diff options
Diffstat (limited to 'system/xen/xsa/xsa206-4.8-0013-oxenstored-do-not-commit-read-only-transactions.patch')
| -rw-r--r-- | system/xen/xsa/xsa206-4.8-0013-oxenstored-do-not-commit-read-only-transactions.patch | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/system/xen/xsa/xsa206-4.8-0013-oxenstored-do-not-commit-read-only-transactions.patch b/system/xen/xsa/xsa206-4.8-0013-oxenstored-do-not-commit-read-only-transactions.patch new file mode 100644 index 0000000000..e6b066e40a --- /dev/null +++ b/system/xen/xsa/xsa206-4.8-0013-oxenstored-do-not-commit-read-only-transactions.patch @@ -0,0 +1,59 @@ +From f45ce51771c7e96c8ac8179c44476f8fc6168636 Mon Sep 17 00:00:00 2001 +From: Thomas Sanders <thomas.sanders@citrix.com> +Date: Fri, 24 Mar 2017 16:16:10 +0000 +Subject: [PATCH 13/15] oxenstored: do not commit read-only transactions + +The packet telling us to end the transaction has always carried an +argument telling us whether to commit. + +If the transaction made no modifications to the tree, now we ignore +that argument and do not commit: it is just a waste of effort. + +This makes read-only transactions immune to conflicts, and means that +we do not need to store any of their details in the history that is +used for assigning blame for conflicts. + +We count a transaction as a read-only transaction only if it contains +no operations that modified the tree. + +This means that (for example) a transaction that creates a new node +then deletes it would NOT count as read-only, even though it makes no +change overall. A more sophisticated algorithm could judge the +transaction based on comparison of its initial and final states, but +this would add complexity and computational cost. + +Reported-by: Juergen Gross <jgross@suse.com> +Signed-off-by: Thomas Sanders <thomas.sanders@citrix.com> +Reviewed-by: Jonathan Davies <jonathan.davies@citrix.com> +--- + tools/ocaml/xenstored/process.ml | 1 + + tools/ocaml/xenstored/transaction.ml | 1 + + 2 files changed, 2 insertions(+) + +diff --git a/tools/ocaml/xenstored/process.ml b/tools/ocaml/xenstored/process.ml +index b56e3fc..adfc7a4 100644 +--- a/tools/ocaml/xenstored/process.ml ++++ b/tools/ocaml/xenstored/process.ml +@@ -393,6 +393,7 @@ let do_transaction_end con t domains cons data = + | x :: _ -> raise (Invalid_argument x) + | _ -> raise Invalid_Cmd_Args + in ++ let commit = commit && not (Transaction.is_read_only t) in + let success = + let commit = if commit then Some (fun con trans -> transaction_replay con trans domains cons) else None in + History.end_transaction t con (Transaction.get_id t) commit in +diff --git a/tools/ocaml/xenstored/transaction.ml b/tools/ocaml/xenstored/transaction.ml +index edd1178..8f95301 100644 +--- a/tools/ocaml/xenstored/transaction.ml ++++ b/tools/ocaml/xenstored/transaction.ml +@@ -128,6 +128,7 @@ let make ?(internal=false) id store = + let get_store t = t.store + let get_paths t = t.paths + ++let is_read_only t = t.paths = [] + let add_wop t ty path = t.paths <- (ty, path) :: t.paths + let add_operation ~perm t request response = + if !Define.maxrequests >= 0 +-- +2.1.4 + |