sysfs: make directory dentries and inodes reclaimable

This patch makes dentries and inodes for sysfs directories
reclaimable.

* sysfs_notify() is modified to walk sysfs_dirent tree instead of
  dentry tree.

* sysfs_update_file() and sysfs_chmod_file() use sysfs_get_dentry() to
  grab the victim dentry.

* sysfs_rename_dir() and sysfs_move_dir() grab all dentries using
  sysfs_get_dentry() on startup.

* Dentries for all shadowed directories are pinned in memory to serve
  as lookup start point.

Signed-off-by: Tejun Heo <htejun@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 59 insertions, 75 deletions

diff --git a/fs/sysfs/file.c b/fs/sysfs/file.c
index 69bacf1db596..cc497994b2a8 100644
--- a/fs/sysfs/file.c
+++ b/fs/sysfs/file.c
@@ -362,43 +362,22 @@ static unsigned int sysfs_poll(struct file *filp, poll_table *wait)
         return POLLERR|POLLPRI;
 }
 
-
-static struct dentry *step_down(struct dentry *dir, const char * name)
+void sysfs_notify(struct kobject *k, char *dir, char *attr)
 {
-        struct dentry * de;
-
-        if (dir == NULL || dir->d_inode == NULL)
-                return NULL;
-
-        mutex_lock(&dir->d_inode->i_mutex);
-        de = lookup_one_len(name, dir, strlen(name));
-        mutex_unlock(&dir->d_inode->i_mutex);
-        dput(dir);
-        if (IS_ERR(de))
-                return NULL;
-        if (de->d_inode == NULL) {
-                dput(de);
-                return NULL;
-        }
-        return de;
-}
+        struct sysfs_dirent *sd = k->sd;
 
-void sysfs_notify(struct kobject * k, char *dir, char *attr)
-{
-        struct dentry *de = k->sd->s_dentry;
-        if (de)
-                dget(de);
-        if (de && dir)
-                de = step_down(de, dir);
-        if (de && attr)
-                de = step_down(de, attr);
-        if (de) {
-                struct sysfs_dirent * sd = de->d_fsdata;
-                if (sd)
-                        atomic_inc(&sd->s_event);
+        mutex_lock(&sysfs_mutex);
+
+        if (sd && dir)
+                sd = sysfs_find_dirent(sd, dir);
+        if (sd && attr)
+                sd = sysfs_find_dirent(sd, attr);
+        if (sd) {
+                atomic_inc(&sd->s_event);
                 wake_up_interruptible(&k->poll);
-                dput(de);
         }
+
+        mutex_unlock(&sysfs_mutex);
 }
 EXPORT_SYMBOL_GPL(sysfs_notify);
 
@@ -485,30 +464,31 @@ EXPORT_SYMBOL_GPL(sysfs_add_file_to_group);
  */
 int sysfs_update_file(struct kobject * kobj, const struct attribute * attr)
 {
-        struct dentry *dir = kobj->sd->s_dentry;
-        struct dentry * victim;
-        int res = -ENOENT;
-
-        mutex_lock(&dir->d_inode->i_mutex);
-        victim = lookup_one_len(attr->name, dir, strlen(attr->name));
-        if (!IS_ERR(victim)) {
-                /* make sure dentry is really there */
-                if (victim->d_inode && 
-                    (victim->d_parent->d_inode == dir->d_inode)) {
-                        victim->d_inode->i_mtime = CURRENT_TIME;
-                        fsnotify_modify(victim);
-                        res = 0;
-                } else
-                        d_drop(victim);
-                
-                /**
-                 * Drop the reference acquired from lookup_one_len() above.
-                 */
-                dput(victim);
+        struct sysfs_dirent *victim_sd = NULL;
+        struct dentry *victim = NULL;
+        int rc;
+
+        rc = -ENOENT;
+        victim_sd = sysfs_get_dirent(kobj->sd, attr->name);
+        if (!victim_sd)
+                goto out;
+
+        victim = sysfs_get_dentry(victim_sd);
+        if (IS_ERR(victim)) {
+                rc = PTR_ERR(victim);
+                victim = NULL;
+                goto out;
         }
-        mutex_unlock(&dir->d_inode->i_mutex);
 
-        return res;
+        mutex_lock(&victim->d_inode->i_mutex);
+        victim->d_inode->i_mtime = CURRENT_TIME;
+        fsnotify_modify(victim);
+        mutex_unlock(&victim->d_inode->i_mutex);
+        rc = 0;
+ out:
+        dput(victim);
+        sysfs_put(victim_sd);
+        return rc;
 }
 
 
@@ -521,30 +501,34 @@ int sysfs_update_file(struct kobject * kobj, const struct attribute * attr)
  */
 int sysfs_chmod_file(struct kobject *kobj, struct attribute *attr, mode_t mode)
 {
-        struct dentry *dir = kobj->sd->s_dentry;
-        struct dentry *victim;
+        struct sysfs_dirent *victim_sd = NULL;
+        struct dentry *victim = NULL;
         struct inode * inode;
         struct iattr newattrs;
-        int res = -ENOENT;
-
-        mutex_lock(&dir->d_inode->i_mutex);
-        victim = lookup_one_len(attr->name, dir, strlen(attr->name));
-        if (!IS_ERR(victim)) {
-                if (victim->d_inode &&
-                    (victim->d_parent->d_inode == dir->d_inode)) {
-                        inode = victim->d_inode;
-                        mutex_lock(&inode->i_mutex);
-                        newattrs.ia_mode = (mode & S_IALLUGO) |
-                                                (inode->i_mode & ~S_IALLUGO);
-                        newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
-                        res = notify_change(victim, &newattrs);
-                        mutex_unlock(&inode->i_mutex);
-                }
-                dput(victim);
+        int rc;
+
+        rc = -ENOENT;
+        victim_sd = sysfs_get_dirent(kobj->sd, attr->name);
+        if (!victim_sd)
+                goto out;
+
+        victim = sysfs_get_dentry(victim_sd);
+        if (IS_ERR(victim)) {
+                rc = PTR_ERR(victim);
+                victim = NULL;
+                goto out;
         }
-        mutex_unlock(&dir->d_inode->i_mutex);
 
-        return res;
+        inode = victim->d_inode;
+        mutex_lock(&inode->i_mutex);
+        newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
+        newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
+        rc = notify_change(victim, &newattrs);
+        mutex_unlock(&inode->i_mutex);
+ out:
+        dput(victim);
+        sysfs_put(victim_sd);
+        return rc;
 }
 EXPORT_SYMBOL_GPL(sysfs_chmod_file);