cgroup: rename cgroup_css_from_dir() to css_from_dir() and update its syntax
cgroup_css_from_dir() will grow another user. In preparation, make
the following changes.
* All css functions are prefixed with just "css_", rename it to
css_from_dir().
* Take dentry * instead of file * as dentry is what ultimately
identifies a cgroup and file may not always be available. Note that
the function now checkes whether @dentry->d_inode is NULL as the
caller now may specify a negative dentry.
* Make it take cgroup_subsys * instead of integer subsys_id. This
simplifies the function and allows specifying no subsystem for
cgroup->dummy_css.
* Make return section a bit less verbose.
This patch doesn't introduce any behavior changes.
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Li Zefan <lizefan@huawei.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@redhat.com>
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index ef43e3f..921b138 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -5700,34 +5700,28 @@
EXPORT_SYMBOL_GPL(css_lookup);
/**
- * cgroup_css_from_dir - get corresponding css from file open on cgroup dir
- * @f: directory file of interest
- * @id: subsystem id of interest
+ * css_from_dir - get corresponding css from the dentry of a cgroup dir
+ * @dentry: directory dentry of interest
+ * @ss: subsystem of interest
*
* Must be called under RCU read lock. The caller is responsible for
* pinning the returned css if it needs to be accessed outside the RCU
* critical section.
*/
-struct cgroup_subsys_state *cgroup_css_from_dir(struct file *f, int id)
+struct cgroup_subsys_state *css_from_dir(struct dentry *dentry,
+ struct cgroup_subsys *ss)
{
struct cgroup *cgrp;
- struct inode *inode;
- struct cgroup_subsys_state *css;
WARN_ON_ONCE(!rcu_read_lock_held());
- inode = file_inode(f);
- /* check in cgroup filesystem dir */
- if (inode->i_op != &cgroup_dir_inode_operations)
+ /* is @dentry a cgroup dir? */
+ if (!dentry->d_inode ||
+ dentry->d_inode->i_op != &cgroup_dir_inode_operations)
return ERR_PTR(-EBADF);
- if (id < 0 || id >= CGROUP_SUBSYS_COUNT)
- return ERR_PTR(-EINVAL);
-
- /* get cgroup */
- cgrp = __d_cgrp(f->f_dentry);
- css = cgroup_css(cgrp, id);
- return css ? css : ERR_PTR(-ENOENT);
+ cgrp = __d_cgrp(dentry);
+ return cgroup_css(cgrp, ss->subsys_id) ?: ERR_PTR(-ENOENT);
}
/**