1. 03 4月, 2009 3 次提交
    • K
      cgroup: CSS ID support · 38460b48
      KAMEZAWA Hiroyuki 提交于
      Patch for Per-CSS(Cgroup Subsys State) ID and private hierarchy code.
      
      This patch attaches unique ID to each css and provides following.
      
       - css_lookup(subsys, id)
         returns pointer to struct cgroup_subysys_state of id.
       - css_get_next(subsys, id, rootid, depth, foundid)
         returns the next css under "root" by scanning
      
      When cgroup_subsys->use_id is set, an id for css is maintained.
      
      The cgroup framework only parepares
      	- css_id of root css for subsys
      	- id is automatically attached at creation of css.
      	- id is *not* freed automatically. Because the cgroup framework
      	  don't know lifetime of cgroup_subsys_state.
      	  free_css_id() function is provided. This must be called by subsys.
      
      There are several reasons to develop this.
      	- Saving space .... For example, memcg's swap_cgroup is array of
      	  pointers to cgroup. But it is not necessary to be very fast.
      	  By replacing pointers(8bytes per ent) to ID (2byes per ent), we can
      	  reduce much amount of memory usage.
      
      	- Scanning without lock.
      	  CSS_ID provides "scan id under this ROOT" function. By this, scanning
      	  css under root can be written without locks.
      	  ex)
      	  do {
      		rcu_read_lock();
      		next = cgroup_get_next(subsys, id, root, &found);
      		/* check sanity of next here */
      		css_tryget();
      		rcu_read_unlock();
      		id = found + 1
      	 } while(...)
      
      Characteristics:
      	- Each css has unique ID under subsys.
      	- Lifetime of ID is controlled by subsys.
      	- css ID contains "ID" and "Depth in hierarchy" and stack of hierarchy
      	- Allowed ID is 1-65535, ID 0 is UNUSED ID.
      
      Design Choices:
      	- scan-by-ID v.s. scan-by-tree-walk.
      	  As /proc's pid scan does, scan-by-ID is robust when scanning is done
      	  by following kind of routine.
      	  scan -> rest a while(release a lock) -> conitunue from interrupted
      	  memcg's hierarchical reclaim does this.
      
      	- When subsys->use_id is set, # of css in the system is limited to
      	  65535.
      
      [bharata@linux.vnet.ibm.com: remove rcu_read_lock() from css_get_next()]
      Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Acked-by: NPaul Menage <menage@google.com>
      Cc: Li Zefan <lizf@cn.fujitsu.com>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Cc: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>
      Signed-off-by: NBharata B Rao <bharata@linux.vnet.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      38460b48
    • G
      cgroups: relax ns_can_attach checks to allow attaching to grandchild cgroups · 313e924c
      Grzegorz Nosek 提交于
      The ns_proxy cgroup allows moving processes to child cgroups only one
      level deep at a time.  This commit relaxes this restriction and makes it
      possible to attach tasks directly to grandchild cgroups, e.g.:
      
      ($pid is in the root cgroup)
      echo $pid > /cgroup/CG1/CG2/tasks
      
      Previously this operation would fail with -EPERM and would have to be
      performed as two steps:
      echo $pid > /cgroup/CG1/tasks
      echo $pid > /cgroup/CG1/CG2/tasks
      
      Also, the target cgroup no longer needs to be empty to move a task there.
      Signed-off-by: NGrzegorz Nosek <root@localdomain.pl>
      Acked-by: NSerge Hallyn <serue@us.ibm.com>
      Reviewed-by: NLi Zefan <lizf@cn.fujitsu.com>
      Cc: Paul Menage <menage@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      313e924c
    • P
      cgroups: fix cgroup.h comments · d20a390a
      Paul Menage 提交于
      Fix the style of some multi-line comments in cgroup.h to match
      Documentation/CodingStyle
      Signed-off-by: NPaul Menage <menage@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      d20a390a
  2. 12 2月, 2009 1 次提交
  3. 30 1月, 2009 1 次提交
  4. 09 1月, 2009 4 次提交
    • P
      cgroups: add css_tryget() · e7c5ec91
      Paul Menage 提交于
      Add css_tryget(), that obtains a counted reference on a CSS.  It is used
      in situations where the caller has a "weak" reference to the CSS, i.e.
      one that does not protect the cgroup from removal via a reference count,
      but would instead be cleaned up by a destroy() callback.
      
      css_tryget() will return true on success, or false if the cgroup is being
      removed.
      
