[libvirt] [PATCH v5] qemu: Remove the managed state file only if restoring succeeded

1) Both "qemuDomainStartWithFlags" and "qemuAutostartDomain" try to restore the domain from managedsave'ed image if it exists (by invoking "qemuDomainObjRestore"), but it unlinks the image even if restoring fails, which causes data loss. (This problem exists for "virsh managedsave dom; virsh start dom"). The fix for is to unlink the managed state file only if restoring succeeded. 2) For "virsh save dom; virsh restore dom;", it can cause data corruption if one reuse the saved state file for restoring. Add doc to tell user about it. 3) In "qemuDomainObjStart", if "managed_save" is NULL, we shouldn't fallback to start the domain, skipping it to cleanup as a incidental fix. Discovered by Eric. --- src/qemu/qemu_driver.c | 12 +++++++----- tools/virsh.pod | 6 +++++- 2 files changed, 12 insertions(+), 6 deletions(-) diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c index 48fe266..a84780b 100644 --- a/src/qemu/qemu_driver.c +++ b/src/qemu/qemu_driver.c @@ -3423,18 +3423,20 @@ static int qemudDomainObjStart(virConnectPtr conn, /* * If there is a managed saved state restore it instead of starting - * from scratch. In any case the old state is removed. + * from scratch. The old state is removed once the restoring succeeded. */ managed_save = qemuDomainManagedSavePath(driver, vm); + + if (!managed_save) + goto cleanup; + if ((managed_save) && (virFileExists(managed_save))) { ret = qemuDomainObjRestore(conn, driver, vm, managed_save); - if (unlink(managed_save) < 0) { + if ((ret == 0) && (unlink(managed_save) < 0)) VIR_WARN("Failed to remove the managed state %s", managed_save); - } - if (ret == 0) - goto cleanup; + goto cleanup; } ret = qemuProcessStart(conn, driver, vm, NULL, start_paused, -1, NULL, diff --git a/tools/virsh.pod b/tools/virsh.pod index f4bd294..6319373 100644 --- a/tools/virsh.pod +++ b/tools/virsh.pod @@ -546,7 +546,11 @@ I<on_reboot> parameter in the domain's XML definition. =item B<restore> I<state-file> -Restores a domain from an B<virsh save> state file. See I<save> for more info. +Restores a domain from an B<virsh save> state file. See I<save> for more info. + +B<Note>: To avoid corrupting file system contents within the domain, you +should not reuse the saved state file to B<restore> unless you are convinced +with reverting the domain to the previous state. =item B<save> I<domain-id> I<state-file> -- 1.7.4