linux-kernel - Can ovl_drop_write() be called earlier in ovl_dentry

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Message-ID: <21902.1433166736@warthog.procyon.org.uk>
Date:	Mon, 01 Jun 2015 14:52:16 +0100
From:	David Howells <dhowells@...hat.com>
To:	Miklos Szeredi <miklos@...redi.hu>, viro@...iv.linux.org.uk
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-unionfs@...r.kernel.org, dhowells@...hat.com
Subject: Can ovl_drop_write() be called earlier in ovl_dentry_open()

In ovl_dentry_open(), ovl_drop_write() is called after vfs_open() - but is
this actually necessary?  Can't we just drop it post-copyup?  After all,
that's all we wanted the write lock for, right?

David
---
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -356,16 +356,14 @@ static int ovl_dentry_open(struct dentry *dentry, struct inode *inode,
 			err = ovl_copy_up_last(dentry, NULL, true);
 		else
 			err = ovl_copy_up(dentry);
+		ovl_drop_write(dentry);
 		if (err)
-			goto out_drop_write;
+			goto out;
 
 		ovl_path_upper(dentry, &realpath);
 	}
 
 	err = vfs_open(&realpath, d_backing_inode(realpath.dentry), file, cred);
-out_drop_write:
-	if (want_write)
-		ovl_drop_write(dentry);
 out:
 	return err;
 }
--
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