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[libvirt] [PATCH v3 12/18] blockcopy: expose new API in virsh



Expose the new power of virDomainBlockCopy through virsh (well,
all but the finer-grained bandwidth, as that is its own can of
worms for a later patch).  Continue to use the older API where
possible, for maximum compatibility.

The command now requires either --dest (with optional --format
and --blockdev), to directly describe the file destination, or
--xml, to name a file that contains an XML description such as:

<disk type='network'>
  <driver type='raw'/>
  <source protocol='gluster' name='vol1/img'>
    <host name='red'/>
  </source>
</disk>

Non-zero option parameters are converted into virTypedParameters,
and if anything requires the new API, the command can synthesize
appropriate XML even if the --dest option was used instead of --xml.

The existing --raw flag remains for back-compat, but the preferred
spelling is now --format=raw, since the new API now allows us
to specify all formats rather than just a boolean raw to suppress
probing.

I hope I did justice in describing the effects of granularity and
buf-size on how they get passed through to qemu.

* tools/virsh-domain.c (cmdBlockCopy): Add new options --xml,
--granularity, --buf-size, --format. Make --raw an alias for
--format=raw. Call new API if new parameters are in use.
* tools/virsh.pod (blockcopy): Document new options.

Signed-off-by: Eric Blake <eblake redhat com>
---
 tools/virsh-domain.c | 145 +++++++++++++++++++++++++++++++++++++++++++++------
 tools/virsh.pod      |  45 +++++++++-------
 2 files changed, 156 insertions(+), 34 deletions(-)

diff --git a/tools/virsh-domain.c b/tools/virsh-domain.c
index b92b2eb..16d7f05 100644
--- a/tools/virsh-domain.c
+++ b/tools/virsh-domain.c
@@ -1818,11 +1818,10 @@ static const vshCmdOptDef opts_block_copy[] = {
     {.name = "path",
      .type = VSH_OT_DATA,
      .flags = VSH_OFLAG_REQ,
-     .help = N_("fully-qualified path of disk")
+     .help = N_("fully-qualified path of source disk")
     },
     {.name = "dest",
      .type = VSH_OT_DATA,
-     .flags = VSH_OFLAG_REQ,
      .help = N_("path of the copy to create")
     },
     {.name = "bandwidth",
@@ -1838,8 +1837,8 @@ static const vshCmdOptDef opts_block_copy[] = {
      .help = N_("reuse existing destination")
     },
     {.name = "raw",
-     .type = VSH_OT_BOOL,
-     .help = N_("use raw destination file")
+     .type = VSH_OT_ALIAS,
+     .help = "format=raw"
     },
     {.name = "blockdev",
      .type = VSH_OT_BOOL,
@@ -1869,6 +1868,22 @@ static const vshCmdOptDef opts_block_copy[] = {
      .type = VSH_OT_BOOL,
      .help = N_("with --wait, don't wait for cancel to finish")
     },
+    {.name = "xml",
+     .type = VSH_OT_DATA,
+     .help = N_("filename containing XML description of the copy destination")
+    },
+    {.name = "format",
+     .type = VSH_OT_DATA,
+     .help = N_("format of the destination file")
+    },
+    {.name = "granularity",
+     .type = VSH_OT_INT,
+     .help = N_("power-of-two granularity to use during the copy")
+    },
+    {.name = "buf-size",
+     .type = VSH_OT_INT,
+     .help = N_("maximum amount of in-flight data during the copy")
+    },
     {.name = NULL}
 };

@@ -1876,14 +1891,18 @@ static bool
 cmdBlockCopy(vshControl *ctl, const vshCmd *cmd)
 {
     virDomainPtr dom = NULL;
-    const char *dest;
+    const char *dest = NULL;
+    const char *format = NULL;
     unsigned long bandwidth = 0;
-    unsigned int flags = VIR_DOMAIN_BLOCK_REBASE_COPY;
+    unsigned int granularity = 0;
+    unsigned long long buf_size = 0;
+    unsigned int flags = 0;
     bool ret = false;
     bool blocking = vshCommandOptBool(cmd, "wait");
     bool verbose = vshCommandOptBool(cmd, "verbose");
     bool pivot = vshCommandOptBool(cmd, "pivot");
     bool finish = vshCommandOptBool(cmd, "finish");
+    bool blockdev = vshCommandOptBool(cmd, "blockdev");
     int timeout = 0;
     struct sigaction sig_action;
     struct sigaction old_sig_action;
@@ -1893,6 +1912,23 @@ cmdBlockCopy(vshControl *ctl, const vshCmd *cmd)
     const char *path = NULL;
     bool quit = false;
     int abort_flags = 0;
+    const char *xml = NULL;
+    char *xmlstr = NULL;
+    virTypedParameterPtr params = NULL;
+    int nparams = 0;
+
+    if (vshCommandOptStringReq(ctl, cmd, "path", &path) < 0)
+        return false;
+    if (vshCommandOptString(cmd, "dest", &dest) < 0)
+        return false;
+    if (vshCommandOptString(cmd, "xml", &xml) < 0)
+        return false;
+    if (vshCommandOptString(cmd, "format", &format) < 0)
+        return false;
+
+    VSH_EXCLUSIVE_OPTIONS_VAR(dest, xml);
+    VSH_EXCLUSIVE_OPTIONS_VAR(format, xml);
+    VSH_EXCLUSIVE_OPTIONS_VAR(blockdev, xml);

