X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=blobdiff_plain;f=fs%2Fdcache.c;h=93df95475e43e7a326bd4d995d8dbf052f6a67d1;hp=bb7f4ccdfbdea996fbf4f57d01e19bda4c6e2a6d;hb=99f890a5f4de33ca43ea79b7b54241849e4bf904;hpb=150086ca6bd7493e7753f923a3f55e73701253b3

diff --git a/fs/dcache.c b/fs/dcache.c
index bb7f4ccdfbde..93df95475e43 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -42,7 +42,7 @@
 /*
  * Usage:
  * dcache->d_inode->i_lock protects:
- *   - i_dentry, d_alias, d_inode of aliases
+ *   - i_dentry, d_u.d_alias, d_inode of aliases
  * dcache_hash_bucket lock protects:
  *   - the dcache hash table
  * s_anon bl list spinlock protects:
@@ -57,7 +57,7 @@
  *   - d_unhashed()
  *   - d_parent and d_subdirs
  *   - childrens' d_child and d_parent
- *   - d_alias, d_inode
+ *   - d_u.d_alias, d_inode
  *
  * Ordering:
  * dentry->d_inode->i_lock
@@ -140,7 +140,6 @@ static void __d_free(struct rcu_head *head)
 {
 	struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
 
-	WARN_ON(!list_empty(&dentry->d_alias));
 	if (dname_external(dentry))
 		kfree(dentry->d_name.name);
 	kmem_cache_free(dentry_cache, dentry); 
@@ -151,6 +150,7 @@ static void __d_free(struct rcu_head *head)
  */
 static void d_free(struct dentry *dentry)
 {
+	WARN_ON(!list_empty(&dentry->d_u.d_alias));
 	BUG_ON(dentry->d_count);
 	this_cpu_dec(nr_dentry);
 	if (dentry->d_op && dentry->d_op->d_release)
@@ -189,7 +189,7 @@ static void dentry_iput(struct dentry * dentry)
 	struct inode *inode = dentry->d_inode;
 	if (inode) {
 		dentry->d_inode = NULL;
-		list_del_init(&dentry->d_alias);
+		list_del_init(&dentry->d_u.d_alias);
 		spin_unlock(&dentry->d_lock);
 		spin_unlock(&inode->i_lock);
 		if (!inode->i_nlink)
@@ -213,7 +213,7 @@ static void dentry_unlink_inode(struct dentry * dentry)
 {
 	struct inode *inode = dentry->d_inode;
 	dentry->d_inode = NULL;
-	list_del_init(&dentry->d_alias);
+	list_del_init(&dentry->d_u.d_alias);
 	dentry_rcuwalk_barrier(dentry);
 	spin_unlock(&dentry->d_lock);
 	spin_unlock(&inode->i_lock);
@@ -306,9 +306,9 @@ static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
 	__releases(parent->d_lock)
 	__releases(dentry->d_inode->i_lock)
 {
-	list_del(&dentry->d_u.d_child);
+	__list_del_entry(&dentry->d_child);
 	/*
-	 * Inform try_to_ascend() that we are no longer attached to the
+	 * Inform ascending readers that we are no longer attached to the
 	 * dentry tree
 	 */
 	dentry->d_flags |= DCACHE_DENTRY_KILLED;
@@ -624,7 +624,7 @@ static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
 
 again:
 	discon_alias = NULL;
-	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
+	list_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
 		spin_lock(&alias->d_lock);
  		if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
 			if (IS_ROOT(alias) &&
@@ -677,7 +677,7 @@ void d_prune_aliases(struct inode *inode)
 	struct dentry *dentry;
 restart:
 	spin_lock(&inode->i_lock);
-	list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
+	list_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
 		spin_lock(&dentry->d_lock);
 		if (!dentry->d_count) {
 			__dget_dlock(dentry);
@@ -836,6 +836,7 @@ void shrink_dcache_sb(struct super_block *sb)
 		list_splice_init(&sb->s_dentry_lru, &tmp);
 		spin_unlock(&dcache_lru_lock);
 		shrink_dentry_list(&tmp);
+		cond_resched();
 		spin_lock(&dcache_lru_lock);
 	}
 	spin_unlock(&dcache_lru_lock);
@@ -857,7 +858,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
 		/* descend to the first leaf in the current subtree */
 		while (!list_empty(&dentry->d_subdirs))
 			dentry = list_entry(dentry->d_subdirs.next,
-					    struct dentry, d_u.d_child);
+					    struct dentry, d_child);
 
