get rid of 'parent' argument of ->d_compare()

[cascardo/linux.git] / kernel / cgroup.c

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 33a2f63..9624db8 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -61,6 +61,7 @@
 #include <linux/cpuset.h>
 #include <linux/proc_ns.h>
 #include <linux/nsproxy.h>
+#include <linux/file.h>
 #include <net/sock.h>
 
 /*
@@ -6204,6 +6205,40 @@ struct cgroup *cgroup_get_from_path(const char *path)
 }
 EXPORT_SYMBOL_GPL(cgroup_get_from_path);
 
+/**
+ * cgroup_get_from_fd - get a cgroup pointer from a fd
+ * @fd: fd obtained by open(cgroup2_dir)
+ *
+ * Find the cgroup from a fd which should be obtained
+ * by opening a cgroup directory.  Returns a pointer to the
+ * cgroup on success. ERR_PTR is returned if the cgroup
+ * cannot be found.
+ */
+struct cgroup *cgroup_get_from_fd(int fd)
+{
+       struct cgroup_subsys_state *css;
+       struct cgroup *cgrp;
+       struct file *f;
+
+       f = fget_raw(fd);
+       if (!f)
+               return ERR_PTR(-EBADF);
+
+       css = css_tryget_online_from_dir(f->f_path.dentry, NULL);
+       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);
+
 /*
  * sock->sk_cgrp_data handling.  For more info, see sock_cgroup_data
  * definition in cgroup-defs.h.