cgroup is switching away from multiple hierarchies and will use one
unified default hierarchy where controllers can be dynamically enabled
and disabled per subtree. The default hierarchy will serve as the
unified hierarchy to which all controllers are attached and a css on
the default hierarchy would need to also serve the tasks of descendant
cgroups which don't have the controller enabled - ie. the tree may be
collapsed from leaf towards root when viewed from specific
controllers. This has been implemented through effective css in the
previous patches.
This patch finally implements dynamic subtree controller
enable/disable on the default hierarchy via a new knob -
"cgroup.subtree_control" which controls which controllers are enabled
on the child cgroups. Let's assume a hierarchy like the following.
root - A - B - C
\ D
root's "cgroup.subtree_control" determines which controllers are
enabled on A. A's on B. B's on C and D. This coincides with the
fact that controllers on the immediate sub-level are used to
distribute the resources of the parent. In fact, it's natural to
assume that resource control knobs of a child belong to its parent.
Enabling a controller in "cgroup.subtree_control" declares that
distribution of the respective resources of the cgroup will be
controlled. Note that this means that controller enable states are
shared among siblings.
The default hierarchy has an extra restriction - only cgroups which
don't contain any task may have controllers enabled in
"cgroup.subtree_control". Combined with the other properties of the
default hierarchy, this guarantees that, from the view point of
controllers, tasks are only on the leaf cgroups. In other words, only
leaf csses may contain tasks. This rules out situations where child
cgroups compete against internal tasks of the parent, which is a
competition between two different types of entities without any clear
way to determine resource distribution between the two. Different
controllers handle it differently and all the implemented behaviors
are ambiguous, ad-hoc, cumbersome and/or just wrong. Having this
structural constraints imposed from cgroup core removes the burden
from controller implementations and enables showing one consistent
behavior across all controllers.
When a controller is enabled or disabled, css associations for the
controller in the subtrees of each child should be updated. After
enabling, the whole subtree of a child should point to the new css of
the child. After disabling, the whole subtree of a child should point
to the cgroup's css. This is implemented by first updating cgroup
states such that cgroup_e_css() result points to the appropriate css
and then invoking cgroup_update_dfl_csses() which migrates all tasks
in the affected subtrees to the self cgroup on the default hierarchy.
* When read, "cgroup.subtree_control" lists all the currently enabled
controllers on the children of the cgroup.
* White-space separated list of controller names prefixed with either
'+' or '-' can be written to "cgroup.subtree_control". The ones
prefixed with '+' are enabled on the controller and '-' disabled.
* A controller can be enabled iff the parent's
"cgroup.subtree_control" enables it and disabled iff no child's
"cgroup.subtree_control" has it enabled.
* If a cgroup has tasks, no controller can be enabled via
"cgroup.subtree_control". Likewise, if "cgroup.subtree_control" has
some controllers enabled, tasks can't be migrated into the cgroup.
* All controllers which aren't bound on other hierarchies are
automatically associated with the root cgroup of the default
hierarchy. All the controllers which are bound to the default
hierarchy are listed in the read-only file "cgroup.controllers" in
the root directory.
* "cgroup.controllers" in all non-root cgroups is read-only file whose
content is equal to that of "cgroup.subtree_control" of the parent.
This indicates which controllers can be used in the cgroup's
"cgroup.subtree_control".
This is still experimental and there are some holes, one of which is
that ->can_attach() failure during cgroup_update_dfl_csses() may leave
the cgroups in an undefined state. The issues will be addressed by
future patches.
v2: Non-root cgroups now also have "cgroup.controllers".
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Unified hierarchy implementation would require re-migrating tasks onto
the same cgroup on the default hierarchy to reflect updated effective
csses. Update cgroup_migrate_prepare_dst() so that it accepts NULL as
the destination cgrp. When NULL is specified, the destination is
considered to be the cgroup on the default hierarchy associated with
each css_set.
After this change, the identity check in cgroup_migrate_add_src()
isn't sufficient for noop detection as the associated csses may change
without any cgroup association changing. The only way to tell whether
a migration is noop or not is testing whether the source and
destination csets are identical. The noop check in
cgroup_migrate_add_src() is removed and cset identity test is added to
cgroup_migreate_prepare_dst(). If it's detected that source and
destination csets are identical, the cset is removed removed from
@preloaded_csets and all the migration nodes are cleared which makes
cgroup_migrate() ignore the cset.
Also, make the function append the destination css_sets to
@preloaded_list so that destination css_sets always come after source
css_sets.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Because the default root couldn't have any non-root csses attached to
it, rebinding away from it was always allowed; however, the default
hierarchy will soon host the unified hierarchy and have non-root csses
so the rebind restrictions need to be updated accordingly.
Instead of special casing rebinding from the default hierarchy and
then checking whether the source hierarchy has children cgroups, which
implies non-root csses for !dfl hierarchies, simply check whether the
source hierarchy has non-root csses for the subsystem using
css_next_child().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
To implement the unified hierarchy behavior, we'll need to be able to
determine the associated cgroup on the default hierarchy from css_set.
Let's add css_set->dfl_cgrp so that it can be accessed conveniently
and efficiently.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Now that effective css handling has been added and iterators updated
accordingly, it's safe to allow cgroup creation in the default
hierarchy. Unblock cgroup creation in the default hierarchy.
As the default hierarchy will implement explicit enabling and
disabling of controllers on each cgroup, suppress automatic css
enabling on cgroup creation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
After a css finishes offlining, offline_css() mistakenly performs
RCU_INIT_POINTER(css->cgroup->subsys[ss->id], css) which just sets the
cgroup->subsys[] pointer to the current value. The intention was to
clear it after offline is complete, not reassign the same value.
Update it to assign NULL instead of the current value. This makes
cgroup_css() to return NULL once offline is complete. All the
existing users of the function either can handle NULL return already
or guarantee that the css doesn't get offlined.
While this is a bugfix, as css lifetime is currently tied to the
cgroup it belongs to, this bug doesn't cause any actual problems.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, css_task_iter iterates tasks associated with a css by
visiting each css_set associated with the owning cgroup and walking
tasks of each of them. This works fine for !unified hierarchies as
each cgroup has its own css for each associated subsystem on the
hierarchy; however, on the planned unified hierarchy, a cgroup may not
have csses associated and its tasks would be considered associated
with the matching css of the nearest ancestor which has the subsystem
enabled.
This means that on the default unified hierarchy, just walking all
tasks associated with a cgroup isn't enough to walk all tasks which
are associated with the specified css. If any of its children doesn't
have the matching css enabled, task iteration should also include all
tasks from the subtree. We already added cgroup->e_csets[] to list
all css_sets effectively associated with a given css and walk css_sets
on that list instead to achieve such iteration.
This patch updates css_task_iter iteration such that it walks css_sets
on cgroup->e_csets[] instead of cgroup->cset_links if iteration is
requested on an non-dummy css. Thanks to the previous iteration
update, this change can be achieved with the addition of
css_task_iter->ss and minimal updates to css_advance_task_iter() and
css_task_iter_start().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This patch reorganizes css_task_iter so that adding effective css
support is easier.
* s/->cset_link/->cset_pos/ and s/->task/->task_pos/ for consistency
* ->origin_css is used to determine whether the iteration reached the
last css_set. Replace it with explicit ->cset_head so that
css_advance_task_iter() doesn't have to know the termination
condition directly.
* css_task_iter_next() currently assumes that it's walking list of
cgrp_cset_link and reaches into the current cset through the current
link to determine the termination conditions for task walking. As
this won't always be true for effective css walking, add
->tasks_head and ->mg_tasks_head and use them to control task
walking so that css_task_iter_next() doesn't have to know how
css_sets are being walked.
This patch doesn't make any behavior changes. The iteration logic
stays unchanged after the patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
css_next_child() walks the children of the specified css. It does
this by finding the next cgroup and then returning the requested css.
On the default unified hierarchy, a cgroup may not have a css
associated with it even if the hierarchy has the subsystem enabled.
This patch updates css_next_child() so that it skips children without
the requested css associated.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
On the default unified hierarchy, a cgroup may be associated with
csses of its ancestors, which means that a css of a given cgroup may
be associated with css_sets of descendant cgroups. This means that we
can't walk all tasks associated with a css by iterating the css_sets
associated with the cgroup as there are css_sets which are pointing to
the css but linked on the descendants.
This patch adds per-subsystem list heads cgroup->e_csets[]. Any
css_set which is pointing to a css is linked to
css->cgroup->e_csets[$SUBSYS_ID] through
css_set->e_cset_node[$SUBSYS_ID]. The lists are protected by
css_set_rwsem and will allow us to walk all css_sets associated with a
given css so that we can find out all associated tasks.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
In the planned default unified hierarchy, controllers may get
dynamically attached to and detached from a cgroup and a cgroup may
not have csses for all the controllers associated with the hierarchy.
When a cgroup doesn't have its own css for a given controller, the css
of the nearest ancestor with the controller enabled will be used,
which is called the effective css. This patch introduces
cgroup_e_css() and for_each_e_css() to access the effective csses and
convert compare_css_sets(), find_existing_css_set() and
cgroup_migrate() to use the effective csses so that they can handle
cgroups with partial csses correctly.
This means that for two css_sets to be considered identical, they
should have both matching csses and cgroups. compare_css_sets()
already compares both, not for correctness but for optimization. As
this now becomes a matter of correctness, update the comments
accordingly.
For all !default hierarchies, cgroup_e_css() always equals
cgroup_css(), so this patch doesn't change behavior.
While at it, fix incorrect locking comment for for_each_css().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
944196278d ("cgroup: move ->subsys_mask from cgroupfs_root to
cgroup") moved ->subsys_mask from cgroup_root to cgroup to prepare for
the unified hierarhcy; however, it turns out that carrying the
subsys_mask of the children in the parent, instead of itself, is a lot
more natural. This patch restores cgroup_root->subsys_mask and morphs
cgroup->subsys_mask into cgroup->child_subsys_mask.
* Uses of root->cgrp.subsys_mask are restored to root->subsys_mask.
* Remove automatic setting and clearing of cgrp->subsys_mask and
instead just inherit ->child_subsys_mask from the parent during
cgroup creation. Note that this doesn't affect any current
behaviors.
* Undo __kill_css() separation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_apply_cftypes() skip creating or removing files if the
subsystem is attached to the default hierarchy, which led to missing
files in the root of the default hierarchy.
Skipping made sense when the default hierarchy was dummy; however, now
that the default hierarchy is full functional and planned to be used
as the unified hierarchy, it shouldn't be skipped over.
Reported-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
If we hit the retry path, we'll call parse_cgroupfs_options() again,
but the string we pass to it has been modified by the previous call
to this function.
This bug can be observed by:
# mount -t cgroup -o name=foo,cpuset xxx /mnt && umount /mnt && \
mount -t cgroup -o name=foo,cpuset xxx /mnt
mount: wrong fs type, bad option, bad superblock on xxx,
missing codepage or helper program, or other error
...
The second mount passed "name=foo,cpuset" to the parser, and then it
hit the retry path and call the parser again, but this time the string
passed to the parser is "name=foo".
To fix this, we avoid calling parse_cgroupfs_options() again in this
case.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
While converting cgroup to kernfs, 2bd59d48eb ("cgroup: convert to
kernfs") accidentally dropped the logic which makes newly created
cgroup dirs and files owned by the current uid / gid. This broke
cases where cgroup subtree management is delegated to !root as the sub
manager wouldn't be able to create more than single level of hierarchy
or put tasks into child cgroups it created.
Among other things, this breaks user session management in systemd and
one of the symptoms was 90s hang during shutdown. User session
systemd running as the user creates a sub-service to initiate shutdown
and tries to put kill(1) into it but fails because cgroup.procs is
owned by root. This leads to 90s hang during shutdown.
Implement cgroup_kn_set_ugid() which sets a kn's uid and gid to those
of the caller and use it from file and dir creation paths.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
As mount() and kill_sb() is not a one-to-one match, If we mount the same
cgroupfs in serveral mount points, and then umount all of them, kill_sb()
will be called only once.
Try:
# mount -t cgroup -o cpuacct xxx /cgroup
# mount -t cgroup -o cpuacct xxx /cgroup2
# cat /proc/cgroups | grep cpuacct
cpuacct 2 1 1
# umount /cgroup
# umount /cgroup2
# cat /proc/cgroups | grep cpuacct
cpuacct 2 1 1
You'll see cgroupfs will never be freed.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull cgroup updates from Tejun Heo:
"A lot updates for cgroup:
- The biggest one is cgroup's conversion to kernfs. cgroup took
after the long abandoned vfs-entangled sysfs implementation and
made it even more convoluted over time. cgroup's internal objects
were fused with vfs objects which also brought in vfs locking and
object lifetime rules. Naturally, there are places where vfs rules
don't fit and nasty hacks, such as credential switching or lock
dance interleaving inode mutex and cgroup_mutex with object serial
number comparison thrown in to decide whether the operation is
actually necessary, needed to be employed.
