On Wed, Apr 21, 2010 at 10:38:28PM +0200, Daniel Veillard wrote:
> On Wed, Apr 21, 2010 at 05:56:11PM +0100, 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..50cd982 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_bdev = 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) {
> > + virReportSystemError(errno, _("unable to access %s"), path);
> > + goto endjob;
> > + } else {
> > + is_bdev = 0;
> > + }
>
> what about EACCESS can we fail stat() but still be able to append to
> the file ? That sounds unlikely though...
IMHO, if we get EACCESS we're better just reporting the error because
its not a normal situation to be in.
>
> > + } else {
> > + is_bdev = S_ISBLK(sb.st_mode);
> > + }
> > +
> > +
> > /* Setup hook data needed by virFileOperation hook function */
> > hdata.dom = dom;
> > hdata.path = path;
> > @@ -4849,7 +4866,8 @@ static int qemudDomainSaveFlag(virDomainPtr dom, const char *path,
> > /* Write header to file, followed by XML */
> >
> > /* First try creating the file as root */
> > - if ((rc = virFileOperation(path, O_CREAT|O_TRUNC|O_WRONLY,
> > + if (!is_bdev &&
> > + (rc = virFileOperation(path, O_CREAT|O_TRUNC|O_WRONLY,
> > S_IRUSR|S_IWUSR,
> > getuid(), getgid(),
> > qemudDomainSaveFileOpHook, &hdata,
> > @@ -5014,7 +5032,7 @@ endjob:
> >
> > cleanup:
> > VIR_FREE(xml);
> > - if (ret != 0)
> > + if (ret != 0 && !is_bdev)
> > unlink(path);
> > if (vm)
> > virDomainObjUnlock(vm);
>
> ACK,
Daniel
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