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* cgroup: fail if monitored file and event_control are in different cgroupLi Zefan2013-02-181-0/+11
| | | | | | | | | | | | | | If we pass fd of memory.usage_in_bytes of cgroup A to cgroup.event_control of cgroup B, then we won't get memory usage notification from A but B! What's worse, if A and B are in different mount hierarchy, we'll end up accessing NULL pointer! Disallow this kind of invalid usage. Signed-off-by: Li Zefan <lizefan@huawei.com> Acked-by: Kirill A. Shutemov <kirill@shutemov.name> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: fix cgroup_rmdir() vs close(eventfd) raceLi Zefan2013-02-181-16/+25
| | | | | | | | | | | | | | | | | | | | | | commit 205a872bd6f9a9a09ef035ef1e90185a8245cc58 ("cgroup: fix lockdep warning for event_control") solved a deadlock by introducing a new bug. Move cgrp->event_list to a temporary list doesn't mean you can traverse this list locklessly, because at the same time cgroup_event_wake() can be called and remove the event from the list. The result of this race is disastrous. We adopt the way how kvm irqfd code implements race-free event removal, which is now described in the comments in cgroup_event_wake(). v3: - call eventfd_signal() no matter it's eventfd close or cgroup removal that removes the cgroup event. Acked-by: Kirill A. Shutemov <kirill@shutemov.name> Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: fix exit() vs rmdir() raceLi Zefan2013-02-181-0/+8
| | | | | | | | | | | | | | | | | | | | | In cgroup_exit() put_css_set_taskexit() is called without any lock, which might lead to accessing a freed cgroup: thread1 thread2 --------------------------------------------- exit() cgroup_exit() put_css_set_taskexit() atomic_dec(cgrp->count); rmdir(); /* not safe !! */ check_for_release(cgrp); rcu_read_lock() can be used to make sure the cgroup is alive. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org
* cgroup: remove bogus comments in cgroup_diput()Li Zefan2013-01-241-6/+0
| | | | | | | | | | Since commit 48ddbe194623ae089cc0576e60363f2d2e85662a ("cgroup: make css->refcnt clearing on cgroup removal optional"), each css holds a ref on cgroup's dentry, so cgroup_diput() won't be called until all css' refs go down to 0, which invalids the comments. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: remove synchronize_rcu() from cgroup_diput()Li Zefan2013-01-241-29/+43
| | | | | | | | Free cgroup via call_rcu(). The actual work is done through workqueue. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: remove duplicate RCU free on struct cgroupLi Zefan2013-01-241-1/+1
| | | | | | | | | | | | | | | | | | When destroying a cgroup, though in cgroup_diput() we've called synchronize_rcu(), we then still have to free it via call_rcu(). The story is, long ago to fix a race between reading /proc/sched_debug and freeing cgroup, the code was changed to utilize call_rcu(). See commit a47295e6bc42ad35f9c15ac66f598aa24debd4e2 ("cgroups: make cgroup_path() RCU-safe") As we've fixed cpu cgroup that cpu_cgroup_offline_css() is used to unregister a task_group so there won't be concurrent access to this task_group after synchronize_rcu() in diput(). Now we can just kfree(cgrp). Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: initialize cgrp->dentry before css_alloc()Li Zefan2013-01-241-3/+4
| | | | | | | | | | | With this change, we're guaranteed that cgroup_path() won't see NULL cgrp->dentry, and thus we can remove the NULL check in it. (Well, it's not strictly true, because dummptop.dentry is always NULL but we already handle that separately.) Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: remove a NULL check in cgroup_exit()Li Zefan2013-01-241-2/+1
| | | | | | | | | init_task.cgroups is initialized at boot phase, and whenver a ask is forked, it's cgroups pointer is inherited from its parent, and it's never set to NULL afterwards. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: fix bogus kernel warnings when cgroup_create() failedLi Zefan2013-01-221-9/+12
| | | | | | | | | | | | | | | | | | | | | | If cgroup_create() failed and cgroup_destroy_locked() is called to do cleanup, we'll see a bunch of warnings: cgroup_addrm_files: failed to remove 2MB.limit_in_bytes, err=-2 cgroup_addrm_files: failed to remove 2MB.usage_in_bytes, err=-2 cgroup_addrm_files: failed to remove 2MB.max_usage_in_bytes, err=-2 cgroup_addrm_files: failed to remove 2MB.failcnt, err=-2 cgroup_addrm_files: failed to remove prioidx, err=-2 cgroup_addrm_files: failed to remove ifpriomap, err=-2 ... We failed to remove those files, because cgroup_create() has failed before creating those cgroup files. To fix this, we simply don't warn if cgroup_rm_file() can't find the cft entry. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: remove synchronize_rcu() from rebind_subsystems()Li Zefan2013-01-141-1/+0
