[PATCH 2/3] overlayfs: ovl_lookup(): Use only uppermetacopy state

[Vivek Goyal <vgoyal@xxxxxxxxxx>]

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@xxxxxxxxx>
Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx>
---
 fs/overlayfs/namei.c | 57 ++++++++++++++++++++++----------------------
 1 file changed, 28 insertions(+), 29 deletions(-)

diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index 5d80d8cc0063..a1889a160708 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -823,7 +823,7 @@ 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,
@@ -869,7 +869,7 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry,
 				goto out_put_upper;
 
 			if (d.metacopy)
-				metacopy = true;
+				uppermetacopy = true;
 		}
 
 		if (d.redirect) {
@@ -906,6 +906,22 @@ 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".
@@ -940,17 +956,6 @@ 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++;
@@ -982,23 +987,17 @@ 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;
-		}
+	/* 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;
-		}
-	} else if (!d.is_dir && upperdentry && !ctr && origin_path) {
+	/* For regular non-metacopy upper dentries, there is no lower
+	 * path based lookup, hence ctr will be zero. dentry found using
+	 * ORIGIN xattr on upper, install it in stack.
+	 */
+	if (!d.is_dir && upperdentry && !ctr && origin_path) {
 		if (WARN_ON(stack != NULL)) {
 			err = -EIO;
 			goto out_put;
-- 
2.25.4