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* cgroup: CGRP_ROOT_SUBSYS_BOUND should also be ignored when mounting an ↵Tejun Heo2013-06-291-1/+1
| | | | | | | | | | | | | | | | existing hierarchy 0ce6cba357 ("cgroup: CGRP_ROOT_SUBSYS_BOUND should be ignored when comparing mount options") only updated the remount path but CGRP_ROOT_SUBSYS_BOUND should also be ignored when comparing options while mounting an existing hierarchy. As option mismatch triggers a warning but doesn't fail the mount without sane_behavior, this only triggers a spurious warning message. Fix it by only comparing CGRP_ROOT_OPTION_MASK bits when comparing new and existing root options. Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: CGRP_ROOT_SUBSYS_BOUND should be ignored when comparing mount optionsTejun Heo2013-06-281-1/+4
| | | | | | | | | | | | | | | | 1672d04070 ("cgroup: fix cgroupfs_root early destruction path") introduced CGRP_ROOT_SUBSYS_BOUND which is used to mark completion of subsys binding on a new root; however, this broke remounts. cgroup_remount() doesn't allow changing root options via remount and CGRP_ROOT_SUBSYS_BOUND, which is set on all fully initialized roots, makes the function reject all remounts. Fix it by putting the options part in the lower 16 bits of root->flags and masking the comparions. While at it, make cgroup_remount() emit an error message explaining why it's rejecting a remount request, so that it's less of a mystery. Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: fix deadlock on cgroup_mutex via drop_parsed_module_refcounts()Tejun Heo2013-06-281-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | eb178d06332 ("cgroup: grab cgroup_mutex in drop_parsed_module_refcounts()") made drop_parsed_module_refcounts() grab cgroup_mutex to make lockdep assertion in for_each_subsys() happy. Unfortunately, cgroup_remount() calls the function while holding cgroup_mutex in its failure path leading to the following deadlock. # mount -t cgroup -o remount,memory,blkio cgroup blkio cgroup: option changes via remount are deprecated (pid=525 comm=mount) ============================================= [ INFO: possible recursive locking detected ] 3.10.0-rc4-work+ #1 Not tainted --------------------------------------------- mount/525 is trying to acquire lock: (cgroup_mutex){+.+.+.}, at: [<ffffffff8110a3e1>] drop_parsed_module_refcounts+0x21/0xb0 but task is already holding lock: (cgroup_mutex){+.+.+.}, at: [<ffffffff8110e4e1>] cgroup_remount+0x51/0x200 other info that might help us debug this: Possible unsafe locking scenario: CPU0 ---- lock(cgroup_mutex); lock(cgroup_mutex); *** DEADLOCK *** May be due to missing lock nesting notation 4 locks held by mount/525: #0: (&type->s_umount_key#30){+.+...}, at: [<ffffffff811e9a0d>] do_mount+0x2bd/0xa30 #1: (&sb->s_type->i_mutex_key#9){+.+.+.}, at: [<ffffffff8110e4d3>] cgroup_remount+0x43/0x200 #2: (cgroup_mutex){+.+.+.}, at: [<ffffffff8110e4e1>] cgroup_remount+0x51/0x200 #3: (cgroup_root_mutex){+.+.+.}, at: [<ffffffff8110e4ef>] cgroup_remount+0x5f/0x200 stack backtrace: CPU: 2 PID: 525 Comm: mount Not tainted 3.10.0-rc4-work+ #1 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 ffffffff829651f0 ffff88000ec2fc28 ffffffff81c24bb1 ffff88000ec2fce8 ffffffff810f420d 0000000000000006 0000000000000001 0000000000000056 ffff8800153b4640 ffff880000000000 ffffffff81c2e468 ffff8800153b4640 Call Trace: [<ffffffff81c24bb1>] dump_stack+0x19/0x1b [<ffffffff810f420d>] __lock_acquire+0x15dd/0x1e60 [<ffffffff810f531c>] lock_acquire+0x9c/0x1f0 [<ffffffff81c2a805>] mutex_lock_nested+0x65/0x410 [<ffffffff8110a3e1>] drop_parsed_module_refcounts+0x21/0xb0 [<ffffffff8110e63e>] cgroup_remount+0x1ae/0x200 [<ffffffff811c9bb2>] do_remount_sb+0x82/0x190 [<ffffffff811e9d41>] do_mount+0x5f1/0xa30 [<ffffffff811ea203>] SyS_mount+0x83/0xc0 [<ffffffff81c2fb82>] system_call_fastpath+0x16/0x1b Fix it by moving the drop_parsed_module_refcounts() invocation outside cgroup_mutex. Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: always use RCU accessors for protected accessesTejun Heo2013-06-261-9/+12
| | | | | | | | | | | | | | | | | | | | | | | kernel/cgroup.c still has places where a RCU pointer is set and accessed directly without going through RCU_INIT_POINTER() or rcu_dereference_protected(). They're all properly protected accesses so nothing is broken but it leads to spurious sparse RCU address space warnings. Substitute direct accesses with RCU_INIT_POINTER() and rcu_dereference_protected(). Note that %true is specified as the extra condition for all derference updates. This isn't ideal as all it does is suppressing warning without actually policing synchronization rules; however, most are scheduled to be removed pretty soon along with css_id itself, so no reason to be more elaborate. Combined with the previous changes, this removes all RCU related sparse warnings from cgroup. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Fengguang Wu <fengguang.wu@intel.com> Acked-by; Li Zefan <lizefan@huawei.com>
* cgroup: fix RCU accesses around task->cgroupsTejun Heo2013-06-261-11/+13
