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authorArne Jansen <sensille@gmx.net>2012-08-06 14:18:51 -0600
committerChris Mason <chris.mason@oracle.com>2012-08-28 16:53:32 -0400
commit1fa11e265fa2562fb713171b6a58e72bb7afd276 (patch)
tree9b8e80ef9ef0479d270d46b46c4ca7d0106d3ae0 /fs/btrfs/delayed-ref.c
parent6209526531e70c080f79318ab8f50e26846c40a8 (diff)
downloadop-kernel-dev-1fa11e265fa2562fb713171b6a58e72bb7afd276.zip
op-kernel-dev-1fa11e265fa2562fb713171b6a58e72bb7afd276.tar.gz
Btrfs: fix deadlock in wait_for_more_refs
Commit a168650c introduced a waiting mechanism to prevent busy waiting in btrfs_run_delayed_refs. This can deadlock with btrfs_run_ordered_operations, where a tree_mod_seq is held while waiting for the io to complete, while the end_io calls btrfs_run_delayed_refs. This whole mechanism is unnecessary. If not enough runnable refs are available to satisfy count, just return as count is more like a guideline than a strict requirement. In case we have to run all refs, commit transaction makes sure that no other threads are working in the transaction anymore, so we just assert here that no refs are blocked. Signed-off-by: Arne Jansen <sensille@gmx.net> Signed-off-by: Chris Mason <chris.mason@fusionio.com>
Diffstat (limited to 'fs/btrfs/delayed-ref.c')
-rw-r--r--fs/btrfs/delayed-ref.c8
1 files changed, 0 insertions, 8 deletions
diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
index da7419e..7561431 100644
--- a/fs/btrfs/delayed-ref.c
+++ b/fs/btrfs/delayed-ref.c
@@ -662,9 +662,6 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info,
add_delayed_tree_ref(fs_info, trans, &ref->node, bytenr,
num_bytes, parent, ref_root, level, action,
for_cow);
- if (!need_ref_seq(for_cow, ref_root) &&
- waitqueue_active(&fs_info->tree_mod_seq_wait))
- wake_up(&fs_info->tree_mod_seq_wait);
spin_unlock(&delayed_refs->lock);
if (need_ref_seq(for_cow, ref_root))
btrfs_qgroup_record_ref(trans, &ref->node, extent_op);
@@ -713,9 +710,6 @@ int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info,
add_delayed_data_ref(fs_info, trans, &ref->node, bytenr,
num_bytes, parent, ref_root, owner, offset,
action, for_cow);
- if (!need_ref_seq(for_cow, ref_root) &&
- waitqueue_active(&fs_info->tree_mod_seq_wait))
- wake_up(&fs_info->tree_mod_seq_wait);
spin_unlock(&delayed_refs->lock);
if (need_ref_seq(for_cow, ref_root))
btrfs_qgroup_record_ref(trans, &ref->node, extent_op);
@@ -744,8 +738,6 @@ int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info,
num_bytes, BTRFS_UPDATE_DELAYED_HEAD,
extent_op->is_data);
- if (waitqueue_active(&fs_info->tree_mod_seq_wait))
- wake_up(&fs_info->tree_mod_seq_wait);
spin_unlock(&delayed_refs->lock);
return 0;
}
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