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cgroup: drop module support

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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>
This commit is contained in:
Tejun Heo 2014-02-08 10:36:58 -05:00
parent af6363374c
commit 3ed80a62bf
6 changed files with 32 additions and 308 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

1
block/blk-cgroup.c
View file

@ -914,7 +914,6 @@ struct cgroup_subsys blkio_subsys = {
.can_attach = blkcg_can_attach,
.subsys_id = blkio_subsys_id,
.base_cftypes = blkcg_files,
.module = THIS_MODULE,
};
EXPORT_SYMBOL_GPL(blkio_subsys);

29
include/linux/cgroup.h
View file

@ -37,28 +37,13 @@ extern void cgroup_post_fork(struct task_struct *p);
extern void cgroup_exit(struct task_struct *p, int run_callbacks);
extern int cgroupstats_build(struct cgroupstats *stats,
struct dentry *dentry);
extern int cgroup_load_subsys(struct cgroup_subsys *ss);
extern void cgroup_unload_subsys(struct cgroup_subsys *ss);
extern int proc_cgroup_show(struct seq_file *, void *);
/*
* Define the enumeration of all cgroup subsystems.
*
* We define ids for builtin subsystems and then modular ones.
*/
/* define the enumeration of all cgroup subsystems */
#define SUBSYS(_x) _x ## _subsys_id,
enum cgroup_subsys_id {
#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
#include <linux/cgroup_subsys.h>
#undef IS_SUBSYS_ENABLED
CGROUP_BUILTIN_SUBSYS_COUNT,
__CGROUP_SUBSYS_TEMP_PLACEHOLDER = CGROUP_BUILTIN_SUBSYS_COUNT - 1,
#define IS_SUBSYS_ENABLED(option) IS_MODULE(option)
#include <linux/cgroup_subsys.h>
#undef IS_SUBSYS_ENABLED
CGROUP_SUBSYS_COUNT,
};
#undef SUBSYS
@ -370,10 +355,9 @@ struct css_set {
struct list_head cgrp_links;
/*
* Set of subsystem states, one for each subsystem. This array
* is immutable after creation apart from the init_css_set
* during subsystem registration (at boot time) and modular subsystem
* loading/unloading.
* Set of subsystem states, one for each subsystem. This array is
* immutable after creation apart from the init_css_set during
* subsystem registration (at boot time).
*/
struct cgroup_subsys_state *subsys[CGROUP_SUBSYS_COUNT];
@ -620,15 +604,10 @@ struct cgroup_subsys {
/* base cftypes, automatically [de]registered with subsys itself */
struct cftype *base_cftypes;
struct cftype_set base_cftset;
/* should be defined only by modular subsystems */
struct module *module;
};
#define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
#include <linux/cgroup_subsys.h>
#undef IS_SUBSYS_ENABLED
#undef SUBSYS
/**

24
include/linux/cgroup_subsys.h
View file

@ -3,51 +3,51 @@
*
* DO NOT ADD ANY SUBSYSTEM WITHOUT EXPLICIT ACKS FROM CGROUP MAINTAINERS.
*/
#if IS_SUBSYS_ENABLED(CONFIG_CPUSETS)
#if IS_ENABLED(CONFIG_CPUSETS)
SUBSYS(cpuset)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_DEBUG)
#if IS_ENABLED(CONFIG_CGROUP_DEBUG)
SUBSYS(debug)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_SCHED)
#if IS_ENABLED(CONFIG_CGROUP_SCHED)
SUBSYS(cpu_cgroup)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_CPUACCT)
#if IS_ENABLED(CONFIG_CGROUP_CPUACCT)
SUBSYS(cpuacct)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_MEMCG)
#if IS_ENABLED(CONFIG_MEMCG)
SUBSYS(mem_cgroup)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_DEVICE)
#if IS_ENABLED(CONFIG_CGROUP_DEVICE)
SUBSYS(devices)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_FREEZER)
#if IS_ENABLED(CONFIG_CGROUP_FREEZER)
SUBSYS(freezer)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_NET_CLASSID)
#if IS_ENABLED(CONFIG_CGROUP_NET_CLASSID)
SUBSYS(net_cls)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_BLK_CGROUP)
#if IS_ENABLED(CONFIG_BLK_CGROUP)
SUBSYS(blkio)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_PERF)
#if IS_ENABLED(CONFIG_CGROUP_PERF)
SUBSYS(perf)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_NET_PRIO)
#if IS_ENABLED(CONFIG_CGROUP_NET_PRIO)
SUBSYS(net_prio)
#endif
#if IS_SUBSYS_ENABLED(CONFIG_CGROUP_HUGETLB)
#if IS_ENABLED(CONFIG_CGROUP_HUGETLB)
SUBSYS(hugetlb)
#endif
/*