| | | | | | | | | | | | | | | | | | | There are several places in kernel/cgroup.c where task->cgroups is accessed and modified without going through proper RCU accessors. None is broken as they're all lock protected accesses; however, this still triggers sparse RCU address space warnings. * Consistently use task_css_set() for task->cgroups dereferencing. * Use RCU_INIT_POINTER() to clear task->cgroups to &init_css_set on exit. * Remove unnecessary rcu_dereference_raw() from cset->subsys[] dereference in cgroup_exit(). Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Fengguang Wu <fengguang.wu@intel.com> Acked-by: Li Zefan <lizefan@huawei.com>
* cgroup: grab cgroup_mutex in drop_parsed_module_refcounts()Tejun Heo2013-06-261-5/+5
| | | | | | | | | This isn't strictly necessary as all subsystems specified in @subsys_mask are guaranteed to be pinned; however, it does spuriously trigger lockdep warning. Let's grab cgroup_mutex around it. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* cgroup: fix cgroupfs_root early destruction pathTejun Heo2013-06-261-3/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroupfs_root used to have ->actual_subsys_mask in addition to ->subsys_mask. a8a648c4ac ("cgroup: remove cgroup->actual_subsys_mask") removed it noting that the subsys_mask is essentially temporary and doesn't belong in cgroupfs_root; however, the patch made it impossible to tell whether a cgroupfs_root actually has the subsystems bound or just have the bits set leading to the following BUG when trying to mount with subsystems which are already mounted elsewhere. kernel BUG at kernel/cgroup.c:1038! invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC ... CPU: 1 PID: 7973 Comm: mount Tainted: G W 3.10.0-rc7-next-20130625-sasha-00011-g1c1dc0e #1105 task: ffff880fc0ae8000 ti: ffff880fc0b9a000 task.ti: ffff880fc0b9a000 RIP: 0010:[<ffffffff81249b29>] [<ffffffff81249b29>] rebind_subsystems+0x409/0x5f0 ... Call Trace: [<ffffffff8124bd4f>] cgroup_kill_sb+0xff/0x210 [<ffffffff813d21af>] deactivate_locked_super+0x4f/0x90 [<ffffffff8124f3b3>] cgroup_mount+0x673/0x6e0 [<ffffffff81257169>] cpuset_mount+0xd9/0x110 [<ffffffff813d2580>] mount_fs+0xb0/0x2d0 [<ffffffff81404afd>] vfs_kern_mount+0xbd/0x180 [<ffffffff814070b5>] do_new_mount+0x145/0x2c0 [<ffffffff814085d6>] do_mount+0x356/0x3c0 [<ffffffff8140873d>] SyS_mount+0xfd/0x140 [<ffffffff854eb600>] tracesys+0xdd/0xe2 We still want rebind_subsystems() to take added/removed masks, so let's fix it by marking whether a cgroupfs_root has finished binding or not. Also, document what's going on around ->subsys_mask initialization so that similar mistakes aren't repeated. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Sasha Levin <sasha.levin@oracle.com> Acked-by: Li Zefan <lizefan@huawei.com>
* cgroup: reserve ID 0 for dummy_root and 1 for unified hierarchyTejun Heo2013-06-251-4/+6
| | | | | | | | | | | | | | | Before 1a57423166 ("cgroup: make hierarchy_id use cyclic idr"), hierarchy IDs were allocated from 0. As the dummy hierarchy was always the one first initialized, it got assigned 0 and all other hierarchies from 1. The patch accidentally changed the minimum useable ID to 2. Let's restore ID 0 for dummy_root and while at it reserve 1 for unified hierarchy. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com> Cc: stable@vger.kernel.org
* cgroup: implement for_each_[builtin_]subsys()Tejun Heo2013-06-251-76/+71
| | | | | | | | | | | | | | | | | | | | There are quite a few places where all loaded [builtin] subsys are iterated. Implement for_each_[builtin_]subsys() and replace manual iterations with those to simplify those places a bit. The new iterators automatically skip NULL subsystems. This shouldn't cause any functional difference. Iteration loops which scan all subsystems and then skipping modular ones explicitly are converted to use for_each_builtin_subsys(). While at it, reorder variable declarations and adjust whitespaces a bit in the affected functions. v2: Add lockdep_assert_held() in for_each_subsys() and add comments about synchronization as suggested by Li. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* cgroup: move init_css_set initialization inside cgroup_mutexTejun Heo2013-06-251-4/+4
| | | | | | | | | | cgroup_init() was doing init_css_set initialization outside cgroup_mutex, which is fine but we want to add lockdep annotation on subsystem iterations and cgroup_init() will trigger it spuriously. Move init_css_set initialization inside cgroup_mutex. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* cgroup: s/for_each_subsys()/for_each_root_subsys()/Tejun Heo2013-06-251-25/+22
| | | | | | | | | | | | | | | | | for_each_subsys() walks over subsystems attached to a hierarchy and we're gonna add iterators which walk over all available subsystems. Rename for_each_subsys() to for_each_root_subsys() so that it's more appropriately named and for_each_subsys() can be used to iterate all subsystems. While at it, remove unnecessary underbar prefix from macro arguments, put them inside parentheses, and adjust indentation for the two for_each_*() macros. This patch is purely cosmetic. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* cgroup: clean up find_css_set() and friendsTejun Heo2013-06-251-21/+17
