[patch 12/27] fs: dcache scale subdirs

[npiggin@suse.de]

[-- Attachment #1: fs-dcache-scale-d_subdirs.patch --]
[-- Type: text/plain, Size: 31930 bytes --]

Protect d_subdirs and d_child with d_lock, except in filesystems that aren't
using dcache_lock for these anyway (eg. using i_mutex).

XXX: probably don't need parent lock in inotify (because child lock
should stabilize parent). Also, possibly some filesystems don't need so
much locking (eg. of child dentry when modifying d_child, so long as
parent is locked)... but be on the safe side. Hmm, maybe we should just
say d_child list is protected by d_parent->d_lock. d_parent could remain
protected with d_lock.

---
 drivers/usb/core/inode.c     |    6 +
 fs/autofs4/expire.c          |   81 ++++++++++++++-------
 fs/autofs4/inode.c           |    5 +
 fs/autofs4/root.c            |    9 ++
 fs/coda/cache.c              |    2 
 fs/dcache.c                  |  159 ++++++++++++++++++++++++++++++++++---------
 fs/libfs.c                   |   40 ++++++----
 fs/ncpfs/dir.c               |    3 
 fs/ncpfs/ncplib_kernel.h     |    4 +
 fs/notify/inotify/inotify.c  |    4 -
 fs/smbfs/cache.c             |    4 +
 include/linux/dcache.h       |    1 
 kernel/cgroup.c              |   19 ++++-
 net/sunrpc/rpc_pipe.c        |    2 
 security/selinux/selinuxfs.c |   12 ++-
 15 files changed, 271 insertions(+), 80 deletions(-)

Index: linux-2.6/fs/dcache.c
===================================================================
--- linux-2.6.orig/fs/dcache.c
+++ linux-2.6/fs/dcache.c
@@ -44,6 +44,8 @@
  *   - d_flags
  *   - d_name
  *   - d_lru
+ *   - d_unhashed
+ *   - d_subdirs and children's d_child
  *
  * Ordering:
  * dcache_lock
@@ -205,7 +207,8 @@ static void dentry_lru_del_init(struct d
  *
  * If this is the root of the dentry tree, return NULL.
  *
- * dcache_lock and d_lock must be held by caller, are dropped by d_kill.
+ * dcache_lock and d_lock and d_parent->d_lock must be held by caller, and
+ * are dropped by d_kill.
  */
 static struct dentry *d_kill(struct dentry *dentry)
 	__releases(dentry->d_lock)
@@ -214,12 +217,14 @@ static struct dentry *d_kill(struct dent
 	struct dentry *parent;
 
 	list_del(&dentry->d_u.d_child);
-	/*drops the locks, at that point nobody can reach this dentry */
-	dentry_iput(dentry);
+	if (dentry->d_parent && dentry != dentry->d_parent)
+		spin_unlock(&dentry->d_parent->d_lock);
 	if (IS_ROOT(dentry))
 		parent = NULL;
 	else
 		parent = dentry->d_parent;
+	/*drops the locks, at that point nobody can reach this dentry */
+	dentry_iput(dentry);
 	d_free(dentry);
 	return parent;
 }
@@ -255,6 +260,7 @@ static struct dentry *d_kill(struct dent
 
 void dput(struct dentry *dentry)
 {
+	struct dentry *parent = NULL;
 	if (!dentry)
 		return;
 
@@ -273,6 +279,15 @@ repeat:
 			spin_unlock(&dentry->d_lock);
 			goto repeat;
 		}
+		parent = dentry->d_parent;
+		if (parent) {
+			BUG_ON(parent == dentry);
+			if (!spin_trylock(&parent->d_lock)) {
+				spin_unlock(&dentry->d_lock);
+				spin_unlock(&dcache_lock);
+				goto repeat;
+			}
+		}
 	}
 	dentry->d_count--;
 	if (dentry->d_count) {
@@ -296,6 +311,8 @@ repeat:
 		dentry_lru_add(dentry);
   	}
  	spin_unlock(&dentry->d_lock);
+	if (parent)
+		spin_unlock(&parent->d_lock);
 	spin_unlock(&dcache_lock);
 	return;
 
@@ -521,10 +538,22 @@ static void prune_one_dentry(struct dent
 	 * because dcache_lock needs to be taken anyway.
 	 */
 	while (dentry) {
+		struct dentry *parent = NULL;
+
 		spin_lock(&dcache_lock);
+again:
 		spin_lock(&dentry->d_lock);
+		if (dentry->d_parent && dentry != dentry->d_parent) {
+			if (!spin_trylock(&dentry->d_parent->d_lock)) {
+				spin_unlock(&dentry->d_lock);
+				goto again;
+			}
+ 			parent = dentry->d_parent;
+		}
 		dentry->d_count--;
 		if (dentry->d_count) {
+			if (parent)
+				spin_unlock(&parent->d_lock);
 			spin_unlock(&dentry->d_lock);
 			spin_unlock(&dcache_lock);
 			return;
@@ -602,20 +631,28 @@ again:
 		dentry = list_entry(tmp.prev, struct dentry, d_lru);
 
