blockcopy: allow block device destination

To date, anyone performing a block copy and pivot ends up with
the destination being treated as <disk type='file'>.  While this
works for data access for a block device, it has at least one
noticeable shortcoming: virDomainGetBlockInfo() reports allocation
differently for block devices visited as files (the size of the
device) than for block devices visited as <disk type='block'>
(the maximum sector used, as reported by qemu); and this difference
is significant when trying to manage qcow2 format on block devices
that can be grown as needed.

Of course, the more powerful virDomainBlockCopy() API can already
express the ability to set the <disk> type.  But a new API can't
be backported, while a new flag to an existing API can; and it is
also rather inconvenient to have to resort to the full power of
generating XML when just adding a flag to the older call will do
the trick.  So this patch enhances blockcopy to let the user flag
when the resulting XML after the copy must list the device as
type='block'.

* include/libvirt/libvirt.h.in (VIR_DOMAIN_BLOCK_REBASE_COPY_DEV):
New flag.
* src/libvirt.c (virDomainBlockRebase): Document it.
* tools/virsh-domain.c (opts_block_copy, blockJobImpl): Add
--blockdev option.
* tools/virsh.pod (blockcopy): Document it.
* src/qemu/qemu_driver.c (qemuDomainBlockRebase): Allow new flag.
(qemuDomainBlockCopy): Remember the flag, and make sure it is only
used on actual block devices.
* tests/qemuxml2argvdata/qemuxml2argv-disk-mirror.xml: Test it.

Signed-off-by: Eric Blake <eblake@redhat.com>

diff --git a/include/libvirt/libvirt.h.in b/include/libvirt/libvirt.h.in
index 6d0c042dfde0e1bd385975e5655419480d919472..aced31c5dd38260752b6ea74864bb638f116d7da 100644 (file)
--- a/include/libvirt/libvirt.h.in
+++ b/include/libvirt/libvirt.h.in
@@ -2638,6 +2638,8 @@ typedef enum {
     VIR_DOMAIN_BLOCK_REBASE_RELATIVE  = 1 << 4, /* Keep backing chain
                                                    referenced using relative
                                                    names */
+    VIR_DOMAIN_BLOCK_REBASE_COPY_DEV  = 1 << 5, /* Treat destination as block
+                                                   device instead of file */
 } virDomainBlockRebaseFlags;
 
 int           virDomainBlockRebase(virDomainPtr dom, const char *disk,

diff --git a/src/libvirt.c b/src/libvirt.c
index b00ee16760b431e2e8fe2e8c3b11f6ce64162a32..48065359507f80cb1440aadc3baaea6af00c2a42 100644 (file)
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -19885,7 +19885,10 @@ virDomainBlockPull(virDomainPtr dom, const char *disk,
  * pre-create files with relative backing file names, rather than the default
  * of absolute backing file names; as a security precaution, you should
  * generally only use reuse_ext with the shallow flag and a non-raw
- * destination file.
+ * destination file.  By default, the copy destination will be treated as
+ * type='file', but using VIR_DOMAIN_BLOCK_REBASE_COPY_DEV treats the
+ * destination as type='block' (affecting how virDomainGetBlockInfo() will
+ * report allocation after pivoting).
  *
  * A copy job has two parts; in the first phase, the @bandwidth parameter
  * affects how fast the source is pulled into the destination, and the job
@@ -19960,7 +19963,8 @@ virDomainBlockRebase(virDomainPtr dom, const char *disk,
         virCheckNonNullArgGoto(base, error);
     } else if (flags & (VIR_DOMAIN_BLOCK_REBASE_SHALLOW |
                         VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT |
-                        VIR_DOMAIN_BLOCK_REBASE_COPY_RAW)) {
+                        VIR_DOMAIN_BLOCK_REBASE_COPY_RAW |
+                        VIR_DOMAIN_BLOCK_REBASE_COPY_DEV)) {
         virReportInvalidArg(flags,
                             _("use of flags in %s requires a copy job"),
                             __FUNCTION__);

