fsnotify: take groups mark_lock before mark lock
Race-free addition and removal of a mark to a groups mark list would be easier if we could lock the mark list of group before we lock the specific mark. This patch changes the order used to add/remove marks to/from mark lists from 1. mark->lock 2. group->mark_lock 3. inode->i_lock to 1. group->mark_lock 2. mark->lock 3. inode->i_lock Signed-off-by: Lino Sanfilippo <LinoSanfilippo@gmx.de> Signed-off-by: Eric Paris <eparis@redhat.com>
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@ -127,20 +127,27 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
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struct inode *inode = NULL;
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struct inode *inode = NULL;
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spin_lock(&mark->lock);
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spin_lock(&mark->lock);
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/* dont get the group from a mark that is not alive yet */
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if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
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spin_unlock(&mark->lock);
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return;
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}
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fsnotify_get_group(mark->group);
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fsnotify_get_group(mark->group);
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group = mark->group;
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group = mark->group;
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spin_unlock(&mark->lock);
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spin_lock(&group->mark_lock);
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spin_lock(&mark->lock);
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/* something else already called this function on this mark */
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/* something else already called this function on this mark */
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if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
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if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {
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spin_unlock(&mark->lock);
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spin_unlock(&mark->lock);
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spin_unlock(&group->mark_lock);
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goto put_group;
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goto put_group;
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}
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}
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mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
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mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
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spin_lock(&group->mark_lock);
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if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
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if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {
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inode = mark->i.inode;
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inode = mark->i.inode;
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fsnotify_destroy_inode_mark(mark);
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fsnotify_destroy_inode_mark(mark);
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@ -151,8 +158,8 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark)
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list_del_init(&mark->g_list);
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list_del_init(&mark->g_list);
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spin_unlock(&group->mark_lock);
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spin_unlock(&mark->lock);
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spin_unlock(&mark->lock);
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spin_unlock(&group->mark_lock);
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spin_lock(&destroy_lock);
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spin_lock(&destroy_lock);
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list_add(&mark->destroy_list, &destroy_list);
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list_add(&mark->destroy_list, &destroy_list);
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@ -225,13 +232,13 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
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/*
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/*
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* LOCKING ORDER!!!!
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* LOCKING ORDER!!!!
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* mark->lock
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* group->mark_lock
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* group->mark_lock
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* mark->lock
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* inode->i_lock
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* inode->i_lock
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*/
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*/
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spin_lock(&mark->lock);
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spin_lock(&group->mark_lock);
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spin_lock(&group->mark_lock);
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spin_lock(&mark->lock);
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mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
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mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;
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fsnotify_get_group(group);
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fsnotify_get_group(group);
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@ -252,13 +259,12 @@ int fsnotify_add_mark(struct fsnotify_mark *mark,
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BUG();
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BUG();
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}
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}
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spin_unlock(&group->mark_lock);
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/* this will pin the object if appropriate */
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/* this will pin the object if appropriate */
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fsnotify_set_mark_mask_locked(mark, mark->mask);
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fsnotify_set_mark_mask_locked(mark, mark->mask);
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spin_unlock(&mark->lock);
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spin_unlock(&mark->lock);
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spin_unlock(&group->mark_lock);
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if (inode)
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if (inode)
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__fsnotify_update_child_dentry_flags(inode);
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__fsnotify_update_child_dentry_flags(inode);
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@ -270,8 +276,8 @@ err:
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mark->group = NULL;
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mark->group = NULL;
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atomic_dec(&group->num_marks);
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atomic_dec(&group->num_marks);
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spin_unlock(&group->mark_lock);
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spin_unlock(&mark->lock);
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spin_unlock(&mark->lock);
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spin_unlock(&group->mark_lock);
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spin_lock(&destroy_lock);
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spin_lock(&destroy_lock);
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list_add(&mark->destroy_list, &destroy_list);
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list_add(&mark->destroy_list, &destroy_list);
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