Re: Btrfs resize seems to deadlock

[Filipe Manana <fdmanana@gmail.com>]

On Sat, Oct 20, 2018 at 9:27 PM Liu Bo <obuil.liubo@gmail.com> wrote:
>
> On Fri, Oct 19, 2018 at 7:09 PM Andrew Nelson <andrew.s.nelson@gmail.com> wrote:
> >
> > I am having an issue with btrfs resize in Fedora 28. I am attempting
> > to enlarge my Btrfs partition. Every time I run "btrfs filesystem
> > resize max $MOUNT", the command runs for a few minutes and then hangs
> > forcing the system to be reset. I am not sure what the state of the
> > filesystem really is at this point. Btrfs usage does report the
> > correct size for after resizing. Details below:
> >
>
> Thanks for the report, the stack is helpful, but this needs a few
> deeper debugging, may I ask you to post "btrfs inspect-internal
> dump-tree -t 1 /dev/your_btrfs_disk"?

I believe it's actually easy to understand from the trace alone and
it's kind of a bad luck scenario.
I made this fix a few hours ago:

https://git.kernel.org/pub/scm/linux/kernel/git/fdmanana/linux.git/commit/?h=fix_find_free_extent_deadlock

But haven't done full testing yet and might have missed something.
Bo, can you take a look and let me know what you think?

Thanks.

