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-rw-r--r--fs/sysfs/dir.c98
1 files changed, 98 insertions, 0 deletions
diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
index c6f3b697064..98721129610 100644
--- a/fs/sysfs/dir.c
+++ b/fs/sysfs/dir.c
@@ -63,6 +63,104 @@ void sysfs_unlink_sibling(struct sysfs_dirent *sd)
}
/**
+ * sysfs_get_dentry - get dentry for the given sysfs_dirent
+ * @sd: sysfs_dirent of interest
+ *
+ * Get dentry for @sd. Dentry is looked up if currently not
+ * present. This function climbs sysfs_dirent tree till it
+ * reaches a sysfs_dirent with valid dentry attached and descends
+ * down from there looking up dentry for each step.
+ *
+ * LOCKING:
+ * Kernel thread context (may sleep)
+ *
+ * RETURNS:
+ * Pointer to found dentry on success, ERR_PTR() value on error.
+ */
+struct dentry *sysfs_get_dentry(struct sysfs_dirent *sd)
+{
+ struct sysfs_dirent *cur;
+ struct dentry *parent_dentry, *dentry;
+ int i, depth;
+
+ /* Find the first parent which has valid s_dentry and get the
+ * dentry.
+ */
+ mutex_lock(&sysfs_mutex);
+ restart0:
+ spin_lock(&sysfs_assoc_lock);
+ restart1:
+ spin_lock(&dcache_lock);
+
+ dentry = NULL;
+ depth = 0;
+ cur = sd;
+ while (!cur->s_dentry || !cur->s_dentry->d_inode) {
+ if (cur->s_flags & SYSFS_FLAG_REMOVED) {
+ dentry = ERR_PTR(-ENOENT);
+ depth = 0;
+ break;
+ }
+ cur = cur->s_parent;
+ depth++;
+ }
+ if (!IS_ERR(dentry))
+ dentry = dget_locked(cur->s_dentry);
+
+ spin_unlock(&dcache_lock);
+ spin_unlock(&sysfs_assoc_lock);
+
+ /* from the found dentry, look up depth times */
+ while (depth--) {
+ /* find and get depth'th ancestor */
+ for (cur = sd, i = 0; cur && i < depth; i++)
+ cur = cur->s_parent;
+
+ /* This can happen if tree structure was modified due
+ * to move/rename. Restart.
+ */
+ if (i != depth) {
+ dput(dentry);
+ goto restart0;
+ }
+
+ sysfs_get(cur);
+
+ mutex_unlock(&sysfs_mutex);
+
+ /* look it up */
+ parent_dentry = dentry;
+ dentry = lookup_one_len_kern(cur->s_name, parent_dentry,
+ strlen(cur->s_name));
+ dput(parent_dentry);
+
+ if (IS_ERR(dentry)) {
+ sysfs_put(cur);
+ return dentry;
+ }
+
+ mutex_lock(&sysfs_mutex);
+ spin_lock(&sysfs_assoc_lock);
+
+ /* This, again, can happen if tree structure has
+ * changed and we looked up the wrong thing. Restart.
+ */
+ if (cur->s_dentry != dentry) {
+ dput(dentry);
+ sysfs_put(cur);
+ goto restart1;
+ }
+
+ spin_unlock(&sysfs_assoc_lock);
+
+ sysfs_put(cur);
+ }
+
+ mutex_unlock(&sysfs_mutex);
+ return dentry;
+}
+
+/**
* sysfs_get_active - get an active reference to sysfs_dirent
* @sd: sysfs_dirent to get an active reference to
*