While trying to reproduce an earlier problem on 2.6.39-rc2, we see a
possible deadlock from locks being taken in an inconsistent order:
======================================================[ INFO: possible circular
locking dependency detected ]
2.6.39-rc2-350cd #2
-------------------------------------------------------
btrfs/27867 is trying to acquire lock:
(&sb->s_type->i_mutex_key#13){+.+.+.}, at: [<ffffffff812df249>]
prealloc_file_extent_cluster+0x59/0x180
but task is already holding lock:
(&fs_info->cleaner_mutex){+.+...}, at: [<ffffffff812e0dd7>]
btrfs_relocate_block_group+0x197/0x2d0
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&fs_info->cleaner_mutex){+.+...}:
[<ffffffff81098857>] validate_chain+0x5a7/0x6c0
[<ffffffff81098e05>] __lock_acquire+0x495/0x920
[<ffffffff810992ea>] lock_acquire+0x5a/0x70
[<ffffffff817076de>] mutex_lock_nested+0x5e/0x390
[<ffffffff81293161>] btrfs_commit_super+0x21/0xe0
[<ffffffff81294468>] close_ctree+0x258/0x2d0
[<ffffffff8126f418>] btrfs_put_super+0x18/0x30
[<ffffffff811430bd>] generic_shutdown_super+0x6d/0xf0
[<ffffffff811431d1>] kill_anon_super+0x11/0x60
[<ffffffff811438f5>] deactivate_locked_super+0x45/0x60
[<ffffffff811441c5>] deactivate_super+0x45/0x60
[<ffffffff811611a9>] mntput_no_expire+0x99/0xf0
[<ffffffff81161da7>] sys_umount+0x67/0xd0
[<ffffffff81709ffb>] system_call_fastpath+0x16/0x1b
-> #1 (&type->s_umount_key#32){+++++.}:
[<ffffffff81098857>] validate_chain+0x5a7/0x6c0
[<ffffffff81098e05>] __lock_acquire+0x495/0x920
[<ffffffff810992ea>] lock_acquire+0x5a/0x70
[<ffffffff81707d72>] down_read+0x42/0x60
[<ffffffff81167805>] writeback_inodes_sb_nr_if_idle+0x35/0x60
[<ffffffff812824fe>] shrink_delalloc+0xee/0x180
[<ffffffff81282653>] reserve_metadata_bytes+0xc3/0x200
[<ffffffff81282bf4>] btrfs_delalloc_reserve_metadata+0xc4/0x150
[<ffffffff81282cbb>] btrfs_delalloc_reserve_space+0x3b/0x60
[<ffffffff812a5843>] __btrfs_buffered_write+0x153/0x320
[<ffffffff812a5da0>] btrfs_file_aio_write+0x230/0x310
[<ffffffff81182904>] aio_rw_vect_retry+0x74/0x1d0
[<ffffffff81184501>] aio_run_iocb+0x61/0x180
[<ffffffff81184ddf>] io_submit_one+0x15f/0x210
[<ffffffff81184fa8>] do_io_submit+0x118/0x1d0
[<ffffffff8118506b>] sys_io_submit+0xb/0x10
[<ffffffff81709ffb>] system_call_fastpath+0x16/0x1b
-> #0 (&sb->s_type->i_mutex_key#13){+.+.+.}:
[<ffffffff81097d15>] check_prev_add+0x705/0x720
[<ffffffff81098857>] validate_chain+0x5a7/0x6c0
[<ffffffff81098e05>] __lock_acquire+0x495/0x920
[<ffffffff810992ea>] lock_acquire+0x5a/0x70
[<ffffffff817076de>] mutex_lock_nested+0x5e/0x390
[<ffffffff812df249>] prealloc_file_extent_cluster+0x59/0x180
[<ffffffff812df531>] relocate_file_extent_cluster+0x91/0x380
[<ffffffff812df85f>] relocate_data_extent+0x3f/0xd0
