linux/kernel/cgroup.c, branch v4.0

kernfs: remove KERNFS_STATIC_NAME

2015-02-14T05:21:36Z

When a new kernfs node is created, KERNFS_STATIC_NAME is used to avoid making a separate copy of its name. It's currently only used for sysfs attributes whose filenames are required to stay accessible and unchanged. There are rare exceptions where these names are allocated and formatted dynamically but for the vast majority of cases they're consts in the rodata section. Now that kernfs is converted to use kstrdup_const() and kfree_const(), there's little point in keeping KERNFS_STATIC_NAME around. Remove it. Signed-off-by: Tejun Heo Cc: Andrzej Hajda Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

cgroup: release css->id after css_free

2015-02-13T02:54:09Z

Currently, we release css->id in css_release_work_fn, right before calling css_free callback, so that when css_free is called, the id may have already been reused for a new cgroup. I am going to use css->id to create unique names for per memcg kmem caches. Since kmem caches are destroyed only on css_free, I need css->id to be freed after css_free was called to avoid name clashes. This patch therefore moves css->id removal to css_free_work_fn. To prevent css_from_id from returning a pointer to a stale css, it makes css_release_work_fn replace the css ptr at css_idr:css->id with NULL. Signed-off-by: Vladimir Davydov Cc: Johannes Weiner Cc: Michal Hocko Acked-by: Tejun Heo Cc: Christoph Lameter Cc: Pekka Enberg Cc: David Rientjes Cc: Joonsoo Kim Cc: Dave Chinner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

cgroup: prevent mount hang due to memory controller lifetime

2015-01-22T15:26:43Z

Since b2052564e66d ("mm: memcontrol: continue cache reclaim from offlined groups"), re-mounting the memory controller after using it is very likely to hang. The cgroup core assumes that any remaining references after deleting a cgroup are temporary in nature, and synchroneously waits for them, but the above-mentioned commit has left-over page cache pin its css until it is reclaimed naturally. That being said, swap entries and charged kernel memory have been doing the same indefinite pinning forever, the bug is just more likely to trigger with left-over page cache. Reparenting kernel memory is highly impractical, which leaves changing the cgroup assumptions to reflect this: once a controller has been mounted and used, it has internal state that is independent from mount and cgroup lifetime. It can be unmounted and remounted, but it can't be reconfigured during subsequent mounts. Don't offline the controller root as long as there are any children, dead or alive. A remount will no longer wait for these old references to drain, it will simply mount the persistent controller state again. Reported-by: "Suzuki K. Poulose" Reported-by: Will Deacon Signed-off-by: Johannes Weiner Signed-off-by: Tejun Heo

cgroup: implement cgroup_get_e_css()

2014-11-18T07:49:52Z

Implement cgroup_get_e_css() which finds and gets the effective css for the specified cgroup and subsystem combination. This function always returns a valid pinned css. This will be used by cgroup writeback support. While at it, add comment to cgroup_e_css() to explain why that function is different from cgroup_get_e_css() and has to test cgrp->child_subsys_mask instead of cgroup_css(cgrp, ss). Signed-off-by: Tejun Heo Acked-by: Zefan Li

cgroup: add cgroup_subsys->css_e_css_changed()

2014-11-18T07:49:51Z

Add a new cgroup_subsys operatoin ->css_e_css_changed(). This is invoked if any of the effective csses seen from the css's cgroup may have changed. This will be used to implement cgroup writeback support. Signed-off-by: Tejun Heo Acked-by: Zefan Li

cgroup: add cgroup_subsys->css_released()

2014-11-18T07:49:51Z

Add a new cgroup subsys callback css_released(). This is called when the reference count of the css (cgroup_subsys_state) reaches zero before RCU scheduling free. Signed-off-by: Tejun Heo Acked-by: Zefan Li

cgroup: fix the async css offline wait logic in cgroup_subtree_control_write()