After conversion to kernfs, internal object lifetime and locking
rules are mostly isolated from vfs interactions allowing shedding
of several nasty hacks and overall simplification. This will also
allow implmentation of operations which may affect multiple cgroups
which weren't possible before as it would have required nesting
i_mutexes.
- Various simplifications including dropping of module support,
easier cgroup name/path handling, simplified cgroup file type
handling and task_cg_lists optimization.
- Prepatory changes for the planned unified hierarchy, which is still
a patchset away from being actually operational. The dummy
hierarchy is updated to serve as the default unified hierarchy.
Controllers which aren't claimed by other hierarchies are
associated with it, which BTW was what the dummy hierarchy was for
anyway.
- Various fixes from Li and others. This pull request includes some
patches to add missing slab.h to various subsystems. This was
triggered xattr.h include removal from cgroup.h. cgroup.h
indirectly got included a lot of files which brought in xattr.h
which brought in slab.h.
There are several merge commits - one to pull in kernfs updates
necessary for converting cgroup (already in upstream through
driver-core), others for interfering changes in the fixes branch"
* 'for-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (74 commits)
cgroup: remove useless argument from cgroup_exit()
cgroup: fix spurious lockdep warning in cgroup_exit()
cgroup: Use RCU_INIT_POINTER(x, NULL) in cgroup.c
cgroup: break kernfs active_ref protection in cgroup directory operations
cgroup: fix cgroup_taskset walking order
cgroup: implement CFTYPE_ONLY_ON_DFL
cgroup: make cgrp_dfl_root mountable
cgroup: drop const from @buffer of cftype->write_string()
cgroup: rename cgroup_dummy_root and related names
cgroup: move ->subsys_mask from cgroupfs_root to cgroup
cgroup: treat cgroup_dummy_root as an equivalent hierarchy during rebinding
cgroup: remove NULL checks from [pr_cont_]cgroup_{name|path}()
cgroup: use cgroup_setup_root() to initialize cgroup_dummy_root
cgroup: reorganize cgroup bootstrapping
cgroup: relocate setting of CGRP_DEAD
cpuset: use rcu_read_lock() to protect task_cs()
cgroup_freezer: document freezer_fork() subtleties
cgroup: update cgroup_transfer_tasks() to either succeed or fail
cgroup: drop task_lock() protection around task->cgroups
cgroup: update how a newly forked task gets associated with css_set
...
cgroup_exit() is called in fork and exit path. If it's called in the
failure path during fork, PF_EXITING isn't set, and then lockdep will
complain.
Fix this by removing cgroup_exit() in that failure path. cgroup_fork()
does nothing that needs cleanup.
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
This patch replaces rcu_assign_pointer(x, NULL) with
RCU_INIT_POINTER(x, NULL)
The rcu_assign_pointer() ensures that the initialization of a
structure is carried out before storing a pointer to that structure.
And in the case of the NULL pointer, there is no structure to
initialize. So, rcu_assign_pointer(p, NULL) can be safely converted
to RCU_INIT_POINTER(p, NULL)
Signed-off-by: Monam Agarwal <monamagarwal123@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup_tree_mutex should nest above the kernfs active_ref protection;
however, cgroup_create() and cgroup_rename() were grabbing
cgroup_tree_mutex while under kernfs active_ref protection. This has
actualy possibility to lead to deadlocks in case these operations race
against cgroup_rmdir() which invokes kernfs_remove() on directory
kernfs_node while holding cgroup_tree_mutex.
Neither cgroup_create() or cgroup_rename() requires active_ref
protection. The former already has enough synchronization through
cgroup_lock_live_group() and the latter doesn't care, so this can be
fixed by updating both functions to break all active_ref protections
before grabbing cgroup_tree_mutex.
While this patch fixes the immediate issue, it probably needs further
work in the long term - kernfs directories should enable lockdep
annotations and maybe the better way to handle this is marking
directory nodes as not needing active_ref protection rather than
breaking it in each operation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
cgroup_taskset is used to track and iterate target tasks while
migrating a task or process and should guarantee that the first task
iterated is the task group leader if a process is being migrated.
b3dc094e93 ("cgroup: use css_set->mg_tasks to track target tasks
during migration") replaced flex array cgroup_taskset->tc_array with
css_set->mg_tasks list to remove process size limit and dynamic
allocation during migration; unfortunately, it incorrectly used list
operations which don't preserve order breaking the guarantee that
cgroup_taskset_first() returns the leader for a process target.
Fix it by using order preserving list operations. Note that as
multiple src_csets may map to a single dst_cset, the iteration order
may change across cgroup_task_migrate(); however, the leader is still
guaranteed to be the first entry.
The switch to list_splice_tail_init() at the end of cgroup_migrate()
isn't strictly necessary. Let's still do it for consistency.
Signed-off-by: Tejun Heo <tj@kernel.org>
This cftype flag makes the file only appear on the default hierarchy.
This will later be used for cgroup.controllers file.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgrp_dfl_root will be used as the default unified hierarchy. This
patch makes cgrp_dfl_root mountable by making the following changes.
* cgroup_init_early() now initializes cgrp_dfl_root w/
CGRP_ROOT_SANE_BEHAVIOR. The default hierarchy is always sane.
* parse_cgroupfs_options() and cgroup_mount() are updated such that
cgrp_dfl_root is mounted if sane_behavior is specified w/o any
subsystems.
* rebind_subsystems() now populates the root directory of
cgrp_dfl_root. Note that the function still guarantees success of
rebinding subsystems to cgrp_dfl_root. If populating fails while
rebinding to cgrp_dfl_root, it whines but ignores the error.
* For backward compatibility, the default hierarchy shows up in
/proc/$PID/cgroup only after it's explicitly mounted so that
userland which doesn't make use of it doesn't see any change.
* "current_css_set_cg_links" file of debug cgroup now treats the
default hierarchy the same as other hierarchies. This is visible to
userland. Given that it's for debug controller, this should be
fine.
* While at it, implement cgroup_on_dfl() which tests whether a give
cgroup is on the default hierarchy or not.
The above changes make cgrp_dfl_root mostly equivalent to other
controllers but the actual unified hierarchy behaviors are not
implemented yet. Let's plug child cgroup creation in cgrp_dfl_root
from create_cgroup() for now.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cftype->write_string() just passes on the writeable buffer from kernfs
and there's no reason to add const restriction on the buffer. The
only thing const achieves is unnecessarily complicating parsing of the
buffer. Drop const from @buffer.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
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@ghostprotocols.net>
Cc: Daniel Borkmann <dborkman@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
The dummy root will be repurposed to serve as the default unified
hierarchy. Let's rename things in preparation.
* s/cgroup_dummy_root/cgrp_dfl_root/
* s/cgroupfs_root/cgroup_root/ as we don't do fs part directly anymore
* s/cgroup_root->top_cgroup/cgroup_root->cgrp/ for brevity
This is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroupfs_root->subsys_mask represents the controllers attached to the
hierarchy. This patch moves the field to cgroup. Subsystem
initialization and rebinding updates the top cgroup's subsys_mask.
For !root cgroups, the subsys_mask bits are set from create_css() and
cleared from kill_css(), which effectively means that all cgroups will
have the same subsys_mask as the top cgroup.
While this doesn't make any difference now, this will help
implementation of the default unified hierarchy where !root cgroups
may have subsets of the top_cgroup's subsys_mask.
While at it, __kill_css() is split out of kill_css(). The former
doesn't care about the subsys_mask while the latter becomes noop if
the controller is already killed and clears the matching bit if not
before proceeding to killing the css. This will be used later by the
default unified hierarchy implementation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, while rebinding, cgroup_dummy_root serves as the anchor
point. In addition to the target root, rebind_subsystems() takes
@added_mask and @removed_mask. The subsystems specified in the former
are expected to be on the dummy root and then moved to the target
root. The ones in the latter are moved from non-dummy root to dummy.
Now that the dummy root is a fully functional one and we're planning
to use it for the default unified hierarchy, this level of distinction
between dummy and non-dummy roots is quite awkward.
This patch updates rebind_subsystems() to take the target root and one
subsystem mask and move the specified subsystmes to the target root
which may or may not be the dummy root. IOW, unbinding now becomes
moving the subsystems to the dummy root and binding to non-dummy root.
This makes the dummy root mostly equivalent to other hierarchies in
terms of the mechanism of moving subsystems around; however, we still
retain all the semantical restrictions so that this patch doesn't
introduce any visible behavior differences. Another noteworthy detail
is that rebind_subsystems() guarantees that moving a subsystem to the
dummy root never fails so that valid unmounting attempts always
succeed.
This unifies binding and unbinding of subsystems. The invocation
points of ->bind() were inconsistent between the two and now moved
after whole rebinding is complete. This doesn't break the current
users and generally makes more sense.
All rebind_subsystems() users are converted accordingly. Note that
cgroup_remount() now makes two calls to rebind_subsystems() to bind
and then unbind the requested subsystems.
This will allow repurposing of the dummy hierarchy as the default
unified hierarchy and shouldn't make any userland visible behavior
difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_dummy_root is used to host controllers which aren't attached to
any other hierarchy. The root is minimally set up during kernfs
bootstrap and didn't go through full hierarchy initialization. We're
planning to use cgroup_dummy_root for the default unified hierarchy
and thus want it to be fully functional.
Replace the special initialization, which was collected into
cgroup_init() by the previous patch, with an invocation of
cgroup_setup_root(). This simplifies the init path and makes
cgroup_dummy_root a full hierarchy with its own kernfs_root and all.
As this puts the dummy hierarchy on the cgroup_roots list, rename
for_each_active_root() to for_each_root() and update its users to skip
the dummy root for now.
This patch doesn't cause any userland visible behavior changes at this
point.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
* Fields of init_css_set and css_set_count are now set using
initializer instead of programmatically from cgroup_init_early().
* init_cgroup_root() now also takes @opts and performs the optional
part of initialization too. The leftover part of
cgroup_root_from_opts() is collapsed into its only caller -
cgroup_mount().
* Initialization of cgroup_root_count and linking of init_css_set are
moved from cgroup_init_early() to to cgroup_init(). None of the
early_init users depends on init_css_set being linked.
* Subsystem initializations are moved after dummy hierarchy init and
init_css_set linking.
These changes reorganize the bootstrap logic so that the dummy
hierarchy can share the usual hierarchy init path and be made more
normal. These changes don't make noticeable behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
In cgroup_destroy_locked(), move setting of CGRP_DEAD above
invocations of kill_css(). This doesn't make any visible behavior
difference now but will be used to inhibit manipulating controller
enable states of a dying cgroup on the unified hierarchy.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
If online_css() fails, we should remove cgroup files belonging
to css->ss.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup_transfer_tasks() can currently fail in the middle due to memory
allocation failure. When that happens, the function just aborts and
returns error code and there's no way to tell how many actually got
migrated at the point of failure and or to revert the partial
migration.
Update it to use cgroup_migrate{_add_src|prepare_dst|migrate|finish}()
so that the function either succeeds or fails as a whole as long as
->can_attach() doesn't fail.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
For optimization, task_lock() is additionally used to protect
task->cgroups. The optimization is pretty dubious as either
css_set_rwsem is grabbed anyway or PF_EXITING already protects
task->cgroups. It adds only overhead and confusion at this point.
Let's drop task_[un]lock() and update comments accordingly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
When a new process is forked, cgroup_fork() associates it with the
css_set of its parent but doesn't link it into it. After the new
process is linked to tasklist, cgroup_post_fork() does the linking.
This is problematic for cgroup_transfer_tasks() as there's no way to
tell whether there are tasks which are pointing to a css_set but not
linked yet. It is impossible to implement an operation which transfer
all tasks of a cgroup to another and the current
cgroup_transfer_tasks() can easily be tricked into leaving a newly
forked process behind if it gets called between cgroup_fork() and
cgroup_post_fork().
Let's make association with a css_set and linking atomic by moving it
to cgroup_post_fork(). cgroup_fork() sets child->cgroups to
init_css_set as a placeholder and cgroup_post_fork() is updated to
perform both the association with the parent's cgroup and linking
there. This means that a newly created task will point to
init_css_set without holding a ref to it much like what it does on the
exit path. Empty cg_list is used to indicate that the task isn't
holding a ref to the associated css_set.
