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Commit ca5358ef authored by Al Viro's avatar Al Viro
Browse files

deal with deadlock in d_walk() 



... by not hitting rename_retry for reasons other than rename having
happened.  In other words, do _not_ restart when finding that
between unlocking the child and locking the parent the former got
into __dentry_kill().  Skip the killed siblings instead...

Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 946e51f2

fs/dcache.c

+16 −15
Original line number Diff line number Diff line
@@ -495,7 +495,7 @@ static void __dentry_kill(struct dentry *dentry) 
	}

	/* if it was on the hash then remove it */

	__d_drop(dentry);

	list_del(&dentry->d_child);

	__list_del_entry(&dentry->d_child);

	/*

	 * Inform d_walk() that we are no longer attached to the

	 * dentry tree
@@ -1081,33 +1081,31 @@ static void d_walk(struct dentry *parent, void *data, 
	/*

	 * All done at this level ... ascend and resume the search.

	 */

	rcu_read_lock();

ascend:

	if (this_parent != parent) {

		struct dentry *child = this_parent;

		this_parent = child->d_parent;



		rcu_read_lock();

		spin_unlock(&child->d_lock);

		spin_lock(&this_parent->d_lock);



		/*

		 * might go back up the wrong parent if we have had a rename

		 * or deletion

		 */

		if (this_parent != child->d_parent ||

			 (child->d_flags & DCACHE_DENTRY_KILLED) ||

			 need_seqretry(&rename_lock, seq)) {

			spin_unlock(&this_parent->d_lock);

			rcu_read_unlock();

		/* might go back up the wrong parent if we have had a rename. */

		if (need_seqretry(&rename_lock, seq))

			goto rename_retry;

		next = child->d_child.next;

		while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED)) {

			if (next == &this_parent->d_subdirs)

				goto ascend;

			child = list_entry(next, struct dentry, d_child);

			next = next->next;

		}

		rcu_read_unlock();

		next = child->d_child.next;

		goto resume;

	}

	if (need_seqretry(&rename_lock, seq)) {

		spin_unlock(&this_parent->d_lock);

	if (need_seqretry(&rename_lock, seq))

		goto rename_retry;

	}

	rcu_read_unlock();

	if (finish)

		finish(data);
@@ -1117,6 +1115,9 @@ static void d_walk(struct dentry *parent, void *data, 
	return;



rename_retry:

	spin_unlock(&this_parent->d_lock);

	rcu_read_unlock();

	BUG_ON(seq & 1);

	if (!retry)

		return;

	seq = 1;