[libvirt] [PATCHv4 18/21] lib: Introduce flag VIR_DOMAIN_BLOCK_COMMIT_RELATIVE

[Peter Krempa]

Introduce flag for the block commit API to allow the commit operation to
leave the chain relatively addressed. Also adds a virsh switch to enable
this behavior.
---
 include/libvirt/libvirt.h.in | 4 ++++
 src/libvirt.c                | 5 +++++
 tools/virsh-domain.c         | 7 +++++++
 tools/virsh.pod              | 6 ++++--
 4 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
index 127de11..bacdf57 100644
--- a/include/libvirt/libvirt.h.in
+++ b/include/libvirt/libvirt.h.in
@@ -2592,6 +2592,10 @@ typedef enum {
                                                  have been committed */
     VIR_DOMAIN_BLOCK_COMMIT_ACTIVE  = 1 << 2, /* Allow a two-phase commit when
                                                  top is the active layer */
+    VIR_DOMAIN_BLOCK_COMMIT_RELATIVE = 1 << 3, /* try to keep the backing chain
+                                                  relative if the components
+                                                  removed by the commit are
+                                                  already relative */
 } virDomainBlockCommitFlags;

 int virDomainBlockCommit(virDomainPtr dom, const char *disk, const char *base,
diff --git a/src/libvirt.c b/src/libvirt.c
index 6c4a124..21ef41f 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -19879,6 +19879,11 @@ virDomainBlockRebase(virDomainPtr dom, const char *disk,
  * VIR_DOMAIN_BLOCK_COMMIT_DELETE, then this command will unlink all files
  * that were invalidated, after the commit successfully completes.
  *
+ * If @flags contains VIR_DOMAIN_BLOCK_COMMIT_RELATIVE, the name recorded
+ * into the overlay of the @top image as path to the new backing file
+ * will be kept relative to other images in case the backing chain was
+ * using relative names.
+ *
  * By default, if @base is NULL, the commit target will be the bottom of
  * the backing chain; if @flags contains VIR_DOMAIN_BLOCK_COMMIT_SHALLOW,
  * then the immediate backing file of @top will be used instead.  If @top
diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
index d2bd4f2..f26a133 100644
--- a/tools/virsh-domain.c
+++ b/tools/virsh-domain.c
@@ -1492,6 +1492,8 @@ blockJobImpl(vshControl *ctl, const vshCmd *cmd,
             flags |= VIR_DOMAIN_BLOCK_COMMIT_SHALLOW;
         if (vshCommandOptBool(cmd, "delete"))
             flags |= VIR_DOMAIN_BLOCK_COMMIT_DELETE;
+        if (vshCommandOptBool(cmd, "keep-relative"))
+            flags |= VIR_DOMAIN_BLOCK_COMMIT_RELATIVE;
         ret = virDomainBlockCommit(dom, path, base, top, bandwidth, flags);
         break;
     case VSH_CMD_BLOCK_JOB_COPY:
@@ -1612,6 +1614,11 @@ static const vshCmdOptDef opts_block_commit[] = {
      .type = VSH_OT_BOOL,
      .help = N_("with --wait, don't wait for cancel to finish")
     },
+    {.name = "keep-relative",
+     .type = VSH_OT_BOOL,
+     .help = N_("keep the backing chain relative if it was relatively "
+                "referenced if it was before")
+    },
     {.name = NULL}
 };

diff --git a/tools/virsh.pod b/tools/virsh.pod
index b2fd53b..5816c0b 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -769,7 +769,7 @@ address of virtual interface (such as I<detach-interface> or
 I<domif-setlink>) will accept the MAC address printed by this command.

 =item B<blockcommit> I<domain> I<path> [I<bandwidth>]
-{[I<base>] | [I<--shallow>]} [I<top>] [I<--delete>]
+{[I<base>] | [I<--shallow>]} [I<top>] [I<--delete>] [I<--keep-relative>]
 [I<--wait> [I<--verbose>] [I<--timeout> B<seconds>] [I<--async>]]

 Reduce the length of a backing image chain, by committing changes at the
@@ -781,7 +781,9 @@ I<--shallow> can be used instead of I<base> to specify the immediate
 backing file of the resulting top image to be committed.  The files
 being committed are rendered invalid, possibly as soon as the operation
 starts; using the I<--delete> flag will remove these files at the successful
-completion of the commit operation.
+completion of the commit operation. Using the I<--keep-relative> flag
+will try to keep the backing chain names relative (if they were
+relative before).

 By default, this command returns as soon as possible, and data for
 the entire disk is committed in the background; the progress of the
-- 
1.9.3