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 16a89c85f70a62a415fa349e8ef9ae42c6a23345..4bf754f072e6ae6bab56cadfd99c8af2f4be9354 100644 (file)
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -15372,7 +15372,8 @@ qemuDomainBlockCopy(virDomainObjPtr vm,
 
     /* Preliminaries: find the disk we are editing, sanity checks */
     virCheckFlags(VIR_DOMAIN_BLOCK_REBASE_SHALLOW |
-                  VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT, -1);
+                  VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT |
+                  VIR_DOMAIN_BLOCK_REBASE_COPY_DEV, -1);
 
     priv = vm->privateData;
     cfg = virQEMUDriverGetConfig(driver);
@@ -15433,25 +15434,34 @@ qemuDomainBlockCopy(virDomainObjPtr vm,
             virReportSystemError(errno, _("unable to stat for disk %s: %s"),
                                  disk->dst, dest);
             goto endjob;
-        } else if (flags & VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT) {
+        } else if (flags & (VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT |
+                            VIR_DOMAIN_BLOCK_REBASE_COPY_DEV)) {
             virReportSystemError(errno,
                                  _("missing destination file for disk %s: %s"),
                                  disk->dst, dest);
             goto endjob;
         }
-    } else if (!S_ISBLK(st.st_mode) && st.st_size &&
-               !(flags & VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT)) {
-        virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
-                       _("external destination file for disk %s already "
-                         "exists and is not a block device: %s"),
-                       disk->dst, dest);
-        goto endjob;
+    } else if (!S_ISBLK(st.st_mode)) {
+        if (st.st_size && !(flags & VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT)) {
+            virReportError(VIR_ERR_CONFIG_UNSUPPORTED,
+                           _("external destination file for disk %s already "
+                             "exists and is not a block device: %s"),
+                           disk->dst, dest);
+            goto endjob;
+        }
+        if (flags & VIR_DOMAIN_BLOCK_REBASE_COPY_DEV) {
+            virReportError(VIR_ERR_INVALID_ARG,
+                           _("blockdev flag requested for disk %s, but file "
+                             "'%s' is not a block device"), disk->dst, dest);
+            goto endjob;
+        }
     }
 
     if (VIR_ALLOC(mirror) < 0)
         goto endjob;
     /* XXX Allow non-file mirror destinations */
-    mirror->type = VIR_STORAGE_TYPE_FILE;
+    mirror->type = flags & VIR_DOMAIN_BLOCK_REBASE_COPY_DEV ?
+        VIR_STORAGE_TYPE_BLOCK : VIR_STORAGE_TYPE_FILE;
 
     if (format) {
         if ((mirror->format = virStorageFileFormatTypeFromString(format)) <= 0) {
@@ -15546,7 +15556,8 @@ qemuDomainBlockRebase(virDomainPtr dom, const char *path, const char *base,
                   VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT |
                   VIR_DOMAIN_BLOCK_REBASE_COPY |
                   VIR_DOMAIN_BLOCK_REBASE_COPY_RAW |
-                  VIR_DOMAIN_BLOCK_REBASE_RELATIVE, -1);
+                  VIR_DOMAIN_BLOCK_REBASE_RELATIVE |
+                  VIR_DOMAIN_BLOCK_REBASE_COPY_DEV, -1);
 
     if (!(vm = qemuDomObjFromDomain(dom)))
         return -1;
@@ -15583,7 +15594,8 @@ qemuDomainBlockRebase(virDomainPtr dom, const char *path, const char *base,
     }
 
     flags &= (VIR_DOMAIN_BLOCK_REBASE_SHALLOW |
-              VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT);
+              VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT |
+              VIR_DOMAIN_BLOCK_REBASE_COPY_DEV);
     ret = qemuDomainBlockCopy(vm, dom->conn, path, base, format,
                               bandwidth, flags);
     vm = NULL;

