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2014-06-30cgroup: fix a race between cgroup_mount() and cgroup_kill_sb()Li Zefan1-7/+26
We've converted cgroup to kernfs so cgroup won't be intertwined with vfs objects and locking, but there are dark areas. Run two instances of this script concurrently: for ((; ;)) { mount -t cgroup -o cpuacct xxx /cgroup umount /cgroup } After a while, I saw two mount processes were stuck at retrying, because they were waiting for a subsystem to become free, but the root associated with this subsystem never got freed. This can happen, if thread A is in the process of killing superblock but hasn't called percpu_ref_kill(), and at this time thread B is mounting the same cgroup root and finds the root in the root list and performs percpu_ref_try_get(). To fix this, we try to increase both the refcnt of the superblock and the percpu refcnt of cgroup root. v2: - we should try to get both the superblock refcnt and cgroup_root refcnt, because cgroup_root may have no superblock assosiated with it. - adjust/add comments. tj: Updated comments. Renamed @sb to @pinned_sb. Cc: <stable@vger.kernel.org> # 3.15 Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2014-06-30cgroup: fix mount failure in a corner caseLi Zefan1-0/+23
# cat test.sh #! /bin/bash mount -t cgroup -o cpu xxx /cgroup umount /cgroup mount -t cgroup -o cpu,cpuacct xxx /cgroup umount /cgroup # ./test.sh mount: xxx already mounted or /cgroup busy mount: according to mtab, xxx is already mounted on /cgroup It's because the cgroupfs_root of the first mount was under destruction asynchronously. Fix this by delaying and then retrying mount for this case. v3: - put the refcnt immediately after getting it. (Tejun) v2: - use percpu_ref_tryget_live() rather that introducing percpu_ref_alive(). (Tejun) - adjust comment. tj: Updated the comment a bit. Cc: <stable@vger.kernel.org> # 3.15 Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2014-06-17cgroup: fix broken css_has_online_children()Li Zefan1-1/+1
After running: # mount -t cgroup cpu xxx /cgroup && mkdir /cgroup/sub && \ rmdir /cgroup/sub && umount /cgroup I found the cgroup root still existed: # cat /proc/cgroups #subsys_name hierarchy num_cgroups enabled cpuset 0 1 1 cpu 1 1 1 ... It turned out css_has_online_children() is broken. Signed-off-by: Li Zefan <lizefan@huawei.com> Sigend-off-by: Tejun Heo <tj@kernel.org>
2014-06-09Merge branch 'for-3.16' of ↵Linus Torvalds1-644/+1181
git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup Pull cgroup updates from Tejun Heo: "A lot of activities on cgroup side. Heavy restructuring including locking simplification took place to improve the code base and enable implementation of the unified hierarchy, which currently exists behind a __DEVEL__ mount option. The core support is mostly complete but individual controllers need further work. To explain the design and rationales of the the unified hierarchy Documentation/cgroups/unified-hierarchy.txt is added. Another notable change is css (cgroup_subsys_state - what each controller uses to identify and interact with a cgroup) iteration update. This is part of continuing updates on css object lifetime and visibility. cgroup started with reference count draining on removal way back and is now reaching a point where csses behave and are iterated like normal refcnted objects albeit with some complexities to allow distinguishing the state where they're being deleted. The css iteration update isn't taken advantage of yet but is planned to be used to simplify memcg significantly" * 'for-3.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (77 commits) cgroup: disallow disabled controllers on the default hierarchy cgroup: don't destroy the default root cgroup: disallow debug controller on the default hierarchy cgroup: clean up MAINTAINERS entries cgroup: implement css_tryget() device_cgroup: use css_has_online_children() instead of has_children() cgroup: convert cgroup_has_live_children() into css_has_online_children() cgroup: use CSS_ONLINE instead of CGRP_DEAD cgroup: iterate cgroup_subsys_states directly cgroup: introduce CSS_RELEASED and reduce css iteration fallback window cgroup: move cgroup->serial_nr into cgroup_subsys_state cgroup: link all cgroup_subsys_states in their sibling lists cgroup: move cgroup->sibling and ->children into cgroup_subsys_state cgroup: remove cgroup->parent device_cgroup: remove direct access to cgroup->children memcg: update memcg_has_children() to use css_next_child() memcg: remove tasks/children test from mem_cgroup_force_empty() cgroup: remove css_parent() cgroup: skip refcnting on normal root csses and cgrp_dfl_root self css cgroup: use cgroup->self.refcnt for cgroup refcnting ...
