From 178260b2c14969f29ba39a78df74ed485abc6203 Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Wed, 20 Feb 2013 09:16:24 +0000 Subject: [PATCH] Btrfs: fix the deadlock between the transaction start/attach and commit Now btrfs_commit_transaction() does this ret = btrfs_run_ordered_operations(root, 0) which async flushes all inodes on the ordered operations list, it introduced a deadlock that transaction-start task, transaction-commit task and the flush workers waited for each other. (See the following URL to get the detail http://marc.info/?l=linux-btrfs&m=136070705732646&w=2) As we know, if ->in_commit is set, it means someone is committing the current transaction, we should not try to join it if we are not JOIN or JOIN_NOLOCK, wait is the best choice for it. In this way, we can avoid the above problem. In this way, there is another benefit: there is no new transaction handle to block the transaction which is on the way of commit, once we set ->in_commit. Signed-off-by: Miao Xie Signed-off-by: Josef Bacik --- fs/btrfs/transaction.c | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 425d5b5..5767ea1 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -50,6 +50,14 @@ static noinline void switch_commit_root(struct btrfs_root *root) root->commit_root = btrfs_root_node(root); } +static inline int can_join_transaction(struct btrfs_transaction *trans, + int type) +{ + return !(trans->in_commit && + type != TRANS_JOIN && + type != TRANS_JOIN_NOLOCK); +} + /* * either allocate a new transaction or hop into the existing one */ @@ -85,6 +93,10 @@ loop: spin_unlock(&fs_info->trans_lock); return cur_trans->aborted; } + if (!can_join_transaction(cur_trans, type)) { + spin_unlock(&fs_info->trans_lock); + return -EBUSY; + } atomic_inc(&cur_trans->use_count); atomic_inc(&cur_trans->num_writers); cur_trans->num_joined++; @@ -360,8 +372,11 @@ again: do { ret = join_transaction(root, type); - if (ret == -EBUSY) + if (ret == -EBUSY) { wait_current_trans(root); + if (unlikely(type == TRANS_ATTACH)) + ret = -ENOENT; + } } while (ret == -EBUSY); if (ret < 0) { -- 2.7.4