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@@ -43,6 +43,10 @@ DECLARE_RWSEM(configfs_rename_sem);
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* and configfs_dirent_lock locked, in that order.
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* This allows one to safely traverse configfs_dirent trees and symlinks without
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* having to lock inodes.
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+ *
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+ * Protects setting of CONFIGFS_USET_DROPPING: checking the flag
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+ * unlocked is not reliable unless in detach_groups() called from
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+ * rmdir()/unregister() and from configfs_attach_group()
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*/
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DEFINE_SPINLOCK(configfs_dirent_lock);
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@@ -91,6 +95,11 @@ static struct configfs_dirent *configfs_new_dirent(struct configfs_dirent * pare
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INIT_LIST_HEAD(&sd->s_children);
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sd->s_element = element;
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spin_lock(&configfs_dirent_lock);
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+ if (parent_sd->s_type & CONFIGFS_USET_DROPPING) {
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+ spin_unlock(&configfs_dirent_lock);
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+ kmem_cache_free(configfs_dir_cachep, sd);
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+ return ERR_PTR(-ENOENT);
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+ }
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list_add(&sd->s_sibling, &parent_sd->s_children);
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spin_unlock(&configfs_dirent_lock);
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@@ -349,11 +358,11 @@ static struct dentry * configfs_lookup(struct inode *dir,
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/*
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* Only subdirectories count here. Files (CONFIGFS_NOT_PINNED) are
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- * attributes and are removed by rmdir(). We recurse, taking i_mutex
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- * on all children that are candidates for default detach. If the
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- * result is clean, then configfs_detach_group() will handle dropping
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- * i_mutex. If there is an error, the caller will clean up the i_mutex
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- * holders via configfs_detach_rollback().
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+ * attributes and are removed by rmdir(). We recurse, setting
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+ * CONFIGFS_USET_DROPPING on all children that are candidates for
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+ * default detach.
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+ * If there is an error, the caller will reset the flags via
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+ * configfs_detach_rollback().
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*/
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static int configfs_detach_prep(struct dentry *dentry)
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{
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@@ -370,8 +379,7 @@ static int configfs_detach_prep(struct dentry *dentry)
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if (sd->s_type & CONFIGFS_NOT_PINNED)
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continue;
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if (sd->s_type & CONFIGFS_USET_DEFAULT) {
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- mutex_lock(&sd->s_dentry->d_inode->i_mutex);
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- /* Mark that we've taken i_mutex */
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+ /* Mark that we're trying to drop the group */
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sd->s_type |= CONFIGFS_USET_DROPPING;
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/*
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@@ -392,7 +400,7 @@ out:
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}
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/*
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- * Walk the tree, dropping i_mutex wherever CONFIGFS_USET_DROPPING is
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+ * Walk the tree, resetting CONFIGFS_USET_DROPPING wherever it was
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* set.
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*/
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static void configfs_detach_rollback(struct dentry *dentry)
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@@ -403,11 +411,7 @@ static void configfs_detach_rollback(struct dentry *dentry)
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list_for_each_entry(sd, &parent_sd->s_children, s_sibling) {
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if (sd->s_type & CONFIGFS_USET_DEFAULT) {
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configfs_detach_rollback(sd->s_dentry);
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-
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- if (sd->s_type & CONFIGFS_USET_DROPPING) {
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- sd->s_type &= ~CONFIGFS_USET_DROPPING;
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- mutex_unlock(&sd->s_dentry->d_inode->i_mutex);
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- }
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+ sd->s_type &= ~CONFIGFS_USET_DROPPING;
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}
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}
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}
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@@ -486,16 +490,12 @@ static void detach_groups(struct config_group *group)
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child = sd->s_dentry;
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+ mutex_lock(&child->d_inode->i_mutex);
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+
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configfs_detach_group(sd->s_element);
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child->d_inode->i_flags |= S_DEAD;
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- /*
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- * From rmdir/unregister, a configfs_detach_prep() pass
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- * has taken our i_mutex for us. Drop it.
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- * From mkdir/register cleanup, there is no sem held.
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- */
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- if (sd->s_type & CONFIGFS_USET_DROPPING)
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- mutex_unlock(&child->d_inode->i_mutex);
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+ mutex_unlock(&child->d_inode->i_mutex);
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d_delete(child);
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dput(child);
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@@ -1181,12 +1181,15 @@ static int configfs_rmdir(struct inode *dir, struct dentry *dentry)
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return -EINVAL;
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}
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+ spin_lock(&configfs_dirent_lock);
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ret = configfs_detach_prep(dentry);
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if (ret) {
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configfs_detach_rollback(dentry);
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+ spin_unlock(&configfs_dirent_lock);
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config_item_put(parent_item);
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return ret;
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}
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+ spin_unlock(&configfs_dirent_lock);
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/* Get a working ref for the duration of this function */
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item = configfs_get_config_item(dentry);
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@@ -1476,9 +1479,11 @@ void configfs_unregister_subsystem(struct configfs_subsystem *subsys)
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mutex_lock_nested(&configfs_sb->s_root->d_inode->i_mutex,
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I_MUTEX_PARENT);
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mutex_lock_nested(&dentry->d_inode->i_mutex, I_MUTEX_CHILD);
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+ spin_lock(&configfs_dirent_lock);
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if (configfs_detach_prep(dentry)) {
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printk(KERN_ERR "configfs: Tried to unregister non-empty subsystem!\n");
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}
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+ spin_unlock(&configfs_dirent_lock);
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configfs_detach_group(&group->cg_item);
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dentry->d_inode->i_flags |= S_DEAD;
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mutex_unlock(&dentry->d_inode->i_mutex);
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