3 files changed, 110 insertions, 13 deletions

diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 361174810ce8..092e6e8c9258 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -295,6 +295,88 @@ fail:
 }
 
 /*
+ * Lookup an indexed or hashed overlay dentry by real inode.
+ */
+static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
+					    struct dentry *real,
+					    struct ovl_layer *layer)
+{
+	struct dentry *this = NULL;
+	struct inode *inode;
+
+	inode = ovl_lookup_inode(sb, real, !layer->idx);
+	if (IS_ERR(inode))
+		return ERR_CAST(inode);
+	if (inode) {
+		this = d_find_any_alias(inode);
+		iput(inode);
+	}
+
+	/* TODO: use index when looking up by origin inode */
+	if (!this)
+		return NULL;
+
+	if (WARN_ON(ovl_dentry_real_at(this, layer->idx) != real)) {
+		dput(this);
+		this = ERR_PTR(-EIO);
+	}
+
+	return this;
+}
+
+/*
+ * Lookup an indexed or hashed overlay dentry, whose real dentry is an
+ * ancestor of @real.
+ */
+static struct dentry *ovl_lookup_real_ancestor(struct super_block *sb,
+					       struct dentry *real,
+					       struct ovl_layer *layer)
+{
+	struct dentry *next, *parent = NULL;
+	struct dentry *ancestor = ERR_PTR(-EIO);
+
+	if (real == layer->mnt->mnt_root)
+		return dget(sb->s_root);
+
+	/* Find the topmost indexed or hashed ancestor */
+	next = dget(real);
+	for (;;) {
+		parent = dget_parent(next);
+
+		/*
+		 * Lookup a matching overlay dentry in inode/dentry
+		 * cache or in index by real inode.
+		 */
+		ancestor = ovl_lookup_real_inode(sb, next, layer);
+		if (ancestor)
+			break;
+
+		if (parent == layer->mnt->mnt_root) {
+			ancestor = dget(sb->s_root);
+			break;
+		}
+
+		/*
+		 * If @real has been moved out of the layer root directory,
+		 * we will eventully hit the real fs root. This cannot happen
+		 * by legit overlay rename, so we return error in that case.
+		 */
+		if (parent == next) {
+			ancestor = ERR_PTR(-EXDEV);
+			break;
+		}
+
+		dput(next);
+		next = parent;
+	}
+
+	dput(parent);
+	dput(next);
+
+	return ancestor;
+}
+
+/*
  * Lookup a connected overlay dentry whose real dentry is @real.
  * If @real is on upper layer, we lookup a child overlay dentry with the same
  * path the real dentry. Otherwise, we need to consult index for lookup.
@@ -306,9 +388,10 @@ static struct dentry *ovl_lookup_real(struct super_block *sb,
 	struct dentry *connected;
 	int err = 0;
 
-	/* TODO: use index when looking up by lower real dentry */
+	connected = ovl_lookup_real_ancestor(sb, real, layer);
+	if (IS_ERR(connected))
+		return connected;
 
-	connected = dget(sb->s_root);
 	while (!err) {
 		struct dentry *next, *this;
 		struct dentry *parent = NULL;
@@ -365,11 +448,15 @@ static struct dentry *ovl_lookup_real(struct super_block *sb,
 			 * overlay rename of child away from 'connected' parent.
 			 * In this case, we need to restart the lookup from the
 			 * top, because we cannot trust that 'real_connected' is
-			 * still an ancestor of 'real'.
+			 * still an ancestor of 'real'. There is a good chance
+			 * that the renamed overlay ancestor is now in cache, so
+			 * ovl_lookup_real_ancestor() will find it and we can
+			 * continue to connect exactly from where lookup failed.
 			 */
 			if (err == -ECHILD) {
-				this = dget(sb->s_root);
-				err = 0;
+				this = ovl_lookup_real_ancestor(sb, real,
+								layer);
+				err = IS_ERR(this) ? PTR_ERR(this) : 0;
 			}
 			if (!err) {
 				dput(connected);
@@ -494,7 +581,7 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
 	} else if (is_deleted) {
 		/* Lookup deleted non-dir by origin inode */
 		if (!d_is_dir(origin.dentry))
-			inode = ovl_lookup_inode(sb, origin.dentry);
+			inode = ovl_lookup_inode(sb, origin.dentry, false);
 		err = -ESTALE;
 		if (!inode || atomic_read(&inode->i_count) == 1)
 			goto out_err;
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index 416dc06835db..fcd97b783fa1 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -614,9 +614,15 @@ static int ovl_inode_set(struct inode *inode, void *data)
 }
 
 static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
-			     struct dentry *upperdentry)
+			     struct dentry *upperdentry, bool strict)
 {
-	if (S_ISDIR(inode->i_mode)) {
+	/*
+	 * For directories, @strict verify from lookup path performs consistency
+	 * checks, so NULL lower/upper in dentry must match NULL lower/upper in
+	 * inode. Non @strict verify from NFS handle decode path passes NULL for
+	 * 'unknown' lower/upper.
+	 */
+	if (S_ISDIR(inode->i_mode) && strict) {
 		/* Real lower dir moved to upper layer under us? */
 		if (!lowerdentry && ovl_inode_lower(inode))
 			return false;
@@ -645,15 +651,17 @@ static bool ovl_verify_inode(struct inode *inode, struct dentry *lowerdentry,
 	return true;
 }
 
-struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *origin)
+struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
+			       bool is_upper)
 {
-	struct inode *inode, *key = d_inode(origin);
+	struct inode *inode, *key = d_inode(real);
 
 	inode = ilookup5(sb, (unsigned long) key, ovl_inode_test, key);
 	if (!inode)
 		return NULL;
 
-	if (!ovl_verify_inode(inode, origin, NULL)) {
+	if (!ovl_verify_inode(inode, is_upper ? NULL : real,
+			      is_upper ? real : NULL, false)) {
 		iput(inode);
 		return ERR_PTR(-ESTALE);
 	}
@@ -704,7 +712,8 @@ struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
 			 * Verify that the underlying files stored in the inode
 			 * match those in the dentry.
 			 */
-			if (!ovl_verify_inode(inode, lowerdentry, upperdentry)) {
+			if (!ovl_verify_inode(inode, lowerdentry, upperdentry,
+					      true)) {
 				iput(inode);
 				inode = ERR_PTR(-ESTALE);
 				goto out;
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index a5d415aec131..bf17bf97c50f 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -323,7 +323,8 @@ int ovl_update_time(struct inode *inode, struct timespec *ts, int flags);
 bool ovl_is_private_xattr(const char *name);
 
 struct inode *ovl_new_inode(struct super_block *sb, umode_t mode, dev_t rdev);
-struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *origin);
+struct inode *ovl_lookup_inode(struct super_block *sb, struct dentry *real,
+			       bool is_upper);
 struct inode *ovl_get_inode(struct super_block *sb, struct dentry *upperdentry,
 			    struct dentry *lowerdentry, struct dentry *index,
 			    unsigned int numlower);