Re: [Xen-devel] dom0 panic when using xm block-attach/block-detach -f

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Wed, Jan 13, 2010 at 10:23:17AM +0100, Dietmar Hahn wrote:
> Hi list,
> 
> I tried to verify my problem with xen-4.0.0-rc1.
>

What dom0 kernel did you use? What kernel did you use in the guest?

-- Pasi


> I did again the block-attach:
> 
> # xm block-attach 0 tap:aio:my-image.iso xvda r
> 
> But now I don't get any devices /dev/xvda?
> Now I'am a little bit confused!
> 
> # fdisk -l my-image.iso
> You must set cylinders.
> You can do this from the extra functions menu.
> 
> Disk my-image.iso: 0 MB, 0 bytes
> 255 heads, 63 sectors/track, 0 cylinders
> Units = cylinders of 16065 * 512 = 8225280 bytes
> Disk identifier: 0x00044fcc
> 
>        Device Boot      Start         End      Blocks   Id  System
> my-image.iso1               1          17      136521   82  Linux swap / 
> Solaris
> my-image.iso2   *          18         522     4056412+  83  Linux
> 
> Any help would be appreciated.
> Thanks.
> 
> Dietmar.
> 
> Am 08.01.2010 schrieb Dietmar Hahn:
> > Hi list,
> > 
> > I have an image with a bootable system and do the following steps:
> > # xm block-attach 0 tap:aio:my-image.iso xvda r
> > mount the root partition:
> > # mount /dev/xvda2 /mnt
> > Now forcing block-detach:
> > # xm block-detach 0 51712 -f
> > 
> > This leads to an inconsistent sysfs in dom0.
> > The xen device /sys/devices/xen/vbd-51712 gets removed but lots of links 
> > remain.
> > 
> > In the log I can see the message:
> > [  349.928350] vbd vbd-51712: 16 Device in use; refusing to close
> > 
> > The next call of
> > # xm block-attach 0 tap:aio:my-image.iso xvda r
> > leads to the panic, because creating of a sysfs entry failed
> > (it's already there) and a not existing failure handling (return of
> > register_disk() in add_disk()) leads to the panic later.
> > 
> > [  210.184660] WARNING: at /usr/src/linux-2.6.31.5-0.1/fs/sysfs/dir.c:489 
> > sysfs_add_one+0xde/0x150()
> > [  210.184662] Hardware name: CELSIUS H270
> > [  210.184663] sysfs: cannot create duplicate filename '/dev/block/202:0'
> > [  210.184664] Modules linked in: ext4 jbd2 crc16 netbk blkbk 
> > blkback_pagemap snd_pcm_oss snd_mixer_oss blktap snd_seq snd_seq_device edd 
> > ipv6 af_packet bridge stp llc fuse loop dm_mod arc4 ecb cryptomgr aead 
> > pcompress snd_hda_codec_realtek crypto_blkcipher crypto_hash crypto_algapi 
> > snd_hda_intel iwlagn snd_hda_codec iwlcore pcmcia snd_hwdep led_class 
> > snd_pcm ppdev mac80211 snd_timer 8250_pci yenta_socket parport_pc 8250_pnp 
> > snd tpm_infineon rsrc_nonstatic i2c_i801 parport iTCO_wdt 8250 soundcore 
> > cfg80211 intel_agp tpm e1000e video pcmcia_core i2c_core heci(C) 
> > iTCO_vendor_support sr_mod sg pcspkr serio_raw joydev serial_core 
> > snd_page_alloc rfkill agpgart tpm_bios output container battery button ac 
> > usbhid hid uhci_hcd ehci_hcd xenblk cdrom xennet fan thermal processor 
> > thermal_sys hwmon ide_pci_generic ide_core sata_sil24 ata_generic
> > [  210.184697] Pid: 15, comm: xenwatch Tainted: G         C 
> > 2.6.31.5-0.1-xen-hahn #9
> > [  210.184698] Call Trace:
> > [  210.184701]  [<ffffffff800117e9>] try_stack_unwind+0x189/0x1b0
> > [  210.184704]  [<ffffffff8000f2c6>] dump_trace+0xa6/0x1e0
> > [  210.184707]  [<ffffffff800112f4>] show_trace_log_lvl+0x64/0x90
> > [  210.184710]  [<ffffffff80011343>] show_trace+0x23/0x40
> > [  210.184712]  [<ffffffff80460e6e>] dump_stack+0x81/0x9e
> > [  210.184717]  [<ffffffff8004cf50>] warn_slowpath_common+0x80/0xd0
> > [  210.184720]  [<ffffffff8004d02b>] warn_slowpath_fmt+0x4b/0x70
> > [  210.184723]  [<ffffffff8018f48e>] sysfs_add_one+0xde/0x150
> > [  210.184726]  [<ffffffff8018fb3b>] sysfs_do_create_link+0x17b/0x200
> > [  210.184729]  [<ffffffff8018fc21>] sysfs_create_link+0x21/0x40
> > [  210.184732]  [<ffffffff802e0375>] device_add+0x1d5/0x620
> > [  210.184734]  [<ffffffff80185e76>] register_disk+0x66/0x1c0
> > [  210.184737]  [<ffffffff8022212b>] add_disk+0xcb/0x1b0
> > [  210.184742]  [<ffffffffa0098cb4>] backend_changed+0x354/0x3a0 [xenblk]
> > [  210.184746]  [<ffffffff802fb952>] otherend_changed+0xf2/0x1c0
> > [  210.184749]  [<ffffffff802f931c>] xenwatch_handle_callback+0x2c/0x80
> > [  210.184752]  [<ffffffff802f9538>] xenwatch_thread+0x1c8/0x200
> > [  210.184755]  [<ffffffff8006cf96>] kthread+0xb6/0xc0
> > [  210.184758]  [<ffffffff8000d25a>] child_rip+0xa/0x20
> > [  210.184760] ---[ end trace 2db54c629bf6d53c ]---
> > ...
> > 
> > The problem seems to be that in backend_changed() the device is seen as in 
> > use
> > and so blkfront_closing() -> xlvbd_del() -> del_gendisk()
> > isn't called to remove the links but later the xen device gets removed.
> > 
> > What to do here?
> > If a user of the -f flag "SHOULD know what he is doing" than the manual page
> > of the xm command has to be changed.
> > Ohterwise how can this be solved?
> > 
> > Thanks.
> > Dietmar.
> > 
> > This was testet on OpenSuSE-11.2 with xen-3.4 and linux-2.6.31.5,
> > don't know about xen-unstable!
> > 
> > 
> -- 
> Company details: http://ts.fujitsu.com/imprint.html
> 
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