284
kernel/cgroup.c
View file

@ -47,7 +47,6 @@
#include <linux/string.h>
#include <linux/sort.h>
#include <linux/kmod.h>
#include <linux/module.h>
#include <linux/delayacct.h>
#include <linux/cgroupstats.h>
#include <linux/hashtable.h>
@ -120,15 +119,9 @@ static struct workqueue_struct *cgroup_destroy_wq;
*/
static struct workqueue_struct *cgroup_pidlist_destroy_wq;
/*
* Generate an array of cgroup subsystem pointers. At boot time, this is
* populated with the built in subsystems, and modular subsystems are
* registered after that. The mutable section of this array is protected by
* cgroup_mutex.
*/
/* generate an array of cgroup subsystem pointers */
#define SUBSYS(_x) [_x ## _subsys_id] = &_x ## _subsys,
#define IS_SUBSYS_ENABLED(option) IS_BUILTIN(option)
static struct cgroup_subsys *cgroup_subsys[CGROUP_SUBSYS_COUNT] = {
static struct cgroup_subsys *cgroup_subsys[] = {
#include <linux/cgroup_subsys.h>
};
@ -258,30 +251,13 @@ static int notify_on_release(const struct cgroup *cgrp)
else
/**
* for_each_subsys - iterate all loaded cgroup subsystems
* for_each_subsys - iterate all enabled cgroup subsystems
* @ss: the iteration cursor
* @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
*
* Iterates through all loaded subsystems. Should be called under
* cgroup_mutex or cgroup_root_mutex.
*/
#define for_each_subsys(ss, ssid) \
for (({ cgroup_assert_mutex_or_root_locked(); (ssid) = 0; }); \
(ssid) < CGROUP_SUBSYS_COUNT; (ssid)++) \
if (!((ss) = cgroup_subsys[(ssid)])) { } \
else
/**
* for_each_builtin_subsys - iterate all built-in cgroup subsystems
* @ss: the iteration cursor
* @i: the index of @ss, CGROUP_BUILTIN_SUBSYS_COUNT after reaching the end
*
* Bulit-in subsystems are always present and iteration itself doesn't
* require any synchronization.
*/
#define for_each_builtin_subsys(ss, i) \
for ((i) = 0; (i) < CGROUP_BUILTIN_SUBSYS_COUNT && \
(((ss) = cgroup_subsys[i]) || true); (i)++)
for ((ssid) = 0; (ssid) < CGROUP_SUBSYS_COUNT && \
(((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
/* iterate across the active hierarchies */
#define for_each_active_root(root) \
@ -975,50 +951,24 @@ static void cgroup_d_remove_dir(struct dentry *dentry)
remove_dir(dentry);
}
/*
* Call with cgroup_mutex held. Drops reference counts on modules, including
* any duplicate ones that parse_cgroupfs_options took. If this function
* returns an error, no reference counts are touched.
*/
static int rebind_subsystems(struct cgroupfs_root *root,
unsigned long added_mask, unsigned removed_mask)
{
struct cgroup *cgrp = &root->top_cgroup;
struct cgroup_subsys *ss;
unsigned long pinned = 0;
int i, ret;
BUG_ON(!mutex_is_locked(&cgroup_mutex));
BUG_ON(!mutex_is_locked(&cgroup_root_mutex));
/* Check that any added subsystems are currently free */
for_each_subsys(ss, i) {
if (!(added_mask & (1 << i)))
continue;
/* is the subsystem mounted elsewhere? */
if (ss->root != &cgroup_dummy_root) {
ret = -EBUSY;
goto out_put;
}
/* pin the module */
if (!try_module_get(ss->module)) {
ret = -ENOENT;
goto out_put;
}
pinned |= 1 << i;
}
/* subsys could be missing if unloaded between parsing and here */
if (added_mask != pinned) {
ret = -ENOENT;
goto out_put;
}
for_each_subsys(ss, i)
if ((added_mask & (1 << i)) && ss->root != &cgroup_dummy_root)
return -EBUSY;
ret = cgroup_populate_dir(cgrp, added_mask);
if (ret)
goto out_put;
return ret;
/*
* Nothing can fail from this point on. Remove files for the
@ -1057,9 +1007,6 @@ static int rebind_subsystems(struct cgroupfs_root *root,
RCU_INIT_POINTER(cgrp->subsys[i], NULL);
cgroup_subsys[i]->root = &cgroup_dummy_root;
/* subsystem is now free - drop reference on module */
module_put(ss->module);
root->subsys_mask &= ~bit;
}
}
@ -1071,12 +1018,6 @@ static int rebind_subsystems(struct cgroupfs_root *root,
root->flags |= CGRP_ROOT_SUBSYS_BOUND;
return 0;
out_put:
for_each_subsys(ss, i)
if (pinned & (1 << i))
module_put(ss->module);
return ret;
}