| | | | | | | | Nothing's protected by RCU in rebind_subsystems(), and I can't think of a reason why it is needed. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: remove synchronize_rcu() from cgroup_attach_{task|proc}()Li Zefan2013-01-141-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | These 2 syncronize_rcu()s make attaching a task to a cgroup quite slow, and it can't be ignored in some situations. A real case from Colin Cross: Android uses cgroups heavily to manage thread priorities, putting threads in a background group with reduced cpu.shares when they are not visible to the user, and in a foreground group when they are. Some RPCs from foreground threads to background threads will temporarily move the background thread into the foreground group for the duration of the RPC. This results in many calls to cgroup_attach_task. In cgroup_attach_task() it's task->cgroups that is protected by RCU, and put_css_set() calls kfree_rcu() to free it. If we remove this synchronize_rcu(), there can be threads in RCU-read sections accessing their old cgroup via current->cgroups with concurrent rmdir operation, but this is safe. # time for ((i=0; i<50; i++)) { echo $$ > /mnt/sub/tasks; echo $$ > /mnt/tasks; } real 0m2.524s user 0m0.008s sys 0m0.004s With this patch: real 0m0.004s user 0m0.004s sys 0m0.000s tj: These synchronize_rcu()s are utterly confused. synchornize_rcu() necessarily has to come between two operations to guarantee that the changes made by the former operation are visible to all rcu readers before proceeding to the latter operation. Here, synchornize_rcu() are at the end of attach operations with nothing beyond it. Its only effect would be delaying completion of write(2) to sysfs tasks/procs files until all rcu readers see the change, which doesn't mean anything. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Colin Cross <ccross@google.com>
* cgroup: use new hashtable implementationLi Zefan2013-01-101-53/+39
| | | | | | | Switch cgroup to use the new hashtable implementation. No functional changes. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: implement cgroup_rightmost_descendant()Tejun Heo2013-01-071-0/+26
| | | | | | | | | | | Implement cgroup_rightmost_descendant() which returns the right most descendant of the specified cgroup. This can be used to skip the cgroup's subtree while iterating with cgroup_for_each_descendant_pre(). Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Li Zefan <lizefan@huawei.com>
* Merge branch 'akpm' (Andrew's patch-bomb)Linus Torvalds2012-12-171-1/+0
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Merge misc patches from Andrew Morton: "Incoming: - lots of misc stuff - backlight tree updates - lib/ updates - Oleg's percpu-rwsem changes - checkpatch - rtc - aoe - more checkpoint/restart support I still have a pile of MM stuff pending - Pekka should be merging later today after which that is good to go. A number of other things are twiddling thumbs awaiting maintainer merges." * emailed patches from Andrew Morton <akpm@linux-foundation.org>: (180 commits) scatterlist: don't BUG when we can trivially return a proper error. docs: update documentation about /proc/<pid>/fdinfo/<fd> fanotify output fs, fanotify: add @mflags field to fanotify output docs: add documentation about /proc/<pid>/fdinfo/<fd> output fs, notify: add procfs fdinfo helper fs, exportfs: add exportfs_encode_inode_fh() helper fs, exportfs: escape nil dereference if no s_export_op present fs, epoll: add procfs fdinfo helper fs, eventfd: add procfs fdinfo helper procfs: add ability to plug in auxiliary fdinfo providers tools/testing/selftests/kcmp/kcmp_test.c: print reason for failure in kcmp_test breakpoint selftests: print failure status instead of cause make error kcmp selftests: print fail status instead of cause make error kcmp selftests: make run_tests fix mem-hotplug selftests: print failure status instead of cause make error cpu-hotplug selftests: print failure status instead of cause make error mqueue selftests: print failure status instead of cause make error vm selftests: print failure status instead of cause make error ubifs: use prandom_bytes mtd: nandsim: use prandom_bytes ...
