sysfs: reimplement symlink using sysfs_dirent tree
sysfs symlink is implemented by referencing dentry and kobject from
sysfs_dirent - symlink entry references kobject, dentry is used to
walk the tree. This complicates object lifetimes rules and is
dangerous - for example, there is no way to tell to which module the
target of a symlink belongs and referencing that kobject can make it
linger after the module is gone.
This patch reimplements symlink using only sysfs_dirent tree. sd for
a symlink points and holds reference to the target sysfs_dirent and
all walking is done using sysfs_dirent tree. Simpler and safer.
Please read the following message for more info.
http://article.gmane.org/gmane.linux.kernel/510293
Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
index 718e2e1..6071766 100644
--- a/fs/sysfs/sysfs.h
+++ b/fs/sysfs/sysfs.h
@@ -3,7 +3,7 @@
};
struct sysfs_elem_symlink {
- struct kobject * target_kobj;
+ struct sysfs_dirent * target_sd;
};
struct sysfs_elem_attr {
@@ -100,10 +100,11 @@
spin_lock(&dcache_lock);
if (!d_unhashed(dentry)) {
struct sysfs_dirent * sd = dentry->d_fsdata;
+
if (sd->s_type & SYSFS_KOBJ_LINK)
- kobj = kobject_get(sd->s_elem.symlink.target_kobj);
- else
- kobj = kobject_get(sd->s_elem.dir.kobj);
+ sd = sd->s_elem.symlink.target_sd;
+
+ kobj = kobject_get(sd->s_elem.dir.kobj);
}
spin_unlock(&dcache_lock);