Introduce two helpers - netprio_prio() and netprio_set_prio() - which
hide the details of priomap access and expansion. This will help
implementing hierarchy support.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Tested-and-Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: David S. Miller <davem@davemloft.net>
With priomap expansion no longer depending on knowing max id
allocated, netprio_cgroup can use cgroup->id insted of cs->prioidx.
Drop prioidx alloc/free logic and convert all uses to cgroup->id.
* In cgrp_css_alloc(), parent->id test is moved above @cs allocation
to simplify error path.
* In cgrp_css_free(), @cs assignment is made initialization.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Tested-and-Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: David S. Miller <davem@davemloft.net>
netprio kept track of the highest prioidx allocated and resized
priomaps accordingly when necessary. This makes it necessary to keep
track of prioidx allocation and may end up resizing on every new
prioidx.
Update extend_netdev_table() such that it takes @target_idx which the
priomap should be able to accomodate. If the priomap is large enough,
nothing happens; otherwise, the size is doubled until @target_idx can
be accomodated.
This makes max_prioidx and write_update_netdev_table() unnecessary.
write_priomap() now calls extend_netdev_table() directly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Tested-and-Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: David S. Miller <davem@davemloft.net>
The function is about to go through a rewrite. In preparation,
shorten the variable names so that we don't repeat "priomap" so often.
This patch is cosmetic.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Tested-and-Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: David S. Miller <davem@davemloft.net>
sscanf() doesn't bite.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Tested-and-Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: David S. Miller <davem@davemloft.net>
It turns out that we'll have to live with attributes which are
inherited at cgroup creation time but not affected by further updates
to the parent afterwards - such attributes are already in wide use
e.g. for cpuset.
So, there's nothing to do for netcls_cgroup for hierarchy support.
Its current behavior - inherit only during creation - is good enough.
Move config inheriting from ->css_alloc() to ->css_online() for
consistency, which doesn't change behavior at all, and remove
.broken_hierarchy marking.
Signed-off-by: Tejun Heo <tj@kernel.org>
Tested-and-Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de>
Acked-by: David S. Miller <davem@davemloft.net>
'guarantee' is already removed from cgroup_task_migrate, so remove
the corresponding comments. Some other typos in cgroup are also
changed.
Cc: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
With the introduction of generic cgroup hierarchy iterators, css_id is
being phased out. It was unnecessarily complex, id'ing the wrong
thing (cgroups need IDs, not CSSes) and has other oddities like not
being available at ->css_alloc().
This patch adds cgroup->id, which is a simple per-hierarchy
ida-allocated ID which is assigned before ->css_alloc() and released
after ->css_free().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Currently CGRP_CPUSET_CLONE_CHILDREN triggers ->post_clone(). Now
that clone_children is cpuset specific, there's no reason to have this
rather odd option activation mechanism in cgroup core. cpuset can
check the flag from its ->css_allocate() and take the necessary
action.
Move cpuset_post_clone() logic to the end of cpuset_css_alloc() and
remove cgroup_subsys->post_clone().
Loosely based on Glauber's "generalize post_clone into post_create"
patch.
Signed-off-by: Tejun Heo <tj@kernel.org>
Original-patch-by: Glauber Costa <glommer@parallels.com>
Original-patch: <1351686554-22592-2-git-send-email-glommer@parallels.com>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Glauber Costa <glommer@parallels.com>
clone_children is only meaningful for cpuset and will stay that way.
Rename the flag to reflect that and update documentation. Also, drop
clone_children() wrapper in cgroup.c. The thin wrapper is used only a
few times and one of them will go away soon.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Glauber Costa <glommer@parallels.com>
Rename cgroup_subsys css lifetime related callbacks to better describe
what their roles are. Also, update documentation.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
There could be cases where controllers want to do initialization
operations which may fail from ->post_create(). This patch makes
->post_create() return -errno to indicate failure and online_css()
relay such failures.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Glauber Costa <glommer@parallels.com>
cgroup_create() was ignoring failure of cgroupfs files. Update it
such that, if file creation fails, it rolls back by calling
cgroup_destroy_locked() and returns failure.