| * kernel: remove reference to feature-removal-schedule.txtTao Ma2012-12-171-1/+0
| | | | | | | | | | | | | | | | | | | | In commit 9c0ece069b32 ("Get rid of Documentation/feature-removal.txt"), Linus removed feature-removal-schedule.txt from Documentation, but there is still some reference to this file. So remove them. Signed-off-by: Tao Ma <boyu.mt@taobao.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
* | Merge branch 'for-linus' of ↵Linus Torvalds2012-12-171-1/+1
|\ \ | |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull user namespace changes from Eric Biederman: "While small this set of changes is very significant with respect to containers in general and user namespaces in particular. The user space interface is now complete. This set of changes adds support for unprivileged users to create user namespaces and as a user namespace root to create other namespaces. The tyranny of supporting suid root preventing unprivileged users from using cool new kernel features is broken. This set of changes completes the work on setns, adding support for the pid, user, mount namespaces. This set of changes includes a bunch of basic pid namespace cleanups/simplifications. Of particular significance is the rework of the pid namespace cleanup so it no longer requires sending out tendrils into all kinds of unexpected cleanup paths for operation. At least one case of broken error handling is fixed by this cleanup. The files under /proc/<pid>/ns/ have been converted from regular files to magic symlinks which prevents incorrect caching by the VFS, ensuring the files always refer to the namespace the process is currently using and ensuring that the ptrace_mayaccess permission checks are always applied. The files under /proc/<pid>/ns/ have been given stable inode numbers so it is now possible to see if different processes share the same namespaces. Through the David Miller's net tree are changes to relax many of the permission checks in the networking stack to allowing the user namespace root to usefully use the networking stack. Similar changes for the mount namespace and the pid namespace are coming through my tree. Two small changes to add user namespace support were commited here adn in David Miller's -net tree so that I could complete the work on the /proc/<pid>/ns/ files in this tree. Work remains to make it safe to build user namespaces and 9p, afs, ceph, cifs, coda, gfs2, ncpfs, nfs, nfsd, ocfs2, and xfs so the Kconfig guard remains in place preventing that user namespaces from being built when any of those filesystems are enabled. Future design work remains to allow root users outside of the initial user namespace to mount more than just /proc and /sys." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (38 commits) proc: Usable inode numbers for the namespace file descriptors. proc: Fix the namespace inode permission checks. proc: Generalize proc inode allocation userns: Allow unprivilged mounts of proc and sysfs userns: For /proc/self/{uid,gid}_map derive the lower userns from the struct file procfs: Print task uids and gids in the userns that opened the proc file userns: Implement unshare of the user namespace userns: Implent proc namespace operations userns: Kill task_user_ns userns: Make create_new_namespaces take a user_ns parameter userns: Allow unprivileged use of setns. userns: Allow unprivileged users to create new namespaces userns: Allow setting a userns mapping to your current uid. userns: Allow chown and setgid preservation userns: Allow unprivileged users to create user namespaces. userns: Ignore suid and sgid on binaries if the uid or gid can not be mapped userns: fix return value on mntns_install() failure vfs: Allow unprivileged manipulation of the mount namespace. vfs: Only support slave subtrees across different user namespaces vfs: Add a user namespace reference from struct mnt_namespace ...
