Re: 4.6.0-rc3+: WARNING: CPU: 16 PID: 17257 at fs/btrfs/inode.c:9261 btrfs_destroy_inode

[Chris Mason]

On Wed, Apr 27, 2016 at 02:25:50PM +0200, Christian Borntraeger wrote:
> Folks,
> 
> I can sometimes trigger the following bug
> 
> [  244.493534] ------------[ cut here ]------------
> [  244.493624] WARNING: CPU: 16 PID: 17257 at fs/btrfs/inode.c:9261 btrfs_destroy_inode+0x288/0x2b0 [btrfs]
> [  244.493626] Kernel panic - not syncing: panic_on_warn set ...
> 
> [  244.493629] CPU: 16 PID: 17257 Comm: dwz Not tainted 4.6.0-rc3+ #56
> [  244.493631]        000000fb3d8a3790 000000fb3d8a3820 0000000000000002 0000000000000000 
>        000000fb3d8a38c0 000000fb3d8a3838 000000fb3d8a3838 0000000000239364 
>        0000000000528488 000000000080e46e 00000000007f02c8 000000000000000b 
>        000000fb3d8a3880 000000fb3d8a3820 0000000000000000 0000000000000000 
>        040003ff8185a39e 0000000000113c1e 000000fb3d8a3820 000000fb3d8a3880 
> [  244.493641] Call Trace:
> [  244.493646] ([<0000000000113b0a>] show_trace+0x62/0x78)
> [  244.493647] ([<0000000000113bd2>] show_stack+0x72/0xf0)
> [  244.493650] ([<000000000040a8ca>] dump_stack+0x9a/0xd8)
> [  244.493652] ([<0000000000238b9e>] panic+0xf6/0x230)
> [  244.493656] ([<00000000001398e2>] __warn+0x11a/0x120)
> [  244.493657] ([<000000000040a010>] report_bug+0x90/0xf8)
> [  244.493658] ([<0000000000100a4a>] do_report_trap+0xea/0x108)
> [  244.493660] ([<0000000000100bcc>] illegal_op+0xd4/0x150)
> [  244.493662] ([<000000000067b760>] pgm_check_handler+0x15c/0x1a4)
> [  244.493678] ([<000003ff817d0ff0>] btrfs_destroy_inode+0x288/0x2b0 [btrfs])
> [  244.493680] ([<000000fb42aff1c8>] 0xfb42aff1c8)
> [  244.493683] ([<00000000002de5b6>] __dentry_kill+0x1c6/0x238)
> [  244.493684] ([<00000000002de7fc>] dput+0x1d4/0x298)
> [  244.493687] ([<00000000002c6d24>] __fput+0x144/0x1e8)
> [  244.493689] ([<000000000015a806>] task_work_run+0xc6/0xe8)
> [  244.493714] ([<000000000010923a>] do_notify_resume+0x5a/0x60)
> [  244.493715] ([<000000000067b45c>] system_call+0xdc/0x24c)
> 
> The WARN_ON is
>         WARN_ON(BTRFS_I(inode)->csum_bytes);
> 
> The file system is shared on 4 multipath target on scsi disks.
> In seem to be able to reproduce it on kvm/next (4.6.0-rc3+) but 4.5.0 seems fine.

Dave Jones is able to trigger this reliably with trinity.  I've been
trying to nail it down, it looks like I'm going to have to brute force
printk my way through it.

-chris