From 5cfe8a0e678468318d8af403c197367979ba62a0 Mon Sep 17 00:00:00 2001

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

Date: Tue, 22 Oct 2013 22:28:27 +0100

Subject: [PATCH] builder: Add --no-sync option to avoid sync on exit.

(cherry picked from commit 3f46a92ed5737bb8d75630a39729f95bc96417f6)

---

 builder/builder.ml       |  5 +++--

 builder/cmdline.ml       |  6 +++++-

 builder/virt-builder.pod | 17 +++++++++++++++++

 3 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/builder/builder.ml b/builder/builder.ml

index 477fc3e..7a46174 100644

--- a/builder/builder.ml

+++ b/builder/builder.ml

@@ -38,7 +38,7 @@ let main () =

     attach, cache, check_signature, curl, debug, delete, edit, fingerprint,

     firstboot, run, format, gpg, hostname, install, list_long, network, output,

     password_crypto, quiet, root_password, scrub, scrub_logfile, size, source,

-    upload =

+    sync, upload =

     parse_cmdline () in

   (* Timestamped messages in ordinary, non-debug non-quiet mode. *)

@@ -727,7 +727,8 @@ exec >>%s 2>&1

    * and therefore bypasses the host cache).  In general you should not

    * use cache=none.

    *)

-  Fsync.file output;

+  if sync then

+    Fsync.file output;

   (* Now that we've finished the build, don't delete the output file on

    * exit.

diff --git a/builder/cmdline.ml b/builder/cmdline.ml

index 780e171..41d2a64 100644

--- a/builder/cmdline.ml

+++ b/builder/cmdline.ml

@@ -161,6 +161,8 @@ let parse_cmdline () =

     with Not_found -> "http://libguestfs.org/download/builder/index.asc" in

   let source = ref source in

+  let sync = ref true in

+

   let upload = ref [] in

   let add_upload arg =

     let i =

@@ -232,6 +234,7 @@ let parse_cmdline () =

     "--scrub",   Arg.String add_scrub,      "name" ^ " " ^ s_"Scrub a file";

     "--size",    Arg.String set_size,       "size" ^ " " ^ s_"Set output disk size";

     "--source",  Arg.Set_string source,     "URL" ^ " " ^ s_"Set source URL";

+    "--no-sync", Arg.Clear sync,            " " ^ s_"Do not fsync output file on exit";

     "--upload",  Arg.String add_upload,     "file:dest" ^ " " ^ s_"Upload file to dest";

     "-v",        Arg.Set debug,             " " ^ s_"Enable debugging messages";

     "--verbose", Arg.Set debug,             ditto;

@@ -287,6 +290,7 @@ read the man page virt-builder(1).

   let scrub_logfile = !scrub_logfile in

   let size = !size in

   let source = !source in

+  let sync = !sync in

   let upload = List.rev !upload in

   (* Check options. *)

@@ -343,4 +347,4 @@ read the man page virt-builder(1).

   attach, cache, check_signature, curl, debug, delete, edit, fingerprint,

   firstboot, run, format, gpg, hostname, install, list_long, network, output,

   password_crypto, quiet, root_password, scrub, scrub_logfile, size, source,

-  upload

+  sync, upload

diff --git a/builder/virt-builder.pod b/builder/virt-builder.pod

index 094b327..c3ea581 100644

--- a/builder/virt-builder.pod

+++ b/builder/virt-builder.pod

@@ -410,6 +410,23 @@ You don't have a host network (eg. in secure/restricted environments).

 =back

+=item B<--no-sync>

+

+Do not sync the output file on exit.

+

+Virt-builder fsync's the output file or disk image when it exits.

+

+The reason is that qemu/KVM's default caching mode is C<none> or

+C<directsync>, both of which bypass the host page cache.  Therefore

+these would not work correctly if you immediately started the guest

+after running virt-builder - they would not see the complete output

+file.  (Note that you should not use these caching modes - they are

+fundamentally broken for this and other reasons.)

+

+If you are not using these broken caching modes, you can use

+I<--no-sync> to avoid this unnecessary sync and gain considerable

+extra performance.

+

 =item B<--notes> os-version

 List any notes associated with this guest, then exit (this does not do

-- 

1.8.3.1