Note that error out goto labels are renamed. The labels are a bit
confusing but will become better w/ later cgroup operation renames.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
All cgroup directory i_mutexes nest outside cgroup_mutex; however, new
directory creation is a special case. A new cgroup directory is
created while holding cgroup_mutex. Populating the new directory
requires both the new directory's i_mutex and cgroup_mutex. Because
all directory i_mutexes nest outside cgroup_mutex, grabbing both
requires releasing cgroup_mutex first, which isn't a good idea as the
new cgroup isn't yet ready to be manipulated by other cgroup
opreations.
This is worked around by grabbing the new directory's i_mutex while
holding cgroup_mutex before making it visible. As there's no other
user at that point, grabbing the i_mutex under cgroup_mutex can't lead
to deadlock.
cgroup_create_file() was using I_MUTEX_CHILD to tell lockdep not to
worry about the reverse locking order; however, this creates pseudo
locking dependency cgroup_mutex -> I_MUTEX_CHILD, which isn't true -
all directory i_mutexes are still nested outside cgroup_mutex. This
pseudo locking dependency can lead to spurious lockdep warnings.
Use mutex_trylock() instead. This will always succeed and lockdep
doesn't create any locking dependency for it.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Now that cgroup_unload_subsys() can tell whether the root css is
online or not, we can safely call cgroup_unload_subsys() after idr
init failure in cgroup_load_subsys().
Replace the manual unrolling and invoke cgroup_unload_subsys() on
failure. This drops cgroup_mutex inbetween but should be safe as the
subsystem will fail try_module_get() and thus can't be mounted
inbetween. As this means that cgroup_unload_subsys() can be called
before css_sets are rehashed, remove BUG_ON() on %NULL
css_set->subsys[] from cgroup_unload_subsys().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
New helpers on/offline_css() respectively wrap ->post_create() and
->pre_destroy() invocations. online_css() sets CSS_ONLINE after
->post_create() is complete and offline_css() invokes ->pre_destroy()
iff CSS_ONLINE is set and clears it while also handling the temporary
dropping of cgroup_mutex.
This patch doesn't introduce any behavior change at the moment but
will be used to improve cgroup_create() failure path and allow
->post_create() to fail.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Separate out cgroup_destroy_locked() from cgroup_destroy(). This will
be later used in cgroup_create() failure path.
While at it, add lockdep asserts on i_mutex and cgroup_mutex, and move
@d and @parent assignments to their declarations.
This patch doesn't introduce any functional difference.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
* If idr init fails, cgroup_load_subsys() cleared dummytop->subsys[]
before calilng ->destroy() making CSS inaccessible to the callback,
and didn't unlink ss->sibling. As no modular controller uses
->use_id, this doesn't cause any actual problems.
* cgroup_unload_subsys() was forgetting to free idr, call
->pre_destroy() and clear ->active. As there currently is no
modular controller which uses ->use_id, ->pre_destroy() or ->active,
this doesn't cause any actual problems.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Make cgroup_init_subsys() grab cgroup_mutex while initializing a
subsystem so that all helpers and callbacks are called under the
context they expect. This isn't strictly necessary as
cgroup_init_subsys() doesn't race with anybody but will allow adding
lockdep assertions.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Consistently use @css and @dummytop in these two functions instead of
referring to them indirectly.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, CSS_* flags are defined as bit positions and manipulated
using atomic bitops. There's no reason to use atomic bitops for them
and bit positions are clunkier to deal with than bit masks. Make
CSS_* bit masks instead and use the usual C bitwise operators to
access them.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
cgroup->dentry is marked and used as a RCU pointer; however, it isn't
one - the final dentry put doesn't go through call_rcu(). cgroup and
dentry share the same RCU freeing rule via synchronize_rcu() in
cgroup_diput() (kfree_rcu() used on cgrp is unnecessary). If cgrp is
accessible under RCU read lock, so is its dentry and dereferencing
cgrp->dentry doesn't need any further RCU protection or annotation.
