[libvirt] [PATCH 2/4] Avoid create/unlink with block devs used for QEMU save
Laine Stump
laine at laine.org
Sat Apr 24 04:45:13 UTC 2010
On 04/22/2010 07:43 AM, Daniel P. Berrange wrote:
> It is possible to use block devices with domain save/restore. Upon
> failure QEMU unlinks the path being saved to. This isn't good when
> it is a block device !
>
> * src/qemu/qemu_driver.c: Don't unlink block devices if save fails
> ---
> src/qemu/qemu_driver.c | 22 ++++++++++++++++++++--
> 1 files changed, 20 insertions(+), 2 deletions(-)
>
> diff --git a/src/qemu/qemu_driver.c b/src/qemu/qemu_driver.c
> index 91fe963..41a516c 100644
> --- a/src/qemu/qemu_driver.c
> +++ b/src/qemu/qemu_driver.c
> @@ -4787,6 +4787,8 @@ static int qemudDomainSaveFlag(virDomainPtr dom, const char *path,
> int rc;
> virDomainEventPtr event = NULL;
> qemuDomainObjPrivatePtr priv;
> + struct stat sb;
> + int is_reg = 0;
>
> memset(&header, 0, sizeof(header));
> memcpy(header.magic, QEMUD_SAVE_MAGIC, sizeof(header.magic));
> @@ -4840,6 +4842,21 @@ static int qemudDomainSaveFlag(virDomainPtr dom, const char *path,
> }
> header.xml_len = strlen(xml) + 1;
>
> + /* path might be a pre-existing block dev, in which case
> + * we need to skip the create step, and also avoid unlink
> + * in the failure case */
> + if (stat(path,&sb)< 0) {
> + if (errno != ENOENT) {
>
In the case of a target on a root-squashed NFS server, this stat() will
fail if the directory is not marked as w+rx. In this case, it will
return EACCES. Changing the if to also check for (errno != EACCES)
allows it to pass this point (and shouldn't hurt in any other
circumstances). I tried it with this small modification, and
save/restore to root-squash NFS works properly.
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