 		/* consume the dentries from this leaf up through its parents
 		 * until we find one with children or run out altogether */
@@ -889,17 +890,17 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
 
 			if (IS_ROOT(dentry)) {
 				parent = NULL;
-				list_del(&dentry->d_u.d_child);
+				list_del(&dentry->d_child);
 			} else {
 				parent = dentry->d_parent;
 				parent->d_count--;
-				list_del(&dentry->d_u.d_child);
+				list_del(&dentry->d_child);
 			}
 
 			inode = dentry->d_inode;
 			if (inode) {
 				dentry->d_inode = NULL;
-				list_del_init(&dentry->d_alias);
+				list_del_init(&dentry->d_u.d_alias);
 				if (dentry->d_op && dentry->d_op->d_iput)
 					dentry->d_op->d_iput(dentry, inode);
 				else
@@ -917,7 +918,7 @@ static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
 		} while (list_empty(&dentry->d_subdirs));
 
 		dentry = list_entry(dentry->d_subdirs.next,
-				    struct dentry, d_u.d_child);
+				    struct dentry, d_child);
 	}
 }
 
@@ -949,34 +950,6 @@ void shrink_dcache_for_umount(struct super_block *sb)
 	}
 }
 
-/*
- * This tries to ascend one level of parenthood, but
- * we can race with renaming, so we need to re-check
- * the parenthood after dropping the lock and check
- * that the sequence number still matches.
- */
-static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
-{
-	struct dentry *new = old->d_parent;
-
-	rcu_read_lock();
-	spin_unlock(&old->d_lock);
-	spin_lock(&new->d_lock);
-
-	/*
-	 * might go back up the wrong parent if we have had a rename
-	 * or deletion
-	 */
-	if (new != old->d_parent ||
-		 (old->d_flags & DCACHE_DENTRY_KILLED) ||
-		 (!locked && read_seqretry(&rename_lock, seq))) {
-		spin_unlock(&new->d_lock);
-		new = NULL;
-	}
-	rcu_read_unlock();
-	return new;
-}
-
 
 /*
  * Search for at least 1 mount point in the dentry's subdirs.
@@ -1010,7 +983,7 @@ repeat:
 resume:
 	while (next != &this_parent->d_subdirs) {
 		struct list_head *tmp = next;
-		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
+		struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
 		next = tmp->next;
 
 		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
@@ -1032,30 +1005,48 @@ resume:
 	/*
 	 * 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 = try_to_ascend(this_parent, locked, seq);
-		if (!this_parent)
+		this_parent = child->d_parent;
+
+		spin_unlock(&child->d_lock);
+		spin_lock(&this_parent->d_lock);
+
+		/* might go back up the wrong parent if we have had a rename */
+		if (!locked && read_seqretry(&rename_lock, seq))
 			goto rename_retry;
-		next = child->d_u.d_child.next;
+		/* go into the first sibling still alive */
+		do {
+			next = child->d_child.next;
+			if (next == &this_parent->d_subdirs)
+				goto ascend;
+			child = list_entry(next, struct dentry, d_child);
+		} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
+		rcu_read_unlock();
 		goto resume;
 	}
-	spin_unlock(&this_parent->d_lock);
 	if (!locked && read_seqretry(&rename_lock, seq))
 		goto rename_retry;
+	spin_unlock(&this_parent->d_lock);
+	rcu_read_unlock();
 	if (locked)
 		write_sequnlock(&rename_lock);
 	return 0; /* No mount points found in tree */
 positive:
 	if (!locked && read_seqretry(&rename_lock, seq))
-		goto rename_retry;
+		goto rename_retry_unlocked;
 	if (locked)
 		write_sequnlock(&rename_lock);
 	return 1;
 
 rename_retry:
+	spin_unlock(&this_parent->d_lock);
+	rcu_read_unlock();
 	if (locked)
 		goto again;
+rename_retry_unlocked:
 	locked = 1;
 	write_seqlock(&rename_lock);
 	goto again;
@@ -1093,7 +1084,7 @@ repeat:
 resume:
 	while (next != &this_parent->d_subdirs) {
 		struct list_head *tmp = next;
-		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
+		struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
 		next = tmp->next;
 
 		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
@@ -1120,6 +1111,7 @@ resume:
 		 */
 		if (found && need_resched()) {
 			spin_unlock(&dentry->d_lock);
+			rcu_read_lock();
 			goto out;
 		}
 