2014-06-05cgroup: disallow disabled controllers on the default hierarchyLi Zefan1-5/+9
After booting with cgroup_disable=memory, I still saw memcg files in the default hierarchy, and I can write to them, though it won't take effect. # dmesg ... Disabling memory control group subsystem ... # mount -t cgroup -o __DEVEL__sane_behavior xxx /cgroup # ls /cgroup ... memory.failcnt memory.move_charge_at_immigrate memory.force_empty memory.numa_stat memory.limit_in_bytes memory.oom_control ... # cat /cgroup/memory.usage_in_bytes 0 tj: Minor comment update. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2014-06-04cgroup: don't destroy the default rootLi Zefan1-1/+4
The default root is allocated and initialized at boot phase, so we shouldn't destroy the default root when it's umounted, otherwise it will lead to disaster. Just try mount and then umount the default root, and the kernel will crash immediately. v2: - No need to check for CSS_NO_REF in cgroup_get/put(). (Tejun) - Better call cgroup_put() for the default root in kill_sb(). (Tejun) - Add a comment. Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Tejun Heo <tj@kernel.org>
2014-06-03kernfs: move the last knowledge of sysfs out from kernfsJianyu Zhan1-1/+3
There is still one residue of sysfs remaining: the sb_magic SYSFS_MAGIC. However this should be kernfs user specific, so this patch moves it out. Kerrnfs user should specify their magic number while mouting. Signed-off-by: Jianyu Zhan <nasa4836@gmail.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2014-05-19cgroup: disallow debug controller on the default hierarchyTejun Heo1-3/+18
The debug controller, as its name suggests, exposes cgroup core internals to userland to aid debugging. Unfortunately, except for the name, there's no provision to prevent its usage in production configurations and the controller is widely enabled and mounted leaking internal details to userland. Like most other debug information, the information exposed by debug isn't interesting even for debugging itself once the related parts are working reliably. This controller has no reason for existing. This patch implements cgrp_dfl_root_inhibit_ss_mask which can suppress specific subsystems on the default hierarchy and adds the debug subsystem to it so that it can be gradually deprecated as usages move towards the unified hierarchy. Signed-off-by: Tejun Heo <tj@kernel.org>
2014-05-16cgroup: convert cgroup_has_live_children() into css_has_online_children()Tejun Heo1-12/+20
Now that cgroup liveliness and css onliness are the same state, convert cgroup_has_live_children() into css_has_online_children() so that it can be used for actual csses too. The function now uses css_for_each_child() for iteration and is published. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-16cgroup: use CSS_ONLINE instead of CGRP_DEADTejun Heo1-3/+4
Use CSS_ONLINE on the self css to indicate whether a cgroup has been killed instead of CGRP_DEAD. This will allow re-using css online test for cgroup liveliness test. This doesn't introduce any functional change. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-16cgroup: iterate cgroup_subsys_states directlyTejun Heo1-25/+37
Currently, css_next_child() is implemented as finding the next child cgroup which has the css enabled, which used to be the only way to do it as only cgroups participated in sibling lists and thus could be iteratd. This works as long as what's required during iteration is not missing online csses; however, it turns out that there are use cases where offlined but not yet released csses need to be iterated. This is difficult to implement through cgroup iteration the unified hierarchy as there may be multiple dying csses for the same subsystem associated with single cgroup. After the recent changes, the cgroup self and regular csses behave identically in how they're linked and unlinked from the sibling lists including assertion of CSS_RELEASED and css_next_child() can simply switch to iterating csses directly. This both simplifies the logic and ensures that all visible non-released csses are included in the iteration whether there are multiple dying csses for a subsystem or not. As all other iterators depend on css_next_child() for sibling iteration, this changes behaviors of all css iterators. Add and update explanations on the css states which are included in traversal to all iterators. As css iteration could always contain offlined csses, this shouldn't break any of the current users and new usages which need iteration of all on and offline csses can make use of the new semantics. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Johannes Weiner <hannes@cmpxchg.org>
2014-05-16cgroup: introduce CSS_RELEASED and reduce css iteration fallback windowTejun Heo1-21/+20