| | | | | | | | | | | | | | | | | | | | | find_css_set() passes uninitialized on-stack template[] array to find_existing_css_set() which sets the entries for all subsystems. Passing around an uninitialized array is a bit icky and we want to introduce an iterator which only iterates loaded subsystems. Let's initialize it on definition. While at it, also make the following cosmetic cleanups. * Convert to proper /** comments. * Reorder variable declarations. * Replace comment on synchronization with lockdep_assert_held(). This patch doesn't make any functional differences. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* cgroup: remove cgroup->actual_subsys_maskTejun Heo2013-06-251-10/+12
| | | | | | | | | | | | | | | | | | | | cgroup curiously has two subsystem masks, ->subsys_mask and ->actual_subsys_mask. The latter only exists because the new target subsys_mask is passed into rebind_subsystems() via @root>subsys_mask. rebind_subsystems() needs to know what the current mask is to decide how to reach the target mask so ->actual_subsys_mask is used as the temp location to remember the current state. Adding a temporary field to a permanent data structure is rather silly and can be misleading. Update rebind_subsystems() to take @added_mask and @removed_mask instead and remove @root->actual_subsys_mask. This patch shouldn't introduce any behavior changes. v2: Comment and description updated as suggested by Li. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* cgroup: prefix global variables with "cgroup_"Tejun Heo2013-06-251-76/+77
| | | | | | | | | | | | | | | | | | | | | Global variable names in kernel/cgroup.c are asking for trouble - subsys, roots, rootnode and so on. Rename them to have "cgroup_" prefix. * s/subsys/cgroup_subsys/ * s/rootnode/cgroup_dummy_root/ * s/dummytop/cgroup_cummy_top/ * s/roots/cgroup_roots/ * s/root_count/cgroup_root_count/ This patch is purely cosmetic. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* cgroup: rename cont to cgrpLi Zefan2013-06-191-11/+11
| | | | | | | | | | | Cont is short for container. control group was named process container at first, but then people found container already has a meaning in linux kernel. Clean up the leftover variable name @cont. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: clean up cgroup_serial_nr_cursorTejun Heo2013-06-181-7/+8
| | | | | | | | | | | | | | | | cgroup_serial_nr_cursor was created atomic64_t because I thought it was never gonna used for anything other than assigning unique numbers to cgroups and didn't want to worry about synchronization; however, now we're using it as an event-stamp to distinguish cgroups created before and after certain point which assumes that it's protected by cgroup_mutex. Let's make it clear by making it a u64. Also, rename it to cgroup_serial_nr_next and make it point to the next nr to allocate so that where it's pointing to is clear and more conventional. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Li Zefan <lizefan@huawei.com>
* cgroup: convert cgroup_cft_commit() to use cgroup_for_each_descendant_pre()Li Zefan2013-06-181-36/+44
| | | | | | | | | | | | We used root->allcg_list to iterate cgroup hierarchy because at that time cgroup_for_each_descendant_pre() hasn't been invented. tj: In cgroup_cfts_commit(), s/@serial_nr/@update_upto/, move the assignment right above releasing cgroup_mutex and explain what's going on there. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: make serial_nr_cursor available throughout cgroup.cLi Zefan2013-06-181-8/+10
| | | | | | | | | | The next patch will use it to determine if a cgroup is newly created while we're iterating the cgroup hierarchy. tj: Rephrased the comment on top of cgroup_serial_nr_cursor. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: fix memory leak in cgroup_rm_cftypes()Li Zefan2013-06-181-1/+2
| | | | | | | | | The memory allocated in cgroup_add_cftypes() should be freed. The effect of this bug is we leak a bit memory everytime we unload cfq-iosched module if blkio cgroup is enabled. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* cgroup: fix umount vs cgroup_event_remove() raceLi Zefan2013-06-181-6/+19
| | | | | | | | | | | | | | | commit 5db9a4d99b0157a513944e9a44d29c9cec2e91dc Author: Tejun Heo <tj@kernel.org> Date: Sat Jul 7 16:08:18 2012 -0700 cgroup: fix cgroup hierarchy umount race This commit fixed a race caused by the dput() in css_dput_fn(), but the dput() in cgroup_event_remove() can also lead to the same BUG(). Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org
* cgroup: fix umount vs cgroup_cfts_commit() raceLi Zefan2013-06-181-1/+8
