From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail202.messagelabs.com (mail202.messagelabs.com [216.82.254.227]) by kanga.kvack.org (Postfix) with ESMTP id 8044A6B005A for ; Thu, 24 Sep 2009 19:51:06 -0400 (EDT) Date: Fri, 25 Sep 2009 08:39:54 +0900 From: Daisuke Nishimura Subject: Re: [RFC][PATCH 1/8] cgroup: introduce cancel_attach() Message-Id: <20090925083954.90baa2b0.nishimura@mxp.nes.nec.co.jp> In-Reply-To: <20090924153309.ed78007f.kamezawa.hiroyu@jp.fujitsu.com> 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> <20090924153309.ed78007f.kamezawa.hiroyu@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: KAMEZAWA Hiroyuki Cc: nishimura@mxp.nes.nec.co.jp, linux-mm , Balbir Singh , Paul Menage , Li Zefan List-ID: On Thu, 24 Sep 2009 15:33:09 +0900, KAMEZAWA Hiroyuki wrote: > 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. > == > O.K. will add in next post. > > 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. > Indeed.. these part are different now. My patches are based on mmotm-2009-09-14-01-57, I'm sorry for cunfusing you. Thanks, Daisuke Nishimura. > > > > 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. 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