While not being accurate, before the previous patch, the RCU accessors
served a purpose as memory barriers - cgroup->dentry used to be
assigned after the cgroup was made visible to cgroup_path(), so the
assignment and dereferencing in cgroup_path() needed the memory
barrier pair. Now that list_add_tail_rcu() happens after
cgroup->dentry is assigned, this no longer is necessary.
Remove the now unnecessary and misleading RCU annotations from
cgroup->dentry. To make up for the removal of rcu_dereference_check()
in cgroup_path(), add an explicit rcu_lockdep_assert(), which asserts
the dereference rule of @cgrp, not cgrp->dentry.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
While creating a new cgroup, cgroup_create() links the newly allocated
cgroup into various places before trying to create its directory.
Because cgroup life-cycle is tied to the vfs objects, this makes it
impossible to use cgroup_rmdir() for rolling back creation - the
removal logic depends on having full vfs objects.
This patch moves directory creation above linking and collect linking
operations to one place. This allows directory creation failure to
share error exit path with css allocation failures and any failure
sites afterwards (to be added later) can use cgroup_rmdir() logic to
undo creation.
Note that this also makes the memory barriers around cgroup->dentry,
which currently is misleadingly using RCU operations, unnecessary.
This will be handled in the next patch.
While at it, locking BUG_ON() on i_mutex is converted to
lockdep_assert_held().
v2: Patch originally removed %NULL dentry check in cgroup_path();
however, Li pointed out that this patch doesn't make it
unnecessary as ->create() may call cgroup_path(). Drop the
change for now.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
The operation order of cgroup creation is about to change and
cgroup_create_dir() is more of a hindrance than a proper abstraction.
Open-code it by moving the parent nlink adjustment next to self nlink
adjustment in cgroup_create_file() and the rest to cgroup_create().
This patch doesn't introduce any behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Not strictly necessary but it's annoying to have uninitialized
list_head around.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Up until now, cgroup_freezer didn't implement hierarchy properly.
cgroups could be arranged in hierarchy but it didn't make any
difference in how each cgroup_freezer behaved. They all operated
separately.
This patch implements proper hierarchy support. If a cgroup is
frozen, all its descendants are frozen. A cgroup is thawed iff it and
all its ancestors are THAWED. freezer.self_freezing shows the current
freezing state for the cgroup itself. freezer.parent_freezing shows
whether the cgroup is freezing because any of its ancestors is
freezing.
freezer_post_create() locks the parent and new cgroup and inherits the
parent's state and freezer_change_state() applies new state top-down
using cgroup_for_each_descendant_pre() which guarantees that no child
can escape its parent's state. update_if_frozen() uses
cgroup_for_each_descendant_post() to propagate frozen states
bottom-up.
Synchronization could be coarser and easier by using a single mutex to
protect all hierarchy operations. Finer grained approach was used
because it wasn't too difficult for cgroup_freezer and I think it's
beneficial to have an example implementation and cgroup_freezer is
rather simple and can serve a good one.
As this makes cgroup_freezer properly hierarchical,
freezer_subsys.broken_hierarchy marking is removed.
Note that this patch changes userland visible behavior - freezing a
cgroup now freezes all its descendants too. This behavior change is
intended and has been warned via .broken_hierarchy.
v2: Michal spotted a bug in freezer_change_state() - descendants were
inheriting from the wrong ancestor. Fixed.
v3: Documentation/cgroups/freezer-subsystem.txt updated.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
A cgroup is online and visible to iteration between ->post_create()
and ->pre_destroy(). This patch introduces CGROUP_FREEZER_ONLINE and
toggles it from the newly added freezer_post_create() and
freezer_pre_destroy() while holding freezer->lock such that a
cgroup_freezer can be reilably distinguished to be online. This will
be used by full hierarchy support.