 		if (!spin_trylock(&dentry->d_lock)) {
+again1:
 			spin_unlock(&dcache_lru_lock);
 			goto again;
 		}
-		__dentry_lru_del_init(dentry);
 		/*
 		 * We found an inuse dentry which was not removed from
 		 * the LRU because of laziness during lookup.  Do not free
 		 * it - just keep it off the LRU list.
 		 */
 		if (dentry->d_count) {
+			__dentry_lru_del_init(dentry);
 			spin_unlock(&dentry->d_lock);
 			continue;
 		}
-
+		if (dentry->d_parent) {
+			BUG_ON(dentry == dentry->d_parent);
+			if (!spin_trylock(&dentry->d_parent->d_lock)) {
+				spin_unlock(&dentry->d_lock);
+				goto again1;
+			}
+		}
+		__dentry_lru_del_init(dentry);
 		spin_unlock(&dcache_lru_lock);
 		prune_one_dentry(dentry);
 		/* dcache_lock and dentry->d_lock dropped */
@@ -752,14 +789,15 @@ static void shrink_dcache_for_umount_sub
 			/* this is a branch with children - detach all of them
 			 * from the system in one go */
 			spin_lock(&dcache_lock);
+			spin_lock(&dentry->d_lock);
 			list_for_each_entry(loop, &dentry->d_subdirs,
 					    d_u.d_child) {
-				spin_lock(&loop->d_lock);
+				spin_lock_nested(&loop->d_lock, DENTRY_D_LOCK_NESTED);
 				dentry_lru_del_init(loop);
 				__d_drop(loop);
 				spin_unlock(&loop->d_lock);
-				cond_resched_lock(&dcache_lock);
 			}
+			spin_unlock(&dentry->d_lock);
 			spin_unlock(&dcache_lock);
 
 			/* move to the first child */
@@ -787,16 +825,17 @@ static void shrink_dcache_for_umount_sub
 				BUG();
 			}
 
-			if (IS_ROOT(dentry))
+			if (IS_ROOT(dentry)) {
 				parent = NULL;
-			else {
+				list_del(&dentry->d_u.d_child);
+			} else {
 				parent = dentry->d_parent;
 				spin_lock(&parent->d_lock);
 				parent->d_count--;
+				list_del(&dentry->d_u.d_child);
 				spin_unlock(&parent->d_lock);
 			}
 
-			list_del(&dentry->d_u.d_child);
 			detached++;
 
 			inode = dentry->d_inode;
@@ -881,6 +920,7 @@ int have_submounts(struct dentry *parent
 	spin_lock(&dcache_lock);
 	if (d_mountpoint(parent))
 		goto positive;
+	spin_lock(&this_parent->d_lock);
 repeat:
 	next = this_parent->d_subdirs.next;
 resume:
@@ -888,22 +928,34 @@ resume:
 		struct list_head *tmp = next;
 		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
 		next = tmp->next;
+
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
 		/* Have we found a mount point ? */
-		if (d_mountpoint(dentry))
+		if (d_mountpoint(dentry)) {
+			spin_unlock(&dentry->d_lock);
+			spin_unlock(&this_parent->d_lock);
 			goto positive;
+		}
 		if (!list_empty(&dentry->d_subdirs)) {
+			spin_unlock(&this_parent->d_lock);
+			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
 			this_parent = dentry;
+			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
 			goto repeat;
 		}
+		spin_unlock(&dentry->d_lock);
 	}
 	/*
 	 * All done at this level ... ascend and resume the search.
 	 */
 	if (this_parent != parent) {
 		next = this_parent->d_u.d_child.next;
+		spin_unlock(&this_parent->d_lock);
 		this_parent = this_parent->d_parent;
+		spin_lock(&this_parent->d_lock);
 		goto resume;
 	}
+	spin_unlock(&this_parent->d_lock);
 	spin_unlock(&dcache_lock);
 	return 0; /* No mount points found in tree */
 positive:
@@ -932,6 +984,7 @@ static int select_parent(struct dentry *
 	int found = 0;
 
 	spin_lock(&dcache_lock);
+	spin_lock(&this_parent->d_lock);
 repeat:
 	next = this_parent->d_subdirs.next;
 resume:
@@ -939,8 +992,9 @@ resume:
 		struct list_head *tmp = next;
 		struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
 		next = tmp->next;
+		BUG_ON(this_parent == dentry);
 
-		spin_lock(&dentry->d_lock);
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
 		dentry_lru_del_init(dentry);
 		/* 
 		 * move only zero ref count dentries to the end 
@@ -950,33 +1004,45 @@ resume:
 			dentry_lru_add_tail(dentry);
 			found++;
 		}
-		spin_unlock(&dentry->d_lock);
 
 		/*
 		 * We can return to the caller if we have found some (this
 		 * ensures forward progress). We'll be coming back to find
 		 * the rest.
 		 */
-		if (found && need_resched())
+		if (found && need_resched()) {
+			spin_unlock(&dentry->d_lock);
 			goto out;
+		}
 
