From 59bc5c758ece00fb0b2a170dd8fbbf31f1856c8a Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Fri, 24 Apr 2009 14:39:25 -0400 Subject: [PATCH] Btrfs: fix deadlocks and stalls on dead root removal After a transaction commit, the old root of the subvol btrees are sent through snapshot removal. This is what actually frees up any blocks replaced by COW, and anything the old blocks pointed to. Snapshot deletion will pause when a transaction commit has started, which helps to avoid a huge amount of delayed reference count updates piling up as the transaction is trying to close. But, this pause happens after the snapshot deletion process has asked other procs on the system to throttle back a bit so that it can make progress. We don't want to throttle everyone while we're waiting for the transaction commit, it leads to deadlocks in the user transaction ioctls used by Ceph and makes things slower in general. This patch changes things to avoid the throttling while we sleep. Signed-off-by: Chris Mason --- fs/btrfs/transaction.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 2869b33..01b1436 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -687,7 +687,13 @@ static noinline int wait_transaction_pre_flush(struct btrfs_fs_info *info) prepare_to_wait(&info->transaction_wait, &wait, TASK_UNINTERRUPTIBLE); mutex_unlock(&info->trans_mutex); + + atomic_dec(&info->throttles); + wake_up(&info->transaction_throttle); + schedule(); + + atomic_inc(&info->throttles); mutex_lock(&info->trans_mutex); finish_wait(&info->transaction_wait, &wait); } -- 2.7.4