提交 e6a1105b 编写于 作者: B Ben Blum 提交者: Linus Torvalds

cgroups: subsystem module loading interface

Add interface between cgroups subsystem management and module loading

This patch implements rudimentary module-loading support for cgroups -
namely, a cgroup_load_subsys (similar to cgroup_init_subsys) for use as a
module initcall, and a struct module pointer in struct cgroup_subsys.

Several functions that might be wanted by modules have had EXPORT_SYMBOL
added to them, but it's unclear exactly which functions want it and which
won't.
Signed-off-by: NBen Blum <bblum@andrew.cmu.edu>
Acked-by: NLi Zefan <lizf@cn.fujitsu.com>
Cc: Paul Menage <menage@google.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
上级 aae8aab4
......@@ -488,6 +488,10 @@ 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(&its_subsys_struct). It
should also set its_subsys.module = THIS_MODULE in its .c file.
Each subsystem may export the following methods. The only mandatory
methods are create/destroy. Any others that are null are presumed to
be successful no-ops.
......
......@@ -37,6 +37,7 @@ 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 const struct file_operations proc_cgroup_operations;
......@@ -486,6 +487,9 @@ struct cgroup_subsys {
/* used when use_id == true */
struct idr idr;
spinlock_t id_lock;
/* should be defined only by modular subsystems */
struct module *module;
};
#define SUBSYS(_x) extern struct cgroup_subsys _x ## _subsys;
......
......@@ -44,6 +44,7 @@
#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/hash.h>
......@@ -254,7 +255,8 @@ struct cg_cgroup_link {
static struct css_set init_css_set;
static struct cg_cgroup_link init_css_set_link;
static int cgroup_subsys_init_idr(struct cgroup_subsys *ss);
static int cgroup_init_idr(struct cgroup_subsys *ss,
struct cgroup_subsys_state *css);
/* css_set_lock protects the list of css_set objects, and the
* chain of tasks off each css_set. Nests outside task->alloc_lock
......@@ -2125,6 +2127,7 @@ int cgroup_add_file(struct cgroup *cgrp,
error = PTR_ERR(dentry);
return error;
}
EXPORT_SYMBOL_GPL(cgroup_add_file);
int cgroup_add_files(struct cgroup *cgrp,
struct cgroup_subsys *subsys,
......@@ -2139,6 +2142,7 @@ int cgroup_add_files(struct cgroup *cgrp,
}
return 0;
}
EXPORT_SYMBOL_GPL(cgroup_add_files);
/**
* cgroup_task_count - count the number of tasks in a cgroup.
......@@ -3292,7 +3296,144 @@ static void __init cgroup_init_subsys(struct cgroup_subsys *ss)
mutex_init(&ss->hierarchy_mutex);
lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
ss->active = 1;
/* 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
* subsytem 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)
{
int i;
struct cgroup_subsys_state *css;
/* check name and function validity */
if (ss->name == NULL || strlen(ss->name) > MAX_CGROUP_TYPE_NAMELEN ||
ss->create == NULL || ss->destroy == 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 few sanity checks */
BUG_ON(ss->subsys_id >= CGROUP_BUILTIN_SUBSYS_COUNT);
BUG_ON(subsys[ss->subsys_id] != ss);
return 0;
}
/*
* need to register a subsys id before anything else - for example,
* init_cgroup_css needs it.
*/
mutex_lock(&cgroup_mutex);
/* find the first empty slot in the array */
for (i = CGROUP_BUILTIN_SUBSYS_COUNT; i < CGROUP_SUBSYS_COUNT; i++) {
if (subsys[i] == NULL)
break;
}
if (i == CGROUP_SUBSYS_COUNT) {
/* maximum number of subsystems already registered! */
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
/* assign ourselves the subsys_id */
ss->subsys_id = i;
subsys[i] = ss;
/*
* no ss->create seems to need anything important in the ss struct, so
* this can happen first (i.e. before the rootnode attachment).
*/
css = ss->create(ss, dummytop);
if (IS_ERR(css)) {
/* failure case - need to deassign the subsys[] slot. */
subsys[i] = NULL;
mutex_unlock(&cgroup_mutex);
return PTR_ERR(css);
}
list_add(&ss->sibling, &rootnode.subsys_list);
ss->root = &rootnode;
/* our new subsystem will be attached to the dummy hierarchy. */
init_cgroup_css(css, ss, dummytop);
/* init_idr must be after init_cgroup_css because it sets css->id. */
if (ss->use_id) {
int ret = cgroup_init_idr(ss, css);
if (ret) {
dummytop->subsys[ss->subsys_id] = NULL;
ss->destroy(ss, dummytop);
subsys[i] = NULL;
mutex_unlock(&cgroup_mutex);
return ret;
}
}
/*
* 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);
for (i = 0; i < CSS_SET_TABLE_SIZE; i++) {
struct css_set *cg;
struct hlist_node *node, *tmp;
struct hlist_head *bucket = &css_set_table[i], *new_bucket;
hlist_for_each_entry_safe(cg, node, tmp, bucket, hlist) {
/* skip entries that we already rehashed */
if (cg->subsys[ss->subsys_id])
continue;
/* remove existing entry */
hlist_del(&cg->hlist);
/* set new value */
cg->subsys[ss->subsys_id] = css;
/* recompute hash and restore entry */
new_bucket = css_set_hash(cg->subsys);
hlist_add_head(&cg->hlist, new_bucket);
}
}
write_unlock(&css_set_lock);
mutex_init(&ss->hierarchy_mutex);
lockdep_set_class(&ss->hierarchy_mutex, &ss->subsys_key);
ss->active = 1;
/*
* pin the subsystem's module so it doesn't go away. this shouldn't
* fail, since the module's initcall calls us.
* TODO: with module unloading, move this elsewhere
*/
BUG_ON(!try_module_get(ss->module));
/* success! */
mutex_unlock(&cgroup_mutex);
return 0;
}
EXPORT_SYMBOL_GPL(cgroup_load_subsys);
/**
* cgroup_init_early - cgroup initialization at system boot
......@@ -3364,7 +3505,7 @@ int __init cgroup_init(void)
if (!ss->early_init)
cgroup_init_subsys(ss);
if (ss->use_id)
cgroup_subsys_init_idr(ss);
cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
}
/* Add init_css_set to the hash table */
......@@ -4033,15 +4174,14 @@ static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
}
static int __init cgroup_subsys_init_idr(struct cgroup_subsys *ss)
static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
struct cgroup_subsys_state *rootcss)
{
struct css_id *newid;
struct cgroup_subsys_state *rootcss;
spin_lock_init(&ss->id_lock);
idr_init(&ss->idr);
rootcss = init_css_set.subsys[ss->subsys_id];
newid = get_new_cssid(ss, 0);
if (IS_ERR(newid))
return PTR_ERR(newid);
......
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