[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: NTrond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fs/nfs/write.c

@@ -590,10 +590,10 @@ static void nfs_cancel_commit_list(struct list_head *head)
 
 	while(!list_empty(head)) {
 		req = nfs_list_entry(head->next);
+		dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
 		nfs_list_remove_request(req);
 		nfs_inode_remove_request(req);
-		dec_zone_page_state(req->wb_page, NR_UNSTABLE_NFS);
-		nfs_clear_page_writeback(req);
+		nfs_unlock_request(req);
 	}
 }