This fixes an actual bug with cgroup_transfer_tasks(); however, I'm
not marking it for -stable. The whole thing is broken in multiple
other ways which require invasive updates to fix and I don't think
it's worthwhile to bother with backporting this particular one.
Fortunately, the only user is cpuset and these bugs don't crash the
machine.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, process / task migration is a single operation which may
fail depending on memory pressure or the involved controllers'
->can_attach() callbacks. One problem with this approach is migration
of multiple targets. It's impossible to tell whether a given target
will be successfully migrated beforehand and cgroup core can't keep
track of enough states to roll back after intermediate failure.
This is already an issue with cgroup_transfer_tasks(). Also, we're
gonna need multiple target migration for unified hierarchy.
This patch splits migration into four stages -
cgroup_migrate_add_src(), cgroup_migrate_prepare_dst(),
cgroup_migrate() and cgroup_migrate_finish(), where
cgroup_migrate_prepare_dst() performs all the operations which may
fail due to allocation failure without actually migrating the target.
The four separate stages mean that, disregarding ->can_attach()
failures, the success or failure of multi target migration can be
determined before performing any actual migration. If preparations of
all targets succeed, the whole thing will succeed. If not, the whole
operation can fail without any side-effect.
Since the previous patch to use css_set->mg_tasks to keep track of
migration targets, the only thing which may need memory allocation
during migration is the target css_sets. cgroup_migrate_prepare()
pins all source and target css_sets and link them up. Note that this
can be performed without holding threadgroup_lock even if the target
is a process. As long as cgroup_mutex is held, no new css_set can be
put into play.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, while migrating tasks from one cgroup to another,
cgroup_attach_task() builds a flex array of all target tasks;
unfortunately, this has a couple issues.
* Flex array has size limit. On 64bit, struct task_and_cgroup is
24bytes making the flex element limit around 87k. It is a high
number but not impossible to hit. This means that the current
cgroup implementation can't migrate a process with more than 87k
threads.
* Process migration involves memory allocation whose size is dependent
on the number of threads the process has. This means that cgroup
core can't guarantee success or failure of multi-process migrations
as memory allocation failure can happen in the middle. This is in
part because cgroup can't grab threadgroup locks of multiple
processes at the same time, so when there are multiple processes to
migrate, it is imposible to tell how many tasks are to be migrated
beforehand.
Note that this already affects cgroup_transfer_tasks(). cgroup
currently cannot guarantee atomic success or failure of the
operation. It may fail in the middle and after such failure cgroup
doesn't have enough information to roll back properly. It just
aborts with some tasks migrated and others not.
To resolve the situation, this patch updates the migration path to use
task->cg_list to track target tasks. The previous patch already added
css_set->mg_tasks and updated iterations in non-migration paths to
include them during task migration. This patch updates migration path
to actually make use of it.
Instead of putting onto a flex_array, each target task is moved from
its css_set->tasks list to css_set->mg_tasks and the migration path
keeps trace of all the source css_sets and the associated cgroups.
Once all source css_sets are determined, the destination css_set for
each is determined, linked to the matching source css_set and put on a
separate list.
To iterate the target tasks, migration path just needs to iterat
through either the source or target css_sets, depending on whether
migration has been committed or not, and the tasks on their ->mg_tasks
lists. cgroup_taskset is updated to contain the list_heads for source
and target css_sets and the iteration cursor. cgroup_taskset_*() are
accordingly updated to walk through css_sets and their ->mg_tasks.
This resolves the above listed issues with moderate additional
complexity.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, while migrating tasks from one cgroup to another,
cgroup_attach_task() builds a flex array of all target tasks;
unfortunately, this has a couple issues.
* Flex array has size limit. On 64bit, struct task_and_cgroup is
24bytes making the flex element limit around 87k. It is a high
number but not impossible to hit. This means that the current
cgroup implementation can't migrate a process with more than 87k
threads.
* Process migration involves memory allocation whose size is dependent
on the number of threads the process has. This means that cgroup
core can't guarantee success or failure of multi-process migrations
as memory allocation failure can happen in the middle. This is in
part because cgroup can't grab threadgroup locks of multiple
processes at the same time, so when there are multiple processes to
migrate, it is imposible to tell how many tasks are to be migrated
beforehand.
Note that this already affects cgroup_transfer_tasks(). cgroup
currently cannot guarantee atomic success or failure of the
operation. It may fail in the middle and after such failure cgroup
doesn't have enough information to roll back properly. It just
aborts with some tasks migrated and others not.
To resolve the situation, we're going to use task->cg_list during
migration too. Instead of building a separate array, target tasks
will be linked into a dedicated migration list_head on the owning
css_set. Tasks on the migration list are treated the same as tasks on
the usual tasks list; however, being on a separate list allows cgroup
migration code path to keep track of the target tasks by simply
keeping the list of css_sets with tasks being migrated, making
unpredictable dynamic allocation unnecessary.
In prepartion of such migration path update, this patch introduces
css_set->mg_tasks list and updates css_set task iterations so that
they walk both css_set->tasks and ->mg_tasks. Note that ->mg_tasks
isn't used yet.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Pull in for-3.14-fixes to receive 532de3fc72 ("cgroup: update
cgroup_enable_task_cg_lists() to grab siglock") which conflicts with
afeb0f9fd4 ("cgroup: relocate cgroup_enable_task_cg_lists()") and
the following cg_lists updates. This is likely to cause further
conflicts down the line too, so let's merge it early.
As cgroup_enable_task_cg_lists() is relocated in for-3.15, this merge
causes conflict in the original position. It's resolved by applying
siglock changes to the updated version in the new location.
Conflicts:
kernel/cgroup.c
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently, there's nothing preventing cgroup_enable_task_cg_lists()
from missing set PF_EXITING and race against cgroup_exit(). Depending
on the timing, cgroup_exit() may finish with the task still linked on
css_set leading to list corruption. Fix it by grabbing siglock in
cgroup_enable_task_cg_lists() so that PF_EXITING is guaranteed to be
visible.
This whole on-demand cg_list optimization is extremely fragile and has
ample possibility to lead to bugs which can cause things like
once-a-year oops during boot. I'm wondering whether the better
approach would be just adding "cgroup_disable=all" handling which
disables the whole cgroup rather than tempting fate with this
on-demand craziness.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: stable@vger.kernel.org
Fengguang reported this bug:
BUG: unable to handle kernel NULL pointer dereference at 0000003c
IP: [<cc90b4ad>] cgroup_cfts_commit+0x27/0x1c1
...
Call Trace:
[<cc9d1129>] ? kmem_cache_alloc_trace+0x33f/0x3b7
[<cc90c6fc>] cgroup_add_cftypes+0x8f/0xca
[<cd78b646>] cgroup_init+0x6a/0x26a
[<cd764d7d>] start_kernel+0x4d7/0x57a
[<cd7642ef>] i386_start_kernel+0x92/0x96
This happens in a corner case. If CGROUP_SCHED=y but CFS_BANDWIDTH=n &&
FAIR_GROUP_SCHED=n && RT_GROUP_SCHED=n, we have:
cpu_files[] = {
{ } /* terminate */
}
When we pass cpu_files to cgroup_apply_cftypes(), as cpu_files[0].ss
is NULL, we'll access NULL pointer.
The bug was introduced by commit de00ffa56e
("cgroup: make cgroup_subsys->base_cftypes use cgroup_add_cftypes()").
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
We should free the memory allocated in parse_cgroupfs_options() before
calling this function again.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
css_set_lock has been converted to css_set_rwsem, and rwsem can't nest
inside rcu_read_lock.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
kernel/cgroup.c:2256:1-3: WARNING: PTR_RET can be used
Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR
Generated by: coccinelle/api/ptr_ret.cocci
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
With module support gone, a lot of functions no longer need to be
exported. Unexport them.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_attach_task() is planned to go through restructuring. Let's
tidy it up a bit in preparation.
* Update cgroup_attach_task() to receive the target task argument in
@leader instead of @tsk.
* Rename @tsk to @task.
* Rename @retval to @ret.
This is purely cosmetic.
v2: get_nr_threads() was using uninitialized @task instead of @leader.
Fixed. Reported by Dan Carpenter.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
The two functions don't have any users left. Remove them along with
cgroup_taskset->cur_cgrp.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Instead of repeatedly locking and unlocking css_set_rwsem inside
cgroup_task_migrate(), update cgroup_attach_task() to grab it outside
of the loop and update cgroup_task_migrate() to use
put_css_set_locked().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
put_css_set() is performed in two steps - it first tries to put
without grabbing css_set_rwsem if such put wouldn't make the count
zero. If that fails, it puts after write-locking css_set_rwsem. This
patch separates out the second phase into put_css_set_locked() which
should be called with css_set_rwsem locked.
Also, put_css_set_taskexit() is droped and put_css_set() is made to
take @taskexit. There are only a handful users of these functions.
No point in providing different variants.
put_css_locked() will be used by later changes. This patch doesn't
introduce any functional changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently there are two ways to walk tasks of a cgroup -
css_task_iter_start/next/end() and css_scan_tasks(). The latter
builds on the former but allows blocking while iterating.
Unfortunately, the way css_scan_tasks() is implemented is rather
nasty, it uses a priority heap of pointers to extract some number of
tasks in task creation order and loops over them invoking the callback
and repeats that until it reaches the end. It requires either
preallocated heap or may fail under memory pressure, while unlikely to
be problematic, the complexity is O(N^2), and in general just nasty.
We're gonna convert all css_scan_users() to
css_task_iter_start/next/end() and remove css_scan_users(). As
css_scan_tasks() users may block, let's convert css_set_lock to a
rwsem so that tasks can block during css_task_iter_*() is in progress.
While this does increase the chance of possible deadlock scenarios,
given the current usage, the probability is relatively low, and even
if that happens, the right thing to do is updating the iteration in
the similar way to css iterators so that it can handle blocking.
Most conversions are trivial; however, task_cgroup_path() now expects
to be called with css_set_rwsem locked instead of locking itself.
This is because the function is called with RCU read lock held and
rwsem locking should nest outside RCU read lock.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Reimplement cgroup_transfer_tasks() so that it repeatedly fetches the
first task in the cgroup and then tranfers it. This achieves the same
result without using css_scan_tasks() which is scheduled to be
removed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_task_count() read-locks css_set_lock and walks all tasks to
count them and then returns the result. The only thing all the users
want is determining whether the cgroup is empty or not. This patch
implements cgroup_has_tasks() which tests whether cgroup->cset_links
is empty, replaces all cgroup_task_count() usages and unexports it.
Note that the test isn't synchronized. This is the same as before.
The test has always been racy.
This will help planned css_set locking update.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Move it above so that prototype isn't necessary. Let's also move the
definition of use_task_css_set_links next to it.
This is purely cosmetic.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Tasks are not linked on their css_sets until cgroup task iteration is
actually used. This is to avoid incurring overhead on the fork and
exit paths for systems which have cgroup compiled in but don't use it.
This lazy binding also affects the task migration path. It has to be
careful so that it doesn't link tasks to css_sets when task_cg_lists
linking is not enabled yet. Unfortunately, this conditional linking
in the migration path interferes with planned migration updates.
This patch moves the lazy binding a bit earlier, to the first cgroup
mount. It's a clear indication that cgroup is being used on the
system and task_cg_lists linking is highly likely to be enabled soon
anyway through "tasks" and "cgroup.procs" files.
This allows cgroup_task_migrate() to always link @tsk->cg_list. Note
that it may still race with cgroup_post_fork() but who wins that race
is inconsequential.
While at it, make use_task_css_set_links a bool, add sanity checks in
cgroup_enable_task_cg_lists() and css_task_iter_start(), and update
the former so that it's guaranteed and assumes to run only once.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Before kernfs conversion, due to the way super_block lookup works,
cgroup roots were created and made visible before being fully
initialized. This in turn required a special flag to mark that the
root hasn't been fully initialized so that the destruction path can
tell fully bound ones from half initialized.
That flag is CGRP_ROOT_SUBSYS_BOUND and no longer necessary after the
kernfs conversion as the lookup and creation of new root are atomic
w.r.t. cgroup_mutex. This patch removes the flag and passes the
requests subsystem mask to cgroup_setup_root() so that it can set the
respective mask bits as subsystems are bound.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Disallow more mount options if sane_behavior. Note that xattr used to
generate warning.
While at it, simplify option check in cgroup_mount() and update
sane_behavior comment in cgroup.h.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
This reverts commit ab3f5faa62.
Explanation from Hugh:
It's because more thorough testing, by others here, found that it
wasn't always solving the problem: so I asked Tejun privately to
hold off from sending it in, until we'd worked out why not.