[<ffffffff812e0963>] relocate_block_group+0x323/0x600
[<ffffffff812e0de8>] btrfs_relocate_block_group+0x1a8/0x2d0
[<ffffffff812c14ed>] btrfs_relocate_chunk+0x6d/0x3b0
[<ffffffff812c1a4a>] btrfs_shrink_device+0x21a/0x3d0
[<ffffffff812c1fdb>] btrfs_balance+0x10b/0x280
[<ffffffff812c9ec0>] btrfs_ioctl+0x450/0x590
[<ffffffff81152e8d>] do_vfs_ioctl+0x8d/0x330
[<ffffffff8115317a>] sys_ioctl+0x4a/0x80
[<ffffffff81709ffb>] system_call_fastpath+0x16/0x1b
other info that might help us debug this:
2 locks held by btrfs/27867:
#0: (&fs_info->volume_mutex){+.+...}, at: [<ffffffff812c1f5b>]
btrfs_balance+0x8b/0x280
#1: (&fs_info->cleaner_mutex){+.+...}, at: [<ffffffff812e0dd7>]
btrfs_relocate_block_group+0x197/0x2d0
stack backtrace:
Pid: 27867, comm: btrfs Tainted: G W 2.6.39-rc2-350cd #2
Call Trace:
[<ffffffff81096d7b>] print_circular_bug+0xeb/0xf0
[<ffffffff81097d15>] check_prev_add+0x705/0x720
[<ffffffff81098857>] validate_chain+0x5a7/0x6c0
[<ffffffff81098e05>] __lock_acquire+0x495/0x920
[<ffffffff812b5b2e>] ? unmap_extent_buffer+0xe/0x40
[<ffffffff81271d5c>] ? generic_bin_search+0x19c/0x210
[<ffffffff812df249>] ? prealloc_file_extent_cluster+0x59/0x180
[<ffffffff810992ea>] lock_acquire+0x5a/0x70
[<ffffffff812df249>] ? prealloc_file_extent_cluster+0x59/0x180
[<ffffffff810558fd>] ? add_preempt_count+0x7d/0xd0
[<ffffffff817076de>] mutex_lock_nested+0x5e/0x390
[<ffffffff812df249>] ? prealloc_file_extent_cluster+0x59/0x180
[<ffffffff81095f9c>] ? mark_held_locks+0x6c/0xa0
[<ffffffff8112eb7d>] ? __slab_alloc+0x18d/0x480
[<ffffffff8109629d>] ? trace_hardirqs_on_caller+0x14d/0x190
[<ffffffff812df249>] prealloc_file_extent_cluster+0x59/0x180
[<ffffffff812df516>] ? relocate_file_extent_cluster+0x76/0x380
[<ffffffff812df531>] relocate_file_extent_cluster+0x91/0x380
[<ffffffff8129737f>] ? __btrfs_end_transaction+0x15f/0x240
[<ffffffff812df85f>] relocate_data_extent+0x3f/0xd0
[<ffffffff812e0963>] relocate_block_group+0x323/0x600
[<ffffffff812e0de8>] btrfs_relocate_block_group+0x1a8/0x2d0
[<ffffffff812c14ed>] btrfs_relocate_chunk+0x6d/0x3b0
[<ffffffff8105584d>] ? sub_preempt_count+0x9d/0xd0
[<ffffffff812b5b2e>] ? unmap_extent_buffer+0xe/0x40
[<ffffffff812ab4a5>] ? btrfs_dev_extent_chunk_offset+0xe5/0xf0
[<ffffffff812c1a4a>] btrfs_shrink_device+0x21a/0x3d0
[<ffffffff812c1fdb>] btrfs_balance+0x10b/0x280
[<ffffffff81085b9e>] ? up_read+0x1e/0x40
[<ffffffff81031d5c>] ? do_page_fault+0x1cc/0x440
[<ffffffff812c9ec0>] btrfs_ioctl+0x450/0x590
[<ffffffff81152e8d>] do_vfs_ioctl+0x8d/0x330
[<ffffffff8114148f>] ? fget_light+0x2bf/0x3c0
[<ffffffff8109629d>] ? trace_hardirqs_on_caller+0x14d/0x190
[<ffffffff8115317a>] sys_ioctl+0x4a/0x80
[<ffffffff81709ffb>] system_call_fastpath+0x16/0x1b
--
Daniel J Blueman
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