ovl: Copy up only metadata during copy up where it makes sense

If it makes sense to copy up only metadata during copy up, do it.  This is
done for regular files which are not opened for WRITE.

Right now ->metacopy is set to 0 always.  Last patch in the series will
remove the hard coded statement and enable metacopy feature.
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

fs/overlayfs/copy_up.c

@@ -388,6 +388,7 @@ struct ovl_copy_up_ctx {
 	bool tmpfile;
 	bool origin;
 	bool indexed;
+	bool metacopy;
 };
 
 static int ovl_link_up(struct ovl_copy_up_ctx *c)
@@ -507,7 +508,7 @@ static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
 			return err;
 	}
 
-	if (S_ISREG(c->stat.mode)) {
+	if (S_ISREG(c->stat.mode) && !c->metacopy) {
 		struct path upperpath;
 
 		ovl_path_upper(c->dentry, &upperpath);
@@ -660,6 +661,26 @@ static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
 	return err;
 }
 
+static bool ovl_need_meta_copy_up(struct dentry *dentry, umode_t mode,
+				  int flags)
+{
+	struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+
+	/* TODO: Will enable metacopy in last patch of series */
+	return false;
+
+	if (!ofs->config.metacopy)
+		return false;
+
+	if (!S_ISREG(mode))
+		return false;
+
+	if (flags && ((OPEN_FMODE(flags) & FMODE_WRITE) || (flags & O_TRUNC)))
+		return false;
+
+	return true;
+}
+
 static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 			   int flags)
 {
@@ -681,6 +702,8 @@ static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
 	if (err)
 		return err;
 
+	ctx.metacopy = ovl_need_meta_copy_up(dentry, ctx.stat.mode, flags);
+
 	if (parent) {
 		ovl_path_upper(parent, &parentpath);
 		ctx.destdir = parentpath.dentry;