From: Christoph Hellwig <hch@lst.de>
Date: Tue, 5 May 2009 13:41:25 +0000 (+0200)
Subject: enforce ->sync_fs is only called for rw superblock
X-Git-Tag: v2.6.31-rc1~375^2~50
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=5af7926ff33b68b3ba46531471c6e0564b285efc;p=pandora-kernel.git

enforce ->sync_fs is only called for rw superblock

Make sure a superblock really is writeable by checking MS_RDONLY
under s_umount.  sync_filesystems needed some re-arragement for
that, but all but one sync_filesystem caller had the correct locking
already so that we could add that check there.  cachefiles grew
s_umount locking.

I've also added a WARN_ON to sync_filesystem to assert this for
future callers.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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