Most of our testing being on a v3,11-based kernel, it was perfectly
possible that the problem was merely our own e.g. missing Tejun's
8a2b753844 ("workqueue: fix ordered workqueues in NUMA setups").
But that turned out not to be enough to fix it either. Then Filipe
pointed out how percpu_ref_kill_and_confirm() uses call_rcu_sched()
before we ever get to put the offline on to the workqueue: by the
time we get to the workqueue, the ordering has already been lost.
So, thanks for the Acks, but I'm afraid that this ordered workqueue
solution is just not good enough: we should simply forget that patch
and provide a different answer."
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Hugh Dickins <hughd@google.com>
Currently, cgroupfs_root and its ->top_cgroup are separated reference
counted and the latter's is ignored. There's no reason to do this
separately. This patch removes cgroupfs_root->refcnt and destroys
cgroupfs_root when the top_cgroup is released.
* cgroup_put() updated to ignore cgroup_is_dead() test for top
cgroups. cgroup_free_fn() updated to handle root destruction when
releasing a top cgroup.
* As root destruction is now bounced through cgroup destruction, it is
asynchronous. Update cgroup_mount() so that it waits for pending
release which is currently implemented using msleep(). Converting
this to proper wait_queue isn't hard but likely unnecessary.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
root->number_of_cgroups is currently an integer protected with
cgroup_mutex. Except for sanity checks and proc reporting, the only
place it's used is to check whether the root has any child during
remount; however, this is a bit flawed as the counter is not
decremented when the cgroup is unlinked but when it's released,
meaning that there could be an extended period where all cgroups are
removed but remount is still not allowed because some internal objects
are lingering. While not perfect either, it'd be better to use
emptiness test on root->top_cgroup.children.
This patch updates cgroup_remount() to test top_cgroup's children
instead, which makes number_of_cgroups only actual usage statistics
printing in proc implemented in proc_cgroupstats_show(). Let's
shorten its name and make it an atomic_t so that we don't have to
worry about its synchronization. It's purely auxiliary at this point.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup->name handling became quite complicated over time involving
dedicated struct cgroup_name for RCU protection. Now that cgroup is
on kernfs, we can drop all of it and simply use kernfs_name/path() and
friends. Replace cgroup->name and all related code with kernfs
name/path constructs.
* Reimplement cgroup_name() and cgroup_path() as thin wrappers on top
of kernfs counterparts, which involves semantic changes.
pr_cont_cgroup_name() and pr_cont_cgroup_path() added.
* cgroup->name handling dropped from cgroup_rename().
* All users of cgroup_name/path() updated to the new semantics. Users
which were formatting the string just to printk them are converted
to use pr_cont_cgroup_name/path() instead, which simplifies things
quite a bit. As cgroup_name() no longer requires RCU read lock
around it, RCU lockings which were protecting only cgroup_name() are
removed.
v2: Comment above oom_info_lock updated as suggested by Michal.
v3: dummy_top doesn't have a kn associated and
pr_cont_cgroup_name/path() ended up calling the matching kernfs
functions with NULL kn leading to oops. Test for NULL kn and
print "/" if so. This issue was reported by Fengguang Wu.
v4: Rebased on top of 0ab02ca8f8 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
cgroup currently releases its kernfs_node when it gets removed. While
not buggy, this makes cgroup->kn access rules complicated than
necessary and leads to things like get/put protection around
kernfs_remove() in cgroup_destroy_locked(). In addition, we want to
use kernfs_name/path() and friends but also want to be able to
determine a cgroup's name between removal and release.
This patch makes cgroup hold onto its kernfs_node until freed so that
cgroup->kn is always accessible.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Dynamic cftype addition and removal using cgroup_add/rm_cftypes()
respectively has been quite hairy due to vfs i_mutex. As i_mutex
nests outside cgroup_mutex, cgroup_mutex has to be released and
regrabbed on each iteration through the hierarchy complicating the
process. Now that i_mutex is no longer in play, it can be simplified.
* Just holding cgroup_tree_mutex is enough. No need to meddle with
cgroup_mutex.
* No reason to play the unlock - relock - check serial_nr dancing.
Everything can be atomically while holding cgroup_tree_mutex.
* cgroup_cfts_prepare() is replaced with direct locking of
cgroup_tree_mutex.
* cgroup_cfts_commit() no longer fiddles with locking. It just
applies the cftypes change to the existing cgroups in the hierarchy.
Renamed to cgroup_cfts_apply().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cftype_set was added primarily to allow registering the same cftype
array more than once for different subsystems. Nobody uses or needs
such thing and it's already broken because each cftype has ->ss
pointer which is initialized during registration.
Let's add list_head ->node to cftype and use the first cftype entry in
the array to link them instead of allocating separate cftype_set.
While at it, trigger WARN if cft seems previously initialized during
registration.
This simplifies cftype handling a bit.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cftype handling is about to be revamped. Relocate cgroup_rm_cftypes()
above cgroup_add_cftypes() in preparation. This is pure relocation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Mount option "xattr" is no longer necessary as it's enabled by default
on kernfs. Warn if "xattr" is specified with "sane_behavior" so that
the option can be removed in the future.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup filesystem code was derived from the original sysfs
implementation which was heavily intertwined with vfs objects and
locking with the goal of re-using the existing vfs infrastructure.
That experiment turned out rather disastrous and sysfs switched, a
long time ago, to distributed filesystem model where a separate
representation is maintained which is queried by vfs. Unfortunately,
cgroup stuck with the failed experiment all these years and
accumulated even more problems over time.
Locking and object lifetime management being entangled with vfs is
probably the most egregious. vfs is never designed to be misused like
this and cgroup ends up jumping through various convoluted dancing to
make things work. Even then, operations across multiple cgroups can't
be done safely as it'll deadlock with rename locking.
Recently, kernfs is separated out from sysfs so that it can be used by
users other than sysfs. This patch converts cgroup to use kernfs,
which will bring the following benefits.
* Separation from vfs internals. Locking and object lifetime
management is contained in cgroup proper making things a lot
simpler. This removes significant amount of locking convolutions,
hairy object lifetime rules and the restriction on multi-cgroup
operations.
* Can drop a lot of code to implement filesystem interface as most are
provided by kernfs.
* Proper "severing" semantics, which allows controllers to not worry
about lingering file accesses after offline.
While the preceding patches did as much as possible to make the
transition less painful, large part of the conversion has to be one
discrete step making this patch rather large. The rest of the commit
message lists notable changes in different areas.
Overall
-------
* vfs constructs replaced with kernfs ones. cgroup->dentry w/ ->kn,
cgroupfs_root->sb w/ ->kf_root.
* All dentry accessors are removed. Helpers to map from kernfs
constructs are added.
* All vfs plumbing around dentry, inode and bdi removed.
* cgroup_mount() now directly looks for matching root and then
proceeds to create a new one if not found.
Synchronization and object lifetime
-----------------------------------
* vfs inode locking removed. Among other things, this removes the
need for the convolution in cgroup_cfts_commit(). Future patches
will further simplify it.
* vfs refcnting replaced with cgroup internal ones. cgroup->refcnt,
cgroupfs_root->refcnt added. cgroup_put_root() now directly puts
root->refcnt and when it reaches zero proceeds to destroy it thus
merging cgroup_put_root() and the former cgroup_kill_sb().
Simliarly, cgroup_put() now directly schedules cgroup_free_rcu()
when refcnt reaches zero.
* Unlike before, kernfs objects don't hold onto cgroup objects. When
cgroup destroys a kernfs node, all existing operations are drained
and the association is broken immediately. The same for
cgroupfs_roots and mounts.
* All operations which come through kernfs guarantee that the
associated cgroup is and stays valid for the duration of operation;
however, there are two paths which need to find out the associated
cgroup from dentry without going through kernfs -
css_tryget_from_dir() and cgroupstats_build(). For these two,
kernfs_node->priv is RCU managed so that they can dereference it
under RCU read lock.
File and directory handling
---------------------------
* File and directory operations converted to kernfs_ops and
kernfs_syscall_ops.
* xattrs is implicitly supported by kernfs. No need to worry about it
from cgroup. This means that "xattr" mount option is no longer
necessary. A future patch will add a deprecated warning message
when sane_behavior.
* When cftype->max_write_len > PAGE_SIZE, it's necessary to make a
private copy of one of the kernfs_ops to set its atomic_write_len.
cftype->kf_ops is added and cgroup_init/exit_cftypes() are updated
to handle it.
* cftype->lockdep_key added so that kernfs lockdep annotation can be
per cftype.
* Inidividual file entries and open states are now managed by kernfs.
No need to worry about them from cgroup. cfent, cgroup_open_file
and their friends are removed.
* kernfs_nodes are created deactivated and kernfs_activate()
invocations added to places where creation of new nodes are
committed.
* cgroup_rmdir() uses kernfs_[un]break_active_protection() for
self-removal.
v2: - Li pointed out in an earlier patch that specifying "name="
during mount without subsystem specification should succeed if
there's an existing hierarchy with a matching name although it
should fail with -EINVAL if a new hierarchy should be created.
Prior to the conversion, this used by handled by deferring
failure from NULL return from cgroup_root_from_opts(), which was
necessary because root was being created before checking for
existing ones. Note that cgroup_root_from_opts() returned an
ERR_PTR() value for error conditions which require immediate
mount failure.
As we now have separate search and creation steps, deferring
failure from cgroup_root_from_opts() is no longer necessary.
cgroup_root_from_opts() is updated to always return ERR_PTR()
value on failure.
- The logic to match existing roots is updated so that a mount
attempt with a matching name but different subsys_mask are
rejected. This was handled by a separate matching loop under
the comment "Check for name clashes with existing mounts" but
got lost during conversion. Merge the check into the main
search loop.
- Add __rcu __force casting in RCU_INIT_POINTER() in
cgroup_destroy_locked() to avoid the sparse address space
warning reported by kbuild test bot. Maybe we want an explicit
interface to use kn->priv as RCU protected pointer?
v3: Make CONFIG_CGROUPS select CONFIG_KERNFS.
v4: Rebased on top of 0ab02ca8f8 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: kbuild test robot fengguang.wu@intel.com>
Relocate cgroup_init/exit_root_id(), cgroup_free_root(),
cgroup_kill_sb() and cgroup_file_name() in preparation of kernfs
conversion.
These are pure relocations to make kernfs conversion easier to follow.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
* Un-inline seq_css(). After kernfs conversion, the function will
need to dereference internal data structures.
* Add cgroup_get/put_root() and replace direct super_block->s_active
manipulatinos with them. These will be converted to kernfs_root
refcnting.
* Add cgroup_get/put() and replace dget/put() on cgrp->dentry with
them. These will be converted to kernfs refcnting.
* Update current_css_set_cg_links_read() to use cgroup_name() instead
of reaching into the dentry name. The end result is the same.
These changes don't make functional differences but will make
transition to kernfs easier.
v2: Rebased on top of 0ab02ca8f8 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
mm/memory-failure.c::hwpoison_filter_task() has been reaching into
cgroup to extract the associated ino to be used as a filtering
criterion. This is an implementation detail which shouldn't be
depended upon from outside cgroup proper and is about to change with
the scheduled kernfs conversion.
This patch introduces a proper interface to determine the associated
ino, cgroup_ino(), and updates hwpoison_filter_task() to use it
instead of reaching directly into cgroup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Factor out cft->ss initialization into cgroup_init_cftypes() from
cgroup_add_cftypes() and add cft->ss clearing to cgroup_rm_cftypes()
through cgroup_exit_cftypes().
This doesn't make any meaningful difference now but the two new
functions will be expanded during kernfs transition.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cftype->max_write_len is used to extend the maximum size of writes.
It's interpreted in such a way that the actual maximum size is one
less than the specified value. The default size is defined by
CGROUP_LOCAL_BUFFER_SIZE. Its interpretation is quite confusing - its
value is decremented by 1 and then compared for equality with max
size, which means that the actual default size is
CGROUP_LOCAL_BUFFER_SIZE - 2, which is 62 chars.
There's no point in having a limit that low. Update its definition so
that it means the actual string length sans termination and anything
below PAGE_SIZE-1 is treated as PAGE_SIZE-1.
.max_write_len for "release_agent" is updated to PATH_MAX-1 and
cgroup_release_agent_write() is updated so that the redundant strlen()
check is removed and it uses strlcpy() instead of strcpy().
.max_write_len initializations in blk-throttle.c and cfq-iosched.c are
no longer necessary and removed. The one in cpuset is kept unchanged
as it's an approximated value to begin with.
