From 81317fdeddcef259b6ecf7b5c0d04caa167c6b54 Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Sun, 24 Jul 2011 15:45:34 -0400 Subject: [PATCH] Btrfs: fix deadlock when throttling transactions Hit this nice little deadlock. What happens is this __btrfs_end_transaction with throttle set, --use_count so it equals 0 btrfs_commit_transaction btrfs_end_transaction --use_count so now its -1 <== BAD we just return and wait on the transaction This is bad because we just return after our use_count is -1 and don't let go of our num_writer count on the transaction, so the guy committing the transaction just sits there forever. Fix this by inc'ing our use_count if we're going to call commit_transaction so that if we call btrfs_end_transaction it's valid. Thanks, Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/transaction.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 654755b18951..eb55863bb4ae 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -497,10 +497,17 @@ static int __btrfs_end_transaction(struct btrfs_trans_handle *trans, } if (lock && cur_trans->blocked && !cur_trans->in_commit) { - if (throttle) + if (throttle) { + /* + * We may race with somebody else here so end up having + * to call end_transaction on ourselves again, so inc + * our use_count. + */ + trans->use_count++; return btrfs_commit_transaction(trans, root); - else + } else { wake_up_process(info->transaction_kthread); + } } WARN_ON(cur_trans != info->running_transaction); -- 2.30.2