      This is similar to Kamezawa Hiroyuki's patch from a week or two ago, but
      with the difference that in the event of css_tryget() racing with a
      cgroup_rmdir(), css_tryget() will only return false if the cgroup really
      does get removed.
      
      This implementation is done by biasing css->refcnt, so that a refcnt of 1
      means "releasable" and 0 means "released or releasing".  In the event of a
      race, css_tryget() distinguishes between "released" and "releasing" by
      checking for the CSS_REMOVED flag in css->flags.
      Signed-off-by: NPaul Menage <menage@google.com>
      Tested-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Li Zefan <lizf@cn.fujitsu.com>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      e7c5ec91
    • P
      cgroups: add a per-subsystem hierarchy_mutex · 999cd8a4
      Paul Menage 提交于
      These patches introduce new locking/refcount support for cgroups to
      reduce the need for subsystems to call cgroup_lock(). This will
      ultimately allow the atomicity of cgroup_rmdir() (which was removed
      recently) to be restored.
      
      These three patches give:
      
      1/3 - introduce a per-subsystem hierarchy_mutex which a subsystem can
           use to prevent changes to its own cgroup tree
      
      2/3 - use hierarchy_mutex in place of calling cgroup_lock() in the
           memory controller
      
      3/3 - introduce a css_tryget() function similar to the one recently
            proposed by Kamezawa, but avoiding spurious refcount failures in
            the event of a race between a css_tryget() and an unsuccessful
            cgroup_rmdir()
      
      Future patches will likely involve:
      
      - using hierarchy mutex in place of cgroup_lock() in more subsystems
       where appropriate
      
      - restoring the atomicity of cgroup_rmdir() with respect to cgroup_create()
      
      This patch:
      
      Add a hierarchy_mutex to the cgroup_subsys object that protects changes to
      the hierarchy observed by that subsystem.  It is taken by the cgroup
      subsystem (in addition to cgroup_mutex) for the following operations:
      
      - linking a cgroup into that subsystem's cgroup tree
      - unlinking a cgroup from that subsystem's cgroup tree
      - moving the subsystem to/from a hierarchy (including across the
        bind() callback)
      
      Thus if the subsystem holds its own hierarchy_mutex, it can safely
      traverse its own hierarchy.
      Signed-off-by: NPaul Menage <menage@google.com>
      Tested-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Li Zefan <lizf@cn.fujitsu.com>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      999cd8a4
    • P
      cgroups: make cgroup_path() RCU-safe · a47295e6
      Paul Menage 提交于
      Fix races between /proc/sched_debug by freeing cgroup objects via an RCU
      callback.  Thus any cgroup reference obtained from an RCU-safe source will
      remain valid during the RCU section.  Since dentries are also RCU-safe,
      this allows us to traverse up the tree safely.
      
      Additionally, make cgroup_path() check for a NULL cgrp->dentry to avoid
      trying to report a path for a partially-created cgroup.
      
      [lizf@cn.fujitsu.com: call deactive_super() in cgroup_diput()]
      Signed-off-by: NPaul Menage <menage@google.com>
      Reviewed-by: NLi Zefan <lizf@cn.fujitsu.com>
      Tested-by: NLi Zefan <lizf@cn.fujitsu.com>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a47295e6
    • L
      cgroups: don't put struct cgroupfs_root protected by RCU · b2aa30f7
      Lai Jiangshan 提交于
      We don't access struct cgroupfs_root in fast path, so we should not put
      struct cgroupfs_root protected by RCU
      
      But the comment in struct cgroup_subsys.root confuse us.
      
      struct cgroup_subsys.root is used in these places:
      
      1 find_css_set(): if (ss->root->subsys_list.next == &ss->sibling)
      2 rebind_subsystems(): if (ss->root != &rootnode)
                             rcu_assign_pointer(ss->root, root);
                             rcu_assign_pointer(subsys[i]->root, &rootnode);
      3 cgroup_has_css_refs(): if (ss->root != cgrp->root)
      4 cgroup_init_subsys(): ss->root = &rootnode;
      5 proc_cgroupstats_show(): ss->name, ss->root->subsys_bits,
                                 ss->root->number_of_cgroups, !ss->disabled);
      6 cgroup_clone(): root = subsys->root;
                        if ((root != subsys->root) ||
      
