In the past we added 1024 bytes of padding to saved state images so that
users can run "virsh managedsave-edit $GUEST" and make XML changes which
increase the size of the XML document. This padding was accidentally
lost a while back
commit 6b9b21db7079888a05d192b079e68290bdf14a76
Author: Peter Krempa <pkrempa@redhat.com>
Date: Wed Feb 17 13:10:11 2016 +0100
qemu: Remove unnecessary calculations in qemuDomainSaveMemory
The original 1024 bytes was unreasonably stingy when we consider that
the QEMU state is typically going to be many 100's of MB in size. Thus
this adds 64 KB of padding after the XML which should cope with any
plausible modifications a user will want to make.
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
src/qemu/qemu_driver.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
index 01330e55e7..d5aeeac66d 100644
--- a/src/qemu/qemu_driver.c
+++ b/src/qemu/qemu_driver.c
@@ -2922,20 +2922,23 @@ virQEMUSaveDataWrite(virQEMUSaveDataPtr data,
len = xml_len + cookie_len;
- if (header->data_len > 0) {
+ if (header->data_len == 0) {
+ /* This 64kb padding allows the user to edit the XML in
+ * a saved state image and have the new XML be larger
+ * that what was originally saved
+ */
+ header->data_len = len + (64 * 1024);
+ } else {
if (len > header->data_len) {
virReportError(VIR_ERR_OPERATION_FAILED, "%s",
_("new xml too large to fit in file"));
return -1;
}
-
- zerosLen = header->data_len - len;
- if (VIR_ALLOC_N(zeros, zerosLen) < 0)
- return -1;
- } else {
- header->data_len = len;
}
+ zerosLen = header->data_len - len;
+ zeros = g_new0(char, zerosLen);
+
if (data->cookie)
header->cookieOffset = xml_len;
--
2.25.3
On 4/27/20 8:41 AM, Daniel P. Berrangé wrote: > In the past we added 1024 bytes of padding to saved state images so that > users can run "virsh managedsave-edit $GUEST" and make XML changes which > increase the size of the XML document. This padding was accidentally > lost a while back > > commit 6b9b21db7079888a05d192b079e68290bdf14a76 > Author: Peter Krempa <pkrempa@redhat.com> > Date: Wed Feb 17 13:10:11 2016 +0100 > > qemu: Remove unnecessary calculations in qemuDomainSaveMemory > > The original 1024 bytes was unreasonably stingy when we consider that > the QEMU state is typically going to be many 100's of MB in size. Thus > this adds 64 KB of padding after the XML which should cope with any > plausible modifications a user will want to make. > > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> > --- > src/qemu/qemu_driver.c | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) Reviewed-by: Eric Blake <eblake@redhat.com> -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org
On Mon, 2020-04-27 at 14:41 +0100, Daniel P. Berrangé wrote: > In the past we added 1024 bytes of padding to saved state images so that > users can run "virsh managedsave-edit $GUEST" and make XML changes which > increase the size of the XML document. This padding was accidentally > lost a while back > > commit 6b9b21db7079888a05d192b079e68290bdf14a76 > Author: Peter Krempa <pkrempa@redhat.com> > Date: Wed Feb 17 13:10:11 2016 +0100 > > qemu: Remove unnecessary calculations in qemuDomainSaveMemory > > The original 1024 bytes was unreasonably stingy when we consider that > the QEMU state is typically going to be many 100's of MB in size. Thus > this adds 64 KB of padding after the XML which should cope with any > plausible modifications a user will want to make. > > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> > --- > src/qemu/qemu_driver.c | 17 ++++++++++------- > 1 file changed, 10 insertions(+), 7 deletions(-) Please consider including a link to https://bugzilla.redhat.com/show_bug.cgi?id=1229255 in the commit message. -- Andrea Bolognani / Red Hat / Virtualization
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