[Libguestfs] [PATCH v2] resize: support non-local output disks (RHBZ#1404182)

[Pino Toscano]

Parse the output disk as URI, and use all its attributes just like
it is done for the input disk.  The only change is that the fsync of the
output disk is limited now for local URIs only, since it will not work
with remote protocols.
---
 resize/resize.ml       | 43 +++++++++++++++++++++++++++++++------------
 resize/virt-resize.pod |  6 +++---
 2 files changed, 34 insertions(+), 15 deletions(-)

diff --git a/resize/resize.ml b/resize/resize.ml
index 19cd8df..7e16cb5 100644
--- a/resize/resize.ml
+++ b/resize/resize.ml
@@ -315,6 +315,13 @@ read the man page virt-resize(1).
         error (f_"error parsing URI '%s'. Look for error messages printed above.")
           infile in
 
+    (* outfile can be a URI. *)
+    let outfile =
+      try (outfile, URI.parse_uri outfile)
+      with Invalid_argument "URI.parse_uri" ->
+        error (f_"error parsing URI '%s'. Look for error messages printed above.")
+          outfile in
+
     infile, outfile, align_first, alignment, copy_boot_loader,
     deletes,
     dryrun, expand, expand_content, extra_partition, format, ignores,
@@ -333,9 +340,12 @@ read the man page virt-resize(1).
              server = server; username = username;
              password = password } = infile in
     g#add_drive ?format ~readonly:true ~protocol ?server ?username ?secret:password path;
+    let _, { URI.path = path; protocol = protocol;
+             server = server; username = username;
+             password = password } = outfile in
     (* The output disk is being created, so use cache=unsafe here. *)
     g#add_drive ?format:output_format ~readonly:false ~cachemode:"unsafe"
-      outfile;
+      ~protocol ?server ?username ?secret:password path;
     if not (quiet ()) then Progress.set_up_progress_bar ~machine_readable g;
     g#launch ();
 
@@ -368,7 +378,7 @@ read the man page virt-resize(1).
     let insize = g#blockdev_getsize64 "/dev/sda" in
     let outsize = g#blockdev_getsize64 "/dev/sdb" in
     debug "%s size %Ld bytes" (fst infile) insize;
-    debug "%s size %Ld bytes" outfile outsize;
+    debug "%s size %Ld bytes" (fst outfile) outsize;
     sectsize, insize, outsize in
 
   let max_bootloader =
@@ -390,7 +400,7 @@ read the man page virt-resize(1).
       (fst infile) insize;
   if outsize < Int64.of_int max_bootloader then
     error (f_"%s: file is too small to be a disk image (%Ld bytes)")
-      outfile outsize;
+      (fst outfile) outsize;
 
   (* Get the source partition type. *)
   let parttype, parttype_string =
@@ -983,7 +993,7 @@ read the man page virt-resize(1).
     (* Try hard to initialize the partition table.  This might involve
      * relaunching another handle.
      *)
-    message (f_"Setting up initial partition table on %s") outfile;
+    message (f_"Setting up initial partition table on %s") (fst outfile);
 
     let last_error = ref "" in
     let rec initialize_partition_table g attempts =
@@ -1300,9 +1310,12 @@ read the man page virt-resize(1).
       g#close ();
 
       let g = open_guestfs () in
+      let _, { URI.path = path; protocol = protocol;
+               server = server; username = username;
+               password = password } = outfile in
       (* The output disk is being created, so use cache=unsafe here. *)
       g#add_drive ?format:output_format ~readonly:false ~cachemode:"unsafe"
-        outfile;
+        ~protocol ?server ?username ?secret:password path;
       if not (quiet ()) then Progress.set_up_progress_bar ~machine_readable g;
       g#launch ();
 
@@ -1378,13 +1391,19 @@ read the man page virt-resize(1).
   g#shutdown ();
   g#close ();
 
-  (* Because we used cache=unsafe when writing the output file, the
-   * file might not be committed to disk.  This is a problem if qemu is
-   * immediately used afterwards with cache=none (which uses O_DIRECT
-   * and therefore bypasses the host cache).  In general you should not
-   * use cache=none.
-   *)
-  Fsync.file outfile;
+  (* Try to sync the destination disk only if it is a local file. *)
+  let () =
+    let _, { URI.protocol = protocol; path = path } = outfile in
+    match protocol with
+    | "" | "file" ->
+      (* Because we used cache=unsafe when writing the output file, the
+       * file might not be committed to disk.  This is a problem if qemu is
+       * immediately used afterwards with cache=none (which uses O_DIRECT
+       * and therefore bypasses the host cache).  In general you should not
+       * use cache=none.
+       *)
+      Fsync.file path
+    | _ -> () in
 
   if not (quiet ()) then (
     print_newline ();
diff --git a/resize/virt-resize.pod b/resize/virt-resize.pod
index 2344056..98c4b10 100644
--- a/resize/virt-resize.pod
+++ b/resize/virt-resize.pod
@@ -121,9 +121,9 @@ Or use L<virsh(1)> vol-create-as to create a libvirt storage volume:
 
 =item 5. Resize
 
-virt-resize takes two mandatory parameters, the input disk
-(eg. device, file, or a URI to a remote disk) and the output disk.
-The output disk is the one created in the previous step.
+virt-resize takes two mandatory parameters, the input disk and the
+output disk (both can be e.g. a device, a file, or a URI to a remote
+disk).  The output disk is the one created in the previous step.
 
  # virt-resize indisk outdisk
 
-- 
2.9.3