ovl: remove redundant ofs->indexdir member

When the index feature is disabled, ofs->indexdir is NULL.
When the index feature is enabled, ofs->indexdir has the same value as
ofs->workdir and takes an extra reference.

This makes the code harder to understand when it is not always clear
that ofs->indexdir in one function is the same dentry as ofs->workdir
in another function.

Remove this redundancy, by referencing ofs->workdir directly in index
helpers and by using the ovl_indexdir() accessor in generic code.
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

fs/overlayfs/export.c

@@ -460,7 +460,7 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
 	 * For decoded lower dir file handle, lookup index by origin to check
 	 * if lower dir was copied up and and/or removed.
 	 */
-	if (!this && layer->idx && ofs->indexdir && !WARN_ON(!d_is_dir(real))) {
+	if (!this && layer->idx && ovl_indexdir(sb) && !WARN_ON(!d_is_dir(real))) {
 		index = ovl_lookup_index(ofs, NULL, real, false);
 		if (IS_ERR(index))
 			return index;
@@ -733,7 +733,7 @@ static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
 	}
 
 	/* Then lookup indexed upper/whiteout by origin fh */
-	if (ofs->indexdir) {
+	if (ovl_indexdir(sb)) {
 		index = ovl_get_index_fh(ofs, fh);
 		err = PTR_ERR(index);
 		if (IS_ERR(index)) {

fs/overlayfs/namei.c

@@ -754,7 +754,7 @@ struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh)
 	if (err)
 		return ERR_PTR(err);
 
-	index = lookup_positive_unlocked(name.name, ofs->indexdir, name.len);
+	index = lookup_positive_unlocked(name.name, ofs->workdir, name.len);
 	kfree(name.name);
 	if (IS_ERR(index)) {
 		if (PTR_ERR(index) == -ENOENT)
@@ -787,7 +787,7 @@ struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
 		return ERR_PTR(err);
 
 	index = lookup_one_positive_unlocked(ovl_upper_mnt_idmap(ofs), name.name,
-					     ofs->indexdir, name.len);
+					     ofs->workdir, name.len);
 	if (IS_ERR(index)) {
 		err = PTR_ERR(index);
 		if (err == -ENOENT) {

fs/overlayfs/ovl_entry.h

@@ -63,10 +63,8 @@ struct ovl_fs {
 	struct ovl_sb *fs;
 	/* workbasedir is the path at workdir= mount option */
 	struct dentry *workbasedir;
-	/* workdir is the 'work' directory under workbasedir */
+	/* workdir is the 'work' or 'index' directory under workbasedir */
 	struct dentry *workdir;
-	/* index directory listing overlay inodes by origin file handle */
-	struct dentry *indexdir;
 	long namelen;
 	/* pathnames of lower and upper dirs, for show_options */
 	struct ovl_config config;
@@ -81,7 +79,6 @@ struct ovl_fs {
 	/* Traps in ovl inode cache */
 	struct inode *workbasedir_trap;
 	struct inode *workdir_trap;
-	struct inode *indexdir_trap;
 	/* -1: disabled, 0: same fs, 1..32: number of unused ino bits */
 	int xino_mode;
 	/* For allocation of non-persistent inode numbers */

fs/overlayfs/params.c

@@ -743,10 +743,8 @@ void ovl_free_fs(struct ovl_fs *ofs)
 	unsigned i;
 
 	iput(ofs->workbasedir_trap);
-	iput(ofs->indexdir_trap);
 	iput(ofs->workdir_trap);
 	dput(ofs->whiteout);
-	dput(ofs->indexdir);
 	dput(ofs->workdir);
 	if (ofs->workdir_locked)
 		ovl_inuse_unlock(ofs->workbasedir);

fs/overlayfs/readdir.c

@@ -1169,7 +1169,7 @@ int ovl_workdir_cleanup(struct ovl_fs *ofs, struct inode *dir,
 int ovl_indexdir_cleanup(struct ovl_fs *ofs)
 {
 	int err;
-	struct dentry *indexdir = ofs->indexdir;
+	struct dentry *indexdir = ofs->workdir;
 	struct dentry *index = NULL;
 	struct inode *dir = indexdir->d_inode;
 	struct path path = { .mnt = ovl_upper_mnt(ofs), .dentry = indexdir };

fs/overlayfs/super.c

@@ -853,10 +853,8 @@ static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
 	if (IS_ERR(indexdir)) {
 		err = PTR_ERR(indexdir);
 	} else if (indexdir) {
-		ofs->indexdir = indexdir;
-		ofs->workdir = dget(indexdir);
-
-		err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
+		ofs->workdir = indexdir;
+		err = ovl_setup_trap(sb, indexdir, &ofs->workdir_trap,
 				     "indexdir");
 		if (err)
 			goto out;
@@ -869,16 +867,15 @@ static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
 		 * ".overlay.upper" to indicate that index may have
 		 * directory entries.
 		 */
-		if (ovl_check_origin_xattr(ofs, ofs->indexdir)) {
-			err = ovl_verify_origin_xattr(ofs, ofs->indexdir,
+		if (ovl_check_origin_xattr(ofs, indexdir)) {
+			err = ovl_verify_origin_xattr(ofs, indexdir,
 						      OVL_XATTR_ORIGIN,
 						      upperpath->dentry, true,
 						      false);
 			if (err)
 				pr_err("failed to verify index dir 'origin' xattr\n");
 		}
-		err = ovl_verify_upper(ofs, ofs->indexdir, upperpath->dentry,
-				       true);
+		err = ovl_verify_upper(ofs, indexdir, upperpath->dentry, true);
 		if (err)
 			pr_err("failed to verify index dir 'upper' xattr\n");
 
@@ -886,7 +883,7 @@ static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
 		if (!err)
 			err = ovl_indexdir_cleanup(ofs);
 	}
-	if (err || !ofs->indexdir)
+	if (err || !indexdir)
 		pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
 
 out:
@@ -1406,7 +1403,7 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
 			goto out_free_oe;
 
 		/* Force r/o mount with no index dir */
-		if (!ofs->indexdir)
+		if (!ofs->workdir)
 			sb->s_flags |= SB_RDONLY;
 	}
 
@@ -1415,7 +1412,7 @@ int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
 		goto out_free_oe;
 
 	/* Show index=off in /proc/mounts for forced r/o mount */
-	if (!ofs->indexdir) {
+	if (!ofs->workdir) {
 		ofs->config.index = false;
 		if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) {
 			pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");

fs/overlayfs/util.c

@@ -91,7 +91,7 @@ struct dentry *ovl_indexdir(struct super_block *sb)
 {
 	struct ovl_fs *ofs = OVL_FS(sb);
 
-	return ofs->indexdir;
+	return ofs->config.index ? ofs->workdir : NULL;
 }
 
 /* Index all files on copy up. For now only enabled for NFS export */