static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
@ -4506,7 +4447,7 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
return ret;
}
static void __init_or_module cgroup_init_cftsets(struct cgroup_subsys *ss)
static void __init cgroup_init_cftsets(struct cgroup_subsys *ss)
{
INIT_LIST_HEAD(&ss->cftsets);
@ -4559,185 +4500,8 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
BUG_ON(online_css(css));
mutex_unlock(&cgroup_mutex);
/* this function shouldn't be used with modular subsystems, since they
* need to register a subsys_id, among other things */
BUG_ON(ss->module);
}
/**
* cgroup_load_subsys: load and register a modular subsystem at runtime
* @ss: the subsystem to load
*
* This function should be called in a modular subsystem's initcall. If the
* subsystem is built as a module, it will be assigned a new subsys_id and set
* up for use. If the subsystem is built-in anyway, work is delegated to the
* simpler cgroup_init_subsys.
*/
int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
{
struct cgroup_subsys_state *css;
int i, ret;
struct hlist_node *tmp;
struct css_set *cset;
unsigned long key;
/* check name and function validity */
if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
ss->css_alloc == NULL || ss->css_free == NULL)
return -EINVAL;
/*
* we don't support callbacks in modular subsystems. this check is
* before the ss->module check for consistency; a subsystem that could
* be a module should still have no callbacks even if the user isn't
* compiling it as one.
*/
if (ss->fork || ss->exit)
return -EINVAL;
/*
* an optionally modular subsystem is built-in: we want to do nothing,
* since cgroup_init_subsys will have already taken care of it.
*/
if (ss->module == NULL) {
/* a sanity check */
BUG_ON(cgroup_subsys[ss->subsys_id] != ss);
return 0;
}
/* init base cftset */
cgroup_init_cftsets(ss);
mutex_lock(&cgroup_mutex);
mutex_lock(&cgroup_root_mutex);
cgroup_subsys[ss->subsys_id] = ss;
/*
* no ss->css_alloc seems to need anything important in the ss
* struct, so this can happen first (i.e. before the dummy root
* attachment).
*/
css = ss->css_alloc(cgroup_css(cgroup_dummy_top, ss));
if (IS_ERR(css)) {
/* failure case - need to deassign the cgroup_subsys[] slot. */
cgroup_subsys[ss->subsys_id] = NULL;
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
return PTR_ERR(css);
}
ss->root = &cgroup_dummy_root;
/* our new subsystem will be attached to the dummy hierarchy. */
init_css(css, ss, cgroup_dummy_top);
/*
* Now we need to entangle the css into the existing css_sets. unlike
* in cgroup_init_subsys, there are now multiple css_sets, so each one
* will need a new pointer to it; done by iterating the css_set_table.
* furthermore, modifying the existing css_sets will corrupt the hash
* table state, so each changed css_set will need its hash recomputed.
* this is all done under the css_set_lock.
*/
write_lock(&css_set_lock);
hash_for_each_safe(css_set_table, i, tmp, cset, hlist) {
/* skip entries that we already rehashed */
if (cset->subsys[ss->subsys_id])
continue;
/* remove existing entry */
hash_del(&cset->hlist);
/* set new value */
cset->subsys[ss->subsys_id] = css;
/* recompute hash and restore entry */
key = css_set_hash(cset->subsys);
hash_add(css_set_table, &cset->hlist, key);
}
write_unlock(&css_set_lock);
ret = online_css(css);
if (ret) {
ss->css_free(css);
goto err_unload;
}
/* success! */
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
return 0;
err_unload:
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
/* @ss can't be mounted here as try_module_get() would fail */
cgroup_unload_subsys(ss);
return ret;
}
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
/**
* cgroup_unload_subsys: unload a modular subsystem
* @ss: the subsystem to unload
*
* This function should be called in a modular subsystem's exitcall. When this
* function is invoked, the refcount on the subsystem's module will be 0, so
* the subsystem will not be attached to any hierarchy.
