Merge branch 'for-4.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

Pull cgroup updates from Tejun Heo:
"Nothing too interesting. Documentation updates and trivial changes;
however, this pull request does containt he previusly discussed
dropping of __must_check from strscpy()"

* 'for-4.16' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
Documentation: Fix 'file_mapped' -> 'mapped_file'
string: drop __must_check from strscpy() and restore strscpy() usages in cgroup
cgroup, docs: document the root cgroup behavior of cpu and io controllers
cgroup-v2.txt: fix typos
cgroup: Update documentation reference
Documentation/cgroup-v1: fix outdated programming details
cgroup, docs: document cgroup v2 device controller

Documentation/cgroup-v1/cgroups.txt

···
 Each subsystem should:
 
 - add an entry in linux/cgroup_subsys.h
-- define a cgroup_subsys object called <name>_subsys
-
-If a subsystem can be compiled as a module, it should also have in its
-module initcall a call to cgroup_load_subsys(), and in its exitcall a
-call to cgroup_unload_subsys(). It should also set its_subsys.module =
-THIS_MODULE in its .c file.
+- define a cgroup_subsys object called <name>_cgrp_subsys
 
 Each subsystem may export the following methods. The only mandatory
 methods are css_alloc/free. Any others that are null are presumed to

Documentation/cgroup-v1/memory.txt

···
 	Only anonymous and swap cache memory is listed as part of 'rss' stat.
 	This should not be confused with the true 'resident set size' or the
 	amount of physical memory used by the cgroup.
-	'rss + file_mapped" will give you resident set size of cgroup.
+	'rss + mapped_file" will give you resident set size of cgroup.
 	(Note: file and shmem may be shared among other cgroups. In that case,
-	 file_mapped is accounted only when the memory cgroup is owner of page
+	 mapped_file is accounted only when the memory cgroup is owner of page
 	 cache.)
 
 5.3 swappiness

Documentation/cgroup-v2.txt

···
        5-3-2. Writeback
      5-4. PID
        5-4-1. PID Interface Files
-     5-5. RDMA
-       5-5-1. RDMA Interface Files
-     5-6. Misc
-       5-6-1. perf_event
+     5-5. Device
+     5-6. RDMA
+       5-6-1. RDMA Interface Files
+     5-7. Misc
+       5-7-1. perf_event
+     5-N. Non-normative information
+       5-N-1. CPU controller root cgroup process behaviour
+       5-N-2. IO controller root cgroup process behaviour
    6. Namespace
      6-1. Basics
      6-2. The Root and Views
···
   exempt from this requirement.
 
 Topology-wise, a cgroup can be in an invalid state.  Please consider
-the following toplogy::
+the following topology::
 
   A (threaded domain) - B (threaded) - C (domain, just created)
 
···
 processes and anonymous resource consumption which can't be associated
 with any other cgroups and requires special treatment from most
 controllers.  How resource consumption in the root cgroup is governed
-is up to each controller.
+is up to each controller (for more information on this topic please
+refer to the Non-normative information section in the Controllers
+chapter).
 
 Note that the restriction doesn't get in the way if there is no
 enabled controller in the cgroup's "cgroup.subtree_control".  This is
···
 		reached the limit and allocation was about to fail.
 
 		Depending on context result could be invocation of OOM
-		killer and retrying allocation or failing alloction.
+		killer and retrying allocation or failing allocation.
 
 		Failed allocation in its turn could be returned into
-		userspace as -ENOMEM or siletly ignored in cases like
+		userspace as -ENOMEM or silently ignored in cases like
 		disk readahead.  For now OOM in memory cgroup kills
 		tasks iff shortage has happened inside page fault.
 
···
 	cgroups.  The default is "max".
 
 	Swap usage hard limit.  If a cgroup's swap usage reaches this
-	limit, anonymous meomry of the cgroup will not be swapped out.
+	limit, anonymous memory of the cgroup will not be swapped out.
 
