Btrfs: add sequence numbers to delayed refs
Sequence numbers are needed to reconstruct the backrefs of a given extent to
a certain point in time. The total set of backrefs consist of the set of
backrefs recorded on disk plus the enqueued delayed refs for it that existed
at that moment.
This patch also adds a list that records all delayed refs which are
currently in the process of being added.
When walking all refs of an extent in btrfs_find_all_roots(), we freeze the
current state of delayed refs, honor anythinh up to this point and prevent
processing newer delayed refs to assert consistency.
Signed-off-by: Arne Jansen <sensille@gmx.net>
Signed-off-by: Jan Schmidt <list.btrfs@jan-o-sch.net>
diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
index babd37b..a405db0 100644
--- a/fs/btrfs/delayed-ref.c
+++ b/fs/btrfs/delayed-ref.c
@@ -101,6 +101,11 @@
return -1;
if (ref1->type > ref2->type)
return 1;
+ /* merging of sequenced refs is not allowed */
+ if (ref1->seq < ref2->seq)
+ return -1;
+ if (ref1->seq > ref2->seq)
+ return 1;
if (ref1->type == BTRFS_TREE_BLOCK_REF_KEY ||
ref1->type == BTRFS_SHARED_BLOCK_REF_KEY) {
return comp_tree_refs(btrfs_delayed_node_to_tree_ref(ref2),
@@ -209,6 +214,24 @@
return 0;
}
+int btrfs_check_delayed_seq(struct btrfs_delayed_ref_root *delayed_refs,
+ u64 seq)
+{
+ struct seq_list *elem;
+
+ assert_spin_locked(&delayed_refs->lock);
+ if (list_empty(&delayed_refs->seq_head))
+ return 0;
+
+ elem = list_first_entry(&delayed_refs->seq_head, struct seq_list, list);
+ if (seq >= elem->seq) {
+ pr_debug("holding back delayed_ref %llu, lowest is %llu (%p)\n",
+ seq, elem->seq, delayed_refs);
+ return 1;
+ }
+ return 0;
+}
+
int btrfs_find_ref_cluster(struct btrfs_trans_handle *trans,
struct list_head *cluster, u64 start)
{
@@ -438,6 +461,7 @@
ref->action = 0;
ref->is_head = 1;
ref->in_tree = 1;
+ ref->seq = 0;
head_ref = btrfs_delayed_node_to_head(ref);
head_ref->must_insert_reserved = must_insert_reserved;
@@ -479,6 +503,7 @@
struct btrfs_delayed_ref_node *existing;
struct btrfs_delayed_tree_ref *full_ref;
struct btrfs_delayed_ref_root *delayed_refs;
+ u64 seq = 0;
if (action == BTRFS_ADD_DELAYED_EXTENT)
action = BTRFS_ADD_DELAYED_REF;
@@ -494,6 +519,10 @@
ref->is_head = 0;
ref->in_tree = 1;
+ if (need_ref_seq(for_cow, ref_root))
+ seq = inc_delayed_seq(delayed_refs);
+ ref->seq = seq;
+
full_ref = btrfs_delayed_node_to_tree_ref(ref);
full_ref->parent = parent;
full_ref->root = ref_root;
@@ -534,6 +563,7 @@
struct btrfs_delayed_ref_node *existing;
struct btrfs_delayed_data_ref *full_ref;
struct btrfs_delayed_ref_root *delayed_refs;
+ u64 seq = 0;
if (action == BTRFS_ADD_DELAYED_EXTENT)
action = BTRFS_ADD_DELAYED_REF;
@@ -549,6 +579,10 @@
ref->is_head = 0;
ref->in_tree = 1;
+ if (need_ref_seq(for_cow, ref_root))
+ seq = inc_delayed_seq(delayed_refs);
+ ref->seq = seq;
+
full_ref = btrfs_delayed_node_to_data_ref(ref);
full_ref->parent = parent;
full_ref->root = ref_root;