ovl: make consistent use of OVL_FS()

Always use OVL_FS() to retrieve the corresponding struct ovl_fs from a
struct super_block.

Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 6d54f3f..c8c8588b 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -183,7 +183,7 @@ static int ovl_connect_layer(struct dentry *dentry)
  */
 static int ovl_check_encode_origin(struct dentry *dentry)
 {
-	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(dentry->d_sb);
 	bool decodable = ofs->config.nfs_export;
 
 	/* Lower file handle for non-upper non-decodable */
@@ -444,7 +444,7 @@ static struct dentry *ovl_lookup_real_inode(struct super_block *sb,
 					    struct dentry *real,
 					    const struct ovl_layer *layer)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 	struct dentry *index = NULL;
 	struct dentry *this = NULL;
 	struct inode *inode;
@@ -665,7 +665,7 @@ static struct dentry *ovl_get_dentry(struct super_block *sb,
 				     struct ovl_path *lowerpath,
 				     struct dentry *index)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 	const struct ovl_layer *layer = upper ? &ofs->layers[0] : lowerpath->layer;
 	struct dentry *real = upper ?: (index ?: lowerpath->dentry);
 
@@ -690,7 +690,7 @@ static struct dentry *ovl_get_dentry(struct super_block *sb,
 static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
 					struct ovl_fh *fh)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 	struct dentry *dentry;
 	struct dentry *upper;
 
@@ -710,7 +710,7 @@ static struct dentry *ovl_upper_fh_to_d(struct super_block *sb,
 static struct dentry *ovl_lower_fh_to_d(struct super_block *sb,
 					struct ovl_fh *fh)
 {
-	struct ovl_fs *ofs = sb->s_fs_info;
+	struct ovl_fs *ofs = OVL_FS(sb);
 	struct ovl_path origin = { };
 	struct ovl_path *stack = &origin;
 	struct dentry *dentry = NULL;