Commit 104d06f0 authored by Lino Sanfilippo's avatar Lino Sanfilippo Committed by Eric Paris
Browse files

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: default avatarLino Sanfilippo <LinoSanfilippo@gmx.de>
Signed-off-by: default avatarEric Paris <eparis@redhat.com>
parent 23e964c2

fs/notify/mark.c

+16 −10
Original line number Diff line number Diff line
@@ -127,20 +127,27 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark) 
	struct inode *inode = NULL;



	spin_lock(&mark->lock);



	/* dont get the group from a mark that is not alive yet */

	if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {

		spin_unlock(&mark->lock);

		return;

	}

	fsnotify_get_group(mark->group);

	group = mark->group;

	spin_unlock(&mark->lock);



	spin_lock(&group->mark_lock);

	spin_lock(&mark->lock);



	/* something else already called this function on this mark */

	if (!(mark->flags & FSNOTIFY_MARK_FLAG_ALIVE)) {

		spin_unlock(&mark->lock);

		spin_unlock(&group->mark_lock);

		goto put_group;

	}



	mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;



	spin_lock(&group->mark_lock);



	if (mark->flags & FSNOTIFY_MARK_FLAG_INODE) {

		inode = mark->i.inode;

		fsnotify_destroy_inode_mark(mark);
@@ -151,8 +158,8 @@ void fsnotify_destroy_mark(struct fsnotify_mark *mark) 


	list_del_init(&mark->g_list);



	spin_unlock(&group->mark_lock);

	spin_unlock(&mark->lock);

	spin_unlock(&group->mark_lock);



	spin_lock(&destroy_lock);

	list_add(&mark->destroy_list, &destroy_list);
@@ -225,13 +232,13 @@ int fsnotify_add_mark(struct fsnotify_mark *mark, 


	/*

	 * LOCKING ORDER!!!!

	 * mark->lock

	 * group->mark_lock

	 * mark->lock

	 * inode->i_lock

	 */

	spin_lock(&mark->lock);

	spin_lock(&group->mark_lock);



	spin_lock(&mark->lock);

	mark->flags |= FSNOTIFY_MARK_FLAG_ALIVE;



	fsnotify_get_group(group);
@@ -252,13 +259,12 @@ int fsnotify_add_mark(struct fsnotify_mark *mark, 
		BUG();

	}



	spin_unlock(&group->mark_lock);



	/* this will pin the object if appropriate */

	fsnotify_set_mark_mask_locked(mark, mark->mask);



	spin_unlock(&mark->lock);



	spin_unlock(&group->mark_lock);



	if (inode)

		__fsnotify_update_child_dentry_flags(inode);
@@ -270,8 +276,8 @@ err: 
	mark->group = NULL;

	atomic_dec(&group->num_marks);



	spin_unlock(&group->mark_lock);

	spin_unlock(&mark->lock);

	spin_unlock(&group->mark_lock);



	spin_lock(&destroy_lock);

	list_add(&mark->destroy_list, &destroy_list);

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