X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=blobdiff_plain;f=fs%2Fdcache.c;h=01c68ae3129c952336cb3b8e367ffe84d8ccc43a;hp=10ba92def3f675985871f0fc72e9c6d7126357a3;hb=4829b2f4eba6394081a1c98e18be8e4f3ebaba44;hpb=11d814a20166461358e1cefaf6bcd425698b8460

diff --git a/fs/dcache.c b/fs/dcache.c
index 10ba92def3f6..01c68ae3129c 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);
@@ -242,6 +242,7 @@ static void dentry_lru_add(struct dentry *dentry)
 static void __dentry_lru_del(struct dentry *dentry)
 {
 	list_del_init(&dentry->d_lru);
+	dentry->d_flags &= ~DCACHE_SHRINK_LIST;
 	dentry->d_sb->s_nr_dentry_unused--;
 	dentry_stat.nr_unused--;
 }
@@ -275,15 +276,15 @@ static void dentry_lru_prune(struct dentry *dentry)
 	}
 }
 
-static void dentry_lru_move_tail(struct dentry *dentry)
+static void dentry_lru_move_list(struct dentry *dentry, struct list_head *list)
 {
 	spin_lock(&dcache_lru_lock);
 	if (list_empty(&dentry->d_lru)) {
-		list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
+		list_add_tail(&dentry->d_lru, list);
 		dentry->d_sb->s_nr_dentry_unused++;
 		dentry_stat.nr_unused++;
 	} else {
-		list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
+		list_move_tail(&dentry->d_lru, list);
 	}
 	spin_unlock(&dcache_lru_lock);
 }
@@ -305,12 +306,12 @@ 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_DISCONNECTED;
+	dentry->d_flags |= DCACHE_DENTRY_KILLED;
 	if (parent)
 		spin_unlock(&parent->d_lock);
 	dentry_iput(dentry);
@@ -623,7 +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) &&
@@ -676,7 +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);
@@ -769,14 +770,18 @@ static void shrink_dentry_list(struct list_head *list)
 }
 
 /**
- * __shrink_dcache_sb - shrink the dentry LRU on a given superblock
- * @sb:		superblock to shrink dentry LRU.
- * @count:	number of entries to prune
- * @flags:	flags to control the dentry processing
+ * prune_dcache_sb - shrink the dcache
+ * @sb: superblock
+ * @count: number of entries to try to free
+ *
+ * Attempt to shrink the superblock dcache LRU by @count entries. This is
+ * done when we need more memory an called from the superblock shrinker
+ * function.
  *
- * If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
+ * This function may fail to free any resources if all the dentries are in
+ * use.
  */
-static void __shrink_dcache_sb(struct super_block *sb, int count, int flags)
+void prune_dcache_sb(struct super_block *sb, int count)
 {
 	struct dentry *dentry;
 	LIST_HEAD(referenced);
@@ -795,18 +800,13 @@ relock:
 			goto relock;
 		}
 
-		/*
-		 * If we are honouring the DCACHE_REFERENCED flag and the
-		 * dentry has this flag set, don't free it.  Clear the flag
-		 * and put it back on the LRU.
-		 */
-		if (flags & DCACHE_REFERENCED &&
-				dentry->d_flags & DCACHE_REFERENCED) {
+		if (dentry->d_flags & DCACHE_REFERENCED) {
 			dentry->d_flags &= ~DCACHE_REFERENCED;
 			list_move(&dentry->d_lru, &referenced);
 			spin_unlock(&dentry->d_lock);
 		} else {
 			list_move_tail(&dentry->d_lru, &tmp);
+			dentry->d_flags |= DCACHE_SHRINK_LIST;
 			spin_unlock(&dentry->d_lock);
 			if (!--count)
 				break;
@@ -820,23 +820,6 @@ relock:
 	shrink_dentry_list(&tmp);
 }
 
-/**
- * prune_dcache_sb - shrink the dcache
- * @sb: superblock
- * @nr_to_scan: number of entries to try to free
- *
- * Attempt to shrink the superblock dcache LRU by @nr_to_scan entries. This is
- * done when we need more memory an called from the superblock shrinker
- * function.
- *
- * This function may fail to free any resources if all the dentries are in
- * use.
- */
-void prune_dcache_sb(struct super_block *sb, int nr_to_scan)
-{
-	__shrink_dcache_sb(sb, nr_to_scan, DCACHE_REFERENCED);
-}
-
 /**
  * shrink_dcache_sb - shrink dcache for a superblock
  * @sb: superblock
@@ -874,7 +857,7 @@ 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 */
@@ -906,17 +889,17 @@ 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
@@ -934,7 +917,7 @@ 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);
 	}
 }
 
