+ memset(acxt, 0, sizeof(*acxt));
+ acxt->parent_sd = parent_sd;
+
+ /* Lookup parent inode. inode initialization and I_NEW
+ * clearing are protected by sysfs_mutex. By grabbing it and
+ * looking up with _nowait variant, inode state can be
+ * determined reliably.
+ */
+ mutex_lock(&sysfs_mutex);
+
+ inode = ilookup5_nowait(sysfs_sb, parent_sd->s_ino, sysfs_ilookup_test,
+ parent_sd);
+
+ if (inode && !(inode->i_state & I_NEW)) {
+ /* parent inode available */
+ acxt->parent_inode = inode;
+
+ /* sysfs_mutex is below i_mutex in lock hierarchy.
+ * First, trylock i_mutex. If fails, unlock
+ * sysfs_mutex and lock them in order.
+ */
+ if (!mutex_trylock(&inode->i_mutex)) {
+ mutex_unlock(&sysfs_mutex);
+ mutex_lock(&inode->i_mutex);
+ mutex_lock(&sysfs_mutex);
+ }
+ } else
+ iput(inode);
+}
+
+/**
+ * sysfs_add_one - add sysfs_dirent to parent
+ * @acxt: addrm context to use
+ * @sd: sysfs_dirent to be added
+ *
+ * Get @acxt->parent_sd and set sd->s_parent to it and increment
+ * nlink of parent inode if @sd is a directory. @sd is NOT
+ * linked into the children list of the parent. The caller
+ * should invoke sysfs_link_sibling() after this function
+ * completes if @sd needs to be on the children list.
+ *
+ * This function should be called between calls to
+ * sysfs_addrm_start() and sysfs_addrm_finish() and should be
+ * passed the same @acxt as passed to sysfs_addrm_start().
+ *
+ * LOCKING:
+ * Determined by sysfs_addrm_start().
+ */
+void sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
+{
+ sd->s_parent = sysfs_get(acxt->parent_sd);
+
+ if (sysfs_type(sd) == SYSFS_DIR && acxt->parent_inode)
+ inc_nlink(acxt->parent_inode);
+
+ acxt->cnt++;
+}
+
+/**
+ * sysfs_remove_one - remove sysfs_dirent from parent
+ * @acxt: addrm context to use
+ * @sd: sysfs_dirent to be added
+ *
+ * Mark @sd removed and drop nlink of parent inode if @sd is a
+ * directory. @sd is NOT unlinked from the children list of the
+ * parent. The caller is repsonsible for removing @sd from the
+ * children list before calling this function.
+ *
+ * This function should be called between calls to
+ * sysfs_addrm_start() and sysfs_addrm_finish() and should be
+ * passed the same @acxt as passed to sysfs_addrm_start().
+ *
+ * LOCKING:
+ * Determined by sysfs_addrm_start().
+ */
+void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
+{
+ BUG_ON(sd->s_sibling || (sd->s_flags & SYSFS_FLAG_REMOVED));
+
+ sd->s_flags |= SYSFS_FLAG_REMOVED;
+ sd->s_sibling = acxt->removed;
+ acxt->removed = sd;
+
+ if (sysfs_type(sd) == SYSFS_DIR && acxt->parent_inode)
+ drop_nlink(acxt->parent_inode);
+
+ acxt->cnt++;
+}
+
+/**
+ * sysfs_addrm_finish - finish up sysfs_dirent add/remove
+ * @acxt: addrm context to finish up
+ *
+ * Finish up sysfs_dirent add/remove. Resources acquired by
+ * sysfs_addrm_start() are released and removed sysfs_dirents are
+ * cleaned up. Timestamps on the parent inode are updated.
+ *
+ * LOCKING:
+ * All mutexes acquired by sysfs_addrm_start() are released.
+ *
+ * RETURNS:
+ * Number of added/removed sysfs_dirents since sysfs_addrm_start().
+ */
+int sysfs_addrm_finish(struct sysfs_addrm_cxt *acxt)
+{
+ /* release resources acquired by sysfs_addrm_start() */
+ mutex_unlock(&sysfs_mutex);
+ if (acxt->parent_inode) {
+ struct inode *inode = acxt->parent_inode;
+
+ /* if added/removed, update timestamps on the parent */
+ if (acxt->cnt)
+ inode->i_ctime = inode->i_mtime = CURRENT_TIME;
+
+ mutex_unlock(&inode->i_mutex);
+ iput(inode);
+ }
+
+ /* kill removed sysfs_dirents */
+ while (acxt->removed) {
+ struct sysfs_dirent *sd = acxt->removed;
+
+ acxt->removed = sd->s_sibling;
+ sd->s_sibling = NULL;
+
+ sysfs_drop_dentry(sd);
+ sysfs_deactivate(sd);
+ sysfs_put(sd);