@@ -1139,23 +1131,40 @@ resume:
 	/*
 	 * 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 = try_to_ascend(this_parent, locked, seq);
-		if (!this_parent)
+		this_parent = child->d_parent;
+
+		spin_unlock(&child->d_lock);
+		spin_lock(&this_parent->d_lock);
+
+		/* might go back up the wrong parent if we have had a rename */
+		if (!locked && read_seqretry(&rename_lock, seq))
 			goto rename_retry;
-		next = child->d_u.d_child.next;
+		/* go into the first sibling still alive */
+		do {
+			next = child->d_child.next;
+			if (next == &this_parent->d_subdirs)
+				goto ascend;
+			child = list_entry(next, struct dentry, d_child);
+		} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
+		rcu_read_unlock();
 		goto resume;
 	}
 out:
-	spin_unlock(&this_parent->d_lock);
 	if (!locked && read_seqretry(&rename_lock, seq))
 		goto rename_retry;
+	spin_unlock(&this_parent->d_lock);
+	rcu_read_unlock();
 	if (locked)
 		write_sequnlock(&rename_lock);
 	return found;
 
 rename_retry:
+	spin_unlock(&this_parent->d_lock);
+	rcu_read_unlock();
 	if (found)
 		return found;
 	if (locked)
@@ -1176,8 +1185,10 @@ void shrink_dcache_parent(struct dentry * parent)
 	LIST_HEAD(dispose);
 	int found;
 
-	while ((found = select_parent(parent, &dispose)) != 0)
+	while ((found = select_parent(parent, &dispose)) != 0) {
 		shrink_dentry_list(&dispose);
+		cond_resched();
+	}
 }
 EXPORT_SYMBOL(shrink_dcache_parent);
 
@@ -1228,8 +1239,8 @@ struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
 	INIT_HLIST_BL_NODE(&dentry->d_hash);
 	INIT_LIST_HEAD(&dentry->d_lru);
 	INIT_LIST_HEAD(&dentry->d_subdirs);
-	INIT_LIST_HEAD(&dentry->d_alias);
-	INIT_LIST_HEAD(&dentry->d_u.d_child);
+	INIT_LIST_HEAD(&dentry->d_u.d_alias);
+	INIT_LIST_HEAD(&dentry->d_child);
 	d_set_d_op(dentry, dentry->d_sb->s_d_op);
 
 	this_cpu_inc(nr_dentry);
@@ -1251,7 +1262,7 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
 	struct dentry *dentry = __d_alloc(parent->d_sb, name);
 	if (!dentry)
 		return NULL;
-
+	dentry->d_flags |= DCACHE_RCUACCESS;
 	spin_lock(&parent->d_lock);
 	/*
 	 * don't need child lock because it is not subject
@@ -1259,7 +1270,7 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
 	 */
 	__dget_dlock(parent);
 	dentry->d_parent = parent;
-	list_add(&dentry->d_u.d_child, &parent->d_subdirs);
+	list_add(&dentry->d_child, &parent->d_subdirs);
 	spin_unlock(&parent->d_lock);
 
 	return dentry;
@@ -1316,7 +1327,7 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode)
 	if (inode) {
 		if (unlikely(IS_AUTOMOUNT(inode)))
 			dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
-		list_add(&dentry->d_alias, &inode->i_dentry);
+		list_add(&dentry->d_u.d_alias, &inode->i_dentry);
 	}
 	dentry->d_inode = inode;
 	dentry_rcuwalk_barrier(dentry);
@@ -1341,7 +1352,7 @@ static void __d_instantiate(struct dentry *dentry, struct inode *inode)
  
 void d_instantiate(struct dentry *entry, struct inode * inode)
 {
-	BUG_ON(!list_empty(&entry->d_alias));
+	BUG_ON(!list_empty(&entry->d_u.d_alias));
 	if (inode)
 		spin_lock(&inode->i_lock);
 	__d_instantiate(entry, inode);
@@ -1380,7 +1391,7 @@ static struct dentry *__d_instantiate_unique(struct dentry *entry,
 		return NULL;
 	}
 
-	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
+	list_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
 		struct qstr *qstr = &alias->d_name;
 
 		/*
@@ -1406,7 +1417,7 @@ struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
 {
 	struct dentry *result;
 
