ovl: reorder ovl_want_write() after ovl_inode_lock()

Make the locking order of ovl_inode_lock() strictly between the two
vfs stacked layers, i.e.:
- ovl vfs locks: sb_writers, inode_lock, ...
- ovl_inode_lock
- upper vfs locks: sb_writers, inode_lock, ...

To that effect, move ovl_want_write() into the helpers ovl_nlink_start()
and ovl_copy_up_start which currently take the ovl_inode_lock() after
ovl_want_write().

Signed-off-by: Amir Goldstein <amir73il@gmail.com>

1 files changed, 1 insertions, 6 deletions

diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c
index 26b782c53910..7e16bbcad95e 100644
--- a/fs/overlayfs/export.c
+++ b/fs/overlayfs/export.c
@@ -23,12 +23,7 @@ static int ovl_encode_maybe_copy_up(struct dentry *dentry)
 	if (ovl_dentry_upper(dentry))
 		return 0;
 
-	err = ovl_want_write(dentry);
-	if (!err) {
-		err = ovl_copy_up(dentry);
-		ovl_drop_write(dentry);
-	}
-
+	err = ovl_copy_up(dentry);
 	if (err) {
 		pr_warn_ratelimited("failed to copy up on encode (%pd2, err=%i)\n",
 				    dentry, err);