[Unionfs] Oops when inserting rw branch with unionfs on root
filesystem
Dave Miller
justdave at mozilla.com
Tue Mar 4 15:06:39 EST 2008
What version of unionfs are you using with that kernel? There's been a
whole mess of OOPS-causing race conditions cleaned up in the last couple
revs. Anything earlier than 2.2.4 I wouldn't call stable on systems
that do frequent remounts or branch reordering. 2.2.4 seems really
stable in that regard though, to me (I've been purposely trying to break
it for the last 2 1/2 weeks and haven't been able to, because we had
frequent problems with the older versions).
Klaus Fuerstberger wrote on 3/4/08 5:34 AM:
> Hi,
>
> I have a unionfs root filesystem. Sometimes I want to sync the unionfs
> changes in ram back to the CF card. This is done with rsync and ist no
> problem. But now I want to free the used ram of the unionfs. Mostly it
> works, if I simlpe delete the /ram/changes/*, but sometimes the system
> freezes.
> Now I thought it would be the cleanest to insert another leftmost
> read-write branch at highest priority and delete the old read-write
> branch with the used memory. This resulted in the crash below.
> Is there any clean method, beside a reboot, to free the used memory of
> the union after the rsync?
>
> ### This ist what I tried and what caused the Oops:
> mount -t unionfs -o remount,incgen none /
> mount -t ext3 -o remount,rw /dev/hda1 /ram/rootfs
> # Synchronize the changes to the CF-Card
> rsync -av --exclude=/tmp/ --exclude=/ram/ --exclude=/proc/
> --exclude=/sys/ --exclude=/dev/ --delete / /ram/rootfs/
> # Try to free the used memory in /rootfs/changes in inserting a leftmost
> RW branch and deleting the old RW branch
> mkdir /ram/changes2
> mount -t unionfs -o remount,add=/ram/changes2=rw none /
> ..............Oops...............
>
> # The initramfs script
> ### /usr/share/initramfs-tools/scripts/union
> mountroot()
> {
> RAM=/ram
> ROOTFS=$RAM/rootfs
> CHANGES=$RAM/changes
>
> mkdir $RAM
> mount -t tmpfs -o size=90% tmpfs $RAM
> mkdir $ROOTFS
> mkdir $CHANGES
> mount -r -t ext3 /dev/hda1 $ROOTFS
> mount -t unionfs -o dirs=$CHANGES=rw:$ROOTFS=ro unionfs ${rootmnt}
>
> # Das overlay zugaenglich machen
> mkdir ${rootmnt}$RAM 2>/dev/null
> mount -o move $RAM ${rootmnt}$RAM
> }
> ###############################
>
> ### /etc/fstab
> proc /proc proc defaults 0 0
> none / unionfs dirs=/ram/changes=rw:/=ro 0 0
> ###############################
>
> ### Oops
> BUG: unable to handle kernel NULL pointer dereference at virtual address
> 00000060
> printing eip: d0827646 *pde = 00000000
> Oops: 0000 [#1]
> Modules linked in: ipv6 dm_snapshot dm_mirror dm_mod leds_alix led_class
> xt_mac xt_limit ips
>
> Pid: 1816, comm: mount Not tainted (2.6.24.2-alix #3)
> EIP: 0060:[<d0827646>] EFLAGS: 00010206 CPU: 0
> EIP is at unionfs_remount_fs+0x4be/0x748 [unionfs]
> EAX: 00000060 EBX: 00000003 ECX: 00000002 EDX: cf6da6c0
> ESI: ce556400 EDI: cf7bf004 EBP: ce6ecce0 ESP: cec55db0
> DS: 007b ES: 007b FS: 0000 GS: 0033 SS: 0068
> Process mount (pid: 1816, ti=cec54000 task=ce5ed030 task.ti=cec54000)
> Stack: ce74a6e0 cec55df4 00000002 cec55df4 cec55e10 ce556400 cf4ab620
> ce6ecce0
> 00000002 cf4ab620 cf4ab620 ce74a6e0 ce74a6e0 00000000 ffffffff
> 7fffffff
> 00000000 00000002 00000000 d0833de8 ce556400 cf7bf000 00000000
> c0153337
> Call Trace:
> [<c0153337>] do_remount_sb+0xc2/0xe9
> [<c0163539>] do_mount+0x193/0x5e5
> [<c0129d7c>] update_wall_time+0x540/0x6ae
> [<c0114ee0>] update_curr+0x52/0xc8
> [<c01283ef>] hrtimer_run_queues+0x12/0x133
> [<c011e8b0>] run_timer_softirq+0x12/0x141
> [<c012bd73>] tick_handle_periodic+0xf/0x54
> [<c011c038>] tasklet_action+0x32/0x52
> [<c011bfa0>] __do_softirq+0x35/0x75
> [<c0105b9c>] do_IRQ+0x58/0x6b
> [<c013dcfd>] __alloc_pages+0x5d/0x2d4
> [<c0104553>] common_interrupt+0x23/0x28
> [<c01625ca>] copy_mount_options+0xa3/0x10d
> [<c01639fd>] sys_mount+0x72/0xa9
> [<c0103baa>] syscall_call+0x7/0xb
> =======================
> Code: d2 eb 12 8b 4c 24 24 89 d0 c1 e0 04 8b 04 08 83 c0 60 ff 00 42 39
> da 7c ea 31 c9 eb 1
> EIP: [<d0827646>] unionfs_remount_fs+0x4be/0x748 [unionfs] SS:ESP
> 0068:cec55db0
> ---[ end trace a38d4d4b3dc9a968 ]---
> WARNING: at kernel/exit.c:917 do_exit()
> Pid: 1816, comm: mount Tainted: G D 2.6.24.2-alix #3
> [<c011ab0c>] do_exit+0x48/0x5ed
> [<c0118ee9>] printk+0x1b/0x1f
> [<c0104d9b>] die+0x1b1/0x1b9
> [<c011408e>] do_page_fault+0x43c/0x51a
> [<c0113c52>] do_page_fault+0x0/0x51a
> [<c02a0f9a>] error_code+0x6a/0x70
> [<d0827646>] unionfs_remount_fs+0x4be/0x748 [unionfs]
> [<c0153337>] do_remount_sb+0xc2/0xe9
> [<c0163539>] do_mount+0x193/0x5e5
> [<c0129d7c>] update_wall_time+0x540/0x6ae
> [<c0114ee0>] update_curr+0x52/0xc8
> [<c01283ef>] hrtimer_run_queues+0x12/0x133
> [<c011e8b0>] run_timer_softirq+0x12/0x141
> [<c012bd73>] tick_handle_periodic+0xf/0x54
> [<c011c038>] tasklet_action+0x32/0x52
> [<c011bfa0>] __do_softirq+0x35/0x75
> [<c0105b9c>] do_IRQ+0x58/0x6b
> [<c013dcfd>] __alloc_pages+0x5d/0x2d4
> [<c0104553>] common_interrupt+0x23/0x28
> [<c01625ca>] copy_mount_options+0xa3/0x10d
> [<c01639fd>] sys_mount+0x72/0xa9
> [<c0103baa>] syscall_call+0x7/0xb
> ###############################
>
> Bye,
> Klaus
> _______________________________________________
> unionfs mailing list: http://unionfs.filesystems.org/
> unionfs at mail.fsl.cs.sunysb.edu
> http://www.fsl.cs.sunysb.edu/mailman/listinfo/unionfs
--
Dave Miller http://www.justdave.net/
System Administrator, Mozilla Corporation http://www.mozilla.com/
Project Leader, Bugzilla Bug Tracking System http://www.bugzilla.org/
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