css iterations allow the caller to drop RCU read lock. As long as the caller keeps the current position accessible, it can simply re-grab RCU read lock later and continue iteration. This is achieved by using CGRP_DEAD to detect whether the current positions next pointer is safe to dereference and if not re-iterate from the beginning to the next position using ->serial_nr. CGRP_DEAD is used as the marker to invalidate the next pointer and the only requirement is that the marker is set before the next sibling starts its RCU grace period. Because CGRP_DEAD is set at the end of cgroup_destroy_locked() but the cgroup is unlinked when the reference count reaches zero, we currently have a rather large window where this fallback re-iteration logic can be triggered. This patch introduces CSS_RELEASED which is set when a css is unlinked from its sibling list. This still keeps the re-iteration logic working while drastically reducing the window of its activation. While at it, rewrite the comment in css_next_child() to reflect the new flag and better explain the synchronization. This will also enable iterating csses directly instead of through cgroups. v2: CSS_RELEASED now assigned to 1 << 2 as 1 << 0 is used by CSS_NO_REF. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-16cgroup: move cgroup->serial_nr into cgroup_subsys_stateTejun Heo1-9/+11
We're moving towards using cgroup_subsys_states as the fundamental structural blocks. All csses including the cgroup->self and actual ones now form trees through css->children and ->sibling which follow the same rules as what cgroup->children and ->sibling followed. This patch moves cgroup->serial_nr which is used to implement css iteration into css. Note that all csses, regardless of their types, allocate their serial numbers from the same monotonically increasing counter. This doesn't affect the ordering needed by css iteration or cause any other material behavior changes. This will be used to update css iteration. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-16cgroup: link all cgroup_subsys_states in their sibling listsTejun Heo1-7/+12
Currently, while all csses have ->children and ->sibling, only the self csses of cgroups make use of them. This patch makes all other csses to link themselves on the sibling lists too. This will be used to update css iteration. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-16cgroup: move cgroup->sibling and ->children into cgroup_subsys_stateTejun Heo1-18/+20
We're moving towards using cgroup_subsys_states as the fundamental structural blocks. Let's move cgroup->sibling and ->children into cgroup_subsys_state. This is pure move without functional change and only cgroup->self's fields are actually used. Other csses will make use of the fields later. While at it, update init_and_link_css() so that it zeroes the whole css before initializing it and remove explicit zeroing of ->flags. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-16cgroup: remove cgroup->parentTejun Heo1-22/+30
cgroup->parent is redundant as cgroup->self.parent can also be used to determine the parent cgroup and we're moving towards using cgroup_subsys_states as the fundamental structural blocks. This patch introduces cgroup_parent() which follows cgroup->self.parent and removes cgroup->parent. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-16cgroup: remove css_parent()Tejun Heo1-4/+4
cgroup in general is moving towards using cgroup_subsys_state as the fundamental structural component and css_parent() was introduced to convert from using cgroup->parent to css->parent. It was quite some time ago and we're moving forward with making css more prominent. This patch drops the trivial wrapper css_parent() and let the users dereference css->parent. While at it, explicitly mark fields of css which are public and immutable. v2: New usage from device_cgroup.c converted. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Neil Horman <nhorman@tuxdriver.com> Acked-by: "David S. Miller" <davem@davemloft.net> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Johannes Weiner <hannes@cmpxchg.org>
2014-05-16cgroup: skip refcnting on normal root csses and cgrp_dfl_root self cssTejun Heo1-2/+9