2014-11-18T07:49:51Z

When a subsystem is offlined, its entry on @cgrp->subsys[] is cleared asynchronously. If cgroup_subtree_control_write() is requested to enable the subsystem again before the entry is cleared, it has to wait for the previous offlining to finish and clear the @cgrp->subsys[] entry before trying to enable the subsystem again. This is currently done while verifying the input enable / disable parameters. This used to be correct but f63070d350e3 ("cgroup: make interface files visible iff enabled on cgroup->subtree_control") breaks it. The commit is one of the commits implementing subsystem dependency. Through subsystem dependency, some subsystems may be enabled and disabled implicitly in addition to the explicitly requested ones. The actual subsystems to be enabled and disabled are determined during @css_enable/disable calculation. The current offline wait logic skips the ones which are already implicitly enabled and then waits for subsystems in @enable; however, this misses the subsystems which may be implicitly enabled through dependency from @enable. If such implicitly subsystem hasn't yet finished offlining yet, the function ends up trying to create a css when its @cgrp->subsys[] slot is already occupied triggering BUG_ON() in init_and_link_css(). Fix it by moving the wait logic after @css_enable is calculated and waiting for all the subsystems in @css_enable. This fixes the above bug as the mask contains all subsystems which are to be enabled including the ones enabled through dependencies. Signed-off-by: Tejun Heo Fixes: f63070d350e3 ("cgroup: make interface files visible iff enabled on cgroup->subtree_control") Acked-by: Zefan Li

cgroup: restructure child_subsys_mask handling in cgroup_subtree_control_write()

2014-11-18T07:49:50Z

Make cgroup_subtree_control_write() first calculate new subtree_control (new_sc), child_subsys_mask (new_ss) and css_enable/disable masks before applying them to the cgroup. Also, store the original subtree_control (old_sc) and child_subsys_mask (old_ss) and use them to restore the orignal state after failure. This patch shouldn't cause any behavior changes. This prepares for a fix for a bug in the async css offline wait logic. Signed-off-by: Tejun Heo Acked-by: Zefan Li

cgroup: separate out cgroup_calc_child_subsys_mask() from cgroup_refresh_child_subsys_mask()

2014-11-18T07:49:50Z

cgroup_refresh_child_subsys_mask() calculates and updates the effective @cgrp->child_subsys_maks according to the current @cgrp->subtree_control. Separate out the calculation part into cgroup_calc_child_subsys_mask(). This will be used to fix a bug in the async css offline wait logic. Signed-off-by: Tejun Heo Acked-by: Zefan Li

Merge branch 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu

2014-10-10T11:26:02Z

Pull percpu updates from Tejun Heo: "A lot of activities on percpu front. Notable changes are... - percpu allocator now can take @gfp. If @gfp doesn't contain GFP_KERNEL, it tries to allocate from what's already available to the allocator and a work item tries to keep the reserve around certain level so that these atomic allocations usually succeed. This will replace the ad-hoc percpu memory pool used by blk-throttle and also be used by the planned blkcg support for writeback IOs. Please note that I noticed a bug in how @gfp is interpreted while preparing this pull request and applied the fix 6ae833c7fe0c ("percpu: fix how @gfp is interpreted by the percpu allocator") just now. - percpu_ref now uses longs for percpu and global counters instead of ints. It leads to more sparse packing of the percpu counters on 64bit machines but the overhead should be negligible and this allows using percpu_ref for refcnting pages and in-memory objects directly. - The switching between percpu and single counter modes of a percpu_ref is made independent of putting the base ref and a percpu_ref can now optionally be initialized in single or killed mode. This allows avoiding percpu shutdown latency for cases where the refcounted objects may be synchronously created and destroyed in rapid succession with only a fraction of them reaching fully operational status (SCSI probing does this when combined with blk-mq support). It's also planned to be used to implement forced single mode to detect underflow more timely for debugging. There's a separate branch percpu/for-3.18-consistent-ops which cleans up the duplicate percpu accessors. That branch causes a number of conflicts with s390 and other trees. I'll send a separate pull request w/ resolutions once other branches are merged" * 'for-3.18' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/percpu: (33 commits) percpu: fix how @gfp is interpreted by the percpu allocator blk-mq, percpu_ref: start q->mq_usage_counter in atomic mode percpu_ref: make INIT_ATOMIC and switch_to_atomic() sticky percpu_ref: add PERCPU_REF_INIT_* flags percpu_ref: decouple switching to percpu mode and reinit percpu_ref: decouple switching to atomic mode and killing percpu_ref: add PCPU_REF_DEAD percpu_ref: rename things to prepare for decoupling percpu/atomic mode switch percpu_ref: replace pcpu_ prefix with percpu_ percpu_ref: minor code and comment updates percpu_ref: relocate percpu_ref_reinit() Revert "blk-mq, percpu_ref: implement a kludge for SCSI blk-mq stall during probe" Revert "percpu: free percpu allocation info for uniprocessor system" percpu-refcount: make percpu_ref based on longs instead of ints percpu-refcount: improve WARN messages percpu: fix locking regression in the failure path of pcpu_alloc() percpu-refcount: add @gfp to percpu_ref_init() proportions: add @gfp to init functions percpu_counter: add @gfp to percpu_counter_init() percpu_counter: make percpu_counters_lock irq-safe ...