ONLINE test is added to freezer_apply_state() but it currently doesn't
make any difference as freezer_write() can only be called for an
online cgroup.
Adjusting system_freezing_cnt on destruction is moved from
freezer_destroy() to the new freezer_pre_destroy() for consistency.
This patch doesn't introduce any noticeable behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Introduce FREEZING_SELF and FREEZING_PARENT and make FREEZING OR of
the two flags. This is to prepare for full hierarchy support.
freezer_apply_date() is updated such that it can handle setting and
clearing of both flags. The two flags are also exposed to userland
via read-only files self_freezing and parent_freezing.
Other than the added cgroupfs files, this patch doesn't introduce any
behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
freezer->state was an enum value - one of THAWED, FREEZING and FROZEN.
As the scheduled full hierarchy support requires more than one
freezing condition, switch it to mask of flags. If FREEZING is not
set, it's thawed. FREEZING is set if freezing or frozen. If frozen,
both FREEZING and FROZEN are set. Now that tasks can be attached to
an already frozen cgroup, this also makes freezing condition checks
more natural.
This patch doesn't introduce any behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
* Make freezer_change_state() take bool @freeze instead of enum
freezer_state.
* Separate out freezer_apply_state() out of freezer_change_state().
This makes freezer_change_state() a rather silly thin wrapper. It
will be filled with hierarchy handling later on.
This patch doesn't introduce any behavior change.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
* Clean-up indentation and line-breaks. Drop the invalid comment
about freezer->lock.
* Make all internal functions take @freezer instead of both @cgroup
and @freezer.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Currently, cgroup doesn't provide any generic helper for walking a
given cgroup's children or descendants. This patch adds the following
three macros.
* cgroup_for_each_child() - walk immediate children of a cgroup.
* cgroup_for_each_descendant_pre() - visit all descendants of a cgroup
in pre-order tree traversal.
* cgroup_for_each_descendant_post() - visit all descendants of a
cgroup in post-order tree traversal.
All three only require the user to hold RCU read lock during
traversal. Verifying that each iterated cgroup is online is the
responsibility of the user. When used with proper synchronization,
cgroup_for_each_descendant_pre() can be used to propagate state
updates to descendants in reliable way. See comments for details.
v2: s/config/state/ in commit message and comments per Michal. More
documentation on synchronization rules.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujisu.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: Li Zefan <lizefan@huawei.com>
Use RCU safe list operations for cgroup->children. This will be used
to implement cgroup children / descendant walking which can be used by
controllers.
Note that cgroup_create() now puts a new cgroup at the end of the
->children list instead of head. This isn't strictly necessary but is
done so that the iteration order is more conventional.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Currently, there's no way for a controller to find out whether a new
cgroup finished all ->create() allocatinos successfully and is
considered "live" by cgroup.
This becomes a problem later when we add generic descendants walking
to cgroup which can be used by controllers as controllers don't have a
synchronization point where it can synchronize against new cgroups
appearing in such walks.
This patch adds ->post_create(). It's called after all ->create()
succeeded and the cgroup is linked into the generic cgroup hierarchy.
This plays the counterpart of ->pre_destroy().
When used in combination with the to-be-added generic descendant
iterators, ->post_create() can be used to implement reliable state
inheritance. It will be explained with the descendant iterators.
v2: Added a paragraph about its future use w/ descendant iterators per
Michal.
v3: Forgot to add ->post_create() invocation to cgroup_load_subsys().
Fixed.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Glauber Costa <glommer@parallels.com>
'start' is set to buf + buflen and do the '--' immediately.
Just set it to 'buf + buflen - 1' directly.
Signed-off-by: Tao Ma <boyu.mt@taobao.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Li Zefan <lizefan@huawei.com>
device_cgroup uses RCU safe ->exceptions list which is write-protected
by devcgroup_mutex and has had some issues using locking correctly.