*/
void cgroup_unload_subsys(struct cgroup_subsys *ss)
{
struct cgrp_cset_link *link;
struct cgroup_subsys_state *css;
BUG_ON(ss->module == NULL);
/*
* we shouldn't be called if the subsystem is in use, and the use of
* try_module_get() in rebind_subsystems() should ensure that it
* doesn't start being used while we're killing it off.
*/
BUG_ON(ss->root != &cgroup_dummy_root);
mutex_lock(&cgroup_mutex);
mutex_lock(&cgroup_root_mutex);
css = cgroup_css(cgroup_dummy_top, ss);
if (css)
offline_css(css);
/* deassign the subsys_id */
cgroup_subsys[ss->subsys_id] = NULL;
/*
* disentangle the css from all css_sets attached to the dummy
* top. as in loading, we need to pay our respects to the hashtable
* gods.
*/
write_lock(&css_set_lock);
list_for_each_entry(link, &cgroup_dummy_top->cset_links, cset_link) {
struct css_set *cset = link->cset;
unsigned long key;
hash_del(&cset->hlist);
cset->subsys[ss->subsys_id] = NULL;
key = css_set_hash(cset->subsys);
hash_add(css_set_table, &cset->hlist, key);
}
write_unlock(&css_set_lock);
/*
* remove subsystem's css from the cgroup_dummy_top and free it -
* need to free before marking as null because ss->css_free needs
* the cgrp->subsys pointer to find their state.
*/
if (css)
ss->css_free(css);
RCU_INIT_POINTER(cgroup_dummy_top->subsys[ss->subsys_id], NULL);
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
}
EXPORT_SYMBOL_GPL(cgroup_unload_subsys);
/**
* cgroup_init_early - cgroup initialization at system boot
*
@ -4763,8 +4527,7 @@ int __init cgroup_init_early(void)
list_add(&init_cgrp_cset_link.cset_link, &cgroup_dummy_top->cset_links);
list_add(&init_cgrp_cset_link.cgrp_link, &init_css_set.cgrp_links);
/* at bootup time, we don't worry about modular subsystems */
for_each_builtin_subsys(ss, i) {
for_each_subsys(ss, i) {
BUG_ON(!ss->name);
BUG_ON(strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN);
BUG_ON(!ss->css_alloc);
@ -4797,7 +4560,7 @@ int __init cgroup_init(void)
if (err)
return err;
for_each_builtin_subsys(ss, i) {
for_each_subsys(ss, i) {
if (!ss->early_init)
cgroup_init_subsys(ss);
}
@ -5032,15 +4795,7 @@ void cgroup_post_fork(struct task_struct *child)
* and addition to css_set.
*/
if (need_forkexit_callback) {
/*
* fork/exit callbacks are supported only for builtin
* subsystems, and the builtin section of the subsys
* array is immutable, so we don't need to lock the
* subsys array here. On the other hand, modular section
* of the array can be freed at module unload, so we
* can't touch that.
*/
for_each_builtin_subsys(ss, i)
for_each_subsys(ss, i)
if (ss->fork)
ss->fork(child);
}
@ -5105,11 +4860,8 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
RCU_INIT_POINTER(tsk->cgroups, &init_css_set);
if (run_callbacks && need_forkexit_callback) {
/*
* fork/exit callbacks are supported only for builtin
* subsystems, see cgroup_post_fork() for details.
*/
for_each_builtin_subsys(ss, i) {
/* see cgroup_post_fork() for details */
for_each_subsys(ss, i) {
if (ss->exit) {
struct cgroup_subsys_state *old_css = cset->subsys[i];
struct cgroup_subsys_state *css = task_css(tsk, i);
@ -5228,11 +4980,7 @@ static int __init cgroup_disable(char *str)
if (!*token)
continue;
/*
* cgroup_disable, being at boot time, can't know about
* module subsystems, so we don't worry about them.
*/
for_each_builtin_subsys(ss, i) {
for_each_subsys(ss, i) {
if (!strcmp(token, ss->name)) {
ss->disabled = 1;
printk(KERN_INFO "Disabling %s control group"

1
net/core/netclassid_cgroup.c
View file

@ -110,5 +110,4 @@ struct cgroup_subsys net_cls_subsys = {
.attach = cgrp_attach,
.subsys_id = net_cls_subsys_id,
.base_cftypes = ss_files,
.module = THIS_MODULE,
};

1
net/core/netprio_cgroup.c
View file

@ -252,7 +252,6 @@ struct cgroup_subsys net_prio_subsys = {
.attach = net_prio_attach,
.subsys_id = net_prio_subsys_id,
.base_cftypes = ss_files,
.module = THIS_MODULE,
};
static int netprio_device_event(struct notifier_block *unused,