Re: [libvirt] [PATCH 2/4] Avoid create/unlink with block devs used for QEMU save

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...

> + } 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,