On Wed, 5 Sep 2012, Josef Bacik wrote:
> Sage reported the following lockdep backtrace
>
> =====================================
> [ BUG: bad unlock balance detected! ]
> 3.6.0-rc2-ceph-00171-gc7ed62d #1 Not tainted
> -------------------------------------
> btrfs-cleaner/7607 is trying to release lock (sb_internal) at:
> [<ffffffffa00422ae>] btrfs_commit_transaction+0xa6e/0xb20 [btrfs]
> but there are no more locks to release!
>
> other info that might help us debug this:
> 1 lock held by btrfs-cleaner/7607:
> #0: (&fs_info->cleaner_mutex){+.+...}, at: [<ffffffffa003b405>] cleaner_kthread+0x95/0x120 [btrfs]
>
> stack backtrace:
> Pid: 7607, comm: btrfs-cleaner Not tainted 3.6.0-rc2-ceph-00171-gc7ed62d #1
> Call Trace:
> [<ffffffffa00422ae>] ? btrfs_commit_transaction+0xa6e/0xb20 [btrfs]
> [<ffffffff810afa9e>] print_unlock_inbalance_bug+0xfe/0x110
> [<ffffffff810b289e>] lock_release_non_nested+0x1ee/0x310
> [<ffffffff81172f9b>] ? kmem_cache_free+0x7b/0x160
> [<ffffffffa004106c>] ? put_transaction+0x8c/0x130 [btrfs]
> [<ffffffffa00422ae>] ? btrfs_commit_transaction+0xa6e/0xb20 [btrfs]
> [<ffffffff810b2a95>] lock_release+0xd5/0x220
> [<ffffffff81173071>] ? kmem_cache_free+0x151/0x160
> [<ffffffff8117d9ed>] __sb_end_write+0x7d/0x90
> [<ffffffffa00422ae>] btrfs_commit_transaction+0xa6e/0xb20 [btrfs]
> [<ffffffff81079850>] ? __init_waitqueue_head+0x60/0x60
> [<ffffffff81634c6b>] ? _raw_spin_unlock+0x2b/0x40
> [<ffffffffa0042758>] __btrfs_end_transaction+0x368/0x3c0 [btrfs]
> [<ffffffffa0042808>] btrfs_end_transaction_throttle+0x18/0x20 [btrfs]
> [<ffffffffa00318f0>] btrfs_drop_snapshot+0x410/0x600 [btrfs]
> [<ffffffff8132babd>] ? do_raw_spin_unlock+0x5d/0xb0
> [<ffffffffa00430ef>] btrfs_clean_old_snapshots+0xaf/0x150 [btrfs]
> [<ffffffffa003b405>] ? cleaner_kthread+0x95/0x120 [btrfs]
> [<ffffffffa003b419>] cleaner_kthread+0xa9/0x120 [btrfs]
> [<ffffffffa003b370>] ? btrfs_destroy_delayed_refs.isra.102+0x220/0x220 [btrfs]
> [<ffffffff810791ee>] kthread+0xae/0xc0
> [<ffffffff810b379d>] ? trace_hardirqs_on+0xd/0x10
> [<ffffffff8163e744>] kernel_thread_helper+0x4/0x10
> [<ffffffff81635430>] ? retint_restore_args+0x13/0x13
> [<ffffffff81079140>] ? flush_kthread_work+0x1a0/0x1a0
> [<ffffffff8163e740>] ? gs_change+0x13/0x13
>
> This is because the throttle stuff can commit the transaction, which expects to
> be the one stopping the intwrite stuff, but we've already done it in the
> __btrfs_end_transaction. Moving the sb_end_intewrite after this logic makes the
> lockdep go away. Thanks,
>
> Signed-off-by: Josef Bacik <jbacik@xxxxxxxxxxxx>
This appears to have done the trick (at least so far). I'm running it on
top of -rc5 and the 3 patches I posted on Aug 30th.
Tested-by: Sage Weil <sage@xxxxxxxxxxx>
Thanks!
sage
> ---
> fs/btrfs/transaction.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> index a86fc72..0163afa 100644
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -551,8 +551,6 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
> btrfs_trans_release_metadata(trans, root);
> trans->block_rsv = NULL;
>
> - sb_end_intwrite(root->fs_info->sb);
> -
> if (lock && !atomic_read(&root->fs_info->open_ioctl_trans) &&
> should_end_transaction(trans, root)) {
> trans->transaction->blocked = 1;
> @@ -573,6 +571,8 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans,
> }
> }
>
> + sb_end_intwrite(root->fs_info->sb);
> +
> WARN_ON(cur_trans != info->running_transaction);
> WARN_ON(atomic_read(&cur_trans->num_writers) < 1);
> atomic_dec(&cur_trans->num_writers);
> --
> 1.7.11.4
>
>
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