diff --git a/tests/qemuxml2argvdata/qemuxml2argv-disk-mirror.xml b/tests/qemuxml2argvdata/qemuxml2argv-disk-mirror.xml
index 46f2a3eef0c68a4134271cbfe945670bace5ba4d..7495a4585658ffc3222a2c5df19a6287e9f427cd 100644 (file)
--- a/tests/qemuxml2argvdata/qemuxml2argv-disk-mirror.xml
+++ b/tests/qemuxml2argvdata/qemuxml2argv-disk-mirror.xml
@@ -17,8 +17,8 @@
     <disk type='block' device='disk'>
       <source dev='/dev/HostVG/QEMUGuest1'/>
       <backingStore/>
-      <mirror type='file' file='/dev/HostVG/QEMUGuest1Copy' job='copy' ready='yes'>
-        <source file='/dev/HostVG/QEMUGuest1Copy'/>
+      <mirror type='block' job='copy' ready='yes'>
+        <source dev='/dev/HostVG/QEMUGuest1Copy'/>
       </mirror>
       <target dev='hda' bus='ide'/>
       <address type='drive' controller='0' bus='0' target='0' unit='0'/>

diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
index 2bb3bbc48ffc8c00afadaf9862d2e1e4d81abda3..99336d294d1f9d0a3c8717feb56aee5dc1ef1683 100644 (file)
--- a/tools/virsh-domain.c
+++ b/tools/virsh-domain.c
@@ -1544,6 +1544,8 @@ blockJobImpl(vshControl *ctl, const vshCmd *cmd,
             flags |= VIR_DOMAIN_BLOCK_REBASE_REUSE_EXT;
         if (vshCommandOptBool(cmd, "raw"))
             flags |= VIR_DOMAIN_BLOCK_REBASE_COPY_RAW;
+        if (vshCommandOptBool(cmd, "blockdev"))
+            flags |= VIR_DOMAIN_BLOCK_REBASE_COPY_DEV;
         if (vshCommandOptStringReq(ctl, cmd, "dest", &base) < 0)
             goto cleanup;
         if (virDomainBlockRebase(dom, path, base, bandwidth, flags) < 0)
@@ -1855,6 +1857,10 @@ static const vshCmdOptDef opts_block_copy[] = {
      .type = VSH_OT_BOOL,
      .help = N_("use raw destination file")
     },
+    {.name = "blockdev",
+     .type = VSH_OT_BOOL,
+     .help = N_("copy destination is block device instead of regular file")
+    },
     {.name = "wait",
      .type = VSH_OT_BOOL,
      .help = N_("wait for job to reach mirroring phase")

diff --git a/tools/virsh.pod b/tools/virsh.pod
index d95df364d86da0d6e4e810aa02218c8eecc413e8..df198e6c650b04b86555888619dc9d83b14d11c7 100644 (file)
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -899,7 +899,8 @@ unlimited. The hypervisor can choose whether to reject the value or
 convert it to the maximum value allowed.
 
 =item B<blockcopy> I<domain> I<path> I<dest> [I<bandwidth>] [I<--shallow>]
-[I<--reuse-external>] [I<--raw>] [I<--wait> [I<--async>] [I<--verbose>]]
+[I<--reuse-external>] [I<--raw>] [I<--blockdev>]
+[I<--wait> [I<--async>] [I<--verbose>]]
 [{I<--pivot> | I<--finish>}] [I<--timeout> B<seconds>]
 
 Copy a disk backing image chain to I<dest>. By default, this command
@@ -917,7 +918,9 @@ The format of the destination is determined by the first match in the
 following list: if I<--raw> is specified, it will be raw; if
 I<--reuse-external> is specified, the existing destination is probed
 for a format; and in all other cases, the destination format will
-match the source format.
+match the source format.  The destination is treated as a regular
+file unless I<--blockdev> is used to signal that it is a block
+device.
 
 By default, the copy job runs in the background, and consists of two
 phases.  Initially, the job must copy all data from the source, and