-	BUG_ON(!list_empty(&entry->d_alias));
+	BUG_ON(!list_empty(&entry->d_u.d_alias));
 
 	if (inode)
 		spin_lock(&inode->i_lock);
@@ -1456,7 +1467,7 @@ static struct dentry * __d_find_any_alias(struct inode *inode)
 
 	if (list_empty(&inode->i_dentry))
 		return NULL;
-	alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias);
+	alias = list_first_entry(&inode->i_dentry, struct dentry, d_u.d_alias);
 	__dget(alias);
 	return alias;
 }
@@ -1523,7 +1534,7 @@ struct dentry *d_obtain_alias(struct inode *inode)
 	spin_lock(&tmp->d_lock);
 	tmp->d_inode = inode;
 	tmp->d_flags |= DCACHE_DISCONNECTED;
-	list_add(&tmp->d_alias, &inode->i_dentry);
+	list_add(&tmp->d_u.d_alias, &inode->i_dentry);
 	hlist_bl_lock(&tmp->d_sb->s_anon);
 	hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
 	hlist_bl_unlock(&tmp->d_sb->s_anon);
@@ -1929,7 +1940,7 @@ int d_validate(struct dentry *dentry, struct dentry *dparent)
 	struct dentry *child;
 
 	spin_lock(&dparent->d_lock);
-	list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
+	list_for_each_entry(child, &dparent->d_subdirs, d_child) {
 		if (dentry == child) {
 			spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
 			__dget_dlock(dentry);
@@ -2001,7 +2012,6 @@ static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
 {
 	BUG_ON(!d_unhashed(entry));
 	hlist_bl_lock(b);
-	entry->d_flags |= DCACHE_RCUACCESS;
 	hlist_bl_add_head_rcu(&entry->d_hash, b);
 	hlist_bl_unlock(b);
 }
@@ -2176,8 +2186,8 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
 	/* Unhash the target: dput() will then get rid of it */
 	__d_drop(target);
 
-	list_del(&dentry->d_u.d_child);
-	list_del(&target->d_u.d_child);
+	list_del(&dentry->d_child);
+	list_del(&target->d_child);
 
 	/* Switch the names.. */
 	switch_names(dentry, target);
@@ -2185,17 +2195,18 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
 
 	/* ... and switch the parents */
 	if (IS_ROOT(dentry)) {
+		dentry->d_flags |= DCACHE_RCUACCESS;
 		dentry->d_parent = target->d_parent;
 		target->d_parent = target;
-		INIT_LIST_HEAD(&target->d_u.d_child);
+		INIT_LIST_HEAD(&target->d_child);
 	} else {
 		swap(dentry->d_parent, target->d_parent);
 
 		/* And add them back to the (new) parent lists */
-		list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
+		list_add(&target->d_child, &target->d_parent->d_subdirs);
 	}
 
-	list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
+	list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
 
 	write_seqcount_end(&target->d_seq);
 	write_seqcount_end(&dentry->d_seq);
@@ -2301,19 +2312,20 @@ static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
 	switch_names(dentry, anon);
 	swap(dentry->d_name.hash, anon->d_name.hash);
 
+	dentry->d_flags |= DCACHE_RCUACCESS;
 	dentry->d_parent = (aparent == anon) ? dentry : aparent;
-	list_del(&dentry->d_u.d_child);
+	list_del(&dentry->d_child);
 	if (!IS_ROOT(dentry))
-		list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
+		list_add(&dentry->d_child, &dentry->d_parent->d_subdirs);
 	else
-		INIT_LIST_HEAD(&dentry->d_u.d_child);
+		INIT_LIST_HEAD(&dentry->d_child);
 
 	anon->d_parent = (dparent == dentry) ? anon : dparent;
-	list_del(&anon->d_u.d_child);
+	list_del(&anon->d_child);
 	if (!IS_ROOT(anon))
-		list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
+		list_add(&anon->d_child, &anon->d_parent->d_subdirs);
 	else
-		INIT_LIST_HEAD(&anon->d_u.d_child);
+		INIT_LIST_HEAD(&anon->d_child);
 
 	write_seqcount_end(&dentry->d_seq);
 	write_seqcount_end(&anon->d_seq);
@@ -2442,14 +2454,23 @@ static int prepend_path(const struct path *path,
 {
 	struct dentry *dentry = path->dentry;
 	struct vfsmount *vfsmnt = path->mnt;
+	char *orig_buffer = *buffer;
+	int orig_len = *buflen;
 	bool slash = false;
 	int error = 0;
 
-	br_read_lock(vfsmount_lock);
 	while (dentry != root->dentry || vfsmnt != root->mnt) {
 		struct dentry * parent;
 
 		if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
+			/* Escaped? */
+			if (dentry != vfsmnt->mnt_root) {
+				*buffer = orig_buffer;
+				*buflen = orig_len;
+				slash = false;
+				error = 3;
+				goto global_root;
+			}
 			/* Global root? */
 			if (vfsmnt->mnt_parent == vfsmnt) {
 				goto global_root;
@@ -2475,8 +2496,6 @@ static int prepend_path(const struct path *path,
 	if (!error && !slash)
 		error = prepend(buffer, buflen, "/", 1);
 
