From 0d92a42aab3fb0e7569294675666976724156128 Mon Sep 17 00:00:00 2001

From: "Richard W.M. Jones" <rjones@redhat.com>

Date: Thu, 14 Jul 2022 13:15:49 +0100

Subject: [PATCH] -o rhv: Unmount the temporary NFS mountpoint as late as

 possible

To partially avoid a potential race against nbdkit or qemu-nbd

releasing files on the mountpoint before they exit, unmount as late as

we can.

See also https://bugzilla.redhat.com/show_bug.cgi?id=1953286#c26

Reviewed-by: Laszlo Ersek <lersek@redhat.com>

(cherry picked from commit e96357fc3b26aaf96eaa21afa36c894a27af6261)

---

 common               | 2 +-

 output/output_rhv.ml | 4 ++--

 2 files changed, 3 insertions(+), 3 deletions(-)

Submodule common fd964c1b..1000604f:

diff --git a/common/mltools/on_exit.ml b/common/mltools/on_exit.ml

index cae12e73..f8ef74e1 100644

--- a/common/mltools/on_exit.ml

+++ b/common/mltools/on_exit.ml

@@ -23,39 +23,39 @@ open Common_gettext.Gettext

 open Unix

 open Printf

-(* List of files to unlink. *)

-let files = ref []

+type action =

+  | Unlink of string     (* filename *)

+  | Rm_rf of string      (* directory *)

+  | Kill of int * int    (* signal, pid *)

+  | Fn of (unit -> unit) (* generic function *)

-(* List of directories to remove. *)

-let rmdirs = ref []

-

-(* List of PIDs to kill. *)

-let kills = ref []

-

-(* List of functions to call. *)

-let fns = ref []

+(* List of (priority, action). *)

+let actions = ref []

 (* Perform a single exit action, printing any exception but

  * otherwise ignoring failures.

  *)

-let do_action f arg =

-  try f arg with exn -> debug "%s" (Printexc.to_string exn)

+let do_action action =

+  try

+    match action with

+    | Unlink file -> Unix.unlink file

+    | Rm_rf dir ->

+       let cmd = sprintf "rm -rf -- %s" (Filename.quote dir) in

+       ignore (Tools_utils.shell_command cmd)

+    | Kill (signal, pid) ->

+       kill pid signal

+    | Fn f -> f ()

+  with exn -> debug "%s" (Printexc.to_string exn)

 (* Make sure the actions are performed only once. *)

 let done_actions = ref false

-(* Perform the exit actions. *)

+(* Perform the exit actions in priority order (lowest prio first). *)

 let do_actions () =

   if not !done_actions then (

-    List.iter (do_action (fun f -> f ())) !fns;

-    List.iter (do_action (fun (signal, pid) -> kill pid signal)) !kills;

-    List.iter (do_action (fun file -> Unix.unlink file)) !files;

-    List.iter (do_action (

-      fun dir ->

-        let cmd = sprintf "rm -rf -- %s" (Filename.quote dir) in

-        ignore (Tools_utils.shell_command cmd)

-      )

-    ) !rmdirs;

+    let actions = List.sort (fun (a, _) (b, _) -> compare a b) !actions in

+    let actions = List.map snd actions in

+    List.iter do_action actions

   );

   done_actions := true

@@ -94,18 +94,18 @@ let register () =

   );

   registered := true

-let f fn =

+let f ?(prio = 5000) fn =

   register ();

-  List.push_front fn fns

+  List.push_front (prio, Fn fn) actions

-let unlink filename =

+let unlink ?(prio = 5000) filename =

   register ();

-  List.push_front filename files

+  List.push_front (prio, Unlink filename) actions

-let rm_rf dir =

+let rm_rf ?(prio = 5000) dir =

   register ();

-  List.push_front dir rmdirs

+  List.push_front (prio, Rm_rf dir) actions

-let kill ?(signal = Sys.sigterm) pid =

+let kill ?(prio = 5000) ?(signal = Sys.sigterm) pid =

   register ();

-  List.push_front (signal, pid) kills

+  List.push_front (prio, Kill (signal, pid)) actions

diff --git a/common/mltools/on_exit.mli b/common/mltools/on_exit.mli

index 9bcf104f..66a85542 100644

--- a/common/mltools/on_exit.mli

+++ b/common/mltools/on_exit.mli

@@ -28,6 +28,12 @@

     killing another process, so we provide simple

     wrappers for those common actions here.

+    Actions can be ordered by setting the optional [?prio]

+    parameter in the range 0..9999.  By default actions

+    have priority 5000.  Lower numbered actions run first.

+    Higher numbered actions run last.  So to have an action

+    run at the very end before exit you might use [~prio:9999]

+

     Note this module registers signal handlers for

     SIGINT, SIGQUIT, SIGTERM and SIGHUP.  This means

     that any program that links with mltools.cmxa

@@ -39,18 +45,20 @@

     Your cleanup action might no longer run unless the

     program calls {!Stdlib.exit}. *)

-val f : (unit -> unit) -> unit

+val f : ?prio:int -> (unit -> unit) -> unit

 (** Register a function [f] which runs when the program exits.

     Similar to [Stdlib.at_exit] but also runs if the program is

-    killed with a signal that we can catch. *)

+    killed with a signal that we can catch.

-val unlink : string -> unit

+    [?prio] is the priority, default 5000.  See the description above. *)

+

+val unlink : ?prio:int -> string -> unit

 (** Unlink a single temporary file on exit. *)

-val rm_rf : string -> unit

+val rm_rf : ?prio:int -> string -> unit

 (** Recursively remove a temporary directory on exit (using [rm -rf]). *)

-val kill : ?signal:int -> int -> unit

+val kill : ?prio:int -> ?signal:int -> int -> unit

 (** Kill [PID] on exit.  The signal sent defaults to [Sys.sigterm].

     Use this with care since you can end up unintentionally killing

diff --git a/output/output_rhv.ml b/output/output_rhv.ml

index 8571e07b..15a2c14a 100644

--- a/output/output_rhv.ml

+++ b/output/output_rhv.ml

@@ -204,8 +204,8 @@ module RHV = struct

        if run_command cmd <> 0 then

          error (f_"mount command failed, see earlier errors.\n\nThis probably means you didn't specify the right %s path [-os %s], or else you need to rerun virt-v2v as root.") domain_class os;

-       (* Make sure it is unmounted at exit. *)

-       On_exit.f (

+       (* Make sure it is unmounted at exit, as late as possible (prio=9999) *)

+       On_exit.f ~prio:9999 (

          fun () ->

            let cmd = [ "umount"; mp ] in

            ignore (run_command cmd);