| * pidns: Use task_active_pid_ns where appropriateEric W. Biederman2012-11-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The expressions tsk->nsproxy->pid_ns and task_active_pid_ns aka ns_of_pid(task_pid(tsk)) should have the same number of cache line misses with the practical difference that ns_of_pid(task_pid(tsk)) is released later in a processes life. Furthermore by using task_active_pid_ns it becomes trivial to write an unshare implementation for the the pid namespace. So I have used task_active_pid_ns everywhere I can. In fork since the pid has not yet been attached to the process I use ns_of_pid, to achieve the same effect. Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
* | cgroup_rm_file: don't delete the uncreated filesGao feng2012-12-061-6/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | in cgroup_add_file,when creating files for cgroup, some of creation may be skipped. So we need to avoid deleting these uncreated files in cgroup_rm_file, otherwise the warning msg will be triggered. "cgroup_addrm_files: failed to remove memory_pressure_enabled, err=-2" Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com> Acked-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@redhat.com> Cc: stable@vger.kernel.org
* | cgroup: remove subsystem files when remounting cgroupGao feng2012-12-031-2/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroup_clear_directroy is called by cgroup_d_remove_dir and cgroup_remount. when we call cgroup_remount to remount the cgroup,the subsystem may be unlinked from cgroupfs_root->subsys_list in rebind_subsystem,this subsystem's files will not be removed in cgroup_clear_directroy. And the system will panic when we try to access these files. this patch removes subsystems's files before rebind_subsystems, if rebind_subsystems failed, repopulate these removed files. With help from Tejun. Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | cgroup: use cgroup_addrm_files() in cgroup_clear_directory()Gao feng2012-11-301-1/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroup_clear_directory() incorrectly invokes cgroup_rm_file() on each cftset of the target subsystems, which only removes the first file of each set. This leaves dangling files after subsystems are removed from a cgroup root via remount. Use cgroup_addrm_files() to remove all files of target subsystems. tj: Move cgroup_addrm_files() prototype decl upwards next to other global declarations. Commit message updated. Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | cgroup: warn about broken hierarchies only after css_onlineGlauber Costa2012-11-301-9/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | If everything goes right, it shouldn't really matter if we are spitting this warning after css_alloc or css_online. If we fail between then, there are some ill cases where we would previously see the message and now we won't (like if the files fail to be created). I believe it really shouldn't matter: this message is intended in spirit to be shown when creation succeeds, but with insane settings. Signed-off-by: Glauber Costa <glommer@parallels.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | cgroup: list_del_init() on removed eventsGreg Thelen2012-11-281-2/+2
| | | | | | | | | | | | | | | | | | Use list_del_init() rather than list_del() to remove events from cgrp->event_list. No functional change. This is just defensive coding. Signed-off-by: Greg Thelen <gthelen@google.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | cgroup: fix lockdep warning for event_controlGreg Thelen2012-11-281-3/+8
| | | | | | | | | | | | | | | | | | | | | | | | The cgroup_event_wake() function is called with the wait queue head locked and it takes cgrp->event_list_lock. However, in cgroup_rmdir() remove_wait_queue() was being called after taking cgrp->event_list_lock. Correct the lock ordering by using a temporary list to obtain the event list to remove from the wait queue. Signed-off-by: Greg Thelen <gthelen@google.com> Signed-off-by: Aaron Durbin <adurbin@google.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | cgroup: move list add after list head initilizationLi Zhong2012-11-281-1/+1
| | | | | | | | | | | | | | | | | | | | | | 2243076ad1 ("cgroup: initialize cgrp->allcg_node in init_cgroup_housekeeping()") initializes cgrp->allcg_node in init_cgroup_housekeeping(). Then in init_cgroup_root(), we should call init_cgroup_housekeeping() before adding it to &root->allcg_list; otherwise, we are initializing an entry already in a list. Signed-off-by: Li Zhong <zhong@linux.vnet.ibm.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | cgroup: remove obsolete guarantee from cgroup_task_migrate.Tao Ma2012-11-201-5/+3
