[xen stable-4.4] oxenstored: support commit history tracking

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[xen stable-4.4] oxenstored: support commit history tracking

patchbot
commit 69950a74a2f9f8e9dfdaca4809adac78eb176945
Author:     Jonathan Davies <[hidden email]>
AuthorDate: Tue Mar 14 13:20:07 2017 +0000
Commit:     Ian Jackson <[hidden email]>
CommitDate: Wed Apr 5 15:26:38 2017 +0100

    oxenstored: support commit history tracking
   
    Add ability to track xenstore tree operations -- either non-transactional
    operations or committed transactions.
   
    For now, the call to actually retain commits is commented out because history
    can grow without bound.
   
    For now, we call record_commit for all non-transactional operations. A
    subsequent patch will make it retain only the ones with side-effects.
   
    Reported-by: Juergen Gross <[hidden email]>
    Signed-off-by: Jonathan Davies <[hidden email]>
    Signed-off-by: Thomas Sanders <[hidden email]>
    Reviewed-by: Christian Lindig <[hidden email]>
---
 tools/ocaml/xenstored/Makefile     |  1 +
 tools/ocaml/xenstored/history.ml   | 43 ++++++++++++++++++++++++++++++++++++++
 tools/ocaml/xenstored/process.ml   | 24 +++++++++++++++++++--
 tools/ocaml/xenstored/xenstored.ml |  1 +
 4 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/tools/ocaml/xenstored/Makefile b/tools/ocaml/xenstored/Makefile
index 7a4c317..ff3eed9 100644
--- a/tools/ocaml/xenstored/Makefile
+++ b/tools/ocaml/xenstored/Makefile
@@ -31,6 +31,7 @@ OBJS = define \
  domains \
  connection \
  connections \
+ history \
  parse_arg \
  process \
  xenstored
diff --git a/tools/ocaml/xenstored/history.ml b/tools/ocaml/xenstored/history.ml
new file mode 100644
index 0000000..e4b4d70
--- /dev/null
+++ b/tools/ocaml/xenstored/history.ml
@@ -0,0 +1,43 @@
+(*
+ * Copyright (c) 2017 Citrix Systems Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *)
+
+type history_record = {
+ con: Connection.t;   (* connection that made a change *)
+ tid: int;            (* transaction id of the change (may be Transaction.none) *)
+ before: Store.t;     (* the store before the change *)
+ after: Store.t;      (* the store after the change *)
+ finish_count: int64; (* the commit-count at which the transaction finished *)
+}
+
+let history : history_record list ref = ref []
+
+(* Called from periodic_ops to ensure we don't discard symbols that are still needed. *)
+(* There is scope for optimisation here, since in consecutive commits one commit's `after`
+ * is the same thing as the next commit's `before`, but not all commits in history are
+ * consecutive. *)
+let mark_symbols () =
+ (* There are gaps where dom0's commits are missing. Otherwise we could assume that
+ * each element's `before` is the same thing as the next element's `after`
+ * since the next element is the previous commit *)
+ List.iter (fun hist_rec ->
+ Store.mark_symbols hist_rec.before;
+ Store.mark_symbols hist_rec.after;
+ )
+ !history
+
+let push (x: history_record) =
+ let dom = x.con.Connection.dom in
+ match dom with
+ | None -> () (* treat socket connections as always free to conflict *)
+ | Some d -> if not (Domain.is_free_to_conflict d) then history := x :: !history
diff --git a/tools/ocaml/xenstored/process.ml b/tools/ocaml/xenstored/process.ml
index ff5fc24..b48df05 100644
--- a/tools/ocaml/xenstored/process.ml
+++ b/tools/ocaml/xenstored/process.ml
@@ -287,6 +287,16 @@ let write_response_log ~ty ~tid ~con ~response =
  | Packet.Reply x -> write_answer_log ~ty ~tid ~con ~data:x
  | Packet.Error e -> write_answer_log ~ty:(Xenbus.Xb.Op.Error) ~tid ~con ~data:e
 
+let record_commit ~con ~tid ~before ~after =
+ let inc r = r := Int64.add 1L !r in
+ let finish_count = inc Transaction.counter; !Transaction.counter in
+ (* This call would leak memory if historic activity is retained forever
+   so can only be uncommented if history is guaranteed not to grow
+   unboundedly.
+ History.push {History.con=con; tid=tid; before=before; after=after; finish_count=finish_count}
+ *)
+ ()
+
 (* Replay a stored transaction against a fresh store, check the responses are
    all equivalent: if so, commit the transaction. Otherwise send the abort to
    the client. *)
@@ -357,8 +367,14 @@ let do_transaction_end con t domains cons data =
  Connection.end_transaction con (Transaction.get_id t) commit in
  if not success then
  raise Transaction_again;
- if commit then
- process_watch (List.rev (Transaction.get_paths t)) cons
+ if commit then begin
+ process_watch (List.rev (Transaction.get_paths t)) cons;
+ match t.Transaction.ty with
+ | Transaction.No ->
+ () (* no need to record anything *)
+ | Transaction.Full(id, oldstore, cstore) ->
+ record_commit ~con ~tid:id ~before:oldstore ~after:cstore
+ end
 
 let do_introduce con t domains cons data =
  if not (Connection.is_dom0 con)
@@ -441,7 +457,11 @@ let process_packet ~store ~cons ~doms ~con ~req =
  else
  Connection.get_transaction con tid
  in
+
+ let before = Store.copy store in
  let response = input_handle_error ~cons ~doms ~fct ~con ~t ~req in
+ let after = Store.copy store in
+ if tid = Transaction.none then record_commit ~con ~tid ~before ~after;
 
  let response = try
  if tid <> Transaction.none then
diff --git a/tools/ocaml/xenstored/xenstored.ml b/tools/ocaml/xenstored/xenstored.ml
index 9480b21..c009701 100644
--- a/tools/ocaml/xenstored/xenstored.ml
+++ b/tools/ocaml/xenstored/xenstored.ml
@@ -384,6 +384,7 @@ let _ =
  Symbol.mark_all_as_unused ();
  Store.mark_symbols store;
  Connections.iter cons Connection.mark_symbols;
+ History.mark_symbols ();
  Symbol.garbage ()
  end;
 
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.4

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