 		/*
 		 * Descend a level if the d_subdirs list is non-empty.
 		 */
 		if (!list_empty(&dentry->d_subdirs)) {
+			spin_unlock(&this_parent->d_lock);
+			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
 			this_parent = dentry;
+			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
 			goto repeat;
 		}
+
+		spin_unlock(&dentry->d_lock);
 	}
 	/*
 	 * All done at this level ... ascend and resume the search.
 	 */
 	if (this_parent != parent) {
+		struct dentry *tmp;
 		next = this_parent->d_u.d_child.next;
-		this_parent = this_parent->d_parent;
+		tmp = this_parent->d_parent;
+		spin_unlock(&this_parent->d_lock);
+		BUG_ON(tmp == this_parent);
+		this_parent = tmp;
+		spin_lock(&this_parent->d_lock);
 		goto resume;
 	}
 out:
+	spin_unlock(&this_parent->d_lock);
 	spin_unlock(&dcache_lock);
 	return found;
 }
@@ -1072,19 +1138,20 @@ struct dentry *d_alloc(struct dentry * p
 	INIT_LIST_HEAD(&dentry->d_lru);
 	INIT_LIST_HEAD(&dentry->d_subdirs);
 	INIT_LIST_HEAD(&dentry->d_alias);
-
-	if (parent) {
-		dentry->d_parent = dget(parent);
-		dentry->d_sb = parent->d_sb;
-	} else {
-		INIT_LIST_HEAD(&dentry->d_u.d_child);
-	}
+	INIT_LIST_HEAD(&dentry->d_u.d_child);
 
 	if (parent) {
 		spin_lock(&dcache_lock);
+		spin_lock(&parent->d_lock);
+		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+		dentry->d_parent = dget_dlock(parent);
+		dentry->d_sb = parent->d_sb;
 		list_add(&dentry->d_u.d_child, &parent->d_subdirs);
+		spin_unlock(&dentry->d_lock);
+		spin_unlock(&parent->d_lock);
 		spin_unlock(&dcache_lock);
 	}
+
 	atomic_inc(&dentry_stat.nr_dentry);
 
 	return dentry;
@@ -1763,15 +1830,27 @@ static void d_move_locked(struct dentry
 		printk(KERN_WARNING "VFS: moving negative dcache entry\n");
 
 	write_seqlock(&rename_lock);
-	/*
-	 * XXXX: do we really need to take target->d_lock?
-	 */
+
+	if (target->d_parent != dentry->d_parent) {
+		if (target->d_parent < dentry->d_parent) {
+			spin_lock(&target->d_parent->d_lock);
+			spin_lock_nested(&dentry->d_parent->d_lock,
+						DENTRY_D_LOCK_NESTED);
+		} else {
+			spin_lock(&dentry->d_parent->d_lock);
+			spin_lock_nested(&target->d_parent->d_lock,
+						DENTRY_D_LOCK_NESTED);
+		}
+	} else {
+		spin_lock(&target->d_parent->d_lock);
+	}
+
 	if (target < dentry) {
-		spin_lock(&target->d_lock);
-		spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
+		spin_lock_nested(&target->d_lock, 2);
+		spin_lock_nested(&dentry->d_lock, 3);
 	} else {
-		spin_lock(&dentry->d_lock);
-		spin_lock_nested(&target->d_lock, DENTRY_D_LOCK_NESTED);
+		spin_lock_nested(&dentry->d_lock, 2);
+		spin_lock_nested(&target->d_lock, 3);
 	}
 
 	/* Move the dentry to the target hash queue, if on different bucket */
@@ -1804,7 +1883,10 @@ static void d_move_locked(struct dentry
 	}
 
 	list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
+	if (target->d_parent != dentry->d_parent)
+		spin_unlock(&dentry->d_parent->d_lock);
 	spin_unlock(&target->d_lock);
+	spin_unlock(&target->d_parent->d_lock);
 	fsnotify_d_move(dentry);
 	spin_unlock(&dentry->d_lock);
 	write_sequnlock(&rename_lock);
@@ -1903,6 +1985,12 @@ static void __d_materialise_dentry(struc
 	dparent = dentry->d_parent;
 	aparent = anon->d_parent;
 
+	/* XXX: hack */
+	spin_lock(&aparent->d_lock);
+	spin_lock(&dparent->d_lock);
+	spin_lock(&dentry->d_lock);
+	spin_lock(&anon->d_lock);
+
 	dentry->d_parent = (aparent == anon) ? dentry : aparent;
 	list_del(&dentry->d_u.d_child);
 	if (!IS_ROOT(dentry))
@@ -1917,6 +2005,11 @@ static void __d_materialise_dentry(struc
 	else
 		INIT_LIST_HEAD(&anon->d_u.d_child);
 
+	spin_unlock(&anon->d_lock);
+	spin_unlock(&dentry->d_lock);
+	spin_unlock(&dparent->d_lock);
+	spin_unlock(&aparent->d_lock);
+
 	anon->d_flags &= ~DCACHE_DISCONNECTED;
 }
 