| | | | | | | | | | | | | | | | | | | | | | | | cgroup_cfts_commit() uses dget() to keep cgroup alive after cgroup_mutex is dropped, but dget() won't prevent cgroupfs from being umounted. When the race happens, vfs will see some dentries with non-zero refcnt while umount is in process. Keep running this: mount -t cgroup -o blkio xxx /cgroup umount /cgroup And this: modprobe cfq-iosched rmmod cfs-iosched After a while, the BUG() in shrink_dcache_for_umount_subtree() may be triggered: BUG: Dentry xxx{i=0,n=blkio.yyy} still in use (1) [umount of cgroup cgroup] Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org
* cgroup: disallow rename(2) if sane_behaviorTejun Heo2013-06-181-0/+7
| | | | | | | | | | | | | | cgroup's rename(2) isn't a proper migration implementation - it can't move the cgroup to a different parent in the hierarchy. All it can do is swapping the name string for that cgroup. This isn't useful and can mislead users to think that cgroup supports proper cgroup-level migration. Disallow rename(2) if sane_behavior. v2: Fail with -EPERM instead of -EINVAL so that it matches the vfs return value when ->rename is not implemented as suggested by Li. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* cgroup: use percpu refcnt for cgroup_subsys_statesTejun Heo2013-06-141-61/+104
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A css (cgroup_subsys_state) is how each cgroup is represented to a controller. As such, it can be used in hot paths across the various subsystems different controllers are associated with. One of the common operations is reference counting, which up until now has been implemented using a global atomic counter and can have significant adverse impact on scalability. For example, css refcnt can be gotten and put multiple times by blkcg for each IO request. For highops configurations which try to do as much per-cpu as possible, the global frequent refcnting can be very expensive. In general, given the various and hugely diverse paths css's end up being used from, we need to make it cheap and highly scalable. In its usage, css refcnting isn't very different from module refcnting. This patch converts css refcnting to use the recently added percpu_ref. css_get/tryget/put() directly maps to the matching percpu_ref operations and the deactivation logic is no longer necessary as percpu_ref already has refcnt killing. The only complication is that as the refcnt is per-cpu, percpu_ref_kill() in itself doesn't ensure that further tryget operations will fail, which we need to guarantee before invoking ->css_offline()'s. This is resolved collecting kill confirmation using percpu_ref_kill_and_confirm() and initiating the offline phase of destruction after all css refcnt's are confirmed to be seen as killed on all CPUs. The previous patches already splitted destruction into two phases, so percpu_ref_kill_and_confirm() can be hooked up easily. This patch removes css_refcnt() which is used for rcu dereference sanity check in css_id(). While we can add a percpu refcnt API to ask the same question, css_id() itself is scheduled to be removed fairly soon, so let's not bother with it. Just drop the sanity check and use rcu_dereference_raw() instead. v2: - init_cgroup_css() was calling percpu_ref_init() without checking the return value. This causes two problems - the obvious lack of error handling and percpu_ref_init() being called from cgroup_init_subsys() before the allocators are up, which triggers warnings but doesn't cause actual problems as the refcnt isn't used for roots anyway. Fix both by moving percpu_ref_init() to cgroup_create(). - The base references were put too early by percpu_ref_kill_and_confirm() and cgroup_offline_fn() put the refs one extra time. This wasn't noticeable because css's go through another RCU grace period before being freed. Update cgroup_destroy_locked() to grab an extra reference before killing the refcnts. This problem was noticed by Kent. Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Kent Overstreet <koverstreet@google.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Mike Snitzer <snitzer@redhat.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: "Alasdair G. Kergon" <agk@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Mikulas Patocka <mpatocka@redhat.com> Cc: Glauber Costa <glommer@gmail.com>
* Merge branch 'for-3.11' of ↵Tejun Heo2013-06-141-5/+8
|\ | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu into for-3.11 This is to receive percpu_refcount which will replace atomic_t reference count in cgroup_subsys_state. Signed-off-by: Tejun Heo <tj@kernel.org>
| * cgroup: warn about mismatching options of a new mount of an existing hierarchyJeff Liu2013-05-291-5/+8
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | With the new __DEVEL__sane_behavior mount option was introduced, if the root cgroup is alive with no xattr function, to mount a new cgroup with xattr will be rejected in terms of design which just fine. However, if the root cgroup does not mounted with __DEVEL__sane_hehavior, to create a new cgroup with xattr option will succeed although after that the EA function does not works as expected but will get ENOTSUPP for setting up attributes under either cgroup. e.g. setfattr: /cgroup2/test: Operation not supported Instead of keeping silence in this case, it's better to drop a log entry in warning level. That would be helpful to understand the reason behind the scene from the user's perspective, and this is essentially an improvement does not break the backward compatibilities. With this fix, above mount attemption will keep up works as usual but the following line cound be found at the system log: [ ...] cgroup: new mount options do not match the existing superblock tj: minor formatting / message updates. Signed-off-by: Jie Liu <jeff.liu@oracle.com> Reported-by: Alexey Kodanev <alexey.kodanev@oracle.com> Signed-off-by: Tejun Heo <tj@kernel.org> Cc: stable@vger.kernel.org