@@ -966,34 +949,6 @@ 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_DISCONNECTED) ||
-		 (!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.
@@ -1027,7 +982,7 @@ 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);
@@ -1049,28 +1004,48 @@ 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;
@@ -1091,7 +1066,7 @@ EXPORT_SYMBOL(have_submounts);
  * drop the lock and return early due to latency
  * constraints.
  */
-static int select_parent(struct dentry * parent)
+static int select_parent(struct dentry *parent, struct list_head *dispose)
 {
 	struct dentry *this_parent;
 	struct list_head *next;
@@ -1108,22 +1083,26 @@ 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);
 
-		/* 
-		 * move only zero ref count dentries to the end 
-		 * of the unused list for prune_dcache
+		/*
+		 * move only zero ref count dentries to the dispose list.
+		 *
+		 * Those which are presently on the shrink list, being processed
+		 * by shrink_dentry_list(), shouldn't be moved.  Otherwise the
+		 * loop in shrink_dcache_parent() might not make any progress
+		 * and loop forever.
 		 */
-		if (!dentry->d_count) {
-			dentry_lru_move_tail(dentry);
-			found++;
-		} else {
+		if (dentry->d_count) {
 			dentry_lru_del(dentry);
+		} else if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
+			dentry_lru_move_list(dentry, dispose);
+			dentry->d_flags |= DCACHE_SHRINK_LIST;
+			found++;
 		}
-
 		/*
 		 * We can return to the caller if we have found some (this
 		 * ensures forward progress). We'll be coming back to find
@@ -1131,6 +1110,7 @@ resume:
 		 */
 		if (found && need_resched()) {
 			spin_unlock(&dentry->d_lock);
+			rcu_read_lock();
 			goto out;
 		}
 
@@ -1150,25 +1130,44 @@ 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)
+		goto again;
 	locked = 1;
 	write_seqlock(&rename_lock);
 	goto again;
@@ -1180,14 +1179,15 @@ rename_retry:
  *
  * Prune the dcache to remove unused children of the parent dentry.
  */
- 
 void shrink_dcache_parent(struct dentry * parent)
 {
-	struct super_block *sb = parent->d_sb;
+	LIST_HEAD(dispose);
 	int found;
 
-	while ((found = select_parent(parent)) != 0)
-		__shrink_dcache_sb(sb, found, 0);
+	while ((found = select_parent(parent, &dispose)) != 0) {
+		shrink_dentry_list(&dispose);
+		cond_resched();
+	}
 }
 EXPORT_SYMBOL(shrink_dcache_parent);
 
@@ -1238,8 +1238,8 @@ 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);
@@ -1261,7 +1261,7 @@ 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
@@ -1269,7 +1269,7 @@ 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;
@@ -1326,7 +1326,7 @@ 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);
@@ -1351,7 +1351,7 @@ 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);
@@ -1390,7 +1390,7 @@ 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;
 
 		/*
@@ -1416,7 +1416,7 @@ 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);
@@ -1466,7 +1466,7 @@ 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;
 }
@@ -1502,7 +1502,7 @@ static struct dentry * d_find_any_alias(struct inode *inode)
  */
 struct dentry *d_obtain_alias(struct inode *inode)
 {
-	static const struct qstr anonstring = { .name = "" };
+	static const struct qstr anonstring = { .name = "/", .len = 1 };
 	struct dentry *tmp;
 	struct dentry *res;
 
@@ -1533,7 +1533,7 @@ 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);
@@ -1939,7 +1939,7 @@ 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);
@@ -2011,7 +2011,6 @@ 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);
 }
@@ -2186,8 +2185,8 @@ 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);
@@ -2195,17 +2194,18 @@ 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);
@@ -2311,19 +2311,20 @@ 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);
@@ -2371,6 +2372,7 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
 			if (d_ancestor(alias, dentry)) {
 				/* Check for loops */
 				actual = ERR_PTR(-ELOOP);
+				spin_unlock(&inode->i_lock);
 			} else if (IS_ROOT(alias)) {
 				/* Is this an anonymous mountpoint that we
 				 * could splice into our tree? */
@@ -2380,7 +2382,7 @@ struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
 				goto found;
 			} else {
 				/* Nope, but we must(!) avoid directory
-				 * aliasing */
+				 * aliasing. This drops inode->i_lock */
 				actual = __d_unalias(inode, dentry, alias);
 			}
 			write_sequnlock(&rename_lock);
@@ -2439,28 +2441,35 @@ static int prepend_name(char **buffer, int *buflen, struct qstr *name)
 /**
  * prepend_path - Prepend path string to a buffer
  * @path: the dentry/vfsmount to report
- * @root: root vfsmnt/dentry (may be modified by this function)
+ * @root: root vfsmnt/dentry
  * @buffer: pointer to the end of the buffer
  * @buflen: pointer to buffer length
  *
  * Caller holds the rename_lock.
- *
- * If path is not reachable from the supplied root, then the value of
- * root is changed (without modifying refcounts).
  */
-static int prepend_path(const struct path *path, struct path *root,
+static int prepend_path(const struct path *path,
+			const struct path *root,
 			char **buffer, int *buflen)
 {
 	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;
@@ -2483,11 +2492,9 @@ static int prepend_path(const struct path *path, struct path *root,
 		dentry = parent;
 	}
 
