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cgroup: Fixes for v6.4-rc5

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* Fix css_set reference leaks on fork failures.
 
 * Fix CPU hotplug locking in cgroup_transfer_tasks() which is used by
   cgroup1 cpuset.
 
 * Doc update.
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Merge tag 'cgroup-for-6.4-rc5-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup fixes from Tejun Heo:

 - Fix css_set reference leaks on fork failures

 - Fix CPU hotplug locking in cgroup_transfer_tasks() which is used by
   cgroup1 cpuset

 - Doc update

* tag 'cgroup-for-6.4-rc5-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
  cgroup: Documentation: Clarify usage of memory limits
  cgroup: always put cset in cgroup_css_set_put_fork
  cgroup: fix missing cpus_read_{lock,unlock}() in cgroup_transfer_tasks()
This commit is contained in:
Linus Torvalds 2023-06-08 18:52:54 -07:00
commit 9cd6357f10
3 changed files with 20 additions and 23 deletions
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22
Documentation/admin-guide/cgroup-v2.rst
View file

@ -1213,23 +1213,25 @@ PAGE_SIZE multiple when read back.
A read-write single value file which exists on non-root
cgroups. The default is "max".
Memory usage throttle limit. This is the main mechanism to
control memory usage of a cgroup. If a cgroup's usage goes
Memory usage throttle limit. If a cgroup's usage goes
over the high boundary, the processes of the cgroup are
throttled and put under heavy reclaim pressure.
Going over the high limit never invokes the OOM killer and
under extreme conditions the limit may be breached.
under extreme conditions the limit may be breached. The high
limit should be used in scenarios where an external process
monitors the limited cgroup to alleviate heavy reclaim
pressure.
memory.max
A read-write single value file which exists on non-root
cgroups. The default is "max".
Memory usage hard limit. This is the final protection
mechanism. If a cgroup's memory usage reaches this limit and
can't be reduced, the OOM killer is invoked in the cgroup.
Under certain circumstances, the usage may go over the limit
temporarily.
Memory usage hard limit. This is the main mechanism to limit
memory usage of a cgroup. If a cgroup's memory usage reaches
this limit and can't be reduced, the OOM killer is invoked in
the cgroup. Under certain circumstances, the usage may go
over the limit temporarily.
In default configuration regular 0-order allocations always
succeed unless OOM killer chooses current task as a victim.
@ -1238,10 +1240,6 @@ PAGE_SIZE multiple when read back.
Caller could retry them differently, return into userspace
as -ENOMEM or silently ignore in cases like disk readahead.
This is the ultimate protection mechanism. As long as the
high limit is used and monitored properly, this limit's
utility is limited to providing the final safety net.
memory.reclaim
A write-only nested-keyed file which exists for all cgroups.

4
kernel/cgroup/cgroup-v1.c
View file

@ -108,7 +108,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
cgroup_lock();
percpu_down_write(&cgroup_threadgroup_rwsem);
cgroup_attach_lock(true);
/* all tasks in @from are being moved, all csets are source */
spin_lock_irq(&css_set_lock);
@ -144,7 +144,7 @@ int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from)
} while (task && !ret);
out_err:
cgroup_migrate_finish(&mgctx);
percpu_up_write(&cgroup_threadgroup_rwsem);
cgroup_attach_unlock(true);
cgroup_unlock();
return ret;
}

17
kernel/cgroup/cgroup.c
View file

@ -6486,19 +6486,18 @@ static int cgroup_css_set_fork(struct kernel_clone_args *kargs)
static void cgroup_css_set_put_fork(struct kernel_clone_args *kargs)
__releases(&cgroup_threadgroup_rwsem) __releases(&cgroup_mutex)
{
struct cgroup *cgrp = kargs->cgrp;
struct css_set *cset = kargs->cset;
cgroup_threadgroup_change_end(current);
if (cset) {
put_css_set(cset);
kargs->cset = NULL;
}
if (kargs->flags & CLONE_INTO_CGROUP) {
struct cgroup *cgrp = kargs->cgrp;
struct css_set *cset = kargs->cset;
cgroup_unlock();
if (cset) {
put_css_set(cset);
kargs->cset = NULL;
}
if (cgrp) {
cgroup_put(cgrp);
kargs->cgrp = NULL;