 
 Usage Guidelines
···
 of a new process would cause a cgroup policy to be violated.
 
 
+Device controller
+-----------------
+
+Device controller manages access to device files. It includes both
+creation of new device files (using mknod), and access to the
+existing device files.
+
+Cgroup v2 device controller has no interface files and is implemented
+on top of cgroup BPF. To control access to device files, a user may
+create bpf programs of the BPF_CGROUP_DEVICE type and attach them
+to cgroups. On an attempt to access a device file, corresponding
+BPF programs will be executed, and depending on the return value
+the attempt will succeed or fail with -EPERM.
+
+A BPF_CGROUP_DEVICE program takes a pointer to the bpf_cgroup_dev_ctx
+structure, which describes the device access attempt: access type
+(mknod/read/write) and device (type, major and minor numbers).
+If the program returns 0, the attempt fails with -EPERM, otherwise
+it succeeds.
+
+An example of BPF_CGROUP_DEVICE program may be found in the kernel
+source tree in the tools/testing/selftests/bpf/dev_cgroup.c file.
+
+
 RDMA
 ----
 
···
 automatically enabled on the v2 hierarchy so that perf events can
 always be filtered by cgroup v2 path.  The controller can still be
 moved to a legacy hierarchy after v2 hierarchy is populated.
+
+
+Non-normative information
+-------------------------
+
+This section contains information that isn't considered to be a part of
+the stable kernel API and so is subject to change.
+
+
+CPU controller root cgroup process behaviour
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+When distributing CPU cycles in the root cgroup each thread in this
+cgroup is treated as if it was hosted in a separate child cgroup of the
+root cgroup. This child cgroup weight is dependent on its thread nice
+level.
+
+For details of this mapping see sched_prio_to_weight array in
+kernel/sched/core.c file (values from this array should be scaled
+appropriately so the neutral - nice 0 - value is 100 instead of 1024).
+
+
+IO controller root cgroup process behaviour
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Root cgroup processes are hosted in an implicit leaf child node.
+When distributing IO resources this implicit child node is taken into
+account as if it was a normal child cgroup of the root cgroup with a
+weight value of 200.
 
 
 Namespace

include/linux/cgroup-defs.h

···
 
 /*
  * Control Group subsystem type.
- * See Documentation/cgroups/cgroups.txt for details
+ * See Documentation/cgroup-v1/cgroups.txt for details
  */
 struct cgroup_subsys {
 	struct cgroup_subsys_state *(*css_alloc)(struct cgroup_subsys_state *parent_css);

include/linux/string.h

···
 size_t strlcpy(char *, const char *, size_t);
 #endif
 #ifndef __HAVE_ARCH_STRSCPY
-ssize_t __must_check strscpy(char *, const char *, size_t);
+ssize_t strscpy(char *, const char *, size_t);
 #endif
 #ifndef __HAVE_ARCH_STRCAT
 extern char * strcat(char *, const char *);

kernel/cgroup/cgroup.c

···
 			 cgroup_on_dfl(cgrp) ? ss->name : ss->legacy_name,
 			 cft->name);
 	else
-		strlcpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
+		strscpy(buf, cft->name, CGROUP_FILE_NAME_MAX);
 	return buf;
 }
 
···
 
 	root->flags = opts->flags;
 	if (opts->release_agent)
-		strlcpy(root->release_agent_path, opts->release_agent, PATH_MAX);
+		strscpy(root->release_agent_path, opts->release_agent, PATH_MAX);
 	if (opts->name)
-		strlcpy(root->name, opts->name, MAX_CGROUP_ROOT_NAMELEN);
+		strscpy(root->name, opts->name, MAX_CGROUP_ROOT_NAMELEN);
 	if (opts->cpuset_clone_children)
 		set_bit(CGRP_CPUSET_CLONE_CHILDREN, &root->cgrp.flags);
 }