| | | | | | | | | | | | | | | | | | | | | | 'guarantee' is already removed from cgroup_task_migrate, so remove the corresponding comments. Some other typos in cgroup are also changed. Cc: Tejun Heo <tj@kernel.org> Cc: Li Zefan <lizefan@huawei.com> Signed-off-by: Tao Ma <boyu.mt@taobao.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | cgroup: add cgroup->idTejun Heo2012-11-191-1/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With the introduction of generic cgroup hierarchy iterators, css_id is being phased out. It was unnecessarily complex, id'ing the wrong thing (cgroups need IDs, not CSSes) and has other oddities like not being available at ->css_alloc(). This patch adds cgroup->id, which is a simple per-hierarchy ida-allocated ID which is assigned before ->css_alloc() and released after ->css_free(). Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com> Acked-by: Neil Horman <nhorman@tuxdriver.com>
* | cgroup, cpuset: remove cgroup_subsys->post_clone()Tejun Heo2012-11-191-4/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently CGRP_CPUSET_CLONE_CHILDREN triggers ->post_clone(). Now that clone_children is cpuset specific, there's no reason to have this rather odd option activation mechanism in cgroup core. cpuset can check the flag from its ->css_allocate() and take the necessary action. Move cpuset_post_clone() logic to the end of cpuset_css_alloc() and remove cgroup_subsys->post_clone(). Loosely based on Glauber's "generalize post_clone into post_create" patch. Signed-off-by: Tejun Heo <tj@kernel.org> Original-patch-by: Glauber Costa <glommer@parallels.com> Original-patch: <1351686554-22592-2-git-send-email-glommer@parallels.com> Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Glauber Costa <glommer@parallels.com>
* | cgroup: s/CGRP_CLONE_CHILDREN/CGRP_CPUSET_CLONE_CHILDREN/Tejun Heo2012-11-191-16/+12
| | | | | | | | | | | | | | | | | | | | | | | | clone_children is only meaningful for cpuset and will stay that way. Rename the flag to reflect that and update documentation. Also, drop clone_children() wrapper in cgroup.c. The thin wrapper is used only a few times and one of them will go away soon. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Glauber Costa <glommer@parallels.com>
* | cgroup: rename ->create/post_create/pre_destroy/destroy() to ↵Tejun Heo2012-11-191-25/+26
| | | | | | | | | | | | | | | | | | | | ->css_alloc/online/offline/free() Rename cgroup_subsys css lifetime related callbacks to better describe what their roles are. Also, update documentation. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: allow ->post_create() to failTejun Heo2012-11-191-10/+19
| | | | | | | | | | | | | | | | | | | | | | There could be cases where controllers want to do initialization operations which may fail from ->post_create(). This patch makes ->post_create() return -errno to indicate failure and online_css() relay such failures. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Glauber Costa <glommer@parallels.com>
* | cgroup: update cgroup_create() failure pathTejun Heo2012-11-191-7/+14
| | | | | | | | | | | | | | | | | | | | | | | | cgroup_create() was ignoring failure of cgroupfs files. Update it such that, if file creation fails, it rolls back by calling cgroup_destroy_locked() and returns failure. Note that error out goto labels are renamed. The labels are a bit confusing but will become better w/ later cgroup operation renames. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: use mutex_trylock() when grabbing i_mutex of a new cgroup directoryTejun Heo2012-11-191-3/+9
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | All cgroup directory i_mutexes nest outside cgroup_mutex; however, new directory creation is a special case. A new cgroup directory is created while holding cgroup_mutex. Populating the new directory requires both the new directory's i_mutex and cgroup_mutex. Because all directory i_mutexes nest outside cgroup_mutex, grabbing both requires releasing cgroup_mutex first, which isn't a good idea as the new cgroup isn't yet ready to be manipulated by other cgroup opreations. This is worked around by grabbing the new directory's i_mutex while holding cgroup_mutex before making it visible. As there's no other user at that point, grabbing the i_mutex under cgroup_mutex can't lead to deadlock. cgroup_create_file() was using I_MUTEX_CHILD to tell lockdep not to worry about the reverse locking order; however, this creates pseudo locking dependency cgroup_mutex -> I_MUTEX_CHILD, which isn't true - all directory i_mutexes are still nested outside cgroup_mutex. This pseudo locking dependency can lead to spurious lockdep warnings. Use mutex_trylock() instead. This will always succeed and lockdep doesn't create any locking dependency for it. