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* Merge branch 'akpm' (Andrew's patch-bomb)Linus Torvalds2012-12-181-1/+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 Ma2012-12-181-1/+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 Torvalds2012-12-181-1/+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
| * Revert "cgroup: Drop task_lock(parent) on cgroup_fork()"Tejun Heo2012-10-191-17/+6
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This reverts commit 7e381b0eb1e1a9805c37335562e8dc02e7d7848c. 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> Bitterly-Acked-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: stable@vger.kernel.org
| * cgroup: notify_on_release may not be triggered in some casesDaisuke Nishimura2012-10-171-2/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | notify_on_release must be triggered when the last process in a cgroup is move to another. But if the first(and only) process in a cgroup is moved to another, notify_on_release is not triggered. # mkdir /cgroup/cpu/SRC # mkdir /cgroup/cpu/DST # # echo 1 >/cgroup/cpu/SRC/notify_on_release # echo 1 >/cgroup/cpu/DST/notify_on_release # # sleep 300 & [1] 8629 # # echo 8629 >/cgroup/cpu/SRC/tasks # echo 8629 >/cgroup/cpu/DST/tasks -> notify_on_release for /SRC must be triggered at this point, but it isn't. This is because put_css_set() is called before setting CGRP_RELEASABLE in cgroup_task_migrate(), and is a regression introduce by the commit:74a1166d(cgroups: make procs file writable), which was merged into v3.0. Cc: Ben Blum <bblum@andrew.cmu.edu> Cc: <stable@vger.kernel.org> # v3.0.x and later Acked-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by: Tejun Heo <tj@kernel.org>
* | Merge branch 'cgroup-rmdir-updates' into cgroup/for-3.8Tejun Heo2012-11-051-195/+61
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pull rmdir updates into for-3.8 so that further callback updates can be put on top. This pull created a trivial conflict between the following two commits. 8c7f6edbda ("cgroup: mark subsystems with broken hierarchy support and whine if cgroups are nested for them") ed95779340 ("cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs") The former added a field to cgroup_subsys and the latter removed one from it. They happen to be colocated causing the conflict. Keeping what's added and removing what's removed resolves the conflict. Signed-off-by: Tejun Heo <tj@kernel.org>
| * | cgroup: make ->pre_destroy() return voidTejun Heo2012-11-051-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | All ->pre_destory() implementations return 0 now, which is the only allowed return value. Make it return void. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Michal Hocko <mhocko@suse.cz> Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Balbir Singh <bsingharora@gmail.com> Cc: Vivek Goyal <vgoyal@redhat.com>
| * | cgroup: remove CGRP_WAIT_ON_RMDIR, cgroup_exclude_rmdir() and ↵Tejun Heo2012-11-051-51/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroup_release_and_wakeup_rmdir() CGRP_WAIT_ON_RMDIR is another kludge which was added to make cgroup destruction rollback somewhat working. cgroup_rmdir() used to drain CSS references and CGRP_WAIT_ON_RMDIR and the associated waitqueue and helpers were used to allow the task performing rmdir to wait for the next relevant event. Unfortunately, the wait is visible to controllers too and the mechanism got exposed to memcg by 887032670d ("cgroup avoid permanent sleep at rmdir"). Now that the draining and retries are gone, CGRP_WAIT_ON_RMDIR is unnecessary. Remove it and all the mechanisms supporting it. Note that memcontrol.c changes are essentially revert of 887032670d ("cgroup avoid permanent sleep at rmdir"). 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> Cc: Balbir Singh <bsingharora@gmail.com>
| * | cgroup: deactivate CSS's and mark cgroup dead before invoking ->pre_destroy()Tejun Heo2012-11-051-46/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Because ->pre_destroy() could fail and can't be called under cgroup_mutex, cgroup destruction did something very ugly. 1. Grab cgroup_mutex and verify it can be destroyed; fail otherwise. 2. Release cgroup_mutex and call ->pre_destroy(). 3. Re-grab cgroup_mutex and verify it can still be destroyed; fail otherwise. 4. Continue destroying. In addition to being ugly, it has been always broken in various ways. For example, memcg ->pre_destroy() expects the cgroup to be inactive after it's done but tasks can be attached and detached between #2 and #3 and the conditions that memcg verified in ->pre_destroy() might no longer hold by the time control reaches #3. Now that ->pre_destroy() is no longer allowed to fail. We can switch to the following. 