This will also make transition to kernfs smoother.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, cgroup_subsys->base_cftypes registration is different from
dynamic cftypes registartion. Instead of going through
cgroup_add_cftypes(), cgroup_init_subsys() invokes
cgroup_init_cftsets() which makes use of cgroup_subsys->base_cftset
which doesn't involve dynamic allocation.
While avoiding dynamic allocation is somewhat nice, having two
separate paths for cftypes registration is nasty, especially as we're
planning to add more operations during cftypes registration.
This patch drops cgroup_init_cftsets() and cgroup_subsys->base_cftset
and registers base_cftypes using cgroup_add_cftypes(). This is done
as a separate step in cgroup_init() instead of a part of
cgroup_init_subsys(). This is because cgroup_init_subsys() can be
called very early during boot when kmalloc() isn't available yet.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Straightforward updates to cgroup name handling in preparation of
kernfs conversion.
* cgroup_alloc_name() is updated to take const char * isntead of
dentry * for name source.
* cgroup name formatting is separated out into cgroup_file_name().
While at it, buffer length protection is added.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Factor out new root initialization into cgroup_setup_root() from
cgroup_mount(). This makes it easier to follow and will ease kernfs
conversion.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup is scheduled to be converted to kernfs. After conversion,
cgroup_mount() won't use the sget() machinery for finding out existing
super_blocks but instead would do that directly. It'll search the
existing cgroupfs_roots for a matching one and create a new one iff a
match doesn't exist. To ease such conversion, this patch restructures
locking and error handling of the function.
cgroup_tree_mutex and cgroup_mutex are grabbed from the get-go and
held until return. For now, due to the way vfs locks nest outside
cgroup mutexes, the two cgroup mutexes are temporarily dropped across
sget() and inode mutex locking, which looks quite ridiculous; however,
these will be removed through kernfs conversion and structuring the
code this way makes the conversion less painful.
The error goto labels are consolidated to two. This looks unwieldy
now but the next patch will factor out creation of new root into a
separate function with accompanying error handling and it'll look a
lot better.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Now that cftypes and all tree modification operations are protected by
cgroup_tree_mutex, we can drop cgroup_mutex while deleting files and
directories. Drop cgroup_mutex over removals.
This doesn't make any noticeable difference now but is to help kernfs
conversion. In kernfs, removals are sync points which drain in-flight
operations as those operations would grab cgroup_mutex, trying to
delete under cgroup_mutex would deadlock. This can be resolved by
just holding the outer cgroup_tree_mutex which nests outside both
kernfs active reference and cgroup_mutex.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently cgroup uses combination of inode->i_mutex'es and
cgroup_mutex for synchronization. With the scheduled kernfs
conversion, i_mutex'es will be removed. Unfortunately, just using
cgroup_mutex isn't possible. All kernfs file and syscall operations,
most of which require grabbing cgroup_mutex, will be called with
kernfs active ref held and, if we try to perform kernfs removals under
cgroup_mutex, it can deadlock as kernfs_remove() tries to drain the
target node.
Let's introduce a new outer mutex, cgroup_tree_mutex, which protects
stuff used during hierarchy changing operations - cftypes and all the
operations which may affect the cgroupfs. It also covers css
association and iteration. This allows cgroup_css(), for_each_css()
and other css iterators to be called under cgroup_tree_mutex. The new
mutex will nest above both kernfs's active ref protection and
cgroup_mutex. By protecting tree modifications with a separate outer
mutex, we can get rid of the forementioned deadlock condition.
Actual file additions and removals now require cgroup_tree_mutex
instead of cgroup_mutex. Currently, cgroup_tree_mutex is never used
without cgroup_mutex; however, we'll soon add hierarchy modification
sections which are only protected by cgroup_tree_mutex. In the
future, we might want to make the locking more granular by better
splitting the coverages of the two mutexes. For now, this should do.
v2: Rebased on top of 0ab02ca8f8 ("cgroup: protect modifications to
cgroup_idr with cgroup_mutex").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
css_from_dir() returns the matching css (cgroup_subsys_state) given a
dentry and subsystem. The function doesn't pin the css before
returning and requires the caller to be holding RCU read lock or
cgroup_mutex and handling pinning on the caller side.
Given that users of the function are likely to want to pin the
returned css (both existing users do) and that getting and putting
css's are very cheap, there's no reason for the interface to be tricky
like this.
Rename css_from_dir() to css_tryget_from_dir() and make it try to pin
the found css and return it only if pinning succeeded. The callers
are updated so that they no longer do RCU locking and pinning around
the function and just use the returned css.
This will also ease converting cgroup to kernfs.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Pull for-3.14-fixes to receive 0ab02ca8f8 ("cgroup: protect
modifications to cgroup_idr with cgroup_mutex") prior to kernfs
conversion series to avoid non-trivial conflicts.
Signed-off-by: Tejun Heo <tj@kernel.org>
Setup cgroupfs like this:
# mount -t cgroup -o cpuacct xxx /cgroup
# mkdir /cgroup/sub1
# mkdir /cgroup/sub2
Then run these two commands:
# for ((; ;)) { mkdir /cgroup/sub1/tmp && rmdir /mnt/sub1/tmp; } &
# for ((; ;)) { mkdir /cgroup/sub2/tmp && rmdir /mnt/sub2/tmp; } &
After seconds you may see this warning:
------------[ cut here ]------------
WARNING: CPU: 1 PID: 25243 at lib/idr.c:527 sub_remove+0x87/0x1b0()
idr_remove called for id=6 which is not allocated.
...
Call Trace:
[<ffffffff8156063c>] dump_stack+0x7a/0x96
[<ffffffff810591ac>] warn_slowpath_common+0x8c/0xc0
[<ffffffff81059296>] warn_slowpath_fmt+0x46/0x50
[<ffffffff81300aa7>] sub_remove+0x87/0x1b0
[<ffffffff810f3f02>] ? css_killed_work_fn+0x32/0x1b0
[<ffffffff81300bf5>] idr_remove+0x25/0xd0
[<ffffffff810f2bab>] cgroup_destroy_css_killed+0x5b/0xc0
[<ffffffff810f4000>] css_killed_work_fn+0x130/0x1b0
[<ffffffff8107cdbc>] process_one_work+0x26c/0x550
[<ffffffff8107eefe>] worker_thread+0x12e/0x3b0
[<ffffffff81085f96>] kthread+0xe6/0xf0
[<ffffffff81570bac>] ret_from_fork+0x7c/0xb0
---[ end trace 2d1577ec10cf80d0 ]---
It's because allocating/removing cgroup ID is not properly synchronized.
The bug was introduced when we converted cgroup_ida to cgroup_idr.
While synchronization is already done inside ida_simple_{get,remove}(),
users are responsible for concurrent calls to idr_{alloc,remove}().
tj: Refreshed on top of b58c89986a ("cgroup: fix error return from
cgroup_create()").
Fixes: 4e96ee8e98 ("cgroup: convert cgroup_ida to cgroup_idr")
Cc: <stable@vger.kernel.org> #3.12+
Reported-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup_root_mutex was added to avoid deadlock involving namespace_sem
via cgroup_show_options(). It added a lot of overhead for the small
purpose of it and, because it's nested under cgroup_mutex, it has very
limited usefulness. The previous patch made cgroup_show_options() not
use cgroup_root_mutex, so nobody needs it anymore. Remove it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_show_options() grabs cgroup_root_mutex to protect the options
changing while printing; however, holding root_mutex or not doesn't
really make much difference for the function. subsys_mask can be
atomically tested and most of the options aren't allowed to change
anyway once mounted.
The only field which needs synchronization is ->release_agent_path.
This patch introduces a dedicated spinlock to synchronize accesses to
the field and drops cgroup_root_mutex locking from
cgroup_show_options(). The next patch will remove cgroup_root_mutex.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
It's no longer referenced outside cgroup core, so renaming is easy.
Let's rename it for consistency & brevity.
This patch is pure rename.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_subsys is a bit messier than it needs to be.
* The name of a subsys can be different from its internal identifier
defined in cgroup_subsys.h. Most subsystems use the matching name
but three - cpu, memory and perf_event - use different ones.
* cgroup_subsys_id enums are postfixed with _subsys_id and each
cgroup_subsys is postfixed with _subsys. cgroup.h is widely
included throughout various subsystems, it doesn't and shouldn't
have claim on such generic names which don't have any qualifier
indicating that they belong to cgroup.
* cgroup_subsys->subsys_id should always equal the matching
cgroup_subsys_id enum; however, we require each controller to
initialize it and then BUG if they don't match, which is a bit
silly.
This patch cleans up cgroup_subsys names and initialization by doing
the followings.
* cgroup_subsys_id enums are now postfixed with _cgrp_id, and each
cgroup_subsys with _cgrp_subsys.
* With the above, renaming subsys identifiers to match the userland
visible names doesn't cause any naming conflicts. All non-matching
identifiers are renamed to match the official names.
cpu_cgroup -> cpu
mem_cgroup -> memory
perf -> perf_event
* controllers no longer need to initialize ->subsys_id and ->name.
They're generated in cgroup core and set automatically during boot.
* Redundant cgroup_subsys declarations removed.
* While updating BUG_ON()s in cgroup_init_early(), convert them to
WARN()s. BUGging that early during boot is stupid - the kernel
can't print anything, even through serial console and the trap
handler doesn't even link stack frame properly for back-tracing.
This patch doesn't introduce any behavior changes.
v2: Rebased on top of fe1217c4f3 ("net: net_cls: move cgroupfs
classid handling into core").
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Acked-by: "David S. Miller" <davem@davemloft.net>
Acked-by: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Acked-by: Aristeu Rozanski <aris@redhat.com>
Acked-by: Ingo Molnar <mingo@redhat.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Serge E. Hallyn <serue@us.ibm.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Thomas Graf <tgraf@suug.ch>
With module supported dropped from net_prio, no controller is using
cgroup module support. None of actual resource controllers can be
built as a module and we aren't gonna add new controllers which don't
control resources. This patch drops module support from cgroup.
* cgroup_[un]load_subsys() and cgroup_subsys->module removed.
* As there's no point in distinguishing IS_BUILTIN() and IS_MODULE(),
cgroup_subsys.h now uses IS_ENABLED() directly.
* enum cgroup_subsys_id now exactly matches the list of enabled
controllers as ordered in cgroup_subsys.h.
* cgroup_subsys[] is now a contiguously occupied array. Size
specification is no longer necessary and dropped.
* for_each_builtin_subsys() is removed and for_each_subsys() is
updated to not require any locking.
* module ref handling is removed from rebind_subsystems().
* Module related comments dropped.
v2: Rebased on top of fe1217c4f3 ("net: net_cls: move cgroupfs
classid handling into core").
v3: Added {} around the if (need_forkexit_callback) block in
cgroup_post_fork() for readability as suggested by Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_cfts_commit() walks the cgroup hierarchy that the target
subsystem is attached to and tries to apply the file changes. Due to
the convolution with inode locking, it can't keep cgroup_mutex locked
while iterating. It currently holds only RCU read lock around the
actual iteration and then pins the found cgroup using dget().
Unfortunately, this is incorrect. Although the iteration does check
cgroup_is_dead() before invoking dget(), there's nothing which
prevents the dentry from going away inbetween. Note that this is
different from the usual css iterations where css_tryget() is used to
pin the css - css_tryget() tests whether the css can be pinned and
fails if not.
The problem can be solved by simply holding cgroup_mutex instead of
RCU read lock around the iteration, which actually reduces LOC.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: stable@vger.kernel.org
cgroup_create() was returning 0 after allocation failures. Fix it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: stable@vger.kernel.org
When cgroup_mount() fails to allocate an id for the root, it didn't
set ret before jumping to unlock_drop ending up returning 0 after a
failure. Fix it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: stable@vger.kernel.org
Sometimes the cleanup after memcg hierarchy testing gets stuck in
mem_cgroup_reparent_charges(), unable to bring non-kmem usage down to 0.
There may turn out to be several causes, but a major cause is this: the
workitem to offline parent can get run before workitem to offline child;
parent's mem_cgroup_reparent_charges() circles around waiting for the
child's pages to be reparented to its lrus, but it's holding cgroup_mutex
which prevents the child from reaching its mem_cgroup_reparent_charges().
Just use an ordered workqueue for cgroup_destroy_wq.
tj: Committing as the temporary fix until the reverse dependency can
be removed from memcg. Comment updated accordingly.
Fixes: e5fca243ab ("cgroup: use a dedicated workqueue for cgroup destruction")
Suggested-by: Filipe Brandenburger <filbranden@google.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull cgroup updates from Tejun Heo:
"The bulk of changes are cleanups and preparations for the upcoming
kernfs conversion.