* | cgroup: split cgroup destruction into two stepsTejun Heo2013-06-141-11/+27
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Split cgroup_destroy_locked() into two steps and put the latter half into cgroup_offline_fn() which is executed from a work item. The latter half is responsible for offlining the css's, removing the cgroup from internal lists, and propagating release notification to the parent. The separation is to allow using percpu refcnt for css. Note that this allows for other cgroup operations to happen between the first and second halves of destruction, including creating a new cgroup with the same name. As the target cgroup is marked DEAD in the first half and cgroup internals don't care about the names of cgroups, this should be fine. A comment explaining this will be added by the next patch which implements the actual percpu refcnting. As RCU freeing is guaranteed to happen after the second step of destruction, we can use the same work item for both. This patch renames cgroup->free_work to ->destroy_work and uses it for both purposes. INIT_WORK() is now performed right before queueing the work item. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: reorder the operations in cgroup_destroy_locked()Tejun Heo2013-06-141-26/+35
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch reorders the operations in cgroup_destroy_locked() such that the userland visible parts happen before css offlining and removal from the ->sibling list. This will be used to make css use percpu refcnt. While at it, split out CGRP_DEAD related comment from the refcnt deactivation one and correct / clarify how different guarantees are met. While this patch changes the specific order of operations, it shouldn't cause any noticeable behavior difference. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: remove cgroup->count and useTejun Heo2013-06-131-16/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | cgroup->count tracks the number of css_sets associated with the cgroup and used only to verify that no css_set is associated when the cgroup is being destroyed. It's superflous as the destruction path can simply check whether cgroup->cset_links is empty instead. Drop cgroup->count and check ->cset_links directly from cgroup_destroy_locked(). Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: drop unnecessary RCU dancing from __put_css_set()Tejun Heo2013-06-131-10/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | __put_css_set() does RCU read access on @cgrp across dropping @cgrp->count so that it can continue accessing @cgrp even if the count reached zero and destruction of the cgroup commenced. Given that both sides - __css_put() and cgroup_destroy_locked() - are cold paths, this is unnecessary. Just making cgroup_destroy_locked() grab css_set_lock while checking @cgrp->count is enough. Remove the RCU read locking from __put_css_set() and make cgroup_destroy_locked() read-lock css_set_lock when checking @cgrp->count. This will also allow removing @cgrp->count. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: rename CGRP_REMOVED to CGRP_DEADTejun Heo2013-06-131-16/+14
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | We will add another flag indicating that the cgroup is in the process of being killed. REMOVING / REMOVED is more difficult to distinguish and cgroup_is_removing()/cgroup_is_removed() are a bit awkward. Also, later percpu_ref usage will involve "kill"ing the refcnt. s/CGRP_REMOVED/CGRP_DEAD/ s/cgroup_is_removed()/cgroup_is_dead() This patch is purely cosmetic. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: use kzalloc() instead of kmalloc()Tejun Heo2013-06-131-7/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | There's no point in using kmalloc() instead of the clearing variant for trivial stuff. We can live dangerously elsewhere. Use kzalloc() instead and drop 0 inits. While at it, do trivial code reorganization in cgroup_file_open(). This patch doesn't introduce any functional changes. v2: I was caught in the very distant past where list_del() didn't poison and the initial version converted list_del()s to list_del_init()s too. Li and Kent took me out of the stasis chamber. Signed-off-by: Tejun Heo <tj@kernel.org> Cc: Kent Overstreet <koverstreet@google.com> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: bring some sanity to naming around cg_cgroup_linkTejun Heo2013-06-131-113/+113