@@ -2316,6 +2409,7 @@ void d_genocide(struct dentry *root)
 	struct list_head *next;
 
 	spin_lock(&dcache_lock);
+	spin_lock(&this_parent->d_lock);
 repeat:
 	next = this_parent->d_subdirs.next;
 resume:
@@ -2329,8 +2423,10 @@ resume:
 			continue;
 		}
 		if (!list_empty(&dentry->d_subdirs)) {
-			spin_unlock(&dentry->d_lock);
+			spin_unlock(&this_parent->d_lock);
+			spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
 			this_parent = dentry;
+			spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
 			goto repeat;
 		}
 		dentry->d_count--;
@@ -2338,12 +2434,13 @@ resume:
 	}
 	if (this_parent != root) {
 		next = this_parent->d_u.d_child.next;
-		spin_lock(&this_parent->d_lock);
 		this_parent->d_count--;
 		spin_unlock(&this_parent->d_lock);
 		this_parent = this_parent->d_parent;
+		spin_lock(&this_parent->d_lock);
 		goto resume;
 	}
+	spin_unlock(&this_parent->d_lock);
 	spin_unlock(&dcache_lock);
 }
 
Index: linux-2.6/fs/libfs.c
===================================================================
--- linux-2.6.orig/fs/libfs.c
+++ linux-2.6/fs/libfs.c
@@ -82,7 +82,8 @@ int dcache_dir_close(struct inode *inode
 
 loff_t dcache_dir_lseek(struct file *file, loff_t offset, int origin)
 {
-	mutex_lock(&file->f_path.dentry->d_inode->i_mutex);
+	struct dentry *dentry = file->f_path.dentry;
+	mutex_lock(&dentry->d_inode->i_mutex);
 	switch (origin) {
 		case 1:
 			offset += file->f_pos;
@@ -90,7 +91,7 @@ loff_t dcache_dir_lseek(struct file *fil
 			if (offset >= 0)
 				break;
 		default:
-			mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
+			mutex_unlock(&dentry->d_inode->i_mutex);
 			return -EINVAL;
 	}
 	if (offset != file->f_pos) {
@@ -100,23 +101,27 @@ loff_t dcache_dir_lseek(struct file *fil
 			struct dentry *cursor = file->private_data;
 			loff_t n = file->f_pos - 2;
 
-			spin_lock(&dcache_lock);
+			spin_lock(&dentry->d_lock);
+			spin_lock_nested(&cursor->d_lock, DENTRY_D_LOCK_NESTED);
 			list_del(&cursor->d_u.d_child);
-			p = file->f_path.dentry->d_subdirs.next;
-			while (n && p != &file->f_path.dentry->d_subdirs) {
+			spin_unlock(&cursor->d_lock);
+			p = dentry->d_subdirs.next;
+			while (n && p != &dentry->d_subdirs) {
 				struct dentry *next;
 				next = list_entry(p, struct dentry, d_u.d_child);
-				spin_lock(&next->d_lock);
+				spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
 				if (simple_positive(next))
 					n--;
 				spin_unlock(&next->d_lock);
 				p = p->next;
 			}
+			spin_lock_nested(&cursor->d_lock, DENTRY_D_LOCK_NESTED);
 			list_add_tail(&cursor->d_u.d_child, p);
-			spin_unlock(&dcache_lock);
+			spin_unlock(&cursor->d_lock);
+			spin_unlock(&dentry->d_lock);
 		}
 	}
-	mutex_unlock(&file->f_path.dentry->d_inode->i_mutex);
+	mutex_unlock(&dentry->d_inode->i_mutex);
 	return offset;
 }
 
@@ -156,9 +161,12 @@ int dcache_readdir(struct file * filp, v
 			i++;
 			/* fallthrough */
 		default:
-			spin_lock(&dcache_lock);
-			if (filp->f_pos == 2)
+			spin_lock(&dentry->d_lock);
+			if (filp->f_pos == 2) {
+				spin_lock_nested(&cursor->d_lock, DENTRY_D_LOCK_NESTED);
 				list_move(q, &dentry->d_subdirs);
+				spin_unlock(&cursor->d_lock);
+			}
 
 			for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
 				struct dentry *next;
@@ -170,19 +178,21 @@ int dcache_readdir(struct file * filp, v
 				}
 
 				spin_unlock(&next->d_lock);
-				spin_unlock(&dcache_lock);
+				spin_unlock(&dentry->d_lock);
 				if (filldir(dirent, next->d_name.name, 
 					    next->d_name.len, filp->f_pos, 
 					    next->d_inode->i_ino, 
 					    dt_type(next->d_inode)) < 0)
 					return 0;
-				spin_lock(&dcache_lock);
+				spin_lock(&dentry->d_lock);
+				spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
 				/* next is still alive */
 				list_move(q, p);
+				spin_unlock(&next->d_lock);
 				p = q;
 				filp->f_pos++;
 			}
-			spin_unlock(&dcache_lock);
+			spin_unlock(&dentry->d_lock);
 	}
 	return 0;
 }
@@ -279,7 +289,7 @@ int simple_empty(struct dentry *dentry)
 	struct dentry *child;
 	int ret = 0;
 
-	spin_lock(&dcache_lock);
+	spin_lock(&dentry->d_lock);
 	list_for_each_entry(child, &dentry->d_subdirs, d_u.d_child) {
 		spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
 		if (simple_positive(child)) {
@@ -290,7 +300,7 @@ int simple_empty(struct dentry *dentry)
 	}
 	ret = 1;
 out:
-	spin_unlock(&dcache_lock);
+	spin_unlock(&dentry->d_lock);
 	return ret;
 }
 