9395a4500404 ("cgroup: enable refcnting for root csses") enabled reference counting for root csses (cgroup_subsys_states) so that cgroup's self csses can be used to manage the lifetime of the containing cgroups. Unfortunately, this change was incorrect. During early init, cgrp_dfl_root self css refcnt is used. percpu_ref can't initialized during early init and its initialization is deferred till cgroup_init() time. This means that cpu was using percpu_ref which wasn't properly initialized. Due to the way percpu variables are laid out on x86, this didn't blow up immediately on x86 but ended up incrementing and decrementing the percpu variable at offset zero, whatever it may be; however, on other archs, this caused fault and early boot failure. As cgroup self csses for root cgroups of non-dfl hierarchies need working refcounting, we can't revert 9395a4500404. This patch adds CSS_NO_REF which explicitly inhibits reference counting on the css and sets it on all normal (non-self) csses and cgroup_dfl_root self css. v2: cgrp_dfl_root.self is the offending one. Set the flag on it. Signed-off-by: Tejun Heo <tj@kernel.org> Reported-by: Stephen Warren <swarren@nvidia.com> Tested-by: Stephen Warren <swarren@nvidia.com> Fixes: 9395a4500404 ("cgroup: enable refcnting for root csses")
2014-05-14cgroup: use cgroup->self.refcnt for cgroup refcntingTejun Heo1-66/+80
Currently cgroup implements refcnting separately using atomic_t cgroup->refcnt. The destruction paths of cgroup and css are rather complex and bear a lot of similiarities including the use of RCU and bouncing to a work item. This patch makes cgroup use the refcnt of self css for refcnting instead of using its own. This makes cgroup refcnting use css's percpu refcnt and share the destruction mechanism. * css_release_work_fn() and css_free_work_fn() are updated to handle both csses and cgroups. This is a bit messy but should do until we can make cgroup->self a full css, which currently can't be done thanks to multiple hierarchies. * cgroup_destroy_locked() now performs percpu_ref_kill(&cgrp->self.refcnt) instead of cgroup_put(cgrp). * Negative refcnt sanity check in cgroup_get() is no longer necessary as percpu_ref already handles it. * Similarly, as a cgroup which hasn't been killed will never be released regardless of its refcnt value and percpu_ref has sanity check on kill, cgroup_is_dead() sanity check in cgroup_put() is no longer necessary. * As whether a refcnt reached zero or not can only be decided after the reference count is killed, cgroup_root->cgrp's refcnting can no longer be used to decide whether to kill the root or not. Let's make cgroup_kill_sb() explicitly initiate destruction if the root doesn't have any children. This makes sense anyway as unmounted cgroup hierarchy without any children should be destroyed. While this is a bit messy, this will allow pushing more bookkeeping towards cgroup->self and thus handling cgroups and csses in more uniform way. In the very long term, it should be possible to introduce a base subsystem and convert the self css to a proper one making things whole lot simpler and unified. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-14cgroup: enable refcnting for root cssesTejun Heo1-3/+3
Currently, css_get(), css_tryget() and css_tryget_online() are noops for root csses as an optimization; however, we're planning to use css refcnts to track of cgroup lifetime too and root cgroups also need to be reference counted. Since css has been converted to percpu_refcnt, the overhead of refcnting is miniscule and this optimization isn't too meaningful anymore. Furthermore, controllers which optimize the root cgroup often never even invoke these functions in their hot paths. This patch enables refcnting for root csses too. This makes CSS_ROOT flag unused and removes it. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-14cgroup: bounce css release through css->destroy_workTejun Heo1-2/+11
css release is planned to do more and would require process context. Bounce it through css->destroy_work. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-14cgroup: remove cgroup_destory_css_killed()Tejun Heo1-56/+6
cgroup_destroy_css_killed() is cgroup destruction stage which happens after all csses are offlined. After the recent updates, it no longer does anything other than putting the base reference. This patch removes the function and makes cgroup_destroy_locked() put the base ref at the end isntead. This also makes cgroup->nr_css unnecessary. Removed. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-14cgroup: move cgroup->sibling unlinking to cgroup_put()Tejun Heo1-3/+5
Move cgroup->sibling unlinking from cgroup_destroy_css_killed() to cgroup_put(). This is later but still before the RCU grace period, so it doesn't break css_next_child() although there now is a larger window in which a dead cgroup is visible during css iteration. As css iteration always could have included offline csses, this doesn't affect correctness; however, it does make css_next_child() fall back to reiterting mode more often. This also makes cgroup_put() directly take cgroup_mutex, which limits where it can be called from. These are not immediately problematic and will be dealt with later. This change enables simplification of cgroup destruction path. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-14cgroup: move check_for_release(parent) call to the end of ↵Tejun Heo1-6/+4
