[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] libxl_device.c, stat() and remote disks
Hi, I've got a virtual disk stored on a ceph cluster and am trying to use qemu's built-in support for the ceph RBD protocol. However I notice in libxl_device.c:libxl__device_disk_set_backend there's an attempt to stat() the VM's disk, which fails because the disk is remote: there's never any file or device on the local system: } else if (!disk->script) { if (stat(disk->pdev_path, &a.stab)) { LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "Disk vdev=%s " "failed to stat: %s", disk->vdev, disk->pdev_path); return ERROR_INVAL; } [At this point I should confess that I did my testing with xen-4.2.1rather than -unstable, but I didn't spot any relevant changes to libxl_device.c] My attempts to 'xl create' the VM fail as expected with: # xl create ubuntu/ceph-ubuntu1204.cfg Parsing config from ubuntu/ceph-ubuntu1204.cfglibxl: error: libxl_device.c:243:libxl__device_disk_set_backend: Disk vdev=hda failed to stat: rbd:rbd/ubuntu1204.img: No such file or directory I tried to work around the error by adding a dummy hotplug script, but this is incompatible with the qdisk backend: case LIBXL_DISK_BACKEND_QDISK: if (a->disk->script) goto bad_script; return backend; However if I work around the stat() by creating a fake file... # mkdir "rbd:rbd" # touch rbd\:rbd/ubuntu1204.img ... then it now works: # xl create ubuntu/ceph-ubuntu1204.cfg Parsing config from ubuntu/ceph-ubuntu1204.cfg xc: info: VIRTUAL MEMORY ARRANGEMENT: Loader: 0000000000100000->000000000019bb24 TOTAL: 0000000000000000->000000003f800000 ENTRY ADDRESS: 0000000000100000 xc: info: PHYSICAL MEMORY ALLOCATION: 4KB PAGES: 0x0000000000000200 2MB PAGES: 0x00000000000001fb 1GB PAGES: 0x0000000000000000 Daemon running with PID 5895 The resulting qemu has the right command-line argument:-drive file=rbd:rbd/ubuntu1204.img,if=ide,index=0,media=disk,format=raw,cache=writeback The qdisk backend also seems operational: (although the "aio:" prefix is slightly concerning) # xenstore-ls /local/domain/0/backend/qdisk/35/768 frontend = "/local/domain/35/device/vbd/768" params = "aio:rbd:rbd/ubuntu1204.img" frontend-id = "35" online = "1" removable = "0" bootable = "1" state = "4" dev = "hda" type = "qdisk" mode = "w" device-type = "disk" feature-barrier = "1" info = "0" sector-size = "512" sectors = "33554432" hotplug-status = "connected"My PV on HVM linux VM seems happy: it boots up and successfully mounts its root filesystem on /dev/xvda1. Is it safe to remove the stat() from libxl_device.c? For reference my xl config file looks like this: name="ubuntu1204" builder='hvm' boot='dc' vcpus=1 memory=1024disk=[ 'backendtype=qdisk,format=raw,vdev=hda,access=rw,target=rbd:rbd/ubuntu1204.img' ] #vif=[ "bridge=br0" ] device_model_version='qemu-xen' Cheers, Dave _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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