Re: [libvirt] Consultation of the patch "util: Prepare helpers for unpriv_sgio setting"

On 03/13/2013 11:33 AM, Osier Yang wrote: > On 2013年03月13日 11:04, yuxh wrote: >> To Osier Yang >> >> Sorry for disturbing you on the working time, but I really need your >> help. >> I met a problem when I do the virtualization test on the environment of >> (Host: RHEL6.4GA. Guest: RHEL6.4GA) and it seems to have relationship >> with your patch of "util: Prepare helpers for unpriv_sgio setting". > > Never mind, it's the bug I produced. :( > >> >> I added a disk to virtio-scsi bus through the VM's XML file like this: >> <disk type='block' device='disk'> >> <driver name='qemu' type='raw' io='threads'/> >> <source dev='/mnt/test.raw'/> >> <target dev='sdb' bus='scsi'/> >> <shareable/> >> </disk> >> >> Then when I started the VM, I met the error. >> [root@build SOURCES]# virsh start pan64ga >> error: Failed to start domain pan64ga >> error: Unable to get minor number of device '/mnt/test.raw': Invalid >> argument >> >> [root@build SOURCES]# >> >> I tried other source files and other way of using if and I found: >> 1). If we use the files which format is raw, qed and qcow2 as the disk >> this error occur again. >> 2). If we use partition(such as /dev/sdb1) or whole disk(such as >> /dev/sdb) this error doesn't occur. >> 3). If we delete the "<shareable/>" then files, partition and disk all >> can be used correctly. >> >> And I investigate the error msg. it is returned by qemuGetSharedDiskKey >> fuction. >> char * >> qemuGetSharedDiskKey(const char *disk_path) >> { >> ... >> // error occur here. return value is -22 >> if ((rc = virGetDeviceID(disk_path, &maj, &min)) < 0) { >> virReportSystemError(-rc, >> _("Unable to get minor number of device '%s'"), >> disk_path); >> return NULL; >> } >> ... >> } >> >> Go on the virGetDeviceID fuction: >> int >> virGetDeviceID(const char *path, int *maj, int *min) >> { >> ... >> >> if (!S_ISBLK(sb.st_mode)) { >> VIR_FREE(canonical_path); >> return -EINVAL; // error occur here and it return -22 >> } >> ... >> } >> >> So the error occur place is "S_ISBLK(sb.st_mode)" and I tried compiled >> the libvirt with these lines deleted and the error didn't happen again. >> Also I checked the disk if VM and it worked well. >> I found this fuction virGetDeviceID is come from your patch of "util: >> Prepare helpers for unpriv_sgio setting". But I am not familiar with >> libvirt. >> So I have to consult with you about whether this "S_ISBLK" check is >> vital and If we can delete it or >> find out some method to avoid this error so we can use the file as >> shared disk in VM. > > It's fixd by > https://www.redhat.com/archives/libvir-list/2013-February/msg01024.html, > which is already committed to upstream, and backported > to 6.4.z. You will see the fix in the new build, which will come soon. > > Regards, > Osier Sorry, I have tried the the libvirt's upstream code and it still have this error. According to the code, if we use "<disk type='block' device='disk'> " and "<shareable/> " to set the disk's configuration in VM's XML file, it will go through like below: int qemuAddSharedDisk(virQEMUDriverPtr driver, virDomainDiskDefPtr disk, const char *name) { ... if (!(key = qemuGetSharedDiskKey(disk->src))) goto cleanup; ... } char * qemuGetSharedDiskKey(const char *disk_path) { ... if ((rc = virGetDeviceID(disk_path, &maj, &min)) < 0) { virReportSystemError(-rc, _("Unable to get minor number of device '%s'"), disk_path); return NULL; } ... } int virGetDeviceID(const char *path, int *maj, int *min) { struct stat sb; if (stat(path, &sb) < 0) return -errno; if (!S_ISBLK(sb.st_mode)) return -EINVAL; if (maj) *maj = major(sb.st_rdev); if (min) *min = minor(sb.st_rdev); return 0; } To make a long story short, the virGetDeviceID fuction want to get the maj and min number of the source file which we provided as the VM's disk. But the file such as /mnt/test.raw doesn't have the maj and min number. So virGetDeviceID return " -EINVAL" and qemuGetSharedDiskKey print the error message of "Unable to get minor number of device /mnt/test.raw". That's the reason the VM can't be started. So I just want to know now, if the way I used a file to act as VM's disk and set "<disk type='block' device='disk'>" , "<shareable/> " at the same time is reasonable.