Add lockdep asserts to utility functions so that future errors can be
easily detected.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
dev_cgroup->exceptions is protected with devcgroup_mutex for writes
and RCU for reads; however, RCU usage isn't correct.
* dev_exception_clean() doesn't use RCU variant of list_del() and
kfree(). The function can race with may_access() and may_access()
may end up dereferencing already freed memory. Use list_del_rcu()
and kfree_rcu() instead.
* may_access() may be called only with RCU read locked but doesn't use
RCU safe traversal over ->exceptions. Use list_for_each_entry_rcu().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Cc: stable@vger.kernel.org
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
In 4cef7299b4 ("device_cgroup: add proper checking when changing
default behavior") the cgroup parent usage is unchecked. root will not
have a parent and trying to use device.{allow,deny} will cause problems.
For some reason my stressing scripts didn't test the root directory so I
didn't catch it on my regular tests.
Signed-off-by: Aristeu Rozanski <aris@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: James Morris <jmorris@namei.org>
Cc: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull rmdir updates into for-3.8 so that further callback updates can
be put on top. This pull created a trivial conflict between the
following two commits.
8c7f6edbda ("cgroup: mark subsystems with broken hierarchy support and whine if cgroups are nested for them")
ed95779340 ("cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs")
The former added a field to cgroup_subsys and the latter removed one
from it. They happen to be colocated causing the conflict. Keeping
what's added and removing what's removed resolves the conflict.
Signed-off-by: Tejun Heo <tj@kernel.org>
All ->pre_destory() implementations return 0 now, which is the only
allowed return value. Make it return void.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Now that pre_destroy callbacks are called from the context where neither
any task can attach the group nor any children group can be added there
is no other way to fail from hugetlb_pre_destroy.
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Glauber Costa <glommer@parallels.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Now that pre_destroy callbacks are called from the context where neither
any task can attach the group nor any children group can be added there
is no other way to fail from mem_cgroup_pre_destroy.
mem_cgroup_pre_destroy doesn't have to take a reference to memcg's css
because all css' are marked dead already.
tj: Remove now unused local variable @cgrp from
mem_cgroup_reparent_charges().
Signed-off-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: Glauber Costa <glommer@parallels.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
CGRP_WAIT_ON_RMDIR is another kludge which was added to make cgroup
destruction rollback somewhat working. cgroup_rmdir() used to drain
CSS references and CGRP_WAIT_ON_RMDIR and the associated waitqueue and
helpers were used to allow the task performing rmdir to wait for the
next relevant event.
Unfortunately, the wait is visible to controllers too and the
mechanism got exposed to memcg by 887032670d ("cgroup avoid permanent
sleep at rmdir").
Now that the draining and retries are gone, CGRP_WAIT_ON_RMDIR is
unnecessary. Remove it and all the mechanisms supporting it. Note
that memcontrol.c changes are essentially revert of 887032670d
("cgroup avoid permanent sleep at rmdir").
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Balbir Singh <bsingharora@gmail.com>
Because ->pre_destroy() could fail and can't be called under
cgroup_mutex, cgroup destruction did something very ugly.
1. Grab cgroup_mutex and verify it can be destroyed; fail otherwise.
2. Release cgroup_mutex and call ->pre_destroy().
3. Re-grab cgroup_mutex and verify it can still be destroyed; fail
otherwise.
4. Continue destroying.
In addition to being ugly, it has been always broken in various ways.
For example, memcg ->pre_destroy() expects the cgroup to be inactive
after it's done but tasks can be attached and detached between #2 and
#3 and the conditions that memcg verified in ->pre_destroy() might no
longer hold by the time control reaches #3.
Now that ->pre_destroy() is no longer allowed to fail. We can switch
to the following.
1. Grab cgroup_mutex and verify it can be destroyed; fail otherwise.
2. Deactivate CSS's and mark the cgroup removed thus preventing any
further operations which can invalidate the verification from #1.