Index: linux-2.6/fs/notify/inotify/inotify.c
===================================================================
--- linux-2.6.orig/fs/notify/inotify/inotify.c
+++ linux-2.6/fs/notify/inotify/inotify.c
@@ -188,17 +188,19 @@ static void set_dentry_child_flags(struc
 	list_for_each_entry(alias, &inode->i_dentry, d_alias) {
 		struct dentry *child;
 
+		spin_lock(&alias->d_lock);
 		list_for_each_entry(child, &alias->d_subdirs, d_u.d_child) {
 			if (!child->d_inode)
 				continue;
 
-			spin_lock(&child->d_lock);
+			spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
 			if (watched)
 				child->d_flags |= DCACHE_INOTIFY_PARENT_WATCHED;
 			else
 				child->d_flags &=~DCACHE_INOTIFY_PARENT_WATCHED;
 			spin_unlock(&child->d_lock);
 		}
+		spin_unlock(&alias->d_lock);
 	}
 	spin_unlock(&dcache_lock);
 }
Index: linux-2.6/include/linux/dcache.h
===================================================================
--- linux-2.6.orig/include/linux/dcache.h
+++ linux-2.6/include/linux/dcache.h
@@ -338,6 +338,7 @@ static inline struct dentry *dget_dlock(
 	}
 	return dentry;
 }
+
 static inline struct dentry *dget(struct dentry *dentry)
 {
 	if (dentry) {
Index: linux-2.6/drivers/usb/core/inode.c
===================================================================
--- linux-2.6.orig/drivers/usb/core/inode.c
+++ linux-2.6/drivers/usb/core/inode.c
@@ -344,16 +344,18 @@ static int usbfs_empty (struct dentry *d
 	struct list_head *list;
 
 	spin_lock(&dcache_lock);
-
+	spin_lock(&dentry->d_lock);
 	list_for_each(list, &dentry->d_subdirs) {
 		struct dentry *de = list_entry(list, struct dentry, d_u.d_child);
 		if (usbfs_positive(de)) {
+			spin_unlock(&dentry->d_lock);
 			spin_unlock(&dcache_lock);
 			return 0;
 		}
 	}
-
+	spin_unlock(&dentry->d_lock);
 	spin_unlock(&dcache_lock);
+
 	return 1;
 }
 
Index: linux-2.6/fs/autofs4/expire.c
===================================================================
--- linux-2.6.orig/fs/autofs4/expire.c
+++ linux-2.6/fs/autofs4/expire.c
@@ -92,22 +92,63 @@ done:
 /*
  * Calculate next entry in top down tree traversal.
  * From next_mnt in namespace.c - elegant.
+ *
+ * How is this supposed to work if we drop dcache_lock between calls anyway?
+ * How does it cope with renames?
+ * And also callers dput the returned dentry before taking dcache_lock again
+ * so what prevents it from being freed??
  */
-static struct dentry *next_dentry(struct dentry *p, struct dentry *root)
+static struct dentry *get_next_positive_dentry(struct dentry *p,
+						struct dentry *root)
 {
-	struct list_head *next = p->d_subdirs.next;
+	struct list_head *next;
+	struct dentry *ret;
 
+	spin_lock(&dcache_lock);
+	spin_lock(&p->d_lock);
+again:
+	next = p->d_subdirs.next;
 	if (next == &p->d_subdirs) {
 		while (1) {
-			if (p == root)
+			struct dentry *parent;
+
+			if (p == root) {
+				spin_unlock(&p->d_lock);
 				return NULL;
+			}
+
+			parent = p->d_parent;
+			if (!spin_trylock(&parent->d_lock)) {
+				dget_dlock(p);
+				spin_unlock(&p->d_lock);
+				parent = dget_parent(p);
+				spin_unlock(&dcache_lock);
+				dput(p);
+				spin_lock(&dcache_lock);
+				spin_lock(&parent->d_lock);
+			} else
+				spin_unlock(&p->d_lock);
 			next = p->d_u.d_child.next;
-			if (next != &p->d_parent->d_subdirs)
+			p = parent;
+			if (next != &parent->d_subdirs)
 				break;
-			p = p->d_parent;
 		}
 	}
-	return list_entry(next, struct dentry, d_u.d_child);
+	ret = list_entry(next, struct dentry, d_u.d_child);
+
+	spin_lock(&ret->d_lock);
+	/* Negative dentry - give up */
+	if (!simple_positive(ret)) {
+		spin_unlock(&ret->d_lock);
+		p = ret;
+		goto again;
+	}
+	dget_dlock(ret);
+	spin_unlock(&ret->d_lock);
+
+	spin_unlock(&dcache_lock);
+
+	return ret;
 }
 
 /*
@@ -157,18 +198,11 @@ static int autofs4_tree_busy(struct vfsm
 	if (!simple_positive(top))
 		return 1;
 
-	spin_lock(&dcache_lock);
-	for (p = top; p; p = next_dentry(p, top)) {
-		/* Negative dentry - give up */
-		if (!simple_positive(p))
-			continue;
+	for (p = top; p; p = get_next_positive_dentry(p, top)) {
 
 		DPRINTK("dentry %p %.*s",
 			p, (int) p->d_name.len, p->d_name.name);
 