cgroup_destroy_locked() Currently, check_for_release() on the parent of a destroyed cgroup is invoked from cgroup_destroy_css_killed(). This is because this is where the destroyed cgroup can be removed from the parent's children list. check_for_release() tests the emptiness of the list directly, so invoking it before removing the cgroup from the list makes it think that the parent still has children even when it no longer does. This patch updates check_for_release() to use cgroup_has_live_children() instead of directly testing ->children emptiness and moves check_for_release(parent) earlier to the end of cgroup_destroy_locked(). As cgroup_has_live_children() ignores cgroups marked DEAD, check_for_release() functions correctly as long as it's called after asserting DEAD. This makes release notification slightly more timely and more importantly enables further simplification of cgroup destruction path. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-14cgroup: separate out cgroup_has_live_children() from cgroup_destroy_locked()Tejun Heo1-10/+16
We're expecting another user. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-14cgroup: rename cgroup->dummy_css to ->self and move it to the topTejun Heo1-10/+10
cgroup->dummy_css is used as the placeholder css when performing css oriended operations on the cgroup. We're gonna shift more cgroup management to this css. Let's rename it to ->self and move it to the top. This is pure rename and field relocation. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-14cgroup: use restart_syscall() for mount retriesTejun Heo1-4/+4
cgroup_mount() uses dumb delay-and-retry logic to wait for cgroup_root which is being destroyed. The retry currently loops inside cgroup_mount() proper. This patch makes it return with restart_syscall() instead so that retry travels out to userland boundary. This slightly simplifies the logic and more importantly makes the retry logic behave better when the wait for some reason becomes lengthy or infinite by allowing the operation to be suspended or terminated from userland. v2: The original patch forgot to free memory allocated for @opts. Fixed. Caught by Li Zefan. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: remove cgroup_tree_mutexTejun Heo1-55/+9
cgroup_tree_mutex was introduced to work around the circular dependency between cgroup_mutex and kernfs active protection - some kernfs file and directory operations needed cgroup_mutex putting cgroup_mutex under active protection but cgroup also needs to be able to access cgroup hierarchies and cftypes to determine which kernfs_nodes need to be removed. cgroup_tree_mutex nested above both cgroup_mutex and kernfs active protection and used to protect the hierarchy and cftypes. While this worked, it added a lot of double lockings and was generally cumbersome. kernfs provides a mechanism to opt out of active protection and cgroup was already using it for removal and subtree_control. There's no reason to mix both methods of avoiding circular locking dependency and the preceding cgroup_kn_lock_live() changes applied it to all relevant cgroup kernfs operations making it unnecessary to nest cgroup_mutex under kernfs active protection. The previous patch reversed the original lock ordering and put cgroup_mutex above kernfs active protection. After these changes, all cgroup_tree_mutex usages are now accompanied by cgroup_mutex making the former completely redundant. This patch removes cgroup_tree_mutex and all its usages. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: nest kernfs active protection under cgroup_mutexTejun Heo1-11/+16
After the recent cgroup_kn_lock_live() changes, cgroup_mutex is no longer nested below kernfs active protection. The two don't have any relationship now. This patch nests kernfs active protection under cgroup_mutex. All cftype operations now require both cgroup_tree_mutex and cgroup_mutex, temporary cgroup_mutex releases over kernfs operations are removed, and cgroup_add/rm_cftypes() grab both mutexes. This makes cgroup_tree_mutex redundant, which will be removed by the next patch. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: use cgroup_kn_lock_live() in other cgroup kernfs methodsTejun Heo1-27/+12
Make __cgroup_procs_write() and cgroup_release_agent_write() use cgroup_kn_lock_live() and cgroup_kn_unlock() instead of cgroup_lock_live_group(). This puts the operations under both cgroup_tree_mutex and cgroup_mutex protection without circular dependency from kernfs active protection. Also, this means that cgroup_mutex is no longer nested below kernfs active protection. There is no longer any place where the two locks interact. This leaves cgroup_lock_live_group() without any user. Removed. This will help simplifying cgroup locking. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: factor out cgroup_kn_lock_live() and cgroup_kn_unlock()Tejun Heo1-67/+90