>
> So I'd like to know what's the height of your tree "1" which refers to
> root tree in btrfs.
>
> thanks,
> liubo
>
> > $ sudo btrfs filesystem usage $MOUNT
> > Overall:
> >     Device size:                  90.96TiB
> >     Device allocated:             72.62TiB
> >     Device unallocated:           18.33TiB
> >     Device missing:                  0.00B
> >     Used:                         72.62TiB
> >     Free (estimated):             18.34TiB      (min: 9.17TiB)
> >     Data ratio:                       1.00
> >     Metadata ratio:                   2.00
> >     Global reserve:              512.00MiB      (used: 24.11MiB)
> >
> > Data,single: Size:72.46TiB, Used:72.45TiB
> >     $MOUNT        72.46TiB
> >
> > Metadata,DUP: Size:86.00GiB, Used:84.96GiB
> >     $MOUNT       172.00GiB
> >
> > System,DUP: Size:40.00MiB, Used:7.53MiB
> >    $MOUNT        80.00MiB
> >
> > Unallocated:
> >     $MOUNT        18.33TiB
> >
> > $ uname -a
> > Linux localhost.localdomain 4.18.14-200.fc28.x86_64 #1 SMP Mon Oct 15
> > 13:16:27 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
> >
> > btrfs-transacti D    0  2501      2 0x80000000
> > Call Trace:
> >  ? __schedule+0x253/0x860
> >  schedule+0x28/0x80
> >  btrfs_commit_transaction+0x7aa/0x8b0 [btrfs]
> >  ? kmem_cache_alloc+0x166/0x1d0
> >  ? join_transaction+0x22/0x3e0 [btrfs]
> >  ? finish_wait+0x80/0x80
> >  transaction_kthread+0x155/0x170 [btrfs]
> >  ? btrfs_cleanup_transaction+0x550/0x550 [btrfs]
> >  kthread+0x112/0x130
> >  ? kthread_create_worker_on_cpu+0x70/0x70
> >  ret_from_fork+0x35/0x40
> > btrfs           D    0  2504   2502 0x00000002
> > Call Trace:
> >  ? __schedule+0x253/0x860
> >  schedule+0x28/0x80
> >  btrfs_tree_read_lock+0x8e/0x120 [btrfs]
> >  ? finish_wait+0x80/0x80
> >  btrfs_read_lock_root_node+0x2f/0x40 [btrfs]
> >  btrfs_search_slot+0xf6/0x9f0 [btrfs]
> >  ? evict_refill_and_join+0xd0/0xd0 [btrfs]
> >  ? inode_insert5+0x119/0x190
> >  btrfs_lookup_inode+0x3a/0xc0 [btrfs]
> >  ? kmem_cache_alloc+0x166/0x1d0
> >  btrfs_iget+0x113/0x690 [btrfs]
> >  __lookup_free_space_inode+0xd8/0x150 [btrfs]
> >  lookup_free_space_inode+0x5b/0xb0 [btrfs]
> >  load_free_space_cache+0x7c/0x170 [btrfs]
> >  ? cache_block_group+0x72/0x3b0 [btrfs]
> >  cache_block_group+0x1b3/0x3b0 [btrfs]
> >  ? finish_wait+0x80/0x80
> >  find_free_extent+0x799/0x1010 [btrfs]
> >  btrfs_reserve_extent+0x9b/0x180 [btrfs]
> >  btrfs_alloc_tree_block+0x1b3/0x4f0 [btrfs]
> >  __btrfs_cow_block+0x11d/0x500 [btrfs]
> >  btrfs_cow_block+0xdc/0x180 [btrfs]
> >  btrfs_search_slot+0x3bd/0x9f0 [btrfs]
> >  btrfs_lookup_inode+0x3a/0xc0 [btrfs]
> >  ? kmem_cache_alloc+0x166/0x1d0
> >  btrfs_update_inode_item+0x46/0x100 [btrfs]
> >  cache_save_setup+0xe4/0x3a0 [btrfs]
> >  btrfs_start_dirty_block_groups+0x1be/0x480 [btrfs]
> >  btrfs_commit_transaction+0xcb/0x8b0 [btrfs]
> >  ? btrfs_release_path+0x13/0x80 [btrfs]
> >  ? btrfs_update_device+0x8d/0x1c0 [btrfs]
> >  btrfs_ioctl_resize.cold.46+0xf4/0xf9 [btrfs]
> >  btrfs_ioctl+0xa25/0x2cf0 [btrfs]
> >  ? tty_write+0x1fc/0x330
> >  ? do_vfs_ioctl+0xa4/0x620
> >  do_vfs_ioctl+0xa4/0x620
> >  ksys_ioctl+0x60/0x90
> >  ? ksys_write+0x4f/0xb0
> >  __x64_sys_ioctl+0x16/0x20
> >  do_syscall_64+0x5b/0x160
> >  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> > RIP: 0033:0x7fcdc0d78c57
> > Code: Bad RIP value.
> > RSP: 002b:00007ffdd1ee6cf8 EFLAGS: 00000246 ORIG_RAX: 0000000000000010
> > RAX: ffffffffffffffda RBX: 00007ffdd1ee888a RCX: 00007fcdc0d78c57
> > RDX: 00007ffdd1ee6da0 RSI: 0000000050009403 RDI: 0000000000000003
> > RBP: 00007ffdd1ee6da0 R08: 0000000000000000 R09: 00007ffdd1ee67e0
> > R10: 0000000000000000 R11: 0000000000000246 R12: 00007ffdd1ee888e
> > R13: 0000000000000003 R14: 0000000000000000 R15: 0000000000000000
> > kworker/u48:1   D    0  2505      2 0x80000000
> > Workqueue: btrfs-freespace-write btrfs_freespace_write_helper [btrfs]
> > Call Trace:
> >  ? __schedule+0x253/0x860
> >  schedule+0x28/0x80
> >  btrfs_tree_lock+0x130/0x210 [btrfs]
> >  ? finish_wait+0x80/0x80
> >  btrfs_search_slot+0x775/0x9f0 [btrfs]
> >  btrfs_mark_extent_written+0xb0/0xb20 [btrfs]
> >  ? join_transaction+0x22/0x3e0 [btrfs]
> >  btrfs_finish_ordered_io+0x2e0/0x7e0 [btrfs]
> >  ? syscall_return_via_sysret+0x13/0x83
> >  ? __switch_to_asm+0x34/0x70
> >  normal_work_helper+0xd3/0x2f0 [btrfs]
> >  process_one_work+0x1a1/0x350
> >  worker_thread+0x30/0x380
> >  ? pwq_unbound_release_workfn+0xd0/0xd0
> >  kthread+0x112/0x130
> >  ? kthread_create_worker_on_cpu+0x70/0x70
> >  ret_from_fork+0x35/0x40



-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”