-out:
 	if (!error && !slash)
 		error = prepend(buffer, buflen, "/", 1);
 
-	br_read_unlock(vfsmount_lock);
 	return error;
 
 global_root:
@@ -2500,15 +2507,17 @@ global_root:
 		WARN(1, "Root dentry has weird name <%.*s>\n",
 		     (int) dentry->d_name.len, dentry->d_name.name);
 	}
-	root->mnt = vfsmnt;
-	root->dentry = dentry;
-	goto out;
+	if (!slash)
+		error = prepend(buffer, buflen, "/", 1);
+	if (!error)
+		error = vfsmnt->mnt_ns ? 1 : 2;
+	return error;
 }
 
 /**
  * __d_path - return the path of a dentry
  * @path: the dentry/vfsmount to report
- * @root: root vfsmnt/dentry (may be modified by this function)
+ * @root: root vfsmnt/dentry
  * @buf: buffer to return value in
  * @buflen: buffer length
  *
@@ -2519,21 +2528,46 @@ global_root:
  *
  * "buflen" should be positive.
  *
- * If path is not reachable from the supplied root, then the value of
- * root is changed (without modifying refcounts).
+ * If the path is not reachable from the supplied root, return %NULL.
  */
-char *__d_path(const struct path *path, struct path *root,
+char *__d_path(const struct path *path,
+	       const struct path *root,
 	       char *buf, int buflen)
 {
 	char *res = buf + buflen;
 	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)
+	if (error < 0)
+		return ERR_PTR(error);
+	if (error > 0)
+		return NULL;
+	return res;
+}
+
+char *d_absolute_path(const struct path *path,
+	       char *buf, int buflen)
+{
+	struct path root = {};
+	char *res = buf + buflen;
+	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;
+	if (error < 0)
 		return ERR_PTR(error);
 	return res;
 }
@@ -2541,8 +2575,9 @@ char *__d_path(const struct path *path, struct path *root,
 /*
  * same as __d_path but appends "(deleted)" for unlinked files.
  */
-static int path_with_deleted(const struct path *path, struct path *root,
-				 char **buf, int *buflen)
+static int path_with_deleted(const struct path *path,
+			     const struct path *root,
+			     char **buf, int *buflen)
 {
 	prepend(buf, buflen, "\0", 1);
 	if (d_unlinked(path->dentry)) {
@@ -2579,7 +2614,6 @@ char *d_path(const struct path *path, char *buf, int buflen)
 {
 	char *res = buf + buflen;
 	struct path root;
-	struct path tmp;
 	int error;
 
 	/*
@@ -2593,12 +2627,13 @@ 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);
-	tmp = root;
-	error = path_with_deleted(path, &tmp, &res, &buflen);
-	if (error)
-		res = ERR_PTR(error);
+	error = path_with_deleted(path, &root, &res, &buflen);
 	write_sequnlock(&rename_lock);
+	br_read_unlock(vfsmount_lock);
+	if (error < 0)
+		res = ERR_PTR(error);
 	path_put(&root);
 	return res;
 }
@@ -2617,7 +2652,6 @@ char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
 {
 	char *res = buf + buflen;
 	struct path root;
-	struct path tmp;
 	int error;
 
 	if (path->dentry->d_op && path->dentry->d_op->d_dname)
@@ -2625,9 +2659,8 @@ char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
 
 	get_fs_root(current->fs, &root);
 	write_seqlock(&rename_lock);
-	tmp = root;
-	error = path_with_deleted(path, &tmp, &res, &buflen);
-	if (!error && !path_equal(&tmp, &root))
+	error = path_with_deleted(path, &root, &res, &buflen);
+	if (error > 0)
 		error = prepend_unreachable(&res, &buflen);
 	write_sequnlock(&rename_lock);
 	path_put(&root);
@@ -2755,22 +2788,23 @@ 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;
-		struct path tmp = root;
 		char *cwd = page + PAGE_SIZE;
 		int buflen = PAGE_SIZE;
 
 		prepend(&cwd, &buflen, "\0", 1);
-		error = prepend_path(&pwd, &tmp, &cwd, &buflen);
+		error = prepend_path(&pwd, &root, &cwd, &buflen);
 		write_sequnlock(&rename_lock);
+		br_read_unlock(vfsmount_lock);
 
-		if (error)
+		if (error < 0)
 			goto out;
 
 		/* Unreachable from current root */
-		if (!path_equal(&tmp, &root)) {
+		if (error > 0) {
 			error = prepend_unreachable(&cwd, &buflen);
 			if (error)
 				goto out;
@@ -2785,6 +2819,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
 		}
 	} else {
 		write_sequnlock(&rename_lock);
+		br_read_unlock(vfsmount_lock);
 	}
 
 out:
@@ -2877,7 +2912,7 @@ 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);
@@ -2898,26 +2933,45 @@ 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;
 	write_seqlock(&rename_lock);
 	goto again;