1. Grab cgroup_mutex and verify it can be destroyed; fail otherwise. 2. Deactivate CSS's and mark the cgroup removed thus preventing any further operations which can invalidate the verification from #1. 3. Release cgroup_mutex and call ->pre_destroy(). 4. Re-grab cgroup_mutex and continue destroying. After this change, controllers can safely assume that ->pre_destroy() will only be called only once for a given cgroup and, once ->pre_destroy() is called, the cgroup will stay dormant till it's destroyed. This removes the only reason ->pre_destroy() can fail - new task being attached or child cgroup being created inbetween. Error out path is removed and ->pre_destroy() invocation is open coded in cgroup_rmdir(). v2: cgroup_call_pre_destroy() removal moved to this patch per Michal. Commit message updated per Glauber. 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> Cc: Glauber Costa <glommer@parallels.com>
| * | cgroup: use cgroup_lock_live_group(parent) in cgroup_create()Tejun Heo2012-11-051-3/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch makes cgroup_create() fail if @parent is marked removed. This is to prepare for further updates to cgroup_rmdir() path. Note that this change isn't strictly necessary. cgroup can only be created via mkdir and the removed marking and dentry removal happen without releasing cgroup_mutex, so cgroup_create() can never race with cgroup_rmdir(). Even after the scheduled updates to cgroup_rmdir(), cgroup_mkdir() and cgroup_rmdir() are synchronized by i_mutex rendering the added liveliness check unnecessary. Do it anyway such that locking is contained inside cgroup proper and we don't get nasty surprises if we ever grow another caller of cgroup_create(). 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: kill CSS_REMOVEDTejun Heo2012-11-051-19/+12
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | CSS_REMOVED is one of the several contortions which were necessary to support css reference draining on cgroup removal. All css->refcnts which need draining should be deactivated and verified to equal zero atomically w.r.t. css_tryget(). If any one isn't zero, all refcnts needed to be re-activated and css_tryget() shouldn't fail in the process. This was achieved by letting css_tryget() busy-loop until either the refcnt is reactivated (failed removal attempt) or CSS_REMOVED is set (committing to removal). Now that css refcnt draining is no longer used, there's no need for atomic rollback mechanism. css_tryget() simply can look at the reference count and fail if it's deactivated - it's never getting re-activated. This patch removes CSS_REMOVED and updates __css_tryget() to fail if the refcnt is deactivated. As deactivation and removal are a single step now, they no longer need to be protected against css_tryget() happening from irq context. Remove local_irq_disable/enable() from cgroup_rmdir(). Note that this removes css_is_removed() whose only user is VM_BUG_ON() in memcontrol.c. We can replace it with a check on the refcnt but given that the only use case is a debug assert, I think it's better to simply unexport it. v2: Comment updated and explanation on local_irq_disable/enable() added per Michal Hocko. 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> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Balbir Singh <bsingharora@gmail.com>
| * | cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refsTejun Heo2012-11-051-95/+36
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 2ef37d3fe4 ("memcg: Simplify mem_cgroup_force_empty_list error handling") removed the last user of __DEPRECATED_clear_css_refs. This patch removes __DEPRECATED_clear_css_refs and mechanisms to support it. * Conditionals dependent on __DEPRECATED_clear_css_refs removed. * cgroup_clear_css_refs() can no longer fail. All that needs to be done are deactivating refcnts, setting CSS_REMOVED and putting the base reference on each css. Remove cgroup_clear_css_refs() and the failure path, and open-code the loops into cgroup_rmdir(). This patch keeps the two for_each_subsys() loops separate while open coding them. They can be merged now but there are scheduled changes which need them to be separate, so keep them separate to reduce the amount of churn. local_irq_save/restore() from cgroup_clear_css_refs() are replaced with local_irq_disable/enable() for simplicity. This is safe as cgroup_rmdir() is always called with IRQ enabled. Note that this IRQ switching is necessary to ensure that css_tryget() isn't called from IRQ context on the same CPU while lower context is between CSS deactivation and setting CSS_REMOVED as css_tryget() would hang forever in such cases waiting for CSS to be re-activated or CSS_REMOVED set. This will go away soon. v2: cgroup_call_pre_destroy() removal dropped per Michal. Commit message updated to explain local_irq_disable/enable() conversion. 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: cgroup_subsys->fork() should be called after the task is added to ↵Tejun Heo2012-10-171-32/+30
