On Fri, Jan 08, 2010 at 12:27:34AM -0500, Ben Blum wrote:
> On Thu, Jan 07, 2010 at 02:42:19PM +0800, Li Zefan wrote:
> > KAMEZAWA Hiroyuki wrote:
> > > On Wed, 6 Jan 2010 20:26:06 -0500
> > > Ben Blum <bblum@xxxxxxxxxxxxxx> wrote:
> > >
> > >> On Wed, Jan 06, 2010 at 04:04:14PM -0800, Andrew Morton wrote:
> > >>> On Thu, 31 Dec 2009 00:10:50 -0500
> > >>> Ben Blum <bblum@xxxxxxxxxxxxxx> wrote:
> > >>>
> > >>>> This patch series implements support for building, loading, and
> > >>>> unloading subsystems as modules, both within and outside the kernel
> > >>>> source tree. It provides an interface cgroup_load_subsys() and
> > >>>> cgroup_unload_subsys() which modular subsystems can use to register and
> > >>>> depart during runtime. The net_cls classifier subsystem serves as the
> > >>>> example for a subsystem which can be converted into a module using these
> > >>>> changes.
> > >>> What is the value in this? What are the usage scenarios? Why does the
> > >>> benefit of this change exceed the cost/risk/etc of merging it?
> > >> As discussed in the first posting of these patches, this provides the
> > >> ability for arbitrary subsystems to be used with cgroups.. cls_cgroup
> > >> would have already been a module except for a lack of support from
> > >> cgroups, and the change also allows other module-loadable classifiers
> > >> to add subsystems of their own.
> > >
> > > Hmm, do you have your own module in plan ?
> > >
> >
> > Maybe the new blkio_cgroup can also be made module-able.
>
> Ok, the following two patches make this happen (or at least pretend to
> well enough to fool me). The first one adds use_id initialization in
> cgroup_load_subsys, and the second rearranges config options and some
> code as appropriate in block/ and adds EXPORT_SYMBOLs in cgroup.c.
>
> -- bblum
>
> ---
> block/Kconfig | 2 -
> block/Kconfig.iosched | 2 -
> block/blk-cgroup.c | 53 +++++++++++++++++++++++++++++++++++-----------
> block/blk-cgroup.h | 10 ++++++--
> include/linux/iocontext.h | 2 -
> kernel/cgroup.c | 31 +++++++++++++++++++++-----
> 6 files changed, 77 insertions(+), 23 deletions(-)
>
>
This patch adds support for subsys.use_id in module-loadable subsystems.
From: Ben Blum <bblum@xxxxxxxxxxxxxx>
Signed-off-by: Ben Blum <bblum@xxxxxxxxxxxxxx>
---
kernel/cgroup.c | 23 +++++++++++++++++------
1 files changed, 17 insertions(+), 6 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index cc2e1f6..5af59eb 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -240,7 +240,8 @@ 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
@@ -3390,6 +3391,16 @@ int __init_or_module cgroup_load_subsys(struct cgroup_subsys *ss)
mutex_unlock(&cgroup_mutex);
return PTR_ERR(css);
}
+ /* call init_idr here because it has a failure case */
+ if (ss->use_id) {
+ int ret = cgroup_init_idr(ss, css);
+ if (ret) {
+ ss->destroy(ss, dummytop);
+ subsys[i] = NULL;
+ mutex_unlock(&cgroup_mutex);
+ return ret;
+ }
+ }
list_add(&ss->sibling, &rootnode.subsys_list);
ss->root = &rootnode;
@@ -3484,7 +3495,8 @@ void cgroup_unload_subsys(struct cgroup_subsys *ss)
/*
* remove subsystem's css from the dummytop and free it - need to free
* before marking as null because ss->destroy needs the cgrp->subsys
- * pointer to find their state.
+ * pointer to find their state. note that this also takes care of
+ * freeing the css_id.
*/
ss->destroy(ss, dummytop);
dummytop->subsys[ss->subsys_id] = NULL;
@@ -3563,7 +3575,7 @@ 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 */
@@ -4231,15 +4243,14 @@ err_out:
}
-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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