cgroup_mkdir(), cgroup_rmdir() and cgroup_subtree_control_write() share the logic to break active protection so that they can grab cgroup_tree_mutex which nests above active protection and/or remove self. Factor out this logic into cgroup_kn_lock_live() and cgroup_kn_unlock(). This patch doesn't introduce any functional changes. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: move cgroup->kn->priv clearing to cgroup_rmdir()Tejun Heo1-11/+12
The ->priv field of a cgroup directory kernfs_node points back to the cgroup. This field is RCU cleared in cgroup_destroy_locked() for non-kernfs accesses from css_tryget_from_dir() and cgroupstats_build(). As these are only applicable to cgroups which finished creation successfully and fully initialized cgroups are always removed by cgroup_rmdir(), this can be safely moved to the end of cgroup_rmdir(). This will help simplifying cgroup locking and shouldn't introduce any behavior difference. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: grab cgroup_mutex earlier in cgroup_subtree_control_write()Tejun Heo1-8/+8
Move cgroup_lock_live_group() invocation upwards to right below cgroup_tree_mutex in cgroup_subtree_control_write(). This is to help the planned locking simplification. This doesn't make any userland-visible behavioral changes. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: collapse cgroup_create() into croup_mkdir()Tejun Heo1-39/+13
cgroup_mkdir() is the sole user of cgroup_create(). Let's collapse the latter into the former. This will help simplifying locking. While at it, remove now stale comment about inode locking. This patch doesn't introduce any functional changes. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: reorganize cgroup_create()Tejun Heo1-35/+34
Reorganize cgroup_create() so that all paths share unlock out path. * All err_* labels are renamed to out_* as they're now shared by both success and failure paths. * @err renamed to @ret for the similar reason as above and so that it's more consistent with other functions. * cgroup memory allocation moved after locking so that freeing failed cgroup happens before unlocking. While this moves more code inside critical section, memory allocations inside cgroup locking are already pretty common and this is unlikely to make any noticeable difference. * While at it, replace a stray @parent->root dereference with @root. This reorganization will help simplifying locking. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: remove cgroup->control_knTejun Heo1-5/+3
Now that cgroup_subtree_control_write() has access to the associated kernfs_open_file and thus the kernfs_node, there's no need to cache it in cgroup->control_kn on creation. Remove cgroup->control_kn and use @of->kn directly. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: convert "tasks" and "cgroup.procs" handle to use cftype->write()Tejun Heo1-10/+16
cgroup_tasks_write() and cgroup_procs_write() are currently using cftype->write_u64(). This patch converts them to use cftype->write() instead. This allows access to the associated kernfs_open_file which will be necessary to implement the planned kernfs active protection manipulation for these files. This shifts buffer parsing to attach_task_by_pid() and makes it return @nbytes on success. Let's rename it to __cgroup_procs_write() to clearly indicate that this is a write handler implementation. This patch doesn't introduce any visible behavior changes. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: replace cftype->trigger() with cftype->write()Tejun Heo1-4/+1
cftype->trigger() is pointless. It's trivial to ignore the input buffer from a regular ->write() operation. Convert all ->trigger() users to ->write() and remove ->trigger(). This patch doesn't introduce any visible behavior changes. 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>
2014-05-13cgroup: replace cftype->write_string() with cftype->write()Tejun Heo1-19/+19
Convert all cftype->write_string() users to the new cftype->write() which maps directly to kernfs write operation and has full access to kernfs and cgroup contexts. The conversions are mostly mechanical. * @css and @cft are accessed using of_css() and of_cft() accessors respectively instead of being specified as arguments. * Should return @nbytes on success instead of 0. * @buf is not trimmed automatically. Trim if necessary. Note that blkcg and netprio don't need this as the parsers already handle whitespaces. cftype->write_string() has no user left after the conversions and removed. While at it, remove unnecessary local variable @p in cgroup_subtree_control_write() and stale comment about CGROUP_LOCAL_BUFFER_SIZE in cgroup_freezer.c. This patch doesn't introduce any visible behavior changes. v2: netprio was missing from conversion. Converted. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Aristeu Rozanski <arozansk@redhat.com> Acked-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Michal Hocko <mhocko@suse.cz> Cc: Neil Horman <nhorman@tuxdriver.com> Cc: "David S. Miller" <davem@davemloft.net>
