP_SUBSYS_COUNT +}; +#undef SUBSYS + +/* A css_set is a structure holding pointers to a set of + * cgroup_subsys_state objects. + */ + +struct css_set { + + /* Set of subsystem states, one for each subsystem. NULL for + * subsystems that aren't part of this hierarchy. These + * pointers reduce the number of dereferences required to get + * from a task to its state for a given cgroup, but result + * in increased space usage if tasks are in wildly different + * groupings across different hierarchies. This array is + * immutable after creation */ + struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT]; + +}; + +#endif /* CONFIG_CGROUPS */ + struct task_struct { volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */ void *stack; @@ -1130,6 +1158,9 @@ struct task_struct { int cpuset_mems_generation; int cpuset_mem_spread_rotor; #endif +#ifdef CONFIG_CGROUPS + struct css_set cgroups; +#endif #ifdef CONFIG_FUTEX struct robust_list_head __user *robust_list; #ifdef CONFIG_COMPAT @@ -1625,7 +1656,8 @@ static inline int thread_group_empty(struct task_struct *p) /* * Protects ->fs, ->files, ->mm, ->group_info, ->comm, keyring * subscriptions and synchronises with wait4(). Also used in procfs. Also - * pins the final release of task.io_context. Also protects ->cpuset. + * pins the final release of task.io_context. Also protects ->cpuset and + * ->cgroup.subsys[]. * * Nests both inside and outside of read_lock(&tasklist_lock). * It must not be nested with write_lock_irq(&tasklist_lock), diff --git a/init/Kconfig b/init/Kconfig index a29a688..51b3d14 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -270,6 +270,14 @@ config LOG_BUF_SHIFT 13 => 8 KB 12 => 4 KB +config CGROUPS + bool "Control Group support" + help + This option will let you use process cgroup subsystems + such as Cpusets + + Say N if unsure. + config CPUSETS bool "Cpuset support" depends on SMP diff --git a/init/main.c b/init/main.c index 9def935..0dd0e7a 100644 --- a/init/main.c +++ b/init/main.c @@ -39,6 +39,7 @@ #include <linux/writeback.h> #include <linux/cpu.h> #include <linux/cpuset.h> +#include <linux/cgroup.h> #include <linux/efi.h> #include <linux/tick.h> #include <linux/interrupt.h> @@ -523,6 +524,7 @@ asmlinkage void __init start_kernel(void) */ unwind_init(); lockdep_init(); + cgroup_init_early(); local_irq_disable(); early_boot_irqs_off(); @@ -640,6 +642,7 @@ asmlinkage void __init start_kernel(void) #ifdef CONFIG_PROC_FS proc_root_init(); #endif + cgroup_init(); cpuset_init(); taskstats_init_early(); delayacct_init(); diff --git a/kernel/Makefile b/kernel/Makefile index 001bd3b..ea8c8a1 100644 --- a/kernel/Makefile +++ b/kernel/Makefile @@ -36,6 +36,7 @@ obj-$(CONFIG_PM) += power/ obj-$(CONFIG_BSD_PROCESS_ACCT) += acct.o obj-$(CONFIG_KEXEC) += kexec.o obj-$(CONFIG_COMPAT) += compat.o +obj-$(CONFIG_CGROUPS) += cgroup.o obj-$(CONFIG_CPUSETS) += cpuset.o obj-$(CONFIG_IKCONFIG) += configs.o obj-$(CONFIG_STOP_MACHINE) += stop_machine.o 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; +} |
