ovl: lookup connected ancestor of dir in inode cache

Decoding a dir file handle requires walking backward up to layer root and
for lower dir also checking the index to see if any of the parents have
been copied up.

Lookup overlay ancestor dentry in inode/dentry cache by decoded real
parents to shortcut looking up all the way back to layer root.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

1 files changed, 15 insertions, 6 deletions

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;