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sysfs: reimplement symlink using sysfs_dirent tree

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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>
This commit is contained in:
Tejun Heo
2007-06-14 03:45:15 +09:00
committed by Greg Kroah-Hartman
parent aecdcedaab
commit 2b29ac252a
3 changed files with 53 additions and 46 deletions
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9
fs/sysfs/sysfs.h
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@@ -3,7 +3,7 @@ struct sysfs_elem_dir {
};
struct sysfs_elem_symlink {
struct kobject * target_kobj;
struct sysfs_dirent * target_sd;
};
struct sysfs_elem_attr {
@@ -100,10 +100,11 @@ static inline struct kobject *sysfs_get_kobject(struct dentry *dentry)
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);