3. Release cgroup_mutex and call ->pre_destroy().
4. Re-grab cgroup_mutex and continue destroying.
After this change, controllers can safely assume that ->pre_destroy()
will only be called only once for a given cgroup and, once
->pre_destroy() is called, the cgroup will stay dormant till it's
destroyed.
This removes the only reason ->pre_destroy() can fail - new task being
attached or child cgroup being created inbetween. Error out path is
removed and ->pre_destroy() invocation is open coded in
cgroup_rmdir().
v2: cgroup_call_pre_destroy() removal moved to this patch per Michal.
Commit message updated per Glauber.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Glauber Costa <glommer@parallels.com>
This patch makes cgroup_create() fail if @parent is marked removed.
This is to prepare for further updates to cgroup_rmdir() path.
Note that this change isn't strictly necessary. cgroup can only be
created via mkdir and the removed marking and dentry removal happen
without releasing cgroup_mutex, so cgroup_create() can never race with
cgroup_rmdir(). Even after the scheduled updates to cgroup_rmdir(),
cgroup_mkdir() and cgroup_rmdir() are synchronized by i_mutex
rendering the added liveliness check unnecessary.
Do it anyway such that locking is contained inside cgroup proper and
we don't get nasty surprises if we ever grow another caller of
cgroup_create().
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
CSS_REMOVED is one of the several contortions which were necessary to
support css reference draining on cgroup removal. All css->refcnts
which need draining should be deactivated and verified to equal zero
atomically w.r.t. css_tryget(). If any one isn't zero, all refcnts
needed to be re-activated and css_tryget() shouldn't fail in the
process.
This was achieved by letting css_tryget() busy-loop until either the
refcnt is reactivated (failed removal attempt) or CSS_REMOVED is set
(committing to removal).
Now that css refcnt draining is no longer used, there's no need for
atomic rollback mechanism. css_tryget() simply can look at the
reference count and fail if it's deactivated - it's never getting
re-activated.
This patch removes CSS_REMOVED and updates __css_tryget() to fail if
the refcnt is deactivated. As deactivation and removal are a single
step now, they no longer need to be protected against css_tryget()
happening from irq context. Remove local_irq_disable/enable() from
cgroup_rmdir().
Note that this removes css_is_removed() whose only user is VM_BUG_ON()
in memcontrol.c. We can replace it with a check on the refcnt but
given that the only use case is a debug assert, I think it's better to
simply unexport it.
v2: Comment updated and explanation on local_irq_disable/enable()
added per Michal Hocko.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Balbir Singh <bsingharora@gmail.com>
2ef37d3fe4 ("memcg: Simplify mem_cgroup_force_empty_list error
handling") removed the last user of __DEPRECATED_clear_css_refs. This
patch removes __DEPRECATED_clear_css_refs and mechanisms to support
it.
* Conditionals dependent on __DEPRECATED_clear_css_refs removed.
* cgroup_clear_css_refs() can no longer fail. All that needs to be
done are deactivating refcnts, setting CSS_REMOVED and putting the
base reference on each css. Remove cgroup_clear_css_refs() and the
failure path, and open-code the loops into cgroup_rmdir().
This patch keeps the two for_each_subsys() loops separate while open
coding them. They can be merged now but there are scheduled changes
which need them to be separate, so keep them separate to reduce the
amount of churn.
local_irq_save/restore() from cgroup_clear_css_refs() are replaced
with local_irq_disable/enable() for simplicity. This is safe as
cgroup_rmdir() is always called with IRQ enabled. Note that this IRQ
switching is necessary to ensure that css_tryget() isn't called from
IRQ context on the same CPU while lower context is between CSS
deactivation and setting CSS_REMOVED as css_tryget() would hang
forever in such cases waiting for CSS to be re-activated or
CSS_REMOVED set. This will go away soon.
v2: cgroup_call_pre_destroy() removal dropped per Michal. Commit
message updated to explain local_irq_disable/enable() conversion.
Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Tejun Heo