From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jordi Pujol <jordipujolp@gmail.com>
Subject: Re: overlayfs: mounting overlayfs on top of overlayfs
Date: Mon, 6 Jun 2011 20:29:24 +0200
Message-ID: <201106062029.25279.jordipujolp@gmail.com>
References: <201106031529.30103.jordipujolp@gmail.com> <201106040823.25072.jordipujolp@gmail.com>
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Cc: linux-fsdevel@vger.kernel.org,
	Michal Suchanek <hramrach@centrum.cz>
To: Miklos Szeredi <miklos@szeredi.hu>
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Hello,

The attached patch solves the problem,

Thanks,

Jordi Pujol

Live never ending Tale
GNU/Linux Live forever!
http://livenet.selfip.com

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 overlayfs v10:
 - Test for readonly using the vfsmount superblock
  from the main filesystem.
 - Ignore WRITE request for the real filesystems.

Signed-off-by: Jordi Pujol <jordipujolp@gmail.com>

--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c	2011-06-05 10:06:25.323823937 +0200
@@ -54,6 +54,9 @@ int ovl_permission(struct inode *inode,
 	bool is_upper;
 	int err;

+	if (mask & MAY_WRITE && IS_RDONLY(inode))
+		return -EROFS;
+
 	if (S_ISDIR(inode->i_mode)) {
 		oe = inode->i_private;
 	} else if (flags & IPERM_FLAG_RCU) {
@@ -102,6 +105,8 @@ int ovl_permission(struct inode *inode,
 		err = -EACCES;
 		if (IS_IMMUTABLE(realinode))
 			goto out_dput;
+
+		mask &= ~MAY_WRITE;
 	}

 	if (realinode->i_op->permission)

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