[xen stable-4.13] tools/oxenstored: mkdir conflicts were sometimes missed

[patchbot@xxxxxxx]

commit f2e50a048a1430117f14fa42bde75c31ff85a7aa
Author:     Edwin Török <edvin.torok@xxxxxxxxxx>
AuthorDate: Fri Jan 15 19:38:58 2021 +0000
Commit:     Ian Jackson <iwj@xxxxxxxxxxxxxx>
CommitDate: Fri Mar 19 13:44:13 2021 +0000

    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@xxxxxxxxxx>
    Acked-by: Christian Lindig <christian.lindig@xxxxxxxxxx>
    Release-Acked-by: Ian Jackson <iwj@xxxxxxxxxxxxxx>
    (cherry picked from commit 45dee7d92b493bb531e7e77a6f9c0180ab152f87)
---
 tools/ocaml/xenstored/transaction.ml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/ocaml/xenstored/transaction.ml 
b/tools/ocaml/xenstored/transaction.ml
index 25bc8c3b4a..17b1bdf2ea 100644
--- 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
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.13