Merge branch 'work.autofs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs

Pull autofs updates from Al Viro:
 "The most interesting part here is getting rid of the last trylock loop
  on dentry->d_lock.

  The ones in fs/dcache.c had been dealt with several years ago, but
  there'd been leftovers in fs/autofs/expire.c"

* 'work.autofs' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs:
  autofs_lookup(): hold ->d_lock over playing with ->d_flags
  get rid of autofs_info->active_count
  autofs: simplify get_next_positive_...(), get rid of trylocks

fs/autofs/autofs_i.h

@@ -58,7 +58,6 @@ struct autofs_info {
 	struct completion expire_complete;
 
 	struct list_head active;
-	int active_count;
 
 	struct list_head expiring;
 

fs/autofs/expire.c

@@ -70,6 +70,27 @@ static int autofs_mount_busy(struct vfsmount *mnt,
 	return status;
 }
 
+/* p->d_lock held */
+static struct dentry *positive_after(struct dentry *p, struct dentry *child)
+{
+	if (child)
+		child = list_next_entry(child, d_child);
+	else
+		child = list_first_entry(&p->d_subdirs, struct dentry, d_child);
+
+	list_for_each_entry_from(child, &p->d_subdirs, d_child) {
+		spin_lock_nested(&child->d_lock, DENTRY_D_LOCK_NESTED);
+		if (simple_positive(child)) {
+			dget_dlock(child);
+			spin_unlock(&child->d_lock);
+			return child;
+		}
+		spin_unlock(&child->d_lock);
+	}
+
+	return NULL;
+}
+
 /*
  * Calculate and dget next entry in the subdirs list under root.
  */
@@ -77,43 +98,14 @@ static struct dentry *get_next_positive_subdir(struct dentry *prev,
 					       struct dentry *root)
 {
 	struct autofs_sb_info *sbi = autofs_sbi(root->d_sb);
-	struct list_head *next;
 	struct dentry *q;
 
 	spin_lock(&sbi->lookup_lock);
 	spin_lock(&root->d_lock);
-
-	if (prev)
-		next = prev->d_child.next;
-	else {
-		prev = dget_dlock(root);
-		next = prev->d_subdirs.next;
-	}
-
-cont:
-	if (next == &root->d_subdirs) {
-		spin_unlock(&root->d_lock);
-		spin_unlock(&sbi->lookup_lock);
-		dput(prev);
-		return NULL;
-	}
-
-	q = list_entry(next, struct dentry, d_child);
-
-	spin_lock_nested(&q->d_lock, DENTRY_D_LOCK_NESTED);
-	/* Already gone or negative dentry (under construction) - try next */
-	if (!d_count(q) || !simple_positive(q)) {
-		spin_unlock(&q->d_lock);
-		next = q->d_child.next;
-		goto cont;
-	}
-	dget_dlock(q);
-	spin_unlock(&q->d_lock);
+	q = positive_after(root, prev);
 	spin_unlock(&root->d_lock);
 	spin_unlock(&sbi->lookup_lock);
-
 	dput(prev);
-
 	return q;
 }
 
@@ -124,59 +116,28 @@ static struct dentry *get_next_positive_dentry(struct dentry *prev,
 					       struct dentry *root)
 {
 	struct autofs_sb_info *sbi = autofs_sbi(root->d_sb);
-	struct list_head *next;
-	struct dentry *p, *ret;
+	struct dentry *p = prev, *ret = NULL, *d = NULL;
 
 	if (prev == NULL)
 		return dget(root);
 
 	spin_lock(&sbi->lookup_lock);
-relock:
-	p = prev;
 	spin_lock(&p->d_lock);
-again:
-	next = p->d_subdirs.next;
-	if (next == &p->d_subdirs) {
 	while (1) {
 		struct dentry *parent;
 
-			if (p == root) {
-				spin_unlock(&p->d_lock);
-				spin_unlock(&sbi->lookup_lock);
-				dput(prev);
-				return NULL;
-			}
-
+		ret = positive_after(p, d);
+		if (ret || p == root)
+			break;
 		parent = p->d_parent;
-			if (!spin_trylock(&parent->d_lock)) {
 		spin_unlock(&p->d_lock);
-				cpu_relax();
-				goto relock;
-			}
-			spin_unlock(&p->d_lock);
-			next = p->d_child.next;
+		spin_lock(&parent->d_lock);
+		d = p;
 		p = parent;
-			if (next != &parent->d_subdirs)
-				break;
 	}
-	}
-	ret = list_entry(next, struct dentry, d_child);
-
-	spin_lock_nested(&ret->d_lock, DENTRY_D_LOCK_NESTED);
-	/* Negative dentry - try next */
-	if (!simple_positive(ret)) {
-		spin_unlock(&p->d_lock);
-		lock_set_subclass(&ret->d_lock.dep_map, 0, _RET_IP_);
-		p = ret;
-		goto again;
-	}
-	dget_dlock(ret);
-	spin_unlock(&ret->d_lock);
 	spin_unlock(&p->d_lock);
 	spin_unlock(&sbi->lookup_lock);
-
 	dput(prev);
-
 	return ret;
 }
 

fs/autofs/root.c

@@ -60,38 +60,15 @@ const struct dentry_operations autofs_dentry_operations = {
 	.d_release	= autofs_dentry_release,
 };
 
-static void autofs_add_active(struct dentry *dentry)
-{
-	struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
-	struct autofs_info *ino;
-
-	ino = autofs_dentry_ino(dentry);
-	if (ino) {
-		spin_lock(&sbi->lookup_lock);
-		if (!ino->active_count) {
-			if (list_empty(&ino->active))
-				list_add(&ino->active, &sbi->active_list);
-		}
-		ino->active_count++;
-		spin_unlock(&sbi->lookup_lock);
-	}
-}
-
 static void autofs_del_active(struct dentry *dentry)
 {
 	struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
 	struct autofs_info *ino;
 
 	ino = autofs_dentry_ino(dentry);
-	if (ino) {
 	spin_lock(&sbi->lookup_lock);
-		ino->active_count--;
-		if (!ino->active_count) {
-			if (!list_empty(&ino->active))
 	list_del_init(&ino->active);
-		}
 	spin_unlock(&sbi->lookup_lock);
-	}
 }
 
 static int autofs_dir_open(struct inode *inode, struct file *file)
@@ -527,19 +504,22 @@ static struct dentry *autofs_lookup(struct inode *dir,
 		if (!autofs_oz_mode(sbi) && !IS_ROOT(dentry->d_parent))
 			return ERR_PTR(-ENOENT);
 
-		/* Mark entries in the root as mount triggers */
-		if (IS_ROOT(dentry->d_parent) &&
-		    autofs_type_indirect(sbi->type))
-			__managed_dentry_set_managed(dentry);
-
 		ino = autofs_new_ino(sbi);
 		if (!ino)
 			return ERR_PTR(-ENOMEM);
 
+		spin_lock(&sbi->lookup_lock);
+		spin_lock(&dentry->d_lock);
+		/* Mark entries in the root as mount triggers */
+		if (IS_ROOT(dentry->d_parent) &&
+		    autofs_type_indirect(sbi->type))
+			__managed_dentry_set_managed(dentry);
 		dentry->d_fsdata = ino;
 		ino->dentry = dentry;
 
-		autofs_add_active(dentry);
+		list_add(&ino->active, &sbi->active_list);
+		spin_unlock(&sbi->lookup_lock);
+		spin_unlock(&dentry->d_lock);
 	}
 	return NULL;
 }