qemuDomainBlockCopy: Check @granularity to be a power of two

https://bugzilla.redhat.com/show_bug.cgi?id=1206479

As described in virDomainBlockCopy() parameters description, the
VIR_DOMAIN_BLOCK_COPY_GRANULARITY parameter may require the value to
have some specific attributes (e.g. be a power of two or fall within a
certain range). And in qemu, a power of two is required. However, our
code does not check that and let qemu operation fail. Moreover, the
virsh man page is not as exact as it could be in this respect.

Signed-off-by: Luyao Huang <lhuang@redhat.com>
Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 80a21d86cf6df3de619c19201846c51d3e245d35..6132674168f4c6c68573aa70b01014c71965a640 100644 (file)
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -16866,6 +16866,11 @@ qemuDomainBlockCopy(virDomainPtr dom, const char *disk, const char *destxml,
             }
             bandwidth = param->value.ul;
         } else if (STREQ(param->field, VIR_DOMAIN_BLOCK_COPY_GRANULARITY)) {
+            if (param->value.ui != VIR_ROUND_UP_POWER_OF_TWO(param->value.ui)) {
+                virReportError(VIR_ERR_INVALID_ARG, "%s",
+                               _("granularity must be power of 2"));
+                goto cleanup;
+            }
             granularity = param->value.ui;
         } else if (STREQ(param->field, VIR_DOMAIN_BLOCK_COPY_BUF_SIZE)) {
             buf_size = param->value.ul;

diff --git a/tools/virsh.pod b/tools/virsh.pod
index 63325ffd73d16183c6437effbb7e7bdc391e921f..5d52761edee22b6cb8253bc1261e8c9b2a83a6bb 100644 (file)
--- a/tools/virsh.pod
+++ b/tools/virsh.pod
@@ -1039,10 +1039,10 @@ 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).
+usually correct); hypervisors may restrict this to be a power of two or fall
+within a certain range. 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>]]