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroups and css_sets are mapped M:N and this M:N mapping is represented by struct cg_cgroup_link which forms linked lists on both sides. The naming around this mapping is already confusing and struct cg_cgroup_link exacerbates the situation quite a bit. >From cgroup side, it starts off ->css_sets and runs through ->cgrp_link_list. From css_set side, it starts off ->cg_links and runs through ->cg_link_list. This is rather reversed as cgrp_link_list is used to iterate css_sets and cg_link_list cgroups. Also, this is the only place which is still using the confusing "cg" for css_sets. This patch cleans it up a bit. * s/cgroup->css_sets/cgroup->cset_links/ s/css_set->cg_links/css_set->cgrp_links/ s/cgroup_iter->cg_link/cgroup_iter->cset_link/ * s/cg_cgroup_link/cgrp_cset_link/ * s/cgrp_cset_link->cg/cgrp_cset_link->cset/ s/cgrp_cset_link->cgrp_link_list/cgrp_cset_link->cset_link/ s/cgrp_cset_link->cg_link_list/cgrp_cset_link->cgrp_link/ * s/init_css_set_link/init_cgrp_cset_link/ s/free_cg_links/free_cgrp_cset_links/ s/allocate_cg_links/allocate_cgrp_cset_links/ * s/cgl[12]/link[12]/ in compare_css_sets() * s/saved_link/tmp_link/ s/tmp/tmp_links/ and a couple similar adustments. * Comment and whiteline adjustments. After the changes, we have list_for_each_entry(link, &cont->cset_links, cset_link) { struct css_set *cset = link->cset; instead of list_for_each_entry(link, &cont->css_sets, cgrp_link_list) { struct css_set *cset = link->cg; This patch is purely cosmetic. v2: Fix broken sentences in the patch description. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: consistently use @cset for struct css_set variablesTejun Heo2013-06-131-107/+109
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroup.c uses @cg for most struct css_set variables, which in itself could be a bit confusing, but made much worse by the fact that there are places which use @cg for struct cgroup variables. compare_css_sets() epitomizes this confusion - @[old_]cg are struct css_set while @cg[12] are struct cgroup. It's not like the whole deal with cgroup, css_set and cg_cgroup_link isn't already confusing enough. Let's give it some sanity by uniformly using @cset for all struct css_set variables. * s/cg/cset/ for all css_set variables. * s/oldcg/old_cset/ s/oldcgrp/old_cgrp/. The same for the ones prefixed with "new". * s/cg/cgrp/ for cgroup variables in compare_css_sets(). * s/css/cset/ for the cgroup variable in task_cgroup_from_root(). * Whiteline adjustments. This patch is purely cosmetic. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: remove now unused css_depth()Tejun Heo2013-06-131-12/+0
| | | | | | | | | | Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: clean up the cftype array for the base cgroup filesTejun Heo2013-06-051-23/+24
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | * Rename it from files[] (really?) to cgroup_base_files[]. * Drop CGROUP_FILE_GENERIC_PREFIX which was defined as "cgroup." and used inconsistently. Just use "cgroup." directly. * Collect insane files at the end. Note that only the insane ones are missing "cgroup." prefix. This patch doesn't introduce any functional changes. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: mark "notify_on_release" and "release_agent" cgroup files insaneTejun Heo2013-06-051-1/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | The empty cgroup notification mechanism currently implemented in cgroup is tragically outdated. Forking and execing userland process stopped being a viable notification mechanism more than a decade ago. We're gonna have a saner mechanism. Let's make it clear that this abomination is going away. Mark "notify_on_release" and "release_agent" with CFTYPE_INSANE. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: mark "tasks" cgroup file as insaneTejun Heo2013-06-051-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Some resources controlled by cgroup aren't per-task and cgroup core allowing threads of a single thread_group to be in different cgroups forced memcg do explicitly find the group leader and use it. This is gonna be nasty when transitioning to unified hierarchy and in general we don't want and won't support granularity finer than processes. Mark "tasks" with CFTYPE_INSANE. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Balbir Singh <bsingharora@gmail.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: cgroups@vger.kernel.org Cc: Vivek Goyal <vgoyal@redhat.com>
* | cgroup: update iterators to use cgroup_next_sibling()Tejun Heo2013-05-241-6/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This patch converts cgroup_for_each_child(), cgroup_next_descendant_pre/post() and thus cgroup_for_each_descendant_pre/post() to use cgroup_next_sibling() instead of manually dereferencing ->sibling.next. The only reason the iterators couldn't allow dropping RCU read lock while iteration is in progress was because they couldn't determine the next sibling safely once RCU read lock is dropped. Using cgroup_next_sibling() removes that problem and enables all iterators to allow dropping RCU read lock in the middle. Comments are updated accordingly. This makes the iterators easier to use and will simplify controllers. Note that @cgroup argument is renamed to @cgrp in cgroup_for_each_child() because it conflicts with "struct cgroup" used in the new macro body. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com> Reviewed-by: Michal Hocko <mhocko@suse.cz>