-		p = dget(p);
-		spin_unlock(&dcache_lock);
-
 		/*
 		 * Is someone visiting anywhere in the subtree ?
 		 * If there's no mount we need to check the usage
@@ -204,9 +238,7 @@ static int autofs4_tree_busy(struct vfsm
 			}
 		}
 		dput(p);
-		spin_lock(&dcache_lock);
 	}
-	spin_unlock(&dcache_lock);
 
 	/* Timeout of a tree mount is ultimately determined by its top dentry */
 	if (!autofs4_can_expire(top, timeout, do_now))
@@ -225,18 +257,11 @@ static struct dentry *autofs4_check_leav
 	DPRINTK("parent %p %.*s",
 		parent, (int)parent->d_name.len, parent->d_name.name);
 
-	spin_lock(&dcache_lock);
-	for (p = parent; p; p = next_dentry(p, parent)) {
-		/* Negative dentry - give up */
-		if (!simple_positive(p))
-			continue;
+	for (p = parent; p; p = get_next_positive_dentry(p, parent)) {
 
 		DPRINTK("dentry %p %.*s",
 			p, (int) p->d_name.len, p->d_name.name);
 
-		p = dget(p);
-		spin_unlock(&dcache_lock);
-
 		if (d_mountpoint(p)) {
 			/* Can we umount this guy */
 			if (autofs4_mount_busy(mnt, p))
@@ -248,9 +273,7 @@ static struct dentry *autofs4_check_leav
 		}
 cont:
 		dput(p);
-		spin_lock(&dcache_lock);
 	}
-	spin_unlock(&dcache_lock);
 	return NULL;
 }
 
@@ -315,6 +338,7 @@ struct dentry *autofs4_expire_indirect(s
 	timeout = sbi->exp_timeout;
 
 	spin_lock(&dcache_lock);
+	spin_lock(&root->d_lock);
 	next = root->d_subdirs.next;
 
 	/* On exit from the loop expire is set to a dgot dentry
@@ -329,6 +353,7 @@ struct dentry *autofs4_expire_indirect(s
 		}
 
 		dentry = dget(dentry);
+		spin_unlock(&root->d_lock);
 		spin_unlock(&dcache_lock);
 
 		spin_lock(&sbi->fs_lock);
@@ -395,8 +420,10 @@ next:
 		spin_unlock(&sbi->fs_lock);
 		dput(dentry);
 		spin_lock(&dcache_lock);
+		spin_lock(&root->d_lock);
 		next = next->next;
 	}
+	spin_unlock(&root->d_lock);
 	spin_unlock(&dcache_lock);
 	return NULL;
 
@@ -408,7 +435,9 @@ found:
 	init_completion(&ino->expire_complete);
 	spin_unlock(&sbi->fs_lock);
 	spin_lock(&dcache_lock);
+	spin_lock(&expired->d_parent->d_lock);
 	list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child);
+	spin_unlock(&expired->d_parent->d_lock);
 	spin_unlock(&dcache_lock);
 	return expired;
 }
Index: linux-2.6/fs/autofs4/inode.c
===================================================================
--- linux-2.6.orig/fs/autofs4/inode.c
+++ linux-2.6/fs/autofs4/inode.c
@@ -111,6 +111,7 @@ static void autofs4_force_release(struct
 
 	spin_lock(&dcache_lock);
 repeat:
+	spin_lock(&this_parent->d_lock);
 	next = this_parent->d_subdirs.next;
 resume:
 	while (next != &this_parent->d_subdirs) {
@@ -128,6 +129,7 @@ resume:
 		}
 
 		next = next->next;
+		spin_unlock(&this_parent->d_lock);
 		spin_unlock(&dcache_lock);
 
 		DPRINTK("dentry %p %.*s",
@@ -141,15 +143,18 @@ resume:
 		struct dentry *dentry = this_parent;
 
 		next = this_parent->d_u.d_child.next;
+		spin_unlock(&this_parent->d_lock);
 		this_parent = this_parent->d_parent;
 		spin_unlock(&dcache_lock);
 		DPRINTK("parent dentry %p %.*s",
 			dentry, (int)dentry->d_name.len, dentry->d_name.name);
 		dput(dentry);
 		spin_lock(&dcache_lock);
+		spin_lock(&this_parent->d_lock);
 		goto resume;
 	}
 	spin_unlock(&dcache_lock);
+	spin_unlock(&this_parent->d_lock);
 }
 
 void autofs4_kill_sb(struct super_block *sb)
Index: linux-2.6/fs/autofs4/root.c
===================================================================
--- linux-2.6.orig/fs/autofs4/root.c
+++ linux-2.6/fs/autofs4/root.c
@@ -93,10 +93,13 @@ static int autofs4_dir_open(struct inode
 	 * it.
 	 */
 	spin_lock(&dcache_lock);
+	spin_lock(&dentry->d_lock);
 	if (!d_mountpoint(dentry) && __simple_empty(dentry)) {
+		spin_unlock(&dentry->d_lock);
 		spin_unlock(&dcache_lock);
 		return -ENOENT;
 	}
+	spin_unlock(&dentry->d_lock);
 	spin_unlock(&dcache_lock);
 