     if (vshCommandOptStringReq(ctl, cmd, "path", &path) < 0)
         return false;
@@ -1926,24 +1962,101 @@ cmdBlockCopy(vshControl *ctl, const vshCmd *cmd)
     if (!(dom = vshCommandOptDomain(ctl, cmd, NULL)))
         goto cleanup;

+    /* XXX: Parse bandwidth as scaled input, rather than forcing
+     * MiB/s, and either reject negative input or treat it as 0 rather
+     * than trying to guess which value will work well across both
+     * APIs with their different sizes and scales.  */
     if (vshCommandOptULWrap(cmd, "bandwidth", &bandwidth) < 0) {
         vshError(ctl, "%s", _("bandwidth must be a number"));
         goto cleanup;
     }
+    if (vshCommandOptUInt(cmd, "granularity", &granularity) < 0) {
+        vshError(ctl, "%s", _("granularity must be a number"));
+        goto cleanup;
+    }
+    if (vshCommandOptULongLong(cmd, "buf-size", &buf_size) < 0) {
+        vshError(ctl, "%s", _("buf-size must be a number"));
+        goto cleanup;
+    }

+    if (xml) {
+        if (virFileReadAll(xml, 8192, &xmlstr) < 0) {
+            vshReportError(ctl);
+            goto cleanup;
+        }
+    } else if (!dest) {
+        vshError(ctl, "%s", _("need either --dest or --xml"));
+        goto cleanup;
+    }
+
+    /* Exploit that VIR_DOMAIN_BLOCK_REBASE_* and
+     * VIR_DOMAIN_BLOCK_COPY_* flags have the same values.  */
     if (vshCommandOptBool(cmd, "shallow"))
         flags |= VIR_DOMAIN_BLOCK_REBASE_SHALLOW;
     if (vshCommandOptBool(cmd, "reuse-external"))
         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", &dest) < 0)
-        goto cleanup;
-
-    if (virDomainBlockRebase(dom, path, dest, bandwidth, flags) < 0)
-        goto cleanup;
+
+    if (granularity || buf_size || (format && STRNEQ(format, "raw")) || xml) {
+        /* New API */
+        if (bandwidth || granularity || buf_size) {
+            params = vshCalloc(ctl, 3, sizeof(*params));
+            if (bandwidth) {
+                /* bandwidth is ulong MiB/s, but the typed parameter is
+                 * ullong bytes/s; make sure we don't overflow */
+                if (bandwidth > LLONG_MAX >> 20) {
+                    virReportError(VIR_ERR_OVERFLOW,
+                                   _("bandwidth must be less than %llu"),
+                                   LLONG_MAX >> 20);
+                }
+                if (virTypedParameterAssign(&params[nparams++],
+                                            VIR_DOMAIN_BLOCK_COPY_BANDWIDTH,
+                                            VIR_TYPED_PARAM_ULLONG,
+                                            bandwidth << 20ULL) < 0)
+                    goto cleanup;
+            }
+            if (granularity &&
+                virTypedParameterAssign(&params[nparams++],
+                                        VIR_DOMAIN_BLOCK_COPY_GRANULARITY,
+                                        VIR_TYPED_PARAM_UINT,
+                                        granularity) < 0)
+                goto cleanup;
+            if (buf_size &&
+                virTypedParameterAssign(&params[nparams++],
+                                        VIR_DOMAIN_BLOCK_COPY_BUF_SIZE,
+                                        VIR_TYPED_PARAM_ULLONG,
+                                        buf_size) < 0)
+                goto cleanup;
+        }
+
+        if (!xmlstr) {
+            virBuffer buf = VIR_BUFFER_INITIALIZER;
+            virBufferEscapeString(&buf, "<disk type='%s'>\n",
+                                  blockdev ? "block" : "file");
+            virBufferAdjustIndent(&buf, 2);
+            virBufferEscapeString(&buf, "<source %s",
+                                  blockdev ? "dev" : "file");
+            virBufferEscapeString(&buf, "='%s'/>\n", dest);
+            virBufferEscapeString(&buf, "<driver type='%s'/>\n", format);
+            virBufferAdjustIndent(&buf, -2);
+            virBufferAddLit(&buf, "</disk>\n");
+            if (virBufferCheckError(&buf) < 0)
+                goto cleanup;
+            xmlstr = virBufferContentAndReset(&buf);
+        }
+
+        if (virDomainBlockCopy(dom, path, xmlstr, params, nparams, flags) < 0)
+            goto cleanup;
+    } else {
+        /* Old API */
+        flags |= VIR_DOMAIN_BLOCK_REBASE_COPY;
+        if (vshCommandOptBool(cmd, "blockdev"))
+            flags |= VIR_DOMAIN_BLOCK_REBASE_COPY_DEV;
+        if (STREQ_NULLABLE(format, "raw"))
+            flags |= VIR_DOMAIN_BLOCK_REBASE_COPY_RAW;
+
+        if (virDomainBlockRebase(dom, path, dest, bandwidth, flags) < 0)
+            goto cleanup;
+    }

