[libvirt] [PATCHv3 01.6/43] snapshot: fine-tune qemu saved images starting paused

[Eric Blake]

On 08/27/2011 07:16 AM, Eric Blake wrote:
> Implement the new running/paused overrides for saved state management.
>
> Unfortunately, for virDomainSaveImageDefineXML, the saved state
> updates are write-only - I don't know of any way to expose a way
> to query the current run/pause setting of an existing save image
> file to the user without adding a new API or modifying the domain
> xml of virDomainSaveImageGetXMLDesc to include a new element to
> reflect the state bit encoded into the save image.  However, I
> don't think this is a show-stopper, since the API is designed to
> leave the state bit alone unless an explicit flag is used to
> change it.
>
> @@ -4150,11 +4177,8 @@ qemuDomainSaveImageDefineXML(virConnectPtr conn, const char *path,
>           goto cleanup;
>       }
>
> -    if (lseek(fd, sizeof(header), SEEK_SET) != sizeof(header)) {
> -        virReportSystemError(errno, _("cannot seek in '%s'"), path);
> -        goto cleanup;
> -    }
> -    if (safewrite(fd, xml, len) != len ||
> +    if (safewrite(fd,&header, sizeof(header) != sizeof(header)) ||
> +        safewrite(fd, xml, len) != len ||

I need to test this better before posting.  A misplaced ), along with 
the fact that opening the fd does not leave the fd positioned at 0, 
means I need to squash in this:

diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 0498054..8682b98 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -4177,7 +4177,11 @@ qemuDomainSaveImageDefineXML(virConnectPtr conn, 
const char *path,
          goto cleanup;
      }

-    if (safewrite(fd, &header, sizeof(header) != sizeof(header)) ||
+    if (lseek(fd, 0, SEEK_SET) != 0) {
+        virReportSystemError(errno, _("cannot seek in '%s'"), path);
+        goto cleanup;
+    }
+    if (safewrite(fd, &header, sizeof(header)) != sizeof(header) ||
          safewrite(fd, xml, len) != len ||
          VIR_CLOSE(fd) < 0) {
          virReportSystemError(errno, _("failed to write xml to '%s'"), 
path);
-- 
1.7.4.4

-- 
Eric Blake   eblake at redhat.com    +1-801-349-2682
Libvirt virtualization library http://libvirt.org