      All these place we have held cgroup_lock() or we don't dereference to
      struct cgroupfs_root.  It's means wo don't need RCU when use struct
      cgroup_subsys.root, and we should not put struct cgroupfs_root protected
      by RCU.
      Signed-off-by: NLai Jiangshan <laijs@cn.fujitsu.com>
      Reviewed-by: NPaul Menage <menage@google.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Pavel Emelyanov <xemul@openvz.org>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      b2aa30f7
  5. 07 1月, 2009 1 次提交
  6. 31 10月, 2008 1 次提交
  7. 20 10月, 2008 3 次提交
  8. 17 10月, 2008 1 次提交
  9. 26 7月, 2008 5 次提交
  10. 29 4月, 2008 9 次提交
  11. 05 4月, 2008 1 次提交
    • P
      cgroups: add cgroup support for enabling controllers at boot time · 8bab8dde
      Paul Menage 提交于
      The effects of cgroup_disable=foo are:
      
      - foo isn't auto-mounted if you mount all cgroups in a single hierarchy
      - foo isn't visible as an individually mountable subsystem
      
      As a result there will only ever be one call to foo->create(), at init time;
      all processes will stay in this group, and the group will never be mounted on
      a visible hierarchy.  Any additional effects (e.g.  not allocating metadata)
      are up to the foo subsystem.
      
      This doesn't handle early_init subsystems (their "disabled" bit isn't set be,
      but it could easily be extended to do so if any of the early_init systems
      wanted it - I think it would just involve some nastier parameter processing
      since it would occur before the command-line argument parser had been run.
      
      Hugh said:
      
        Ballpark figures, I'm trying to get this question out rather than
        processing the exact numbers: CONFIG_CGROUP_MEM_RES_CTLR adds 15% overhead
        to the affected paths, booting with cgroup_disable=memory cuts that back to
        1% overhead (due to slightly bigger struct page).
      
        I'm no expert on distros, they may have no interest whatever in
        CONFIG_CGROUP_MEM_RES_CTLR=y; and the rest of us can easily build with or
        without it, or apply the cgroup_disable=memory patches.
      
      Unix bench's execl test result on x86_64 was
      
      == just after boot without mounting any cgroup fs.==
      mem_cgorup=off : Execl Throughput       43.0     3150.1      732.6
      mem_cgroup=on  : Execl Throughput       43.0     2932.6      682.0
      ==
      
      [lizf@cn.fujitsu.com: fix boot option parsing]
      Signed-off-by: NBalbir Singh <balbir@linux.vnet.ibm.com>
      Cc: Paul Menage <menage@google.com>
      Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
      Cc: Pavel Emelyanov <xemul@openvz.org>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: Hugh Dickins <hugh@veritas.com>
      Cc: Sudhir Kumar <skumar@linux.vnet.ibm.com>
      Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
      Cc: David Rientjes <rientjes@google.com>
      Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      8bab8dde
  12. 24 2月, 2008 2 次提交
  13. 08 2月, 2008 3 次提交
    • C
      hotplug cpu: move tasks in empty cpusets to parent · 956db3ca
      Cliff Wickman 提交于
      This patch corrects a situation that occurs when one disables all the cpus in
      a cpuset.
      
      Currently, the disabled (cpu-less) cpuset inherits the cpus of its parent,
      which is incorrect because it may then overlap its cpu-exclusive sibling.
      
      Tasks of an empty cpuset should be moved to the cpuset which is the parent of
      their current cpuset.  Or if the parent cpuset has no cpus, to its parent,
      etc.
      
      And the empty cpuset should be released (if it is flagged notify_on_release).
      
      Depends on the cgroup_scan_tasks() function (proposed by David Rientjes) to
      iterate through all tasks in the cpu-less cpuset.  We are deliberately
      avoiding a walk of the tasklist.
      