- cgroup_event mechanism which is and will be used only by memcg is
moved to memcg.
- pidlist handling is updated so that it can be served by seq_file.
Also, the list is not sorted if sane_behavior. cgroup
documentation explicitly states that the file is not sorted but it
has been for quite some time.
- All cgroup file handling now happens on top of seq_file. This is
to prepare for kernfs conversion. In addition, all operations are
restructured so that they map 1-1 to kernfs operations.
- Other cleanups and low-pri fixes"
* 'for-3.14' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (40 commits)
cgroup: trivial style updates
cgroup: remove stray references to css_id
doc: cgroups: Fix typo in doc/cgroups
cgroup: fix fail path in cgroup_load_subsys()
cgroup: fix missing unlock on error in cgroup_load_subsys()
cgroup: remove for_each_root_subsys()
cgroup: implement for_each_css()
cgroup: factor out cgroup_subsys_state creation into create_css()
cgroup: combine css handling loops in cgroup_create()
cgroup: reorder operations in cgroup_create()
cgroup: make for_each_subsys() useable under cgroup_root_mutex
cgroup: css iterations and css_from_dir() are safe under cgroup_mutex
cgroup: unify pidlist and other file handling
cgroup: replace cftype->read_seq_string() with cftype->seq_show()
cgroup: attach cgroup_open_file to all cgroup files
cgroup: generalize cgroup_pidlist_open_file
cgroup: unify read path so that seq_file is always used
cgroup: unify cgroup_write_X64() and cgroup_write_string()
cgroup: remove cftype->read(), ->read_map() and ->write()
hugetlb_cgroup: convert away from cftype->read()
...
* Place newline before function opening brace in cgroup_kill_sb().
* Insert space before assignment in attach_task_by_pid()
tj: merged two patches into one.
Signed-off-by: SeongJae Park <sj38.park@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Hugh reported this bug:
> CONFIG_MEMCG_SWAP is broken in 3.13-rc. Try something like this:
>
> mkdir -p /tmp/tmpfs /tmp/memcg
> mount -t tmpfs -o size=1G tmpfs /tmp/tmpfs
> mount -t cgroup -o memory memcg /tmp/memcg
> mkdir /tmp/memcg/old
> echo 512M >/tmp/memcg/old/memory.limit_in_bytes
> echo $$ >/tmp/memcg/old/tasks
> cp /dev/zero /tmp/tmpfs/zero 2>/dev/null
> echo $$ >/tmp/memcg/tasks
> rmdir /tmp/memcg/old
> sleep 1 # let rmdir work complete
> mkdir /tmp/memcg/new
> umount /tmp/tmpfs
> dmesg | grep WARNING
> rmdir /tmp/memcg/new
> umount /tmp/memcg
>
> Shows lots of WARNING: CPU: 1 PID: 1006 at kernel/res_counter.c:91
> res_counter_uncharge_locked+0x1f/0x2f()
>
> Breakage comes from 34c00c319c ("memcg: convert to use cgroup id").
>
> The lifetime of a cgroup id is different from the lifetime of the
> css id it replaced: memsw's css_get()s do nothing to hold on to the
> old cgroup id, it soon gets recycled to a new cgroup, which then
> mysteriously inherits the old's swap, without any charge for it.
Instead of removing cgroup id right after all the csses have been
offlined, we should do that after csses have been destroyed.
To make sure an invalid css pointer won't be returned after the css
is destroyed, make sure css_from_id() returns NULL in this case.
tj: Updated comment to note planned changes for cgrp->id.
Reported-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Tejun Heo <tj@kernel.org>
Calling cgroup_unload_subsys() from cgroup_load_subsys() after
online_css() failure will result in a NULL ptr dereference on attempt to
offline_css(), because online_css() only assigns css to cgroup on
success. Let's fix that by skipping calls to offline_css() and
css_free() in cgroup_unload_subsys() if there is no css, and freeing css
in cgroup_load_subsys() on online_css() failure.
Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Add the missing unlock before return from function cgroup_load_subsys()
in the error handling case.
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
After the previous patch which introduced for_each_css(),
for_each_root_subsys() only has two users left. This patch replaces
it with for_each_subsys() + explicit subsys_mask testing and remove
for_each_root_subsys() along with cgroupfs_root->subsys_list handling.
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
There are enough places where css's of a cgroup are iterated, which
currently uses for_each_root_subsys() + explicit cgroup_css(). This
patch implements for_each_css() and replaces the above combination
with it.
This patch doesn't introduce any behavior changes.
v2: Updated to apply cleanly on top of v2 of "cgroup: fix css leaks on
online_css() failure"
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Now that all opertations to create a css (cgroup_subsys_state) are
collected into a single loop in cgroup_create(), it's easy to factor
it out into its own function. Factor out css creation into
create_css(). This makes the code easier to follow and will enable
decoupling css creation from cgroup creation which is necessary for
the planned unified hierarchy.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Now that css operations in cgroup_create() are back-to-back, there
isn't much point in allocating css's in one loop and onlining them in
another. Merge the two loops so that a css is allocated and onlined
on each iteration.
css_ar[] is no longer necessary and replaced with a single pointer.
This also simplifies the error handling path.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_create() currently does the followings.
1. alloc cgroup
2. alloc css's
3. create the directory and commit to cgroup creation
4. online css's
5. create cgroup and css files
The sequence performs allocations before other operations but it
doesn't buy anything because each of the above steps may fail and
should be unrollable. Reorganize the sequence such that cgroup
operations are done before css operations.
1. alloc cgroup
2. create the directory and files and commit to cgroup creation
3. alloc css's
4. create files for and online css's
This simplifies the code a bit and enables further simplification and
separating out css creation from cgroup creation which is necessary
for the planned unified hierarchy where css's will be created and
destroyed dynamically across the lifetime of a cgroup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
We want to use for_each_subsys() in cgroupfs_root handling where only
cgroup_root_mutex is held. The only way cgroup_subsys[] can change is
through module load/unload, make cgroup_[un]load_subsys() grab
cgroup_root_mutex too and update the lockdep annotation in
for_each_subsys() to allow either cgroup_mutex or cgroup_root_mutex.
* Lockdep annotation is moved from inner 'if' condition to outer 'for'
init caluse. There's no reason to execute the assertion every loop.
* Loop index @i is renamed to @ssid. Indices iterating through subsys
will be [re]named to @ssid gradually.
v2: cgroup_assert_mutex_or_root_locked() caused build failure if
!CONFIG_LOCKEDP. Conditionalize its definition. The build failure
was reported by kbuild test bot.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: kbuild test robot <fengguang.wu@intel.com>
Currently, all css iterations and css_from_dir() require RCU read lock
whether the caller is holding cgroup_mutex or not, which is
unnecessarily restrictive. They are all safe to use under
cgroup_mutex without holding RCU read lock.
Factor out cgroup_assert_mutex_or_rcu_locked() from css_from_id() and
apply it to all css iteration functions and css_from_dir().
v2: cgroup_assert_mutex_or_rcu_locked() definition doesn't need to be
inside CONFIG_PROVE_RCU ifdef as rcu_lockdep_assert() is always
defined and conditionalized. Move it outside of the ifdef block.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Pulling in as patches depending on 266ccd505e ("cgroup: fix
cgroup_create() error handling path") are scheduled.
Signed-off-by: Tejun Heo <tj@kernel.org>
ae7f164a09 ("cgroup: move cgroup->subsys[] assignment to
online_css()") moved cgroup->subsys[] assignements later in
cgroup_create() but didn't update error handling path accordingly
leading to the following oops and leaking later css's after an
online_css() failure. The oops is from cgroup destruction path being
invoked on the partially constructed cgroup which is not ready to
handle empty slots in cgrp->subsys[] array.
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
IP: [<ffffffff810eeaa8>] cgroup_destroy_locked+0x118/0x2f0
PGD a780a067 PUD aadbe067 PMD 0
Oops: 0000 [#1] SMP
Modules linked in:
CPU: 6 PID: 7360 Comm: mkdir Not tainted 3.13.0-rc2+ #69
Hardware name:
task: ffff8800b9dbec00 ti: ffff8800a781a000 task.ti: ffff8800a781a000
RIP: 0010:[<ffffffff810eeaa8>] [<ffffffff810eeaa8>] cgroup_destroy_locked+0x118/0x2f0
RSP: 0018:ffff8800a781bd98 EFLAGS: 00010282
RAX: ffff880586903878 RBX: ffff880586903800 RCX: ffff880586903820
RDX: ffff880586903860 RSI: ffff8800a781bdb0 RDI: ffff880586903820
RBP: ffff8800a781bde8 R08: ffff88060e0b8048 R09: ffffffff811d7bc1
R10: 000000000000008c R11: 0000000000000001 R12: ffff8800a72286c0
R13: 0000000000000000 R14: ffffffff81cf7a40 R15: 0000000000000001
FS: 00007f60ecda57a0(0000) GS:ffff8806272c0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000008 CR3: 00000000a7a03000 CR4: 00000000000007e0
Stack:
ffff880586903860 ffff880586903910 ffff8800a72286c0 ffff880586903820
ffffffff81cf7a40 ffff880586903800 ffff88060e0b8018 ffffffff81cf7a40
ffff8800b9dbec00 ffff8800b9dbf098 ffff8800a781bec8 ffffffff810ef5bf
Call Trace:
[<ffffffff810ef5bf>] cgroup_mkdir+0x55f/0x5f0
[<ffffffff811c90ae>] vfs_mkdir+0xee/0x140
[<ffffffff811cb07e>] SyS_mkdirat+0x6e/0xf0
[<ffffffff811c6a19>] SyS_mkdir+0x19/0x20
[<ffffffff8169e569>] system_call_fastpath+0x16/0x1b
This patch moves reference bumping inside online_css() loop, clears
css_ar[] as css's are brought online successfully, and updates
err_destroy path so that either a css is fully online and destroyed by
cgroup_destroy_locked() or the error path frees it. This creates a
duplicate css free logic in the error path but it will be cleaned up
soon.
v2: Li pointed out that cgroup_destroy_locked() would do NULL-deref if
invoked with a cgroup which doesn't have all css's populated.
Update cgroup_destroy_locked() so that it skips NULL css's.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Reported-by: Vladimir Davydov <vdavydov@parallels.com>
Cc: stable@vger.kernel.org # v3.12+
In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs. With the previous
changes, the difference between pidlist and other files are very
small. Both are served by seq_file in a pretty standard way with the
only difference being !pidlist files use single_open().
This patch adds cftype->seq_start(), ->seq_next and ->seq_stop() and
implements the matching cgroup_seqfile_start/next/stop() which either
emulates single_open() behavior or invokes cftype->seq_*() operations
if specified. This allows using single seq_operations for both
pidlist and other files and makes cgroup_pidlist_operations and
cgorup_pidlist_open() no longer necessary. As cgroup_pidlist_open()
was the only user of cftype->open(), the method is dropped together.
This brings cftype file interface very close to kernfs interface and
mapping shouldn't be too difficult. Once converted to kernfs, most of
the plumbing code including cgroup_seqfile_*() will be removed as
kernfs provides those facilities.
This patch does not introduce any behavior changes.
v2: Refreshed on top of the updated "cgroup: introduce struct
cgroup_pidlist_open_file".
v3: Refreshed on top of the updated "cgroup: attach cgroup_open_file
to all cgroup files".
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs. This patch
replaces cftype->read_seq_string() with cftype->seq_show() which is
not limited to single_open() operation and will map directcly to
kernfs seq_file interface.
The conversions are mechanical. As ->seq_show() doesn't have @css and
@cft, the functions which make use of them are converted to use
seq_css() and seq_cft() respectively. In several occassions, e.f. if
it has seq_string in its name, the function name is updated to fit the
new method better.
This patch does not introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Aristeu Rozanski <arozansk@redhat.com>
Acked-by: Vivek Goyal <vgoyal@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Neil Horman <nhorman@tuxdriver.com>
In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs. This patch
attaches cgroup_open_file, which used to be attached to pidlist files,
to all cgroup files, introduces seq_css/cft() accessors to determine
the cgroup_subsys_state and cftype associated with a given cgroup
seq_file, exports them as public interface.
This doesn't cause any behavior changes but unifies cgroup file
handling across different file types and will help converting them to
kernfs seq_show() interface.
v2: Li pointed out that the original patch was using
single_open_size() incorrectly assuming that the size param is
private data size. Fix it by allocating @of separately and
passing it to single_open() and explicitly freeing it in the
release path. This isn't the prettiest but this path is gonna be
restructured by the following patches pretty soon.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
In preparation of conversion to kernfs, cgroup file handling is
updated so that it can be easily mapped to kernfs. This patch renames
cgroup_pidlist_open_file to cgroup_open_file and updates it so that it
only contains a field to identify the specific file, ->cfe, and an
opaque ->priv pointer. When cgroup is converted to kernfs, this will
be replaced by kernfs_open_file which contains about the same
information.
