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From: Christian Brauner <christian.brauner@ubuntu.com>
To: linux-api@vger.kernel.org, linux-kernel@vger.kernel.org,
	Tejun Heo <tj@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>,
	Christian Brauner <christian.brauner@ubuntu.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Li Zefan <lizefan@huawei.com>,
	cgroups@vger.kernel.org
Subject: [PATCH v3 2/5] cgroup: add cgroup_get_from_file() helper
Date: Fri, 17 Jan 2020 01:21:40 +0100	[thread overview]
Message-ID: <20200117002143.15559-3-christian.brauner@ubuntu.com> (raw)
In-Reply-To: <20200117002143.15559-1-christian.brauner@ubuntu.com>

Add a helper cgroup_get_from_file(). The helper will be used in
subsequent patches to retrieve a cgroup while holding a reference to the
struct file it was taken from.

Cc: Tejun Heo <tj@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Li Zefan <lizefan@huawei.com>
Cc: cgroups@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
---
/* v1 */
patch not present

/* v2 */
patch not present

/* v3 */
patch introduced
- Tejun Heo <tj@kernel.org>:
  - split cgroup_get_from_file() changes into separate commmit
---
 kernel/cgroup/cgroup.c | 30 +++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 11 deletions(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index ad1f9fea5c14..f05efc2677c8 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -5882,6 +5882,24 @@ void cgroup_fork(struct task_struct *child)
 	INIT_LIST_HEAD(&child->cg_list);
 }
 
+static struct cgroup *cgroup_get_from_file(struct file *f)
+{
+	struct cgroup_subsys_state *css;
+	struct cgroup *cgrp;
+
+	css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
+	if (IS_ERR(css))
+		return ERR_CAST(css);
+
+	cgrp = css->cgroup;
+	if (!cgroup_on_dfl(cgrp)) {
+		cgroup_put(cgrp);
+		return ERR_PTR(-EBADF);
+	}
+
+	return cgrp;
+}
+
 /**
  * cgroup_can_fork - called on a new task before the process is exposed
  * @child: the task in question.
@@ -6170,7 +6188,6 @@ EXPORT_SYMBOL_GPL(cgroup_get_from_path);
  */
 struct cgroup *cgroup_get_from_fd(int fd)
 {
-	struct cgroup_subsys_state *css;
 	struct cgroup *cgrp;
 	struct file *f;
 
@@ -6178,17 +6195,8 @@ struct cgroup *cgroup_get_from_fd(int fd)
 	if (!f)
 		return ERR_PTR(-EBADF);
 
-	css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
+	cgrp = cgroup_get_from_file(f);
 	fput(f);
-	if (IS_ERR(css))
-		return ERR_CAST(css);
-
-	cgrp = css->cgroup;
-	if (!cgroup_on_dfl(cgrp)) {
-		cgroup_put(cgrp);
-		return ERR_PTR(-EBADF);
-	}
-
 	return cgrp;
 }
 EXPORT_SYMBOL_GPL(cgroup_get_from_fd);
-- 
2.25.0


  parent reply	other threads:[~2020-01-17  0:21 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-17  0:21 [PATCH v3 0/5] clone3 & cgroups: allow spawning processes into cgroups Christian Brauner
2020-01-17  0:21 ` [PATCH v3 1/5] cgroup: unify attach permission checking Christian Brauner
2020-01-17  0:21 ` Christian Brauner [this message]
2020-01-17  0:21 ` [PATCH v3 3/5] cgroup: refactor fork helpers Christian Brauner
2020-01-17  0:21 ` [PATCH v3 4/5] clone3: allow spawning processes into cgroups Christian Brauner
2020-01-17  0:21 ` [PATCH v3 5/5] selftests/cgroup: add tests for cloning " Christian Brauner
2020-01-17 16:54 ` [PATCH v3 0/5] clone3 & cgroups: allow spawning processes " Tejun Heo

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