* | cgroup: add cgroup->serial_nr and implement cgroup_next_sibling()Tejun Heo2013-05-241-0/+62
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently, there's no easy way to find out the next sibling cgroup unless it's known that the current cgroup is accessed from the parent's children list in a single RCU critical section. This in turn forces all iterators to require whole iteration to be enclosed in a single RCU critical section, which sometimes is too restrictive. This patch implements cgroup_next_sibling() which can reliably determine the next sibling regardless of the state of the current cgroup as long as it's accessible. It currently is impossible to determine the next sibling after dropping RCU read lock because the cgroup being iterated could be removed anytime and if RCU read lock is dropped, nothing guarantess its ->sibling.next pointer is accessible. A removed cgroup would continue to point to its next sibling for RCU accesses but stop receiving updates from the sibling. IOW, the next sibling could be removed and then complete its grace period while RCU read lock is dropped, making it unsafe to dereference ->sibling.next after dropping and re-acquiring RCU read lock. This can be solved by adding a way to traverse to the next sibling without dereferencing ->sibling.next. This patch adds a monotonically increasing cgroup serial number, cgroup->serial_nr, which guarantees that all cgroup->children lists are kept in increasing serial_nr order. A new function, cgroup_next_sibling(), is implemented, which, if CGRP_REMOVED is not set on the current cgroup, follows ->sibling.next; otherwise, traverses the parent's ->children list until it sees a sibling with higher ->serial_nr. This allows the function to always return the next sibling regardless of the state of the current cgroup without adding overhead in the fast path. Further patches will update the iterators to use cgroup_next_sibling() so that they allow dropping RCU read lock and blocking while iteration is in progress which in turn will be used to simplify controllers. v2: Typo fix as per Serge. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
* | cgroup: make cgroup_is_removed() staticTejun Heo2013-05-241-1/+1
| | | | | | | | | | | | | | | | | | | | cgroup_is_removed() no longer has external users and it shouldn't grow any - controllers should deal with cgroup_subsys_state on/offline state instead of cgroup removal state. Make it static. While at it, make it return bool. Signed-off-by: Tejun Heo <tj@kernel.org>
* | Merge branch 'for-3.10-fixes' into for-3.11Tejun Heo2013-05-241-10/+8
|\| | | | | | | | | | | | | Merging to receive 7805d000db ("cgroup: fix a subtle bug in descendant pre-order walk") so that further iterator updates can build upon it. Signed-off-by: Tejun Heo <tj@kernel.org>
| * cgroup: fix a subtle bug in descendant pre-order walkTejun Heo2013-05-241-6/+3
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When cgroup_next_descendant_pre() initiates a walk, it checks whether the subtree root doesn't have any children and if not returns NULL. Later code assumes that the subtree isn't empty. This is broken because the subtree may become empty inbetween, which can lead to the traversal escaping the subtree by walking to the sibling of the subtree root. There's no reason to have the early exit path. Remove it along with the later assumption that the subtree isn't empty. This simplifies the code a bit and fixes the subtle bug. While at it, fix the comment of cgroup_for_each_descendant_pre() which was incorrectly referring to ->css_offline() instead of ->css_online(). Signed-off-by: Tejun Heo <tj@kernel.org> Reviewed-by: Michal Hocko <mhocko@suse.cz> Cc: stable@vger.kernel.org
| * cgroup: initialize xattr before calling d_instantiate()Li Zefan2013-05-141-4/+5
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | cgroup_create_file() calls d_instantiate(), which may decide to look at the xattrs on the file. Smack always does this and SELinux can be configured to do so. But cgroup_add_file() didn't initialize xattrs before calling cgroup_create_file(), which finally leads to dereferencing NULL dentry->d_fsdata. This bug has been there since cgroup xattr was introduced. Cc: <stable@vger.kernel.org> # 3.8.x Reported-by: Ivan Bulatovic <combuster@archlinux.us> Reported-by: Casey Schaufler <casey@schaufler-ca.com> Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
* | cgroup: implement task_cgroup_path_from_hierarchy()Tejun Heo2013-05-141-0/+32
