On Fri, Jul 06, 2012 at 12:42:50PM +0200, Jan Schmidt wrote:

I've no good idea at the moment how to go on. It might help to get a feeling if
it's shifting around at least a little bit or really constant in the timing of
occurrence. So can you please apply the next patch on top of the other two and
give it some more failure tries? The "checksum mismatch [1234]" line will be of
most interest. I'm also curious what the additional debug variables will say in
the extended version of the very first printk. You can leave out the stack
traces if you like, they won't matter much anyway.

Ok. Also turned on CONFIG_DEBUG_PAGEALLOC and CONFIG_SLUB_DEBUG_ON as
suggested by Chris Mason.

With those and the latest patch, there's an oops already at boot. I
don't have netconsole yet at that point, but here's the important
parts (sure I can capture it fully if you need).

By the way, something seems to be untabifying your patches. I don't
know if it's on my side or yours, but at least some other patches I
receive via linux-btrfs contain tabs. Doing a M-x tabify in emacs
mostly makes them apply cleanly for me.

	Sami


------------------------------------------------------------
btrfs: disk space caching is enabled
BUG: unable to handle kernel NULL pointer dereference at 0000000000000150
IP: [<ffffffffa0223568>] check_node+0x138/0x250 [btrfs]
PGD 0
Oops: 0000 [#1] SMP DEBUG_PAGEALLOC
CPU 6
Modules linked in: <omitted> [last unloaded: scsi_wait_scan]

Pid: 1176, comm: btrfs-endio-met Tainted: G        W     3.4.4+btrfsdebug2 #2 System Product Name/P8P67 EVO
RIP: 0010:[<ffffffffa0223568>]  [<ffffffffa0223568>] check_node+0x138/0x250 [btrfs
[...]
Process btrfs-endio-met (pid: 1176, [...])
Call trace:
 [...] btree_readpage_end_io_hook+0x1e5/0x2d0 [btrfs]
 [...] end_bio_extent_readpage+0xcb/0xa30 [btrfs]
 [...] ? end_workqueue_fn+0x31/0x50 [btrfs]
 [...] bio_endio+0x18/0x30
 [...] end_workqueue_fn+0x3c/0x50 [btrfs]
 [...] worker_loop+0x157/0x560 [btrfs]
 [...] ? btrfs_queue_worker+0x310/0x310 [btrfs]
 [...] kthead+0x8e/0xa0
 [...] kernel_thread_helper+0x4/0x10
 [...] ? flush_kthread_worker+0x70/0x70
 [...] ? gs_change+0x13/0x13
Code: [...]
RIP  [<ffffffffa0223568>] check_node+0x138/0x250 [btrfs]
 RSP <ffff8801f3843cb0>
------------------------------------------------------------