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: simplify cgroup_load_subsys() failure pathTejun Heo2012-11-191-11/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Now that cgroup_unload_subsys() can tell whether the root css is online or not, we can safely call cgroup_unload_subsys() after idr init failure in cgroup_load_subsys(). Replace the manual unrolling and invoke cgroup_unload_subsys() on failure. This drops cgroup_mutex inbetween but should be safe as the subsystem will fail try_module_get() and thus can't be mounted inbetween. As this means that cgroup_unload_subsys() can be called before css_sets are rehashed, remove BUG_ON() on %NULL css_set->subsys[] from cgroup_unload_subsys(). Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: introduce CSS_ONLINE flag and on/offline_css() helpersTejun Heo2012-11-191-23/+42
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | New helpers on/offline_css() respectively wrap ->post_create() and ->pre_destroy() invocations. online_css() sets CSS_ONLINE after ->post_create() is complete and offline_css() invokes ->pre_destroy() iff CSS_ONLINE is set and clears it while also handling the temporary dropping of cgroup_mutex. This patch doesn't introduce any behavior change at the moment but will be used to improve cgroup_create() failure path and allow ->post_create() to fail. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: separate out cgroup_destroy_locked()Tejun Heo2012-11-191-15/+25
| | | | | | | | | | | | | | | | | | | | | | | | | | Separate out cgroup_destroy_locked() from cgroup_destroy(). This will be later used in cgroup_create() failure path. While at it, add lockdep asserts on i_mutex and cgroup_mutex, and move @d and @parent assignments to their declarations. This patch doesn't introduce any functional difference. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: fix harmless bugs in cgroup_load_subsys() fail path and ↵Tejun Heo2012-11-191-1/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroup_unload_subsys() * If idr init fails, cgroup_load_subsys() cleared dummytop->subsys[] before calilng ->destroy() making CSS inaccessible to the callback, and didn't unlink ss->sibling. As no modular controller uses ->use_id, this doesn't cause any actual problems. * cgroup_unload_subsys() was forgetting to free idr, call ->pre_destroy() and clear ->active. As there currently is no modular controller which uses ->use_id, ->pre_destroy() or ->active, this doesn't cause any actual problems. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: lock cgroup_mutex in cgroup_init_subsys()Tejun Heo2012-11-191-0/+4
| | | | | | | | | | | | | | | | | | | | | | Make cgroup_init_subsys() grab cgroup_mutex while initializing a subsystem so that all helpers and callbacks are called under the context they expect. This isn't strictly necessary as cgroup_init_subsys() doesn't race with anybody but will allow adding lockdep assertions. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: trivial cleanup for cgroup_init/load_subsys()Tejun Heo2012-11-191-3/+3
| | | | | | | | | | | | | | | | Consistently use @css and @dummytop in these two functions instead of referring to them indirectly. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: make CSS_* flags bit masks instead of bit positionsTejun Heo2012-11-191-1/+1
| | | | | | | | | | | | | | | | | | | | | | Currently, CSS_* flags are defined as bit positions and manipulated using atomic bitops. There's no reason to use atomic bitops for them and bit positions are clunkier to deal with than bit masks. Make CSS_* bit masks instead and use the usual C bitwise operators to access them. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: cgroup->dentry isn't a RCU pointerTejun Heo2012-11-191-5/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroup->dentry is marked and used as a RCU pointer; however, it isn't one - the final dentry put doesn't go through call_rcu(). cgroup and dentry share the same RCU freeing rule via synchronize_rcu() in cgroup_diput() (kfree_rcu() used on cgrp is unnecessary). If cgrp is accessible under RCU read lock, so is its dentry and dereferencing cgrp->dentry doesn't need any further RCU protection or annotation. While not being accurate, before the previous patch, the RCU accessors served a purpose as memory barriers - cgroup->dentry used to be assigned after the cgroup was made visible to cgroup_path(), so the assignment and dereferencing in cgroup_path() needed the memory barrier pair. Now that list_add_tail_rcu() happens after cgroup->dentry is assigned, this no longer is necessary. Remove the now unnecessary and misleading RCU annotations from cgroup->dentry. To make up for the removal of rcu_dereference_check() in cgroup_path(), add an explicit rcu_lockdep_assert(), which asserts the dereference rule of @cgrp, not cgrp->dentry. