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Date: Mon, 30 Aug 2010 14:44:23 +0900
From: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
To: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Cc: linux-mm@...ck.org,
"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
gthelen@...gle.com, m-ikeda@...jp.nec.com,
"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"menage@...gle.com" <menage@...gle.com>,
"lizf@...fujitsu.com" <lizf@...fujitsu.com>,
Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Subject: Re: [PATCH 1/5] cgroup: do ID allocation under css allocator.
On Wed, 25 Aug 2010 17:06:40 +0900
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com> wrote:
> From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
>
> Now, css'id is allocated after ->create() is called. But to make use of ID
> in ->create(), it should be available before ->create().
>
> In another thinking, considering the ID is tightly coupled with "css",
> it should be allocated when "css" is allocated.
> This patch moves alloc_css_id() to css allocation routine. Now, only 2 subsys,
> memory and blkio are useing ID. (To support complicated hierarchy walk.)
>
> ID will be used in mem cgroup's ->create(), later.
>
> Note:
> If someone changes rules of css allocation, ID allocation should be moved too.
>
> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
I think we need some signs from Paul and Li, but anyway
Reviewed-by: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Thanks,
Daisuke Nishimura.
> ---
> block/blk-cgroup.c | 9 ++++++++
> include/linux/cgroup.h | 16 ++++++++-------
> kernel/cgroup.c | 50 ++++++++++++++-----------------------------------
> mm/memcontrol.c | 5 ++++
> 4 files changed, 38 insertions(+), 42 deletions(-)
>
> Index: mmotm-0811/kernel/cgroup.c
> ===================================================================
> --- mmotm-0811.orig/kernel/cgroup.c
> +++ mmotm-0811/kernel/cgroup.c
> @@ -289,9 +289,6 @@ struct cg_cgroup_link {
> static struct css_set init_css_set;
> static struct cg_cgroup_link init_css_set_link;
>
> -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
> * due to cgroup_iter_start() */
> @@ -770,9 +767,6 @@ static struct backing_dev_info cgroup_ba
> .capabilities = BDI_CAP_NO_ACCT_AND_WRITEBACK,
> };
>
> -static int alloc_css_id(struct cgroup_subsys *ss,
> - struct cgroup *parent, struct cgroup *child);
> -
> static struct inode *cgroup_new_inode(mode_t mode, struct super_block *sb)
> {
> struct inode *inode = new_inode(sb);
> @@ -3257,7 +3251,8 @@ static void init_cgroup_css(struct cgrou
> css->cgroup = cgrp;
> atomic_set(&css->refcnt, 1);
> css->flags = 0;
> - css->id = NULL;
> + if (!ss->use_id)
> + css->id = NULL;
> if (cgrp == dummytop)
> set_bit(CSS_ROOT, &css->flags);
> BUG_ON(cgrp->subsys[ss->subsys_id]);
> @@ -3342,12 +3337,6 @@ static long cgroup_create(struct cgroup
> goto err_destroy;
> }
> init_cgroup_css(css, ss, cgrp);
> - if (ss->use_id) {
> - err = alloc_css_id(ss, parent, cgrp);
> - if (err)
> - goto err_destroy;
> - }
> - /* At error, ->destroy() callback has to free assigned ID. */
> }
>
> cgroup_lock_hierarchy(root);
> @@ -3709,17 +3698,6 @@ int __init_or_module cgroup_load_subsys(
>
> /* 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
> @@ -3888,8 +3866,6 @@ int __init cgroup_init(void)
> struct cgroup_subsys *ss = subsys[i];
> if (!ss->early_init)
> cgroup_init_subsys(ss);
> - if (ss->use_id)
> - cgroup_init_idr(ss, init_css_set.subsys[ss->subsys_id]);
> }
>
> /* Add init_css_set to the hash table */
> @@ -4603,8 +4579,8 @@ err_out:
>
> }
>
> -static int __init_or_module cgroup_init_idr(struct cgroup_subsys *ss,
> - struct cgroup_subsys_state *rootcss)
> +static int cgroup_init_idr(struct cgroup_subsys *ss,
> + struct cgroup_subsys_state *rootcss)
> {
> struct css_id *newid;
>
> @@ -4616,21 +4592,25 @@ static int __init_or_module cgroup_init_
> return PTR_ERR(newid);
>
> newid->stack[0] = newid->id;
> - newid->css = rootcss;
> - rootcss->id = newid;
> + rcu_assign_pointer(newid->css, rootcss);
> + rcu_assign_pointer(rootcss->id, newid);
