Reintroduce support for lzop compression

lzop was removed due to some confusion over whether it provided functional
advantages distinct from xz. This has been addressed in the mailing list post
archived at http://permalink.gmane.org/gmane.comp.emulators.libvirt/16487, and
support for lzop is re-added here.

* libvirt.spec.in: add dependancy on lzop
* src/qemu.conf: update documentation of save_image_format
* src/qemu_driver.c: re-add lzop compression option

libvirt.spec.in

@@ -117,6 +117,7 @@ Requires: /usr/bin/qemu-img
 # For image compression
 Requires: gzip
 Requires: bzip2
+Requires: lzop
 Requires: xz
 %else
 %if %{with_xen}

src/qemu.conf

@@ -134,9 +134,10 @@
 # memory from the domain is dumped out directly to a file.  If you have
 # guests with a large amount of memory, however, this can take up quite
 # a bit of space.  If you would like to compress the images while they
-# are being saved to disk, you can also set "gzip", "bzip2", "lzma", "xz",
-# or "lzop" for save_image_format.  Note that this means you slow down
-# the process of saving a domain in order to save disk space.
+# are being saved to disk, you can also set "lzop", "gzip", "bzip2", or "xz"
+# for save_image_format.  Note that this means you slow down the process of
+# saving a domain in order to save disk space; the list above is in descending
+# order by performance and ascending order by compression ratio.
 #
 # save_image_format = "raw"
 

src/qemu_driver.c

@@ -3624,10 +3624,10 @@ enum qemud_save_formats {
     QEMUD_SAVE_FORMAT_BZIP2 = 2,
     /*
      * Deprecated by xz and never used as part of a release
-     * QEMUD_SAVE_FORMAT_LZMA,
-     * QEMUD_SAVE_FORMAT_LZOP,
+     * QEMUD_SAVE_FORMAT_LZMA
      */
     QEMUD_SAVE_FORMAT_XZ = 3,
+    QEMUD_SAVE_FORMAT_LZOP = 4,
     /* Note: add new members only at the end.
        These values are used in the on-disk format.
        Do not change or re-use numbers. */
@@ -3640,7 +3640,8 @@ VIR_ENUM_IMPL(qemudSaveCompression, QEMUD_SAVE_FORMAT_LAST,
               "raw",
               "gzip",
               "bzip2",
-              "xz")
+              "xz",
+              "lzop")
 
 struct qemud_save_header {
     char magic[sizeof(QEMUD_SAVE_MAGIC)-1];
@@ -4384,6 +4385,8 @@ static int qemudDomainRestore(virConnectPtr conn,
             intermediate_argv[0] = "bzip2";
         else if (header.compressed == QEMUD_SAVE_FORMAT_XZ)
             intermediate_argv[0] = "xz";
+        else if (header.compressed == QEMUD_SAVE_FORMAT_LZOP)
+            intermediate_argv[0] = "lzop";
         else if (header.compressed != QEMUD_SAVE_FORMAT_RAW) {
             qemudReportError(conn, NULL, NULL, VIR_ERR_OPERATION_FAILED,
                              _("Unknown compressed save format %d"),