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | css_set cgroup core has a bug which violates a basic rule about event notifications - when a new entity needs to be added, you add that to the notification list first and then make the new entity conform to the current state. If done in the reverse order, an event happening inbetween will be lost. cgroup_subsys->fork() is invoked way before the new task is added to the css_set. Currently, cgroup_freezer is the only user of ->fork() and uses it to make new tasks conform to the current state of the freezer. If FROZEN state is requested while fork is in progress between cgroup_fork_callbacks() and cgroup_post_fork(), the child could escape freezing - the cgroup isn't frozen when ->fork() is called and the freezer couldn't see the new task on the css_set. This patch moves cgroup_subsys->fork() invocation to cgroup_post_fork() after the new task is added to the css_set. cgroup_fork_callbacks() is removed. Because now a task may be migrated during cgroup_subsys->fork(), freezer_fork() is updated so that it adheres to the usual RCU locking and the rather pointless comment on why locking can be different there is removed (if it doesn't make anything simpler, why even bother?). Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: Rafael J. Wysocki <rjw@sisk.pl> Cc: stable@vger.kernel.org
* | Merge branch 'for-3.7-hierarchy' of ↵Linus Torvalds2012-10-021-1/+11
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup Pull cgroup hierarchy update from Tejun Heo: "Currently, different cgroup subsystems handle nested cgroups completely differently. There's no consistency among subsystems and the behaviors often are outright broken. People at least seem to agree that the broken hierarhcy behaviors need to be weeded out if any progress is gonna be made on this front and that the fallouts from deprecating the broken behaviors should be acceptable especially given that the current behaviors don't make much sense when nested. This patch makes cgroup emit warning messages if cgroups for subsystems with broken hierarchy behavior are nested to prepare for fixing them in the future. This was put in a separate branch because more related changes were expected (didn't make it this round) and the memory cgroup wanted to pull in this and make changes on top." * 'for-3.7-hierarchy' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: cgroup: mark subsystems with broken hierarchy support and whine if cgroups are nested for them
| * | cgroup: mark subsystems with broken hierarchy support and whine if cgroups ↵Tejun Heo2012-09-141-1/+11
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | are nested for them Currently, cgroup hierarchy support is a mess. cpu related subsystems behave correctly - configuration, accounting and control on a parent properly cover its children. blkio and freezer completely ignore hierarchy and treat all cgroups as if they're directly under the root cgroup. Others show yet different behaviors. These differing interpretations of cgroup hierarchy make using cgroup confusing and it impossible to co-mount controllers into the same hierarchy and obtain sane behavior. Eventually, we want full hierarchy support from all subsystems and probably a unified hierarchy. Users using separate hierarchies expecting completely different behaviors depending on the mounted subsystem is deterimental to making any progress on this front. This patch adds cgroup_subsys.broken_hierarchy and sets it to %true for controllers which are lacking in hierarchy support. The goal of this patch is two-fold. * Move users away from using hierarchy on currently non-hierarchical subsystems, so that implementing proper hierarchy support on those doesn't surprise them. * Keep track of which controllers are broken how and nudge the subsystems to implement proper hierarchy support. For now, start with a single warning message. We can whine louder later on. v2: Fixed a typo spotted by Michal. Warning message updated. v3: Updated memcg part so that it doesn't generate warning in the cases where .use_hierarchy=false doesn't make the behavior different from root.use_hierarchy=true. Fixed a typo spotted by Glauber. v4: Check ->broken_hierarchy after cgroup creation is complete so that ->create() can affect the result per Michal. Dropped unnecessary memcg root handling per Michal. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Li Zefan <lizefan@huawei.com> Acked-by: Serge E. Hallyn <serue@us.ibm.com> Cc: Glauber Costa <glommer@parallels.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Paul Turner <pjt@google.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Thomas Graf <tgraf@suug.ch> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Paul Mackerras <paulus@samba.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@ghostprotocols.net> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