      [akpm@linux-foundation.org: coding-style fixes]
      Signed-off-by: NCliff Wickman <cpw@sgi.com>
      Cc: Paul Menage <menage@google.com>
      Cc: Paul Jackson <pj@sgi.com>
      Cc: David Rientjes <rientjes@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      956db3ca
    • C
      cgroups: mechanism to process each task in a cgroup · 31a7df01
      Cliff Wickman 提交于
      Provide cgroup_scan_tasks(), which iterates through every task in a cgroup,
      calling a test function and a process function for each.  And call the process
      function without holding the css_set_lock lock.
      
      The idea is David Rientjes', predicting that such a function will make it much
      easier in the future to extend things that require access to each task in a
      cgroup without holding the lock,
      
      [akpm@linux-foundation.org: cleanup]
      [akpm@linux-foundation.org: coding-style fixes]
      Signed-off-by: NCliff Wickman <cpw@sgi.com>
      Cc: Paul Menage <menage@google.com>
      Cc: Paul Jackson <pj@sgi.com>
      Acked-by: NDavid Rientjes <rientjes@google.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      31a7df01
    • K
      memory cgroup enhancements: add- pre_destroy() handler · 4fca88c8
      KAMEZAWA Hiroyuki 提交于
      Add a handler "pre_destroy" to cgroup_subsys.  It is called before
      cgroup_rmdir() checks all subsys's refcnt.
      
      I think this is useful for subsys which have some extra refs even if there
      are no tasks in cgroup.  By adding pre_destroy(), the kernel keeps the rule
      "destroy() against subsystem is called only when refcnt=0." and allows css
      ref to be used by other objects than tasks.
      Signed-off-by: NKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
      Cc: David Rientjes <rientjes@google.com>
      Cc: Herbert Poetzl <herbert@13thfloor.at>
      Cc: Kirill Korotaev <dev@sw.ru>
      Cc: Nick Piggin <nickpiggin@yahoo.com.au>
      Cc: Paul Menage <menage@google.com>
      Cc: Pavel Emelianov <xemul@openvz.org>
      Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
      Cc: Vaidyanathan Srinivasan <svaidy@linux.vnet.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      4fca88c8
  14. 20 10月, 2007 5 次提交
    • B
      Add cgroupstats · 846c7bb0
      Balbir Singh 提交于
      This patch is inspired by the discussion at
      http://lkml.org/lkml/2007/4/11/187 and implements per cgroup statistics
      as suggested by Andrew Morton in http://lkml.org/lkml/2007/4/11/263.  The
      patch is on top of 2.6.21-mm1 with Paul's cgroups v9 patches (forward
      ported)
      
      This patch implements per cgroup statistics infrastructure and re-uses
      code from the taskstats interface.  A new set of cgroup operations are
      registered with commands and attributes.  It should be very easy to
      *extend* per cgroup statistics, by adding members to the cgroupstats
      structure.
      
      The current model for cgroupstats is a pull, a push model (to post
      statistics on interesting events), should be very easy to add.  Currently
      user space requests for statistics by passing the cgroup file
      descriptor.  Statistics about the state of all the tasks in the cgroup
      is returned to user space.
      
      TODO's/NOTE:
      
      This patch provides an infrastructure for implementing cgroup statistics.
      Based on the needs of each controller, we can incrementally add more statistics,
      event based support for notification of statistics, accumulation of taskstats
      into cgroup statistics in the future.
      
      Sample output
      
      # ./cgroupstats -C /cgroup/a
      sleeping 2, blocked 0, running 1, stopped 0, uninterruptible 0
      
      # ./cgroupstats -C /cgroup/
      sleeping 154, blocked 0, running 0, stopped 0, uninterruptible 0
      
      If the approach looks good, I'll enhance and post the user space utility for
      the same
      
      Feedback, comments, test results are always welcome!
      
      [akpm@linux-foundation.org: build fix]
      Signed-off-by: NBalbir Singh <balbir@linux.vnet.ibm.com>
      Cc: Paul Menage <menage@google.com>
      Cc: Jay Lan <jlan@engr.sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      846c7bb0
    • P
      Task Control Groups: automatic userspace notification of idle cgroups · 81a6a5cd
      Paul Menage 提交于
      Add the following files to the cgroup filesystem:
      
      notify_on_release - configures/reports whether the cgroup subsystem should
      attempt to run a release script when this cgroup becomes unused
      
      release_agent - configures/reports the release agent to be used for this
      hierarchy (top level in each hierarchy only)
      
      releasable - reports whether this cgroup would have been auto-released if
      notify_on_release was true and a release agent was configured (mainly useful
      for debugging)
      
      To avoid locking issues, invoking the userspace release agent is done via a
      workqueue task; cgroups that need to have their release agents invoked by
      the workqueue task are linked on to a list.
      