2014-05-13cgroup: implement cftype->write()Tejun Heo1-6/+8
During the recent conversion to kernfs, cftype's seq_file operations are updated so that they are directly mapped to kernfs operations and thus can fully access the associated kernfs and cgroup contexts; however, write path hasn't seen similar updates and none of the existing write operations has access to, for example, the associated kernfs_open_file. Let's introduce a new operation cftype->write() which maps directly to the kernfs write operation and has access to all the arguments and contexts. This will replace ->write_string() and ->trigger() and ease manipulation of kernfs active protection from cgroup file operations. Two accessors - of_cft() and of_css() - are introduced to enable accessing the associated cgroup context from cftype->write() which only takes kernfs_open_file for the context information. The accessors for seq_file operations - seq_cft() and seq_css() - are rewritten to wrap the of_ accessors. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: rename css_tryget*() to css_tryget_online*()Tejun Heo1-20/+20
Unlike the more usual refcnting, what css_tryget() provides is the distinction between online and offline csses instead of protection against upping a refcnt which already reached zero. cgroup is planning to provide actual tryget which fails if the refcnt already reached zero. Let's rename the existing trygets so that they clearly indicate that they're onliness. I thought about keeping the existing names as-are and introducing new names for the planned actual tryget; however, given that each controller participates in the synchronization of the online state, it seems worthwhile to make it explicit that these functions are about on/offline state. Rename css_tryget() to css_tryget_online() and css_tryget_from_dir() to css_tryget_online_from_dir(). This is pure rename. v2: cgroup_freezer grew new usages of css_tryget(). Update accordingly. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Johannes Weiner <hannes@cmpxchg.org> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Li Zefan <lizefan@huawei.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Paul Mackerras <paulus@samba.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
2014-05-13cgroup: use release_agent_path_lock in cgroup_release_agent_show()Tejun Heo1-3/+2
release_path is now protected by release_agent_path_lock to allow accessing it without grabbing cgroup_mutex; however, cgroup_release_agent_show() was still grabbing cgroup_mutex. Let's convert it to release_agent_path_lock so that we don't have to worry about this one for the planned locking updates. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: use restart_syscall() for retries after offline waits in ↵Tejun Heo1-9/+9
cgroup_subtree_control_write() After waiting for a child to finish offline, cgroup_subtree_control_write() jumps up to retry from after the input parsing and active protection breaking. This retry makes the scheduled locking update - removal of cgroup_tree_mutex - more difficult. Let's simplify it by returning with restart_syscall() for retries. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: update and fix parsing of "cgroup.subtree_control"Tejun Heo1-3/+5
I was confused that strsep() was equivalent to strtok_r() in skipping over consecutive delimiters. strsep() just splits at the first occurrence of one of the delimiters which makes the parsing very inflexible, which makes allowing multiple whitespace chars as delimters kinda moot. Let's just be consistently strict and require list of tokens separated by spaces. This is what Documentation/cgroups/unified-hierarchy.txt describes too. Also, parsing may access beyond the end of the string if the string ends with spaces or is zero-length. Make sure it skips zero-length tokens. Note that this also ensures that the parser doesn't puke on multiple consecutive spaces. v2: Add zero-length token skipping. v3: Added missing space after "==". Spotted by Li. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: css_release() shouldn't clear cgroup->subsys[]Tejun Heo1-1/+0
