tools/oxenstored: mkdir conflicts were sometimes missed

Due to how set_write_lowpath was used here it didn't detect create/delete
conflicts.  When we create an entry we must mark our parent as modified
(this is what creating a new node via write does).

Otherwise we can have 2 transactions one creating, and another deleting a node
both succeeding depending on timing.  Or one transaction reading an entry,
concluding it doesn't exist, do some other work based on that information and
successfully commit even if another transaction creates the node via mkdir
meanwhile.

Signed-off-by: Edwin Török <edvin.torok@citrix.com>
Acked-by: Christian Lindig <christian.lindig@citrix.com>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>
(cherry picked from commit 45dee7d92b493bb531e7e77a6f9c0180ab152f87)

diff --git a/tools/ocaml/xenstored/transaction.ml b/tools/ocaml/xenstored/transaction.ml
index 9e9e28db9bd10104f1e39ad64fc38b15032cb169..7c5be17588b61b450b140c2bca7cdac94c41c2ed 100644 (file)
--- a/tools/ocaml/xenstored/transaction.ml
+++ b/tools/ocaml/xenstored/transaction.ml
@@ -165,7 +165,7 @@ let write t perm path value =
 
 let mkdir ?(with_watch=true) t perm path =
        Store.mkdir t.store perm path;
-       set_write_lowpath t path;
+       set_write_lowpath t (Store.Path.get_parent path);
        if with_watch then
                add_wop t Xenbus.Xb.Op.Mkdir path