[PATCH] NFS: Fix oops in nfs_cancel_commit_list

Fix two bugs:
 - nfs_inode_remove_request will call nfs_clear_request, so we cannot
   reference req->wb_page after it. Move the call to dec_zone_page_state so
   that it occurs while req->wb_page is still valid.
 - Calling nfs_clear_page_writeback is unnecessary since the radix tree
   tags will have been cleared by the call to nfs_inode_remove_request.
   Replace with a simple call to nfs_unlock_request.

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>