From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail172.messagelabs.com (mail172.messagelabs.com [216.82.254.3]) by kanga.kvack.org (Postfix) with SMTP id 86C7F6B004D for ; Thu, 24 Sep 2009 02:35:18 -0400 (EDT) Received: from m3.gw.fujitsu.co.jp ([10.0.50.73]) by fgwmail6.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id n8O6ZHgd008385 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Thu, 24 Sep 2009 15:35:17 +0900 Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 821AB45DE4D for ; Thu, 24 Sep 2009 15:35:17 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id 645B145DE50 for ; Thu, 24 Sep 2009 15:35:17 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 46C99E38003 for ; Thu, 24 Sep 2009 15:35:17 +0900 (JST) Received: from ml13.s.css.fujitsu.com (ml13.s.css.fujitsu.com [10.249.87.103]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id EF51FE08002 for ; Thu, 24 Sep 2009 15:35:16 +0900 (JST) Date: Thu, 24 Sep 2009 15:33:09 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFC][PATCH 1/8] cgroup: introduce cancel_attach() Message-Id: <20090924153309.ed78007f.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090924144327.a3d09d36.nishimura@mxp.nes.nec.co.jp> References: <20090917112304.6cd4e6f6.nishimura@mxp.nes.nec.co.jp> <20090917160103.1bcdddee.nishimura@mxp.nes.nec.co.jp> <20090924144214.508469d1.nishimura@mxp.nes.nec.co.jp> <20090924144327.a3d09d36.nishimura@mxp.nes.nec.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Daisuke Nishimura Cc: linux-mm , Balbir Singh , Paul Menage , Li Zefan List-ID: On Thu, 24 Sep 2009 14:43:27 +0900 Daisuke Nishimura wrote: > This patch adds cancel_attach() operation to struct cgroup_subsys. > cancel_attach() can be used when can_attach() operation prepares something > for the subsys, but we should discard what can_attach() operation has prepared > if attach task/proc fails afterwards. > > Signed-off-by: Daisuke Nishimura > --- > Documentation/cgroups/cgroups.txt | 12 ++++++++++++ > include/linux/cgroup.h | 2 ++ > kernel/cgroup.c | 36 ++++++++++++++++++++++++++++-------- > 3 files changed, 42 insertions(+), 8 deletions(-) > > diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt > index 3df4b9a..07bb678 100644 > --- a/Documentation/cgroups/cgroups.txt > +++ b/Documentation/cgroups/cgroups.txt > @@ -544,6 +544,18 @@ remain valid while the caller holds cgroup_mutex. If threadgroup is > true, then a successful result indicates that all threads in the given > thread's threadgroup can be moved together. > > +void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp, > + struct task_struct *task, bool threadgroup) > +(cgroup_mutex held by caller) > + > +Called when a task attach operation has failed after can_attach() has succeeded. > +For example, this will be called if some subsystems are mounted on the same > +hierarchy, can_attach() operations have succeeded about part of the subsystems, > +but has failed about next subsystem. This will be called only about subsystems > +whose can_attach() operation has succeeded. This may be useful for subsystems > +which prepare something in can_attach() operation but should discard what has > +been prepared on failure. > + Hmm..I'd like to add a text like this .. == +A subsystem whose can_attach() has some side-effects should provide this function. +Then, the subsytem can implement a rollback. If not, not necessary. == > void attach(struct cgroup_subsys *ss, struct cgroup *cgrp, > struct cgroup *old_cgrp, struct task_struct *task, > bool threadgroup) > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > index 642a47f..a08edbc 100644 > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -429,6 +429,8 @@ struct cgroup_subsys { > void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp); > int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp, > struct task_struct *tsk, bool threadgroup); > + void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp, > + struct task_struct *tsk, bool threadgroup); > void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp, > struct cgroup *old_cgrp, struct task_struct *tsk, > bool threadgroup); > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > index 7da6004..2d9a808 100644 > --- a/kernel/cgroup.c > +++ b/kernel/cgroup.c > @@ -1700,7 +1700,7 @@ void threadgroup_fork_unlock(struct sighand_struct *sighand) > int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) > { > int retval; > - struct cgroup_subsys *ss; > + struct cgroup_subsys *ss, *fail = NULL; > struct cgroup *oldcgrp; > struct cgroupfs_root *root = cgrp->root; > > @@ -1712,14 +1712,16 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) > for_each_subsys(root, ss) { > if (ss->can_attach) { > retval = ss->can_attach(ss, cgrp, tsk, false); > - if (retval) > - return retval; > + if (retval) { > + fail = ss; > + goto out; > + } > } > } > > retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, 0); > if (retval) > - return retval; > + goto out; > Hmm...maybe we don't have this code in the latest tree. Ah...ok, this is from cgroups-add-ability-to-move-all-threads-in-a-process-to-a-new-cgroup-atomically .patch which is now hidden. > for_each_subsys(root, ss) { > if (ss->attach) > @@ -1733,7 +1735,15 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) > * is no longer empty. > */ > cgroup_wakeup_rmdir_waiter(cgrp); > - return 0; > +out: > + if (retval) > + for_each_subsys(root, ss) { > + if (ss == fail) > + break; > + if (ss->cancel_attach) > + ss->cancel_attach(ss, cgrp, tsk, false); > + } > + return retval; > } > > /* > @@ -1813,7 +1823,7 @@ static int css_set_prefetch(struct cgroup *cgrp, struct css_set *cg, > int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) > { > int retval; > - struct cgroup_subsys *ss; > + struct cgroup_subsys *ss, *fail = NULL; > struct cgroup *oldcgrp; > struct css_set *oldcg; > struct cgroupfs_root *root = cgrp->root; > @@ -1839,8 +1849,10 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) > for_each_subsys(root, ss) { > if (ss->can_attach) { > retval = ss->can_attach(ss, cgrp, leader, true); > - if (retval) > - return retval; > + if (retval) { > + fail = ss; > + goto out; > + } > } > } > > @@ -1978,6 +1990,14 @@ list_teardown: > put_css_set(cg_entry->cg); > kfree(cg_entry); > } > +out: > + if (retval) > + for_each_subsys(root, ss) { > + if (ss == fail) > + break; > + if (ss->cancel_attach) > + ss->cancel_attach(ss, cgrp, tsk, true); > + } > /* done! */ > return retval; > } No objections from me. just wait for comments from Paul or Li. I wonder if we add cancel_attach(), can_attach() should be renamed to prepare_attach() or some. ;) Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org