     if (!blocking) {
         vshPrint(ctl, "%s", _("Block Copy started"));
@@ -2014,6 +2127,8 @@ cmdBlockCopy(vshControl *ctl, const vshCmd *cmd)

     ret = true;
  cleanup:
+    VIR_FREE(xmlstr);
+    virTypedParamsFree(params, nparams);
     if (dom)
         virDomainFree(dom);
     if (blocking)
diff --git a/tools/virsh.pod b/tools/virsh.pod
index 2923fd9..c3a76dc 100644
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -898,30 +898,31 @@ value is interpreted as an unsigned long long value or essentially
 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<--blockdev>]
-[I<--wait> [I<--async>] [I<--verbose>]]
-[{I<--pivot> | I<--finish>}] [I<--timeout> B<seconds>]
+=item B<blockcopy> I<domain> I<path> { I<dest> [I<format>] [I<--blockdev>]
+| I<xml> } [I<--shallow>] [I<--reuse-external>] [I<bandwidth>]
+[I<--wait> [I<--async>] [I<--verbose>]] [{I<--pivot> | I<--finish>}]
+[I<--timeout> B<seconds>] [I<granularity>] [I<buf-size>]

-Copy a disk backing image chain to I<dest>. By default, this command
-flattens the entire chain; but if I<--shallow> is specified, the copy
-shares the backing chain.
+Copy a disk backing image chain to a destination.  Either I<dest> as
+the destination file name, or I<xml> as the name of an XML file containing
+a top-level <disk> element describing the destination, must be present.
+Additionally, if I<dest> is given, I<format> should be specified to declare
+the format of the destination (if I<format> is omitted, then libvirt
+will reuse the format of the source, or with I<--reuse-external> will
+be forced to probe the destination format, which could be a potential
+security hole).  The command supports I<--raw> as a boolean flag synonym for
+I<--format=raw>.  When using I<dest>, the destination is treated as a regular
+file unless I<--blockdev> is used to signal that it is a block device. By
+default, this command flattens the entire chain; but if I<--shallow> is
+specified, the copy shares the backing chain.

-If I<--reuse-external> is specified, then I<dest> must exist and have
+If I<--reuse-external> is specified, then the destination must exist and have
 sufficient space to hold the copy. If I<--shallow> is used in
 conjunction with I<--reuse-external> then the pre-created image must have
 guest visible contents identical to guest visible contents of the backing
 file of the original image. This may be used to modify the backing file
 names on the destination.

-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.  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
 during this phase, the job can only be canceled to revert back to the
@@ -943,9 +944,15 @@ while longer until the job has actually cancelled.

 I<path> specifies fully-qualified path of the disk.
 I<bandwidth> specifies copying bandwidth limit in MiB/s. Specifying a negative
-value is interpreted as an unsigned long long value or essentially
-unlimited. The hypervisor can choose whether to reject the value or
-convert it to the maximum value allowed.
+value is interpreted as an unsigned long long value that might be essentially
+unlimited, but more likely would overflow; it is safer to use 0 for that
+purpose.  Specifying I<granularity> allows fine-tuning of the granularity that
+will be copied when a dirty region is detected; larger values trigger less
+I/O overhead but may end up copying more data overall (the default value is
+usually correct); this value must be a power of two.  Specifying I<buf-size>
+will control how much data can be simultaneously in-flight during the copy;
+larger values use more memory but may allow faster completion (the default
+value is usually correct).

 =item B<blockpull> I<domain> I<path> [I<bandwidth>] [I<base>]
 [I<--wait> [I<--verbose>] [I<--timeout> B<seconds>] [I<--async>]]
-- 
1.9.3


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