As whether the file is "cgroup.procs" or "tasks" should now be
determined from cgroup_open_file->cfe, the cftype->private for the two
files now carry the file type and cgroup_pidlist_start() reads the
type through cfe->type->private. This makes the distinction between
cgroup_tasks_open() and cgroup_procs_open() unnecessary.
cgroup_pidlist_open() is now directly used as the open method.
This patch doesn't make any behavior changes.
v2: Refreshed on top of the updated "cgroup: introduce struct
cgroup_pidlist_open_file".
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
With the recent removal of cftype->read() and ->read_map(), only three
operations are remaining, ->read_u64(), ->read_s64() and
->read_seq_string(). Currently, the first two are handled directly
while the last is handled through seq_file.
It is trivial to serve the first two through the seq_file path too.
This patch restructures read path so that all operations are served
through cgroup_seqfile_show(). This makes all cgroup files seq_file -
single_open/release() are now used by default,
cgroup_seqfile_operations is dropped, and cgroup_file_operations uses
seq_read() for read.
This simplifies the code and makes the read path easy to convert to
use kernfs.
Note that, while cgroup_file_operations uses seq_read() for read, it
still uses generic_file_llseek() for seeking instead of seq_lseek().
This is different from cgroup_seqfile_operations but shouldn't break
anything and brings the seeking behavior aligned with kernfs.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_write_X64() and cgroup_write_string() both implement about the
same buffering logic. Unify the two into cgroup_file_write() which
always allocates dynamic buffer for simplicity and uses kstrto*()
instead of simple_strto*().
This patch doesn't make any visible behavior changes except for
possibly different error value from kstrsto*().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
In preparation of conversion to kernfs, cgroup file handling is being
consolidated so that it can be easily mapped to the seq_file based
interface of kernfs.
After recent updates, ->read() and ->read_map() don't have any user
left and ->write() never had any user. Remove them.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
For some reason, tasks and cgroup.procs guarantee that the result is
sorted. This is the only reason this whole pidlist logic is necessary
instead of just iterating through sorted member tasks. We can't do
anything about the existing interface but at least ensure that such
expectation doesn't exist for the new interface so that pidlist logic
may be removed in the distant future.
This patch scrambles the sort order if sane_behavior so that the
output is usually not sorted in the new interface.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
After the recent changes, pidlist ref is held only between
cgroup_pidlist_start() and cgroup_pidlist_stop() during which
cgroup->pidlist_mutex is also held. IOW, the reference count is
redundant now. While in use, it's always one and pidlist_mutex is
held - holding the mutex has exactly the same protection.
This patch collapses destroy_dwork queueing into cgroup_pidlist_stop()
so that pidlist_mutex is not released inbetween and drops
pidlist->use_count.
This patch shouldn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, pidlists are reference counted from file open and release
methods. This means that holding onto an open file may waste memory
and reads may return data which is very stale. Both aren't critical
because pidlists are keyed and shared per namespace and, well, the
user isn't supposed to have large delay between open and reads.
cgroup is planned to be converted to use kernfs and it'd be best if we
can stick to just the seq_file operations - start, next, stop and
show. This can be achieved by loading pidlist on demand from start
and release with time delay from stop, so that consecutive reads don't
end up reloading the pidlist on each iteration. This would remove the
need for hooking into open and release while also avoiding issues with
holding onto pidlist for too long.
The previous patches implemented delayed release and restructured
pidlist handling so that pidlists can be loaded and released from
seq_file start / stop. This patch actually moves pidlist load to
start and release to stop.
This means that pidlist is pinned only between start and stop and may
go away between two consecutive read calls if the two calls are apart
by more than CGROUP_PIDLIST_DESTROY_DELAY. cgroup_pidlist_start()
thus can't re-use the stored cgroup_pid_list_open_file->pidlist
directly. During start, it's only used as a hint indicating whether
this is the first start after open or not and pidlist is always looked
up or created.
pidlist_mutex locking and reference counting are moved out of
pidlist_array_load() so that pidlist_array_load() can perform lookup
and creation atomically. While this enlarges the area covered by
pidlist_mutex, given how the lock is used, it's highly unlikely to be
noticeable.
v2: Refreshed on top of the updated "cgroup: introduce struct
cgroup_pidlist_open_file".
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup_pidlist locking is needlessly complicated. It has outer
cgroup->pidlist_mutex to protect the list of pidlists associated with
a cgroup and then each pidlist has rwsem to synchronize updates and
reads. Given that the only read access is from seq_file operations
which are always invoked back-to-back, the rwsem is a giant overkill.
All it does is adding unnecessary complexity.
This patch removes cgroup_pidlist->rwsem and protects all accesses to
pidlists belonging to a cgroup with cgroup->pidlist_mutex.
pidlist->rwsem locking is removed if it's nested inside
cgroup->pidlist_mutex; otherwise, it's replaced with
cgroup->pidlist_mutex locking.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Rename cgroup_pidlist_find() to cgroup_pidlist_find_create() and
separate out finding proper to cgroup_pidlist_find(). Also, move
locking to the caller.
This patch is preparation for pidlist restructure and doesn't
introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
For pidlist files, seq_file->private pointed to the loaded
cgroup_pidlist; however, pidlist loading is planned to be moved to
cgroup_pidlist_start() for kernfs conversion and seq_file->private
needs to carry more information from open to allow that.
This patch introduces struct cgroup_pidlist_open_file which contains
type, cgrp and pidlist and updates pidlist seq_file->private to point
to it using seq_open_private() and seq_release_private(). Note that
this eventually will be replaced by kernfs_open_file.
While this patch makes more information available to seq_file
operations, they don't use it yet and this patch doesn't introduce any
behavior changes except for allocation of the extra private struct.
v2: use __seq_open_private() instead of seq_open_private() for brevity
as suggested by Li.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, pidlists are reference counted from file open and release
methods. This means that holding onto an open file may waste memory
and reads may return data which is very stale. Both aren't critical
because pidlists are keyed and shared per namespace and, well, the
user isn't supposed to have large delay between open and reads.
cgroup is planned to be converted to use kernfs and it'd be best if we
can stick to just the seq_file operations - start, next, stop and
show. This can be achieved by loading pidlist on demand from start
and release with time delay from stop, so that consecutive reads don't
end up reloading the pidlist on each iteration. This would remove the
need for hooking into open and release while also avoiding issues with
holding onto pidlist for too long.
This patch implements delayed release of pidlist. As pidlists could
be lingering on cgroup removal waiting for the timer to expire, cgroup
free path needs to queue the destruction work item immediately and
flush. As those work items are self-destroying, each work item can't
be flushed directly. A new workqueue - cgroup_pidlist_destroy_wq - is
added to serve as flush domain.
Note that this patch just adds delayed release on top of the current
implementation and doesn't change where pidlist is loaded and
released. Following patches will make those changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Now that pidlist files don't use cftype->release(), it doesn't have
any user left. Remove it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, cgroup_pidlist_open() skips seq_open() and pidlist loading
if the file is opened write-only, which is a sensible optimization as
pidlist loading can be costly and there often are occasions where
tasks or cgroup.procs is opened write-only. However, pidlist init and
release are planned to be moved to cgroup_pidlist_start/stop()
respectively which would make this optimization unnecessary.
This patch removes the optimization and always fully initializes
pidlist files regardless of open mode. This will help moving pidlist
handling to start/stop by unifying rw paths and removes the need for
specifying cftype->release() in addition to .release in
cgroup_pidlist_operations as file->f_op is now always overridden. As
pidlist files were the only user of cftype->release(), the next patch
will remove the method.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Pull to receive e605b36575 ("cgroup: fix cgroup_subsys_state leak
for seq_files") as for-3.14 is scheduled to have a lot of changes
which depend on it.
Signed-off-by: Tejun Heo <tj@kernel.org>
If a cgroup file implements either read_map() or read_seq_string(),
such file is served using seq_file by overriding file->f_op to
cgroup_seqfile_operations, which also overrides the release method to
single_release() from cgroup_file_release().
Because cgroup_file_open() didn't use to acquire any resources, this
used to be fine, but since f7d58818ba ("cgroup: pin
cgroup_subsys_state when opening a cgroupfs file"), cgroup_file_open()
pins the css (cgroup_subsys_state) which is put by
cgroup_file_release(). The patch forgot to update the release path
for seq_files and each open/release cycle leaks a css reference.
Fix it by updating cgroup_file_release() to also handle seq_files and
using it for seq_file release path too.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org # v3.12
Merge v3.12 based patch series to move cgroup_event implementation to
memcg into for-3.14. The following two commits cause a conflict in
kernel/cgroup.c
2ff2a7d03b ("cgroup: kill css_id")
79bd9814e5 ("cgroup, memcg: move cgroup_event implementation to memcg")
Each patch removes a struct definition from kernel/cgroup.c. As the
two are adjacent, they cause a context conflict. Easily resolved by
removing both structs.
Signed-off-by: Tejun Heo <tj@kernel.org>
Now that cgroup_event is made memcg specific, the temporarily exported
functions are no longer necessary. Unexport cgroup_css() and remove
__file_cft() which doesn't have any user left.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
cgroup_event is being moved from cgroup core to memcg and the
implementation is already moved by the previous patch. This patch
moves the data fields and callbacks.
* cgroup->event_list[_lock] are moved to mem_cgroup.
* cftype->[un]register_event() are moved to cgroup_event. This makes
it impossible for individual cftype definitions to specify their
event callbacks. This is worked around by simply hard-coding
filename to event callback mapping in cgroup_write_event_control().
This is awkward and inflexible, which is actually desirable given
that we don't want to grow more usages of this feature.
* eventfd_ctx declaration is removed from cgroup.h, which makes
vmpressure.h miss eventfd_ctx declaration. Include eventfd.h from
vmpressure.h.
v2: Use file name from dentry instead of cftype. This will allow
removing all cftype handling in the function.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
cgroup_event is way over-designed and tries to build a generic
flexible event mechanism into cgroup - fully customizable event
specification for each user of the interface. This is utterly
unnecessary and overboard especially in the light of the planned
unified hierarchy as there's gonna be single agent. Simply generating
events at fixed points, or if that's too restrictive, configureable
cadence or single set of configureable points should be enough.
Thankfully, memcg is the only user and gets to keep it. Replacing it
with something simpler on sane_behavior is strongly recommended.
This patch moves cgroup_event and "cgroup.event_control"
implementation to mm/memcontrol.c. Clearing of events on cgroup
destruction is moved from cgroup_destroy_locked() to
mem_cgroup_css_offline(), which shouldn't make any noticeable
difference.
cgroup_css() and __file_cft() are exported to enable the move;
however, this will soon be reverted once the event code is updated to
be memcg specific.
Note that "cgroup.event_control" will now exist only on the hierarchy
with memcg attached to it. While this change is visible to userland,
it is unlikely to be noticeable as the file has never been meaningful
outside memcg.
Aside from the above change, this is pure code relocation.
v2: Per Li Zefan's comments, init/Kconfig updated accordingly and
poll.h inclusion moved from cgroup.c to memcontrol.c.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
Since be44562613 ("cgroup: remove synchronize_rcu() from
cgroup_diput()"), cgroup destruction path makes use of workqueue. css
freeing is performed from a work item from that point on and a later
commit, ea15f8ccdb ("cgroup: split cgroup destruction into two
steps"), moves css offlining to workqueue too.
As cgroup destruction isn't depended upon for memory reclaim, the
destruction work items were put on the system_wq; unfortunately, some
controller may block in the destruction path for considerable duration
while holding cgroup_mutex. As large part of destruction path is
synchronized through cgroup_mutex, when combined with high rate of
cgroup removals, this has potential to fill up system_wq's max_active
of 256.
Also, it turns out that memcg's css destruction path ends up queueing
and waiting for work items on system_wq through work_on_cpu(). If
such operation happens while system_wq is fully occupied by cgroup
destruction work items, work_on_cpu() can't make forward progress
because system_wq is full and other destruction work items on
system_wq can't make forward progress because the work item waiting
for work_on_cpu() is holding cgroup_mutex, leading to deadlock.
This can be fixed by queueing destruction work items on a separate
workqueue. This patch creates a dedicated workqueue -
cgroup_destroy_wq - for this purpose. As these work items shouldn't
have inter-dependencies and mostly serialized by cgroup_mutex anyway,
giving high concurrency level doesn't buy anything and the workqueue's
@max_active is set to 1 so that destruction work items are executed
one by one on each CPU.