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | kdbus folks want a sane way to determine the cgroup path that a given task belongs to on a given hierarchy, which is a reasonble thing to expect from cgroup core. Implement task_cgroup_path_from_hierarchy(). v2: Dropped unnecessary NULL check on the return value of task_cgroup_from_root() as suggested by Li Zefan. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Greg Kroah-Hartman <greg@kroah.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Kay Sievers <kay@vrfy.org> Cc: Lennart Poettering <lennart@poettering.net> Cc: Daniel Mack <daniel@zonque.org>
* | cgroup: make hierarchy_id use cyclic idrTejun Heo2013-05-141-20/+8
| | | | | | | | | | | | | | | | | | We want to be able to lookup a hierarchy from its id and cyclic allocation is a whole lot simpler with idr. Convert to idr and use idr_alloc_cyclc(). Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: drop hierarchy_id_lockTejun Heo2013-05-141-6/+17
| | | | | | | | | | | | | | | | Now that hierarchy_id alloc / free are protected by the cgroup mutexes, there's no need for this separate lock. Drop it. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* | cgroup: refactor hierarchy_id handlingTejun Heo2013-05-141-21/+35
|/ | | | | | | | | | | | | | | | | | | | | | | We're planning to converting hierarchy_ida to an idr and use it to look up hierarchy from its id. As we want the mapping to happen atomically with cgroupfs_root registration, this patch refactors hierarchy_id init / exit so that ida operations happen inside cgroup_[root_]mutex. * s/init_root_id()/cgroup_init_root_id()/ and make it return 0 or -errno like a normal function. * Move hierarchy_id initialization from cgroup_root_from_opts() into cgroup_mount() block where the root is confirmed to be used and being registered while holding both mutexes. * Split cgroup_drop_id() into cgroup_exit_root_id() and cgroup_free_root(), so that ID release can happen before dropping the mutexes in cgroup_kill_sb(). The latter expects hierarchy_id to be exited before being invoked. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
* Merge branch 'for-linus' of ↵Linus Torvalds2013-05-021-14/+1
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs Pull VFS updates from Al Viro, Misc cleanups all over the place, mainly wrt /proc interfaces (switch create_proc_entry to proc_create(), get rid of the deprecated create_proc_read_entry() in favor of using proc_create_data() and seq_file etc). 7kloc removed. * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (204 commits) don't bother with deferred freeing of fdtables proc: Move non-public stuff from linux/proc_fs.h to fs/proc/internal.h proc: Make the PROC_I() and PDE() macros internal to procfs proc: Supply a function to remove a proc entry by PDE take cgroup_open() and cpuset_open() to fs/proc/base.c ppc: Clean up scanlog ppc: Clean up rtas_flash driver somewhat hostap: proc: Use remove_proc_subtree() drm: proc: Use remove_proc_subtree() drm: proc: Use minor->index to label things, not PDE->name drm: Constify drm_proc_list[] zoran: Don't print proc_dir_entry data in debug reiserfs: Don't access the proc_dir_entry in r_open(), r_start() r_show() proc: Supply an accessor for getting the data from a PDE's parent airo: Use remove_proc_subtree() rtl8192u: Don't need to save device proc dir PDE rtl8187se: Use a dir under /proc/net/r8180/ proc: Add proc_mkdir_data() proc: Move some bits from linux/proc_fs.h to linux/{of.h,signal.h,tty.h} proc: Move PDE_NET() to fs/proc/proc_net.c ...
| * take cgroup_open() and cpuset_open() to fs/proc/base.cAl Viro2013-05-011-14/+1
| | | | | | | | Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
* | Merge branch 'sched-core-for-linus' of ↵Linus Torvalds2013-04-301-3/+0
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler changes from Ingo Molnar: "The main changes in this development cycle were: - full dynticks preparatory work by Frederic Weisbecker - factor out the cpu time accounting code better, by Li Zefan - multi-CPU load balancer cleanups and improvements by Joonsoo Kim - various smaller fixes and cleanups" * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (45 commits) sched: Fix init NOHZ_IDLE flag sched: Prevent to re-select dst-cpu in load_balance() sched: Rename load_balance_tmpmask to load_balance_mask sched: Move up affinity check to mitigate useless redoing overhead sched: Don't consider other cpus in our group in case of NEWLY_IDLE sched: Explicitly cpu_idle_type checking in rebalance_domains() sched: Change position of resched_cpu() in load_balance() sched: Fix wrong rq's runnable_avg update with rt tasks sched: Document task_struct::personality field sched/cpuacct/UML: Fix header file dependency bug on the UML build cgroup: Kill subsys.active flag sched/cpuacct: No need to check subsys active state sched/cpuacct: Initialize cpuacct subsystem earlier sched/cpuacct: Initialize root cpuacct earlier sched/cpuacct: Allocate per_cpu cpuusage for root cpuacct statically sched/cpuacct: Clean up cpuacct.h sched/cpuacct: Remove redundant NULL checks in cpuacct_acount_field() sched/cpuacct: Remove redundant NULL checks in cpuacct_charge() sched/cpuacct: Add cpuacct_acount_field() sched/cpuacct: Add cpuacct_init() ...
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