merge d_materialise_unique() into d_splice_alias()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

fs/dcache.c

@@ -2575,11 +2575,11 @@ struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
  * Note: If ever the locking in lock_rename() changes, then please
  * remember to update this too...
  */
-static struct dentry *__d_unalias(struct inode *inode,
+static int __d_unalias(struct inode *inode,
 		struct dentry *dentry, struct dentry *alias)
 {
 	struct mutex *m1 = NULL, *m2 = NULL;
-	struct dentry *ret = ERR_PTR(-EBUSY);
+	int ret = -EBUSY;
 
 	/* If alias and dentry share a parent, then no extra locks required */
 	if (alias->d_parent == dentry->d_parent)
@@ -2594,7 +2594,7 @@ static struct dentry *__d_unalias(struct inode *inode,
 	m2 = &alias->d_parent->d_inode->i_mutex;
 out_unalias:
 	__d_move(alias, dentry, false);
-	ret = alias;
+	ret = 0;
 out_err:
 	spin_unlock(&inode->i_lock);
 	if (m2)
@@ -2629,130 +2629,57 @@ static struct dentry *__d_unalias(struct inode *inode,
  */
 struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
 {
-	struct dentry *new = NULL;
-
 	if (IS_ERR(inode))
 		return ERR_CAST(inode);
 
-	if (inode && S_ISDIR(inode->i_mode)) {
-		spin_lock(&inode->i_lock);
-		new = __d_find_any_alias(inode);
-		if (new) {
-			if (!IS_ROOT(new)) {
-				spin_unlock(&inode->i_lock);
-				dput(new);
-				iput(inode);
-				return ERR_PTR(-EIO);
-			}
-			if (d_ancestor(new, dentry)) {
-				spin_unlock(&inode->i_lock);
-				dput(new);
-				iput(inode);
-				return ERR_PTR(-EIO);
-			}
-			write_seqlock(&rename_lock);
-			__d_move(new, dentry, false);
-			write_sequnlock(&rename_lock);
-			spin_unlock(&inode->i_lock);
-			security_d_instantiate(new, inode);
-			iput(inode);
-		} else {
-			/* already taking inode->i_lock, so d_add() by hand */
-			__d_instantiate(dentry, inode);
-			spin_unlock(&inode->i_lock);
-			security_d_instantiate(dentry, inode);
-			d_rehash(dentry);
-		}
-	} else {
-		d_instantiate(dentry, inode);
-		if (d_unhashed(dentry))
-			d_rehash(dentry);
-	}
-	return new;
-}
-EXPORT_SYMBOL(d_splice_alias);
-
-/**
- * d_materialise_unique - introduce an inode into the tree
- * @dentry: candidate dentry
- * @inode: inode to bind to the dentry, to which aliases may be attached
- *
- * Introduces an dentry into the tree, substituting an extant disconnected
- * root directory alias in its place if there is one. Caller must hold the
- * i_mutex of the parent directory.
- */
-struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
-{
-	struct dentry *actual;
-
 	BUG_ON(!d_unhashed(dentry));
 
 	if (!inode) {
-		actual = dentry;
 		__d_instantiate(dentry, NULL);
-		d_rehash(actual);
-		goto out_nolock;
+		goto out;
 	}
-
 	spin_lock(&inode->i_lock);
-
 	if (S_ISDIR(inode->i_mode)) {
-		struct dentry *alias;
-
-		/* Does an aliased dentry already exist? */
-		alias = __d_find_alias(inode);
-		if (alias) {
-			actual = alias;
+		struct dentry *new = __d_find_any_alias(inode);
+		if (unlikely(new)) {
 			write_seqlock(&rename_lock);
-
-			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? */
-				__d_move(alias, dentry, false);
+			if (unlikely(d_ancestor(new, dentry))) {
 				write_sequnlock(&rename_lock);
-				goto found;
-			} else {
-				/* Nope, but we must(!) avoid directory
-				 * aliasing. This drops inode->i_lock */
-				actual = __d_unalias(inode, dentry, alias);
-			}
-			write_sequnlock(&rename_lock);
-			if (IS_ERR(actual)) {
-				if (PTR_ERR(actual) == -ELOOP)
+				spin_unlock(&inode->i_lock);
+				dput(new);
+				new = ERR_PTR(-ELOOP);
 				pr_warn_ratelimited(
 					"VFS: Lookup of '%s' in %s %s"
 					" would have caused loop\n",
 					dentry->d_name.name,
 					inode->i_sb->s_type->name,
 					inode->i_sb->s_id);
-				dput(alias);
+			} else if (!IS_ROOT(new)) {
+				int err = __d_unalias(inode, dentry, new);
+				write_sequnlock(&rename_lock);
+				if (err) {
+					dput(new);
+					new = ERR_PTR(err);
 				}
-			goto out_nolock;
+			} else {
+				__d_move(new, dentry, false);
+				write_sequnlock(&rename_lock);
+				spin_unlock(&inode->i_lock);
+				security_d_instantiate(new, inode);
 			}
+			iput(inode);
+			return new;
 		}
-
-	/* Add a unique reference */
-	actual = __d_instantiate_unique(dentry, inode);
-	if (!actual)
-		actual = dentry;
-
-	d_rehash(actual);
-found:
+	}
+	/* already taking inode->i_lock, so d_add() by hand */
+	__d_instantiate(dentry, inode);
 	spin_unlock(&inode->i_lock);
-out_nolock:
-	if (actual == dentry) {
+out:
 	security_d_instantiate(dentry, inode);
+	d_rehash(dentry);
 	return NULL;
-	}
-
-	iput(inode);
-	return actual;
 }
-EXPORT_SYMBOL_GPL(d_materialise_unique);
+EXPORT_SYMBOL(d_splice_alias);
 
 static int prepend(char **buffer, int *buflen, const char *str, int namelen)
 {

include/linux/dcache.h

@@ -230,7 +230,7 @@ extern seqlock_t rename_lock;
  */
 extern void d_instantiate(struct dentry *, struct inode *);
 extern struct dentry * d_instantiate_unique(struct dentry *, struct inode *);
-extern struct dentry * d_materialise_unique(struct dentry *, struct inode *);
+#define d_materialise_unique(d, i) d_splice_alias(i, d)
 extern int d_instantiate_no_diralias(struct dentry *, struct inode *);
 extern void __d_drop(struct dentry *dentry);
 extern void d_drop(struct dentry *dentry);