Re: [libvirt] [PATCH] qemu: Forcibly mknod() even if it exists

On Wed, Nov 20, 2019 at 10:51:47AM +0100, Michal Privoznik wrote: > Another weird bug appeared concerning qemu namespaces. Basically > the problem is as follows: > > 1) Issue an API that causes libvirt to create a node in domain's > namespace, say /dev/sda with 8:0 as major:minor (the API can > be attach-disk for instance). Or simply create the node from > a console by hand. > > 2) Detach the disk from qemu. > > 3) Do something that makes /dev/sda change it's minor number. Wait, what ? major/minor numbers for SCSI disks are a defined standard IIUC $ grep SCSI ./admin-guide/devices.txt | grep block 8 block SCSI disk devices (0-15) 11 block SCSI CD-ROM devices 65 block SCSI disk devices (16-31) 66 block SCSI disk devices (32-47) 67 block SCSI disk devices (48-63) 68 block SCSI disk devices (64-79) 69 block SCSI disk devices (80-95) 70 block SCSI disk devices (96-111) 71 block SCSI disk devices (112-127) 128 block SCSI disk devices (128-143) 129 block SCSI disk devices (144-159) 130 block SCSI disk devices (160-175) 131 block SCSI disk devices (176-191) 132 block SCSI disk devices (192-207) 133 block SCSI disk devices (208-223) 134 block SCSI disk devices (224-239) 135 block SCSI disk devices (240-255) IOW, /dev/sda should always be 8,0 There is, however, the possibiity of dynamically assign major/minor numbers so its possible we'll see a block device with a changable number, but AFAIK, such a block device should never be call /dev/sda !??! IOW, the commit is fine, but is this commit message really accurate ?