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Btrfs: pass lockdep rwsem metadata to async commit transaction

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The freeze rwsem is taken by sb_start_intwrite() and dropped during the
commit_ or end_transaction().  In the async case, that happens in a worker
thread.  Tell lockdep the calling thread is releasing ownership of the
rwsem and the async thread is picking it up.

XFS plays the same trick in fs/xfs/xfs_aops.c.

Signed-off-by: Sage Weil <sage@inktank.com>
This commit is contained in:
Sage Weil 2012-08-30 16:26:15 -06:00 committed by Chris Mason
parent 2aaa665581
commit 6fc4e35485
1 changed files with 16 additions and 0 deletions
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16
fs/btrfs/transaction.c
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@ -1229,6 +1229,14 @@ static void do_async_commit(struct work_struct *work)
struct btrfs_async_commit *ac =
container_of(work, struct btrfs_async_commit, work.work);
/*
* We've got freeze protection passed with the transaction.
* Tell lockdep about it.
*/
rwsem_acquire_read(
&ac->root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
0, 1, _THIS_IP_);
btrfs_commit_transaction(ac->newtrans, ac->root);
kfree(ac);
}
@ -1258,6 +1266,14 @@ int btrfs_commit_transaction_async(struct btrfs_trans_handle *trans,
atomic_inc(&cur_trans->use_count);
btrfs_end_transaction(trans, root);
/*
* Tell lockdep we've released the freeze rwsem, since the
* async commit thread will be the one to unlock it.
*/
rwsem_release(&root->fs_info->sb->s_writers.lock_map[SB_FREEZE_FS-1],
1, _THIS_IP_);
schedule_delayed_work(&ac->work, 0);
/* wait for transaction to start and unblock */