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: create directory before linking while creating a new cgroupTejun Heo2012-11-191-18/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | While creating a new cgroup, cgroup_create() links the newly allocated cgroup into various places before trying to create its directory. Because cgroup life-cycle is tied to the vfs objects, this makes it impossible to use cgroup_rmdir() for rolling back creation - the removal logic depends on having full vfs objects. This patch moves directory creation above linking and collect linking operations to one place. This allows directory creation failure to share error exit path with css allocation failures and any failure sites afterwards (to be added later) can use cgroup_rmdir() logic to undo creation. Note that this also makes the memory barriers around cgroup->dentry, which currently is misleadingly using RCU operations, unnecessary. This will be handled in the next patch. While at it, locking BUG_ON() on i_mutex is converted to lockdep_assert_held(). v2: Patch originally removed %NULL dentry check in cgroup_path(); however, Li pointed out that this patch doesn't make it unnecessary as ->create() may call cgroup_path(). Drop the change for now. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: open-code cgroup_create_dir()Tejun Heo2012-11-191-25/+5
| | | | | | | | | | | | | | | | | | | | | | | | The operation order of cgroup creation is about to change and cgroup_create_dir() is more of a hindrance than a proper abstraction. Open-code it by moving the parent nlink adjustment next to self nlink adjustment in cgroup_create_file() and the rest to cgroup_create(). This patch doesn't introduce any behavior change. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: initialize cgrp->allcg_node in init_cgroup_housekeeping()Tejun Heo2012-11-191-0/+1
| | | | | | | | | | | | | | | | Not strictly necessary but it's annoying to have uninitialized list_head around. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: remove incorrect dget/dput() pair in cgroup_create_dir()Tejun Heo2012-11-191-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroup_create_dir() does weird dancing with dentry refcnt. On success, it gets and then puts it achieving nothing. On failure, it puts but there isn't no matching get anywhere leading to the following oops if cgroup_create_file() fails for whatever reason. ------------[ cut here ]------------ kernel BUG at /work/os/work/fs/dcache.c:552! invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC Modules linked in: CPU 2 Pid: 697, comm: mkdir Not tainted 3.7.0-rc4-work+ #3 Bochs Bochs RIP: 0010:[<ffffffff811d9c0c>] [<ffffffff811d9c0c>] dput+0x1dc/0x1e0 RSP: 0018:ffff88001a3ebef8 EFLAGS: 00010246 RAX: 0000000000000000 RBX: ffff88000e5b1ef8 RCX: 0000000000000403 RDX: 0000000000000303 RSI: 2000000000000000 RDI: ffff88000e5b1f58 RBP: ffff88001a3ebf18 R08: ffffffff82c76960 R09: 0000000000000001 R10: ffff880015022080 R11: ffd9bed70f48a041 R12: 00000000ffffffea R13: 0000000000000001 R14: ffff88000e5b1f58 R15: 00007fff57656d60 FS: 00007ff05fcb3800(0000) GS:ffff88001fd00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000004046f0 CR3: 000000001315f000 CR4: 00000000000006e0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400 Process mkdir (pid: 697, threadinfo ffff88001a3ea000, task ffff880015022080) Stack: ffff88001a3ebf48 00000000ffffffea 0000000000000001 0000000000000000 ffff88001a3ebf38 ffffffff811cc889 0000000000000001 ffff88000e5b1ef8 ffff88001a3ebf68 ffffffff811d1fc9 ffff8800198d7f18 ffff880019106ef8 Call Trace: [<ffffffff811cc889>] done_path_create+0x19/0x50 [<ffffffff811d1fc9>] sys_mkdirat+0x59/0x80 [<ffffffff811d2009>] sys_mkdir+0x19/0x20 [<ffffffff81be1e02>] system_call_fastpath+0x16/0x1b Code: 00 48 8d 90 18 01 00 00 48 89 93 c0 00 00 00 4c 89 a0 18 01 00 00 48 8b 83 a0 00 00 00 83 80 28 01 00 00 01 e8 e6 6f a0 00 eb 92 <0f> 0b 66 90 0f 1f 44 00 00 55 48 89 e5 41 57 41 56 49 89 fe 41 RIP [<ffffffff811d9c0c>] dput+0x1dc/0x1e0 RSP <ffff88001a3ebef8> ---[ end trace 1277bcfd9561ddb0 ]--- Fix it by dropping the unnecessary dget/dput() pair. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com> Cc: stable@vger.kernel.org