 out:
@@ -212,8 +215,10 @@ static void *autofs4_follow_link(struct
 	 * mount it again.
 	 */
 	spin_lock(&dcache_lock);
+	spin_lock(&dentry->d_lock);
 	if (dentry->d_flags & DCACHE_AUTOFS_PENDING ||
 	    (!d_mountpoint(dentry) && __simple_empty(dentry))) {
+		spin_unlock(&dentry->d_lock);
 		spin_unlock(&dcache_lock);
 
 		status = try_to_fill_dentry(dentry, 0);
@@ -222,6 +227,7 @@ static void *autofs4_follow_link(struct
 
 		goto follow;
 	}
+	spin_unlock(&dentry->d_lock);
 	spin_unlock(&dcache_lock);
 follow:
 	/*
@@ -731,7 +737,9 @@ static int autofs4_dir_rmdir(struct inod
 		return -EACCES;
 
 	spin_lock(&dcache_lock);
+	spin_lock(&dentry->d_lock);
 	if (!list_empty(&dentry->d_subdirs)) {
+		spin_unlock(&dentry->d_lock);
 		spin_unlock(&dcache_lock);
 		return -ENOTEMPTY;
 	}
@@ -739,7 +747,6 @@ static int autofs4_dir_rmdir(struct inod
 	if (list_empty(&ino->expiring))
 		list_add(&ino->expiring, &sbi->expiring_list);
 	spin_unlock(&sbi->lookup_lock);
-	spin_lock(&dentry->d_lock);
 	__d_drop(dentry);
 	spin_unlock(&dentry->d_lock);
 	spin_unlock(&dcache_lock);
Index: linux-2.6/fs/coda/cache.c
===================================================================
--- linux-2.6.orig/fs/coda/cache.c
+++ linux-2.6/fs/coda/cache.c
@@ -87,6 +87,7 @@ static void coda_flag_children(struct de
 	struct dentry *de;
 
 	spin_lock(&dcache_lock);
+	spin_lock(&parent->d_lock);
 	list_for_each(child, &parent->d_subdirs)
 	{
 		de = list_entry(child, struct dentry, d_u.d_child);
@@ -95,6 +96,7 @@ static void coda_flag_children(struct de
 			continue;
 		coda_flag_inode(de->d_inode, flag);
 	}
+	spin_unlock(&parent->d_lock);
 	spin_unlock(&dcache_lock);
 	return; 
 }
Index: linux-2.6/fs/ncpfs/dir.c
===================================================================
--- linux-2.6.orig/fs/ncpfs/dir.c
+++ linux-2.6/fs/ncpfs/dir.c
@@ -365,6 +365,7 @@ ncp_dget_fpos(struct dentry *dentry, str
 
 	/* If a pointer is invalid, we search the dentry. */
 	spin_lock(&dcache_lock);
+	spin_lock(&parent->d_lock);
 	next = parent->d_subdirs.next;
 	while (next != &parent->d_subdirs) {
 		dent = list_entry(next, struct dentry, d_u.d_child);
@@ -373,11 +374,13 @@ ncp_dget_fpos(struct dentry *dentry, str
 				dget_locked(dent);
 			else
 				dent = NULL;
+			spin_unlock(&parent->d_lock);
 			spin_unlock(&dcache_lock);
 			goto out;
 		}
 		next = next->next;
 	}
+	spin_unlock(&parent->d_lock);
 	spin_unlock(&dcache_lock);
 	return NULL;
 
Index: linux-2.6/fs/ncpfs/ncplib_kernel.h
===================================================================
--- linux-2.6.orig/fs/ncpfs/ncplib_kernel.h
+++ linux-2.6/fs/ncpfs/ncplib_kernel.h
@@ -193,6 +193,7 @@ ncp_renew_dentries(struct dentry *parent
 	struct dentry *dentry;
 
 	spin_lock(&dcache_lock);
+	spin_lock(&parent->d_lock);
 	next = parent->d_subdirs.next;
 	while (next != &parent->d_subdirs) {
 		dentry = list_entry(next, struct dentry, d_u.d_child);
@@ -204,6 +205,7 @@ ncp_renew_dentries(struct dentry *parent
 
 		next = next->next;
 	}
+	spin_unlock(&parent->d_lock);
 	spin_unlock(&dcache_lock);
 }
 
@@ -215,6 +217,7 @@ ncp_invalidate_dircache_entries(struct d
 	struct dentry *dentry;
 
 	spin_lock(&dcache_lock);
+	spin_lock(&parent->d_lock);
 	next = parent->d_subdirs.next;
 	while (next != &parent->d_subdirs) {
 		dentry = list_entry(next, struct dentry, d_u.d_child);
@@ -222,6 +225,7 @@ ncp_invalidate_dircache_entries(struct d
 		ncp_age_dentry(server, dentry);
 		next = next->next;
 	}
+	spin_unlock(&parent->d_lock);
 	spin_unlock(&dcache_lock);
 }
 