-out:
-	br_read_unlock(vfsmount_lock);
 	return error;
 
 global_root:
@@ -2493,7 +2512,7 @@ global_root:
 		error = prepend(buffer, buflen, "/", 1);
 	if (!error)
 		error = vfsmnt->mnt_ns ? 1 : 2;
-	goto out;
+	return error;
 }
 
 /**
@@ -2520,9 +2539,11 @@ char *__d_path(const struct path *path,
 	int error;
 
 	prepend(&res, &buflen, "\0", 1);
+	br_read_lock(vfsmount_lock);
 	write_seqlock(&rename_lock);
 	error = prepend_path(path, root, &res, &buflen);
 	write_sequnlock(&rename_lock);
+	br_read_unlock(vfsmount_lock);
 
 	if (error < 0)
 		return ERR_PTR(error);
@@ -2539,9 +2560,11 @@ char *d_absolute_path(const struct path *path,
 	int error;
 
 	prepend(&res, &buflen, "\0", 1);
+	br_read_lock(vfsmount_lock);
 	write_seqlock(&rename_lock);
 	error = prepend_path(path, &root, &res, &buflen);
 	write_sequnlock(&rename_lock);
+	br_read_unlock(vfsmount_lock);
 
 	if (error > 1)
 		error = -EINVAL;
@@ -2605,11 +2628,13 @@ char *d_path(const struct path *path, char *buf, int buflen)
 		return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
 
 	get_fs_root(current->fs, &root);
+	br_read_lock(vfsmount_lock);
 	write_seqlock(&rename_lock);
 	error = path_with_deleted(path, &root, &res, &buflen);
+	write_sequnlock(&rename_lock);
+	br_read_unlock(vfsmount_lock);
 	if (error < 0)
 		res = ERR_PTR(error);
-	write_sequnlock(&rename_lock);
 	path_put(&root);
 	return res;
 }
@@ -2764,6 +2789,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
 	get_fs_root_and_pwd(current->fs, &root, &pwd);
 
 	error = -ENOENT;
+	br_read_lock(vfsmount_lock);
 	write_seqlock(&rename_lock);
 	if (!d_unlinked(pwd.dentry)) {
 		unsigned long len;
@@ -2773,6 +2799,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
 		prepend(&cwd, &buflen, "\0", 1);
 		error = prepend_path(&pwd, &root, &cwd, &buflen);
 		write_sequnlock(&rename_lock);
+		br_read_unlock(vfsmount_lock);
 
 		if (error < 0)
 			goto out;
@@ -2793,6 +2820,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
 		}
 	} else {
 		write_sequnlock(&rename_lock);
+		br_read_unlock(vfsmount_lock);
 	}
 
 out:
@@ -2885,7 +2913,7 @@ repeat:
 resume:
 	while (next != &this_parent->d_subdirs) {
 		struct list_head *tmp = next;
-		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
+		struct dentry *dentry = list_entry(tmp, struct dentry, d_child);
 		next = tmp->next;
 
 		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
@@ -2906,26 +2934,43 @@ resume:
 		}
 		spin_unlock(&dentry->d_lock);
 	}
+	rcu_read_lock();
+ascend:
 	if (this_parent != root) {
 		struct dentry *child = this_parent;
 		if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
 			this_parent->d_flags |= DCACHE_GENOCIDE;
 			this_parent->d_count--;
 		}
-		this_parent = try_to_ascend(this_parent, locked, seq);
-		if (!this_parent)
+		this_parent = child->d_parent;
+
+		spin_unlock(&child->d_lock);
+		spin_lock(&this_parent->d_lock);
+
+		/* might go back up the wrong parent if we have had a rename */
+		if (!locked && read_seqretry(&rename_lock, seq))
 			goto rename_retry;
-		next = child->d_u.d_child.next;
+		/* go into the first sibling still alive */
+		do {
+			next = child->d_child.next;
+			if (next == &this_parent->d_subdirs)
+				goto ascend;
+			child = list_entry(next, struct dentry, d_child);
+		} while (unlikely(child->d_flags & DCACHE_DENTRY_KILLED));
+		rcu_read_unlock();
 		goto resume;
 	}
-	spin_unlock(&this_parent->d_lock);
 	if (!locked && read_seqretry(&rename_lock, seq))
 		goto rename_retry;
+	spin_unlock(&this_parent->d_lock);
+	rcu_read_unlock();
 	if (locked)
 		write_sequnlock(&rename_lock);
 	return;
 
 rename_retry:
+	spin_unlock(&this_parent->d_lock);
+	rcu_read_unlock();
 	if (locked)
 		goto again;
 	locked = 1;