* | cgroup: Assign subsystem IDs during compile timeDaniel Wagner2012-09-141-19/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | WARNING: With this change it is impossible to load external built controllers anymore. In case where CONFIG_NETPRIO_CGROUP=m and CONFIG_NET_CLS_CGROUP=m is set, corresponding subsys_id should also be a constant. Up to now, net_prio_subsys_id and net_cls_subsys_id would be of the type int and the value would be assigned during runtime. By switching the macro definition IS_SUBSYS_ENABLED from IS_BUILTIN to IS_ENABLED, all *_subsys_id will have constant value. That means we need to remove all the code which assumes a value can be assigned to net_prio_subsys_id and net_cls_subsys_id. A close look is necessary on the RCU part which was introduces by following patch: commit f845172531fb7410c7fb7780b1a6e51ee6df7d52 Author: Herbert Xu <herbert@gondor.apana.org.au> Mon May 24 09:12:34 2010 Committer: David S. Miller <davem@davemloft.net> Mon May 24 09:12:34 2010 cls_cgroup: Store classid in struct sock Tis code was added to init_cgroup_cls() /* We can't use rcu_assign_pointer because this is an int. */ smp_wmb(); net_cls_subsys_id = net_cls_subsys.subsys_id; respectively to exit_cgroup_cls() net_cls_subsys_id = -1; synchronize_rcu(); and in module version of task_cls_classid() rcu_read_lock(); id = rcu_dereference(net_cls_subsys_id); if (id >= 0) classid = container_of(task_subsys_state(p, id), struct cgroup_cls_state, css)->classid; rcu_read_unlock(); Without an explicit explaination why the RCU part is needed. (The rcu_deference was fixed by exchanging it to rcu_derefence_index_check() in a later commit, but that is a minor detail.) So here is my pondering why it was introduced and why it safe to remove it now. Note that this code was copied over to net_prio the reasoning holds for that subsystem too. The idea behind the RCU use for net_cls_subsys_id is to make sure we get a valid pointer back from task_subsys_state(). task_subsys_state() is just blindly accessing the subsys array and returning the pointer. Obviously, passing in -1 as id into task_subsys_state() returns an invalid value (out of lower bound). So this code makes sure that only after module is loaded and the subsystem registered, the id is assigned. Before unregistering the module all old readers must have left the critical section. This is done by assigning -1 to the id and issuing a synchronized_rcu(). Any new readers wont call task_subsys_state() anymore and therefore it is safe to unregister the subsystem. The new code relies on the same trick, but it looks at the subsys pointer return by task_subsys_state() (remember the id is constant and therefore we allways have a valid index into the subsys array). No precautions need to be taken during module loading module. Eventually, all CPUs will get a valid pointer back from task_subsys_state() because rebind_subsystem() which is called after the module init() function will assigned subsys[net_cls_subsys_id] the newly loaded module subsystem pointer. When the subsystem is about to be removed, rebind_subsystem() will called before the module exit() function. In this case, rebind_subsys() will assign subsys[net_cls_subsys_id] a NULL pointer and then it calls synchronize_rcu(). All old readers have left by then the critical section. Any new reader wont access the subsystem anymore. At this point we are safe to unregister the subsystem. No synchronize_rcu() call is needed. Signed-off-by: Daniel Wagner <daniel.wagner@bmw-carit.de> Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com> Acked-by: Neil Horman <nhorman@tuxdriver.com> Cc: "David S. Miller" <davem@davemloft.net> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Eric Dumazet <edumazet@google.com> Cc: Gao feng <gaofeng@cn.fujitsu.com> Cc: Glauber Costa <glommer@parallels.com> Cc: Herbert Xu <herbert@gondor.apana.org.au> Cc: Jamal Hadi Salim <jhs@mojatatu.com> Cc: John Fastabend <john.r.fastabend@intel.com> Cc: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: netdev@vger.kernel.org Cc: cgroups@vger.kernel.org
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