From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Serge E. Hallyn" Subject: Re: [PATCH 3/8] cgroup: implement cgroup_get_from_path() and expose cgroup_put() Date: Mon, 21 Dec 2015 18:22:41 -0600 Message-ID: <20151222002240.GA6682@mail.hallyn.com> References: <1449527935-27056-1-git-send-email-tj@kernel.org> <1449527935-27056-4-git-send-email-tj@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: davem-fT/PcQaiUtIeIZ0/mPfg9Q@public.gmane.org, pablo-Cap9r6Oaw4JrovVCs/uTlw@public.gmane.org, kaber-dcUjhNyLwpNeoWH0uzbU5w@public.gmane.org, kadlec-K40Dz/62t/MgiyqX0sVFJYdd74u8MsAO@public.gmane.org, daniel-FeC+5ew28dpmcu3hnIyYJQ@public.gmane.org, daniel.wagner-98C5kh4wR6ohFhg+JK9F0w@public.gmane.org, nhorman-2XuSBdqkA4R54TAoqtyWWQ@public.gmane.org, lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org, netdev-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, netfilter-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, coreteam-Cap9r6Oaw4JrovVCs/uTlw@public.gmane.org, cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, kernel-team-b10kYP2dOMg@public.gmane.org, ninasc-b10kYP2dOMg@public.gmane.org To: Tejun Heo Return-path: Content-Disposition: inline In-Reply-To: <1449527935-27056-4-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org> Sender: cgroups-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: netdev.vger.kernel.org On Mon, Dec 07, 2015 at 05:38:50PM -0500, Tejun Heo wrote: > Implement cgroup_get_from_path() using kernfs_walk_and_get() which > obtains a default hierarchy cgroup from its path. This will be used > to allow cgroup path based matching from outside cgroup proper - > e.g. networking and perf. Hi Tejun, I'm trying to figure out how to handle this in the cgroup ns patchset. Is this going to be purely used internally? From the user i see in this patchset it looks like I should leave it be (and have @path always be absolute) Is that right? thanks, -serge > v2: Add EXPORT_SYMBOL_GPL(cgroup_get_from_path). > > Signed-off-by: Tejun Heo > --- > include/linux/cgroup.h | 7 +++++++ > kernel/cgroup.c | 39 ++++++++++++++++++++++++++++++++++----- > 2 files changed, 41 insertions(+), 5 deletions(-) > > diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h > index b5ee2c4..4c3ffab 100644 > --- a/include/linux/cgroup.h > +++ b/include/linux/cgroup.h > @@ -81,6 +81,8 @@ struct cgroup_subsys_state *cgroup_get_e_css(struct cgroup *cgroup, > struct cgroup_subsys_state *css_tryget_online_from_dir(struct dentry *dentry, > struct cgroup_subsys *ss); > > +struct cgroup *cgroup_get_from_path(const char *path); > + > int cgroup_attach_task_all(struct task_struct *from, struct task_struct *); > int cgroup_transfer_tasks(struct cgroup *to, struct cgroup *from); > > @@ -351,6 +353,11 @@ static inline void css_put_many(struct cgroup_subsys_state *css, unsigned int n) > percpu_ref_put_many(&css->refcnt, n); > } > > +static inline void cgroup_put(struct cgroup *cgrp) > +{ > + css_put(&cgrp->self); > +} > + > /** > * task_css_set_check - obtain a task's css_set with extra access conditions > * @task: the task to obtain css_set for > diff --git a/kernel/cgroup.c b/kernel/cgroup.c > index 3190040..3db5e8f 100644 > --- a/kernel/cgroup.c > +++ b/kernel/cgroup.c > @@ -434,11 +434,6 @@ static bool cgroup_tryget(struct cgroup *cgrp) > return css_tryget(&cgrp->self); > } > > -static void cgroup_put(struct cgroup *cgrp) > -{ > - css_put(&cgrp->self); > -} > - > struct cgroup_subsys_state *of_css(struct kernfs_open_file *of) > { > struct cgroup *cgrp = of->kn->parent->priv; > @@ -5753,6 +5748,40 @@ struct cgroup_subsys_state *css_from_id(int id, struct cgroup_subsys *ss) > return id > 0 ? idr_find(&ss->css_idr, id) : NULL; > } > > +/** > + * cgroup_get_from_path - lookup and get a cgroup from its default hierarchy path > + * @path: path on the default hierarchy > + * > + * Find the cgroup at @path on the default hierarchy, increment its > + * reference count and return it. Returns pointer to the found cgroup on > + * success, ERR_PTR(-ENOENT) if @path doens't exist and ERR_PTR(-ENOTDIR) > + * if @path points to a non-directory. > + */ > +struct cgroup *cgroup_get_from_path(const char *path) > +{ > + struct kernfs_node *kn; > + struct cgroup *cgrp; > + > + mutex_lock(&cgroup_mutex); > + > + kn = kernfs_walk_and_get(cgrp_dfl_root.cgrp.kn, path); > + if (kn) { > + if (kernfs_type(kn) == KERNFS_DIR) { > + cgrp = kn->priv; > + cgroup_get(cgrp); > + } else { > + cgrp = ERR_PTR(-ENOTDIR); > + } > + kernfs_put(kn); > + } else { > + cgrp = ERR_PTR(-ENOENT); > + } > + > + mutex_unlock(&cgroup_mutex); > + return cgrp; > +} > +EXPORT_SYMBOL_GPL(cgroup_get_from_path); > + > #ifdef CONFIG_CGROUP_DEBUG > static struct cgroup_subsys_state * > debug_css_alloc(struct cgroup_subsys_state *parent_css) > -- > 2.5.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/