btrfs: add and use helper to get lowest sequence number for the tree mod log

There are two places outside the tree mod log module that extract the
lowest sequence number of the tree mod log. These places end up
duplicating code and open coding the logic and internal implementation
details of the tree mod log. So add a helper to the tree mod log module
and header that returns the lowest sequence number or 0 if there aren't
any tree mod log users at the moment.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 9 insertions, 24 deletions

diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
index d87472a68bf4..1c46d9b497bc 100644
--- a/fs/btrfs/delayed-ref.c
+++ b/fs/btrfs/delayed-ref.c
@@ -495,16 +495,7 @@ void btrfs_merge_delayed_refs(struct btrfs_trans_handle *trans,
 	if (head->is_data)
 		return;
 
-	read_lock(&fs_info->tree_mod_log_lock);
-	if (!list_empty(&fs_info->tree_mod_seq_list)) {
-		struct btrfs_seq_list *elem;
-
-		elem = list_first_entry(&fs_info->tree_mod_seq_list,
-					struct btrfs_seq_list, list);
-		seq = elem->seq;
-	}
-	read_unlock(&fs_info->tree_mod_log_lock);
-
+	seq = btrfs_tree_mod_log_lowest_seq(fs_info);
 again:
 	for (node = rb_first_cached(&head->ref_tree); node;
 	     node = rb_next(node)) {
@@ -518,23 +509,17 @@ again:
 
 int btrfs_check_delayed_seq(struct btrfs_fs_info *fs_info, u64 seq)
 {
-	struct btrfs_seq_list *elem;
 	int ret = 0;
-
-	read_lock(&fs_info->tree_mod_log_lock);
-	if (!list_empty(&fs_info->tree_mod_seq_list)) {
-		elem = list_first_entry(&fs_info->tree_mod_seq_list,
-					struct btrfs_seq_list, list);
-		if (seq >= elem->seq) {
-			btrfs_debug(fs_info,
-				"holding back delayed_ref %#x.%x, lowest is %#x.%x",
-				(u32)(seq >> 32), (u32)seq,
-				(u32)(elem->seq >> 32), (u32)elem->seq);
-			ret = 1;
-		}
+	u64 min_seq = btrfs_tree_mod_log_lowest_seq(fs_info);
+
+	if (min_seq != 0 && seq >= min_seq) {
+		btrfs_debug(fs_info,
+			    "holding back delayed_ref %#x.%x, lowest is %#x.%x",
+			    (u32)(seq >> 32), (u32)seq,
+			    (u32)(min_seq >> 32), (u32)min_seq);
+		ret = 1;
 	}
 
-	read_unlock(&fs_info->tree_mod_log_lock);
 	return ret;
 }