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

On 2013年03月13日 15:20, yuxh wrote: > 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. Hum, sorry I didn't read your problem carefully. But... It's not reasonable. As the disk source you use is /mnt/test.raw, I believe it's not a block device. However, you used disk type='block'. Libvirt honors what you specified, and tries to grab the device IDs of the disk source (it expects the disk source is block, but it's not).

Regards, Osier -- libvir-list mailing list libvir-list(a)redhat.com https://www.redhat.com/mailman/listinfo/libvir-list