Index: linux-2.6/fs/smbfs/cache.c
===================================================================
--- linux-2.6.orig/fs/smbfs/cache.c
+++ linux-2.6/fs/smbfs/cache.c
@@ -63,6 +63,7 @@ smb_invalidate_dircache_entries(struct d
 	struct dentry *dentry;
 
 	spin_lock(&dcache_lock);
+	spin_lock(&parent->d_lock);
 	next = parent->d_subdirs.next;
 	while (next != &parent->d_subdirs) {
 		dentry = list_entry(next, struct dentry, d_u.d_child);
@@ -70,6 +71,7 @@ smb_invalidate_dircache_entries(struct d
 		smb_age_dentry(server, dentry);
 		next = next->next;
 	}
+	spin_unlock(&parent->d_lock);
 	spin_unlock(&dcache_lock);
 }
 
@@ -97,6 +99,7 @@ smb_dget_fpos(struct dentry *dentry, str
 
 	/* If a pointer is invalid, we search the dentry. */
 	spin_lock(&dcache_lock);
+	spin_lock(&parent->d_lock);
 	next = parent->d_subdirs.next;
 	while (next != &parent->d_subdirs) {
 		dent = list_entry(next, struct dentry, d_u.d_child);
@@ -111,6 +114,7 @@ smb_dget_fpos(struct dentry *dentry, str
 	}
 	dent = NULL;
 out_unlock:
+	spin_unlock(&parent->d_lock);
 	spin_unlock(&dcache_lock);
 	return dent;
 }
Index: linux-2.6/kernel/cgroup.c
===================================================================
--- linux-2.6.orig/kernel/cgroup.c
+++ linux-2.6/kernel/cgroup.c
@@ -694,23 +694,31 @@ static void cgroup_clear_directory(struc
 
 	BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
 	spin_lock(&dcache_lock);
+	spin_lock(&dentry->d_lock);
 	node = dentry->d_subdirs.next;
 	while (node != &dentry->d_subdirs) {
 		struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
+
+		spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
 		list_del_init(node);
 		if (d->d_inode) {
 			/* This should never be called on a cgroup
 			 * directory with child cgroups */
 			BUG_ON(d->d_inode->i_mode & S_IFDIR);
-			d = dget_locked(d);
+			dget_locked_dlock(d);
+			spin_unlock(&d->d_lock);
+			spin_unlock(&dentry->d_lock);
 			spin_unlock(&dcache_lock);
 			d_delete(d);
 			simple_unlink(dentry->d_inode, d);
 			dput(d);
 			spin_lock(&dcache_lock);
-		}
+			spin_lock(&dentry->d_lock);
+		} else
+			spin_unlock(&d->d_lock);
 		node = dentry->d_subdirs.next;
 	}
+	spin_unlock(&dentry->d_lock);
 	spin_unlock(&dcache_lock);
 }
 
@@ -719,10 +727,17 @@ static void cgroup_clear_directory(struc
  */
 static void cgroup_d_remove_dir(struct dentry *dentry)
 {
+	struct dentry *parent;
+
 	cgroup_clear_directory(dentry);
 
 	spin_lock(&dcache_lock);
+	parent = dentry->d_parent;
+	spin_lock(&parent->d_lock);
+	spin_lock(&dentry->d_lock);
 	list_del_init(&dentry->d_u.d_child);
+	spin_unlock(&dentry->d_lock);
+	spin_unlock(&parent->d_lock);
 	spin_unlock(&dcache_lock);
 	remove_dir(dentry);
 }
Index: linux-2.6/net/sunrpc/rpc_pipe.c
===================================================================
--- linux-2.6.orig/net/sunrpc/rpc_pipe.c
+++ linux-2.6/net/sunrpc/rpc_pipe.c
@@ -548,6 +548,7 @@ static void rpc_depopulate(struct dentry
 	mutex_lock_nested(&dir->i_mutex, I_MUTEX_CHILD);
 repeat:
 	spin_lock(&dcache_lock);
+	spin_lock(&parent->d_lock);
 	list_for_each_safe(pos, next, &parent->d_subdirs) {
 		dentry = list_entry(pos, struct dentry, d_u.d_child);
 		if (!dentry->d_inode ||
@@ -565,6 +566,7 @@ repeat:
 		} else
 			spin_unlock(&dentry->d_lock);
 	}
+	spin_unlock(&parent->d_lock);
 	spin_unlock(&dcache_lock);
 	if (n) {
 		do {
Index: linux-2.6/security/selinux/selinuxfs.c
===================================================================
--- linux-2.6.orig/security/selinux/selinuxfs.c
+++ linux-2.6/security/selinux/selinuxfs.c
@@ -948,22 +948,30 @@ static void sel_remove_entries(struct de
 	struct list_head *node;
 
 	spin_lock(&dcache_lock);
+	spin_lock(&de->d_lock);
 	node = de->d_subdirs.next;
 	while (node != &de->d_subdirs) {
 		struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
+
+		spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
 		list_del_init(node);
 
 		if (d->d_inode) {
-			d = dget_locked(d);
+			dget_locked_dlock(d);
+			spin_unlock(&de->d_lock);
+			spin_unlock(&d->d_lock);
 			spin_unlock(&dcache_lock);
 			d_delete(d);
 			simple_unlink(de->d_inode, d);
 			dput(d);
 			spin_lock(&dcache_lock);
-		}
+			spin_lock(&de->d_lock);
+		} else
+			spin_unlock(&d->d_lock);
 		node = de->d_subdirs.next;
 	}
 
+	spin_unlock(&de->d_lock);
 	spin_unlock(&dcache_lock);
 }