c1a71504e971 ("cgroup: don't recycle cgroup id until all csses' have been destroyed") made cgroup ID persist until a cgroup is released and add cgroup->subsys[] clearing to css_release() so that css_from_id() doesn't return a css which has already been released which happens before cgroup release; however, the right change here was updating offline_css() to clear cgroup->subsys[] which was done by e32978031016 ("cgroup: cgroup->subsys[] should be cleared after the css is offlined") instead of clearing it from css_release(). We're now clearing cgroup->subsys[] twice. This is okay for traditional hierarchies as a css's lifetime is the same as its cgroup's; however, this confuses unified hierarchy and turning on and off a controller repeatedly using "cgroup.subtree_control" can lead to an oops like the following which happens because cgroup->subsys[] is incorrectly cleared asynchronously by css_release(). BUG: unable to handle kernel NULL pointer dereference at 00000000000000 08 IP: [<ffffffff81130c11>] kill_css+0x21/0x1c0 PGD 1170d067 PUD f0ab067 PMD 0 Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC Modules linked in: CPU: 2 PID: 459 Comm: bash Not tainted 3.15.0-rc2-work+ #5 Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011 task: ffff880009296710 ti: ffff88000e198000 task.ti: ffff88000e198000 RIP: 0010:[<ffffffff81130c11>] [<ffffffff81130c11>] kill_css+0x21/0x1c0 RSP: 0018:ffff88000e199dc8 EFLAGS: 00010202 RAX: 0000000000000001 RBX: 0000000000000000 RCX: 0000000000000001 RDX: 0000000000000001 RSI: ffffffff8238a968 RDI: ffff880009296f98 RBP: ffff88000e199de0 R08: 0000000000000001 R09: 02b0000000000000 R10: 0000000000000000 R11: ffff880009296fc0 R12: 0000000000000001 R13: ffff88000db6fc58 R14: 0000000000000001 R15: ffff8800139dcc00 FS: 00007ff9160c5740(0000) GS:ffff88001fb00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 0000000000000008 CR3: 0000000013947000 CR4: 00000000000006e0 Stack: ffff88000e199de0 ffffffff82389160 0000000000000001 ffff88000e199e80 ffffffff8113537f 0000000000000007 ffff88000e74af00 ffff88000e199e48 ffff880009296710 ffff88000db6fc00 ffffffff8239c100 0000000000000002 Call Trace: [<ffffffff8113537f>] cgroup_subtree_control_write+0x85f/0xa00 [<ffffffff8112fd18>] cgroup_file_write+0x38/0x1d0 [<ffffffff8126fc97>] kernfs_fop_write+0xe7/0x170 [<ffffffff811f2ae6>] vfs_write+0xb6/0x1c0 [<ffffffff811f35ad>] SyS_write+0x4d/0xc0 [<ffffffff81d0acd2>] system_call_fastpath+0x16/0x1b Code: 5c 41 5d 41 5e 41 5f 5d c3 90 0f 1f 44 00 00 55 48 89 e5 41 54 53 48 89 fb 48 83 ec 08 8b 05 37 ad 29 01 85 c0 0f 85 df 00 00 00 <48> 8b 43 08 48 8b 3b be 01 00 00 00 8b 48 5c d3 e6 e8 49 ff ff RIP [<ffffffff81130c11>] kill_css+0x21/0x1c0 RSP <ffff88000e199dc8> CR2: 0000000000000008 ---[ end trace e7aae1f877c4e1b4 ]--- Remove the unnecessary cgroup->subsys[] clearing from css_release(). Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: cgroup_idr_lock should be bhTejun Heo1-6/+6
cgroup_idr_remove() can be invoked from bh leading to lockdep detecting possible AA deadlock (IN_BH/ON_BH). Make the lock bh-safe. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13cgroup: fix offlining child waiting in cgroup_subtree_control_write()Tejun Heo1-1/+3
cgroup_subtree_control_write() waits for offline to complete child-by-child before enabling a controller; however, it has a couple bugs. * It doesn't initialize the wait_queue_t. This can lead to infinite hang on the following schedule() among other things. * It forgets to pin the child before releasing cgroup_tree_mutex and performing schedule(). The child may already be gone by the time it wakes up and invokes finish_wait(). Pin the child being waited on. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-13Merge branch 'for-3.15-fixes' of ↵Tejun Heo1-1/+1
git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup into for-3.16 Pull to receive e37a06f10994 ("cgroup: fix the retry path of cgroup_mount()") to avoid unnecessary conflicts with planned cgroup_tree_mutex removal and also to be able to remove the temp fix added by 36c38fb7144a ("blkcg: use trylock on blkcg_pol_mutex in blkcg_reset_stats()") afterwards. Signed-off-by: Tejun Heo <tj@kernel.org>
2014-05-13cgroup: introduce task_css_is_root()Tejun Heo1-1/+1
Determining the css of a task usually requires RCU read lock as that's the only thing which keeps the returned css accessible till its reference is acquired; however, testing whether a task belongs to the root can be performed without dereferencing the returned css by comparing the returned pointer against the root one in init_css_set[] which never changes. Implement task_css_is_root() which can be invoked in any context. This will be used by the scheduled cgroup_freezer change. v2: cgroup no longer supports modular controllers. No need to export init_css_set. Pointed out by Li. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2014-05-05kernel/cgroup.c: fix 2 kernel-doc warningsFabian Frederick1-2/+2
Fix typo and variable name. tj: Updated @cgrp argument description in cgroup_destroy_css_killed() Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Fabian Frederick <fabf@skynet.be> Signed-off-by: Tejun Heo <tj@kernel.org>