* | cgroup: implement generic child / descendant walk macrosTejun Heo2012-11-091-0/+86
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, cgroup doesn't provide any generic helper for walking a given cgroup's children or descendants. This patch adds the following three macros. * cgroup_for_each_child() - walk immediate children of a cgroup. * cgroup_for_each_descendant_pre() - visit all descendants of a cgroup in pre-order tree traversal. * cgroup_for_each_descendant_post() - visit all descendants of a cgroup in post-order tree traversal. All three only require the user to hold RCU read lock during traversal. Verifying that each iterated cgroup is online is the responsibility of the user. When used with proper synchronization, cgroup_for_each_descendant_pre() can be used to propagate state updates to descendants in reliable way. See comments for details. v2: s/config/state/ in commit message and comments per Michal. More documentation on synchronization rules. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujisu.com> Reviewed-by: Michal Hocko <mhocko@suse.cz> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: use rculist ops for cgroup->childrenTejun Heo2012-11-091-5/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Use RCU safe list operations for cgroup->children. This will be used to implement cgroup children / descendant walking which can be used by controllers. Note that cgroup_create() now puts a new cgroup at the end of the ->children list instead of head. This isn't strictly necessary but is done so that the iteration order is more conventional. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Michal Hocko <mhocko@suse.cz> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: add cgroup_subsys->post_create()Tejun Heo2012-11-091-2/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, there's no way for a controller to find out whether a new cgroup finished all ->create() allocatinos successfully and is considered "live" by cgroup. This becomes a problem later when we add generic descendants walking to cgroup which can be used by controllers as controllers don't have a synchronization point where it can synchronize against new cgroups appearing in such walks. This patch adds ->post_create(). It's called after all ->create() succeeded and the cgroup is linked into the generic cgroup hierarchy. This plays the counterpart of ->pre_destroy(). When used in combination with the to-be-added generic descendant iterators, ->post_create() can be used to implement reliable state inheritance. It will be explained with the descendant iterators. v2: Added a paragraph about its future use w/ descendant iterators per Michal. v3: Forgot to add ->post_create() invocation to cgroup_load_subsys(). Fixed. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.cz> Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Glauber Costa <glommer@parallels.com>
* | cgroup: set 'start' with the right value in cgroup_path.Tao Ma2012-11-081-2/+2
| | | | | | | | | | | | | | | | | | 'start' is set to buf + buflen and do the '--' immediately. Just set it to 'buf + buflen - 1' directly. Signed-off-by: Tao Ma <boyu.mt@taobao.com> Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Li Zefan <lizefan@huawei.com>
* | Merge branch 'cgroup/for-3.7-fixes' into cgroup/for-3.8Tejun Heo2012-11-061-31/+10
|\| | | | | | | | | | | | | This is to receive device_cgroup fixes so that further device_cgroup changes can be made in cgroup/for-3.8. Signed-off-by: Tejun Heo <tj@kernel.org>
| * Revert "cgroup: Remove task_lock() from cgroup_post_fork()"Tejun Heo2012-10-191-12/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This reverts commit 7e3aa30ac8c904a706518b725c451bb486daaae9. The commit incorrectly assumed that fork path always performed threadgroup_change_begin/end() and depended on that for synchronization against task exit and cgroup migration paths instead of explicitly grabbing task_lock(). threadgroup_change is not locked when forking a new process (as opposed to a new thread in the same process) and even if it were it wouldn't be effective as different processes use different threadgroup locks. Revert the incorrect optimization. Signed-off-by: Tejun Heo <tj@kernel.org> LKML-Reference: <20121008020000.GB2575@localhost> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: stable@vger.kernel.org
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