[systemd-devel] BTRFS bug with parallel mounts?

[Gustavo Sverzut Barbieri]

On Wed, Nov 10, 2010 at 9:33 AM, Gustavo Sverzut Barbieri
<barbieri at profusion.mobi> wrote:
> On Wednesday, November 10, 2010, Gustavo Sverzut Barbieri
> <barbieri at profusion.mobi> wrote:
>> Hi all,
>>
>> First, I'm not typing much or send the kernel oops since I'm at a
>> phone without access to my lap ATM
>>
>> So yesterday I got my new laptop with quad core i7 and SSD. gentoo's
>> openrc works nice, but systemd triggers a nasty kernel oops with btrfs
>>
>> The oops is while mounting my /home it get a null pointer at
>> btrfs_test_super. After the backtrace (which I had will send later) I
>> get a "btrfs detected SSD devices, enabling SSD mode"
>>
>> So really looks like a race. Ideas?
>>
>> That also bring us to the safety question: should we provide a way to
>> force /etc/fstab entries to be mounted serially and forcefully? This
>> would be helpful for buggy FS while you can't get the fix (or to
>> install and apply the fix -- as I'm using openrc but in future I'll
>> not)
>>
>
> Worths mentioning that all my fs are btrfs: /, /home and /var

----8<--------------------

Part of the log (sorry, I had no way but to type it all):

BUG: unable to handle kernel NULL pointer dereference at 0000000000000128
IP: [<ffffffff811329fb>] btrfs_test_super+0xb/0x30
PGD: 26b5b1067 PUD 26a465067 PMD 0
last sysfs file: /sys/devices/virtual/bdi/btrfs-2/uevent
CPU 0
Modules linked in: nvidia(P) lib80211_crypt_tkip wl(P)
Pid: 434, comm: mount Tainted: P     2.6.36 #3 Mac-F22586C8/MacBookPro6,2
RIP: ... btrfs_test_super+0xb/0x30

---->8--------------------

some part omitted, but the relevant part:

----8<--------------------

Call Trace:
sget+0x6c/0x400
? set_anon_super+0x0/0x100
btrfs_get_sb+0x12d/0x410
vfs_kern_mount+0x83/0x1f0
do_kern_mount+0x4d/0x130
do_mount+0x266/0x860
? memdup_user+0x46/0x90
? strndup_user+0x53/0x70
sys_mount+0x93/0xe0
system_call_fastpath+0x16/0x1b

Code: 55 49 c7 c0 35 0d 79 81 48 89 e5 31 c9 48 c7 c2 00 1a 13 81 e8
d7 5f fb ff c9 c3 90 90 90 90 90 55 48 8b 87 78 02 00 00 48 89 e5 <48>
8b 80 28 01 00 00 48 39 b0 58 22 00 00 c9 0f 94 c0 0f b6 c0

home.mount mount process exited, code=killed status=9
Btrfs detected SSD devices, enabling SSD mode

---->8--------------------

Ideas?

-- 
Gustavo Sverzut Barbieri
http://profusion.mobi embedded systems
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