ovl: use only uppermetacopy state in ovl_lookup()

Currently we use a variable "metacopy" which signifies that dentry could be
either uppermetacopy or lowermetacopy.  Amir suggested that we can move
code around and use d.metacopy in such a way that we don't need
lowermetacopy and just can do away with uppermetacopy.

So this patch replaces "metacopy" with "uppermetacopy".

It also moves some code little higher to keep reading little simpler.

Suggested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

Author: rhvgoyal

fs/overlayfs/namei.c

@@ -812,7 +812,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 	struct dentry *this;
 	unsigned int i;
 	int err;
-	bool metacopy = false;
+	bool uppermetacopy = false;
 	struct ovl_lookup_data d = {
 		.sb = dentry->d_sb,
 		.name = dentry->d_name,
@@ -858,7 +858,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 				goto out_put_upper;
 
 			if (d.metacopy)
-				metacopy = true;
+				uppermetacopy = true;
 		}
 
 		if (d.redirect) {
@@ -895,6 +895,21 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		if (!this)
 			continue;
 
+		if ((uppermetacopy || d.metacopy) && !ofs->config.metacopy) {
+			err = -EPERM;
+			pr_warn_ratelimited("refusing to follow metacopy origin for (%pd2)\n", dentry);
+			goto out_put;
+		}
+
+		/*
+		 * Do not store intermediate metacopy dentries in chain,
+		 * except top most lower metacopy dentry
+		 */
+		if (d.metacopy && ctr) {
+			dput(this);
+			continue;
+		}
+
 		/*
 		 * If no origin fh is stored in upper of a merge dir, store fh
 		 * of lower dir and set upper parent "impure".
@@ -929,17 +944,6 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 			origin = this;
 		}
 
-		if (d.metacopy)
-			metacopy = true;
-		/*
-		 * Do not store intermediate metacopy dentries in chain,
-		 * except top most lower metacopy dentry
-		 */
-		if (d.metacopy && ctr) {
-			dput(this);
-			continue;
-		}
-
 		stack[ctr].dentry = this;
 		stack[ctr].layer = lower.layer;
 		ctr++;
@@ -971,22 +975,17 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 		}
 	}
 
-	if (metacopy) {
-		/*
-		 * Found a metacopy dentry but did not find corresponding
-		 * data dentry
-		 */
-		if (d.metacopy) {
-			err = -EIO;
-			goto out_put;
-		}
-
-		err = -EPERM;
-		if (!ofs->config.metacopy) {
-			pr_warn_ratelimited("refusing to follow metacopy origin for (%pd2)\n",
-					    dentry);
-			goto out_put;
-		}
+	/*
+	 * For regular non-metacopy upper dentries, there is no lower
+	 * path based lookup, hence ctr will be zero. If a dentry is found
+	 * using ORIGIN xattr on upper, install it in stack.
+	 *
+	 * For metacopy dentry, path based lookup will find lower dentries.
+	 * Just make sure a corresponding data dentry has been found.
+	 */
+	if (d.metacopy || (uppermetacopy && !ctr)) {
+		err = -EIO;
+		goto out_put;
 	} else if (!d.is_dir && upperdentry && !ctr && origin_path) {
 		if (WARN_ON(stack != NULL)) {
 			err = -EIO;