Hugh Dickins: Because cgroup_init() is run before init_workqueues(),
cgroup_destroy_wq can't be allocated from cgroup_init(). Do it from a
separate core_initcall(). In the future, we probably want to reorder
so that workqueue init happens before cgroup_init().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Hugh Dickins <hughd@google.com>
Reported-by: Shawn Bohrer <shawn.bohrer@gmail.com>
Link: http://lkml.kernel.org/r/20131111220626.GA7509@sbohrermbp13-local.rgmadvisors.com
Link: http://lkml.kernel.org/g/alpine.LNX.2.00.1310301606080.2333@eggly.anvils
Cc: stable@vger.kernel.org # v3.9+
Rename simple_delete_dentry() to always_delete_dentry() and export it.
Export simple_dentry_operations, while we are at it, and get rid of
their duplicates
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull cgroup changes from Tejun Heo:
"Not too much activity this time around. css_id is finally killed and
a minor update to device_cgroup"
* 'for-3.13' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
device_cgroup: remove can_attach
cgroup: kill css_id
memcg: stop using css id
memcg: fail to create cgroup if the cgroup id is too big
memcg: convert to use cgroup id
memcg: convert to use cgroup_is_descendant()
Pull cgroup fixes from Tejun Heo:
"Two late fixes for cgroup.
One fixes descendant walk introduced during this rc1 cycle. The other
fixes a post 3.9 bug during task attach which can lead to hang. Both
fixes are critical and the fixes are relatively straight-forward"
* 'for-3.12-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup: fix to break the while loop in cgroup_attach_task() correctly
cgroup: fix cgroup post-order descendant walk of empty subtree
Both Anjana and Eunki reported a stall in the while_each_thread loop
in cgroup_attach_task().
It's because, when we attach a single thread to a cgroup, if the cgroup
is exiting or is already in that cgroup, we won't break the loop.
If the task is already in the cgroup, the bug can lead to another thread
being attached to the cgroup unexpectedly:
# echo 5207 > tasks
# cat tasks
5207
# echo 5207 > tasks
# cat tasks
5207
5215
What's worse, if the task to be attached isn't the leader of the thread
group, we might never exit the loop, hence cpu stall. Thanks for Oleg's
analysis.
This bug was introduced by commit 081aa458c3
("cgroup: consolidate cgroup_attach_task() and cgroup_attach_proc()")
[ lizf: - fixed the first continue, pointed out by Oleg,
- rewrote changelog. ]
Cc: <stable@vger.kernel.org> # 3.9+
Reported-by: Eunki Kim <eunki_kim@samsung.com>
Reported-by: Anjana V Kumar <anjanavk12@gmail.com>
Signed-off-by: Anjana V Kumar <anjanavk12@gmail.com>
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The only user of css_id was memcg, and it has been convered to use
cgroup->id, so kill css_id.
Signed-off-by: Li Zefan <lizefan@huwei.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
bd8815a6d8 ("cgroup: make css_for_each_descendant() and friends
include the origin css in the iteration") updated cgroup descendant
iterators to include the origin css; unfortuantely, it forgot to drop
special case handling in css_next_descendant_post() for empty subtree
leading to failure to visit the origin css without any child.
Fix it by dropping the special case handling and always returning the
leftmost descendant on the first iteration.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
kernel/cgroup.c is the only place in the tree that relies on eventfd.h
pulling file.h; move that include there. Switch from eventfd_fget()/fput()
to fdget()/fdput(), while we are at it - eventfd_ctx_fileget() will fail
on non-eventfd descriptors just fine, no need to do that check twice...
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Pull cgroup updates from Tejun Heo:
"A lot of activities on the cgroup front. Most changes aren't visible
to userland at all at this point and are laying foundation for the
planned unified hierarchy.
- The biggest change is decoupling the lifetime management of css
(cgroup_subsys_state) from that of cgroup's. Because controllers
(cpu, memory, block and so on) will need to be dynamically enabled
and disabled, css which is the association point between a cgroup
and a controller may come and go dynamically across the lifetime of
a cgroup. Till now, css's were created when the associated cgroup
was created and stayed till the cgroup got destroyed.
Assumptions around this tight coupling permeated through cgroup
core and controllers. These assumptions are gradually removed,
which consists bulk of patches, and css destruction path is
completely decoupled from cgroup destruction path. Note that
decoupling of creation path is relatively easy on top of these
changes and the patchset is pending for the next window.
- cgroup has its own event mechanism cgroup.event_control, which is
only used by memcg. It is overly complex trying to achieve high
flexibility whose benefits seem dubious at best. Going forward,
new events will simply generate file modified event and the
existing mechanism is being made specific to memcg. This pull
request contains prepatory patches for such change.
- Various fixes and cleanups"
Fixed up conflict in kernel/cgroup.c as per Tejun.
* 'for-3.12' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (69 commits)
cgroup: fix cgroup_css() invocation in css_from_id()
cgroup: make cgroup_write_event_control() use css_from_dir() instead of __d_cgrp()
cgroup: make cgroup_event hold onto cgroup_subsys_state instead of cgroup
cgroup: implement CFTYPE_NO_PREFIX
cgroup: make cgroup_css() take cgroup_subsys * instead and allow NULL subsys
cgroup: rename cgroup_css_from_dir() to css_from_dir() and update its syntax
cgroup: fix cgroup_write_event_control()
cgroup: fix subsystem file accesses on the root cgroup
cgroup: change cgroup_from_id() to css_from_id()
cgroup: use css_get() in cgroup_create() to check CSS_ROOT
cpuset: remove an unncessary forward declaration
cgroup: RCU protect each cgroup_subsys_state release
cgroup: move subsys file removal to kill_css()
cgroup: factor out kill_css()
cgroup: decouple cgroup_subsys_state destruction from cgroup destruction
cgroup: replace cgroup->css_kill_cnt with ->nr_css
cgroup: bounce cgroup_subsys_state ref kill confirmation to a work item
cgroup: move cgroup->subsys[] assignment to online_css()
cgroup: reorganize css init / exit paths
cgroup: add __rcu modifier to cgroup->subsys[]
...
On 3.11-rc we are seeing cgroup directories left behind when they should
have been removed. Here's a trivial reproducer:
cd /sys/fs/cgroup/memory
mkdir parent parent/child; rmdir parent/child parent
rmdir: failed to remove `parent': Device or resource busy
It's because cgroup_destroy_locked() (step 1 of destruction) leaves
cgroup on parent's children list, letting cgroup_offline_fn() (step 2 of
destruction) remove it; but step 2 is run by work queue, which may not
yet have removed the children when parent destruction checks the list.
Fix that by checking through a non-empty list of children: if every one
of them has already been marked CGRP_DEAD, then it's safe to proceed:
those children are invisible to userspace, and should not obstruct rmdir.
(I didn't see any reason to keep the cgrp->children checks under the
unrelated css_set_lock, so moved them out.)
tj: Flattened nested ifs a bit and updated comment so that it's
correct on both for-3.11-fixes and for-3.12.
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
ca8bdcaff0 ("cgroup: make cgroup_css() take cgroup_subsys * instead
and allow NULL subsys") missed one conversion in css_from_id(), which
was newly added. As css_from_id() doesn't have any user yet, this
doesn't break anything other than generating a build warning.
Convert it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Reported-by: kbuild test robot <fengguang.wu@intel.com>
cgroup_event will be moved to its only user - memcg. Replace
__d_cgrp() usage with css_from_dir(), which is already exported. This
also simplifies the code a bit.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Currently, each registered cgroup_event holds an extra reference to
the cgroup. This is a bit weird as events are subsystem specific and
will also be incorrect in the planned unified hierarchy as css
(cgroup_subsys_state) may come and go dynamically across the lifetime
of a cgroup. Holding onto cgroup won't prevent the target css from
going away.
Update cgroup_event to hold onto the css the traget file belongs to
instead of cgroup.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
When cgroup files are created, cgroup core automatically prepends the
name of the subsystem as prefix. This patch adds CFTYPE_NO_ which
disables the automatic prefix. This is to work around historical
baggages and shouldn't be used for new files.
This will be used to move "cgroup.event_control" from cgroup core to
memcg.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Glauber Costa <glommer@gmail.com>
cgroup_css() is no longer used in hot paths. Make it take struct
cgroup_subsys * and allow the users to specify NULL subsys to obtain
the dummy_css. This removes open-coded NULL subsystem testing in a
couple users and generally simplifies the code.
After this patch, css_from_dir() also allows NULL @ss and returns the
matching dummy_css. This behavior change doesn't affect its only user
- perf.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
cgroup_css_from_dir() will grow another user. In preparation, make
the following changes.
* All css functions are prefixed with just "css_", rename it to
css_from_dir().
* Take dentry * instead of file * as dentry is what ultimately
identifies a cgroup and file may not always be available. Note that
the function now checkes whether @dentry->d_inode is NULL as the
caller now may specify a negative dentry.
* Make it take cgroup_subsys * instead of integer subsys_id. This
simplifies the function and allows specifying no subsystem for
cgroup->dummy_css.
* Make return section a bit less verbose.
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
81eeaf0411 ("cgroup: make cftype->[un]register_event() deal with
cgroup_subsys_state inst ead of cgroup") updated the cftype event
methods to take @css (cgroup_subsys_state) instead of @cgroup;
however, it incorrectly used @css passed to
cgroup_write_event_control(), which the dummy_css for the cgroup as
the file is a cgroup core file. This leads to oops on event
registration.
Fix it by using the css matching the event target file. Note that
cgroup_write_event_control() now disallows cgroup core files from
being event sources. This is for simplicity and doesn't matter as
cgroup_event will be moved and made specific to memcg.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
105347ba5 ("cgroup: make cgroup_file_open() rcu_read_lock() around
cgroup_css() and add cfent->css") added cfent->css to cache the
associted cgroup_subsys_state across file operations.
A cfent is associated with single css throughout its lifetime and the
origimal commit initialized the cache pointer during cgroup_add_file()
and verified that it matches the actual one in cgroup_file_open().
While this works fine for !root cgroups, it's broken for root cgroups
as files in a root cgroup are created before the css's are associated
with the cgroup and thus cgroup_css() call in cgroup_add_file()
returns NULL associating all cfents in the root cgroup with NULL css.
This makes cgroup_file_open() trigger WARN and fail with -ENODEV for
all !core subsystem files in the root cgroups.
There's no reason to initialize cfent->css separately from
cgroup_add_file(). As the association never changes,
cgroup_file_open() can set it unconditionally every time and
containing the logic in cgroup_file_open() makes more sense anyway as
the only reason it's necessary is file->private_data being already
occupied.
Fix it by setting cfent->css unconditionally from cgroup_file_open().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Now we want cgroup core to always provide the css to use to the
subsystems, so change this API to css_from_id().
Uninline css_from_id(), because it's getting bigger and cgroup_css()
has been unexported.
While at it, remove the #ifdef, and shuffle the order of the args.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
With the planned unified hierarchy, individual css's will be created
and destroyed dynamically across the lifetime of a cgroup. To enable
such usages, css destruction is being decoupled from cgroup
destruction. Most of the destruction path has been decoupled but the
actual free of css still depends on cgroup free path.
When all css refs are drained, css_release() kicks off
css_free_work_fn() which puts the cgroup. When the cgroup refcnt
reaches zero, cgroup_diput() is invoked which in turn schedules RCU
free of the cgroup. After a grace period, all css's are freed along
with the cgroup itself.
This patch moves the RCU grace period and css freeing from cgroup
release path to css release path. css_release(), instead of kicking
off css_free_work_fn() directly, schedules RCU callback
css_free_rcu_fn() which in turn kicks off css_free_work_fn() after a
RCU grace period. css_free_work_fn() is updated to free the css
directly.
The five-way punting - percpu ref kill confirmation, a work item,
percpu ref release, RCU grace period, and again a work item - is quite
hairy but the work items are there only to provide process context and
the actual sequence is kill confirm -> release -> RCU free, which
isn't simple but not too crazy.
This removes cgroup_css() usage after offline_css() allowing clearing
cgroup->subsys[] from offline_css(), which makes it consistent with
online_css() and brings it closer to proper lifetime management for
individual css's.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
With the planned unified hierarchy, individual css's will be created
and destroyed dynamically across the lifetime of a cgroup. To enable
such usages, css destruction is being decoupled from cgroup
destruction. This patch moves subsys file removal from
cgroup_destroy_locked() to kill_css().
While this changes the order of destruction operations, the changes
shouldn't be noticeable to cgroup subsystems or userland.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