      [pj@sgi.com: Need to include kmod.h]
      Signed-off-by: NPaul Menage <menage@google.com>
      Cc: Serge E. Hallyn <serue@us.ibm.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Dave Hansen <haveblue@us.ibm.com>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Cc: Paul Jackson <pj@sgi.com>
      Cc: Kirill Korotaev <dev@openvz.org>
      Cc: Herbert Poetzl <herbert@13thfloor.at>
      Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
      Cc: Cedric Le Goater <clg@fr.ibm.com>
      Signed-off-by: NPaul Jackson <pj@sgi.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      81a6a5cd
    • P
      Task Control Groups: shared cgroup subsystem group arrays · 817929ec
      Paul Menage 提交于
      Replace the struct css_set embedded in task_struct with a pointer; all tasks
      that have the same set of memberships across all hierarchies will share a
      css_set object, and will be linked via their css_sets field to the "tasks"
      list_head in the css_set.
      
      Assuming that many tasks share the same cgroup assignments, this reduces
      overall space usage and keeps the size of the task_struct down (three pointers
      added to task_struct compared to a non-cgroups kernel, no matter how many
      subsystems are registered).
      
      [akpm@linux-foundation.org: fix a printk]
      [akpm@linux-foundation.org: build fix]
      Signed-off-by: NPaul Menage <menage@google.com>
      Cc: Serge E. Hallyn <serue@us.ibm.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Dave Hansen <haveblue@us.ibm.com>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Cc: Paul Jackson <pj@sgi.com>
      Cc: Kirill Korotaev <dev@openvz.org>
      Cc: Herbert Poetzl <herbert@13thfloor.at>
      Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
      Cc: Cedric Le Goater <clg@fr.ibm.com>
      Cc: Serge E. Hallyn <serue@us.ibm.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Dave Hansen <haveblue@us.ibm.com>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Cc: Paul Jackson <pj@sgi.com>
      Cc: Kirill Korotaev <dev@openvz.org>
      Cc: Herbert Poetzl <herbert@13thfloor.at>
      Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
      Cc: Cedric Le Goater <clg@fr.ibm.com>
      Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      817929ec
    • P
      Task Control Groups: add procfs interface · a424316c
      Paul Menage 提交于
      Add:
      
      /proc/cgroups - general system info
      
      /proc/*/cgroup - per-task cgroup membership info
      
      [a.p.zijlstra@chello.nl: cgroups: bdi init hooks]
      Signed-off-by: NPaul Menage <menage@google.com>
      Cc: Serge E. Hallyn <serue@us.ibm.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Dave Hansen <haveblue@us.ibm.com>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Cc: Paul Jackson <pj@sgi.com>
      Cc: Kirill Korotaev <dev@openvz.org>
      Cc: Herbert Poetzl <herbert@13thfloor.at>
      Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
      Cc: Cedric Le Goater <clg@fr.ibm.com>
      Signed-off-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      a424316c
    • P
      Task Control Groups: add cgroup_clone() interface · 697f4161
      Paul Menage 提交于
      Add support for cgroup_clone(), a way to create new cgroups intended to
      be used for systems such as namespace unsharing.  A new subsystem callback,
      post_clone(), is added to allow subsystems to automatically configure cloned
      cgroups.
      Signed-off-by: NPaul Menage <menage@google.com>
      Cc: Serge E. Hallyn <serue@us.ibm.com>
      Cc: "Eric W. Biederman" <ebiederm@xmission.com>
      Cc: Dave Hansen <haveblue@us.ibm.com>
      Cc: Balbir Singh <balbir@in.ibm.com>
      Cc: Paul Jackson <pj@sgi.com>
      Cc: Kirill Korotaev <dev@openvz.org>
      Cc: Herbert Poetzl <herbert@13thfloor.at>
      Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
      Cc: Cedric Le Goater <clg@fr.ibm.com>
      Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
      Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
      697f4161