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| author | Josef Bacik <josef@redhat.com> | 2011-07-24 15:45:34 -0400 |
|---|---|---|
| committer | Chris Mason <chris.mason@oracle.com> | 2011-07-27 12:46:46 -0400 |
| commit | 81317fdeddcef259b6ecf7b5c0d04caa167c6b54 (patch) | |
| tree | aeca005b8b595539b554a6b8a92dc052ccad5601 | |
| parent | a65917156e345946dbde3d7effd28124c6d6a8c2 (diff) | |
| download | kernel-common-81317fdeddcef259b6ecf7b5c0d04caa167c6b54.tar.gz kernel-common-81317fdeddcef259b6ecf7b5c0d04caa167c6b54.tar.bz2 kernel-common-81317fdeddcef259b6ecf7b5c0d04caa167c6b54.zip | |
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
<somebody else actually manages to start the commit>
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 <josef@redhat.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
| -rw-r--r-- | fs/btrfs/transaction.c | 11 |
1 files 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); |