> return 0;
> }
>
> -static int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *parent,
> - struct cgroup *child)
> +int alloc_css_id(struct cgroup_subsys *ss,
> + struct cgroup *cgrp, struct cgroup_subsys_state *css)
> {
> int subsys_id, i, depth = 0;
> - struct cgroup_subsys_state *parent_css, *child_css;
> + struct cgroup_subsys_state *parent_css;
> + struct cgroup *parent;
> struct css_id *child_id, *parent_id;
>
> + if (cgrp == dummytop)
> + return cgroup_init_idr(ss, css);
> +
> + parent = cgrp->parent;
> subsys_id = ss->subsys_id;
> parent_css = parent->subsys[subsys_id];
> - child_css = child->subsys[subsys_id];
> parent_id = parent_css->id;
> depth = parent_id->depth + 1;
>
> @@ -4645,7 +4625,7 @@ static int alloc_css_id(struct cgroup_su
> * child_id->css pointer will be set after this cgroup is available
> * see cgroup_populate_dir()
> */
> - rcu_assign_pointer(child_css->id, child_id);
> + rcu_assign_pointer(css->id, child_id);
>
> return 0;
> }
> Index: mmotm-0811/include/linux/cgroup.h
> ===================================================================
> --- mmotm-0811.orig/include/linux/cgroup.h
> +++ mmotm-0811/include/linux/cgroup.h
> @@ -583,9 +583,11 @@ int cgroup_attach_task_current_cg(struct
> /*
> * CSS ID is ID for cgroup_subsys_state structs under subsys. This only works
> * if cgroup_subsys.use_id == true. It can be used for looking up and scanning.
> - * CSS ID is assigned at cgroup allocation (create) automatically
> - * and removed when subsys calls free_css_id() function. This is because
> - * the lifetime of cgroup_subsys_state is subsys's matter.
> + * CSS ID must be assigned by subsys itself at cgroup creation and deleted
> + * when subsys calls free_css_id() function. This is because the life time of
> + * of cgroup_subsys_state is subsys's matter.
> + *
> + * ID->css look up is available after cgroup's directory is populated.
> *
> * Looking up and scanning function should be called under rcu_read_lock().
> * Taking cgroup_mutex()/hierarchy_mutex() is not necessary for following calls.
> @@ -593,10 +595,10 @@ int cgroup_attach_task_current_cg(struct
> * destroyed". The caller should check css and cgroup's status.
> */
>
> -/*
> - * Typically Called at ->destroy(), or somewhere the subsys frees
> - * cgroup_subsys_state.
> - */
> +/* Should be called in ->create() by subsys itself */
> +int alloc_css_id(struct cgroup_subsys *ss, struct cgroup *newgr,
> + struct cgroup_subsys_state *css);
> +/* Typically Called at ->destroy(), or somewhere the subsys frees css */
> void free_css_id(struct cgroup_subsys *ss, struct cgroup_subsys_state *css);
>
> /* Find a cgroup_subsys_state which has given ID */
> Index: mmotm-0811/mm/memcontrol.c
> ===================================================================
> --- mmotm-0811.orig/mm/memcontrol.c
> +++ mmotm-0811/mm/memcontrol.c
> @@ -4141,6 +4141,11 @@ mem_cgroup_create(struct cgroup_subsys *
> if (alloc_mem_cgroup_per_zone_info(mem, node))
> goto free_out;
>
> + error = alloc_css_id(ss, cont, &mem->css);
> + if (error)
> + goto free_out;
> + /* Here, css_id(&mem->css) works. but css_lookup(id)->mem doesn't */
> +
> /* root ? */
> if (cont->parent == NULL) {
> int cpu;
> Index: mmotm-0811/block/blk-cgroup.c
> ===================================================================
> --- mmotm-0811.orig/block/blk-cgroup.c
> +++ mmotm-0811/block/blk-cgroup.c
> @@ -958,9 +958,13 @@ blkiocg_create(struct cgroup_subsys *sub
> {
> struct blkio_cgroup *blkcg;
> struct cgroup *parent = cgroup->parent;
> + int ret;
>
> if (!parent) {
> blkcg = &blkio_root_cgroup;
> + ret = alloc_css_id(subsys, cgroup, &blkcg->css);
> + if (ret)
> + return ERR_PTR(ret);
> goto done;
> }
>
> @@ -971,6 +975,11 @@ blkiocg_create(struct cgroup_subsys *sub
> blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
> if (!blkcg)
> return ERR_PTR(-ENOMEM);
> + ret = alloc_css_id(subsys, cgroup, &blkcg->css);
> + if (ret) {
> + kfree(blkcg);
> + return ERR_PTR(ret);
> + }
>
> blkcg->weight = BLKIO_WEIGHT_DEFAULT;
> done:
>
--
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