Btrfs: don't iterate mod seq list when putting a tree mod seq (42836cf4) · Commits · 戴 / test

Each new element added to the mod seq list is always appended to the list, and each one gets a sequence number coming from a counter which gets incremented everytime a new element is added to the list (or a new node is added to the tree mod log rbtree). Therefore the element with the lowest sequence number is always the first element in the list. So just remove the list iteration at btrfs_put_tree_mod_seq() that computes the minimum sequence number in the list and replace it with a check for the first element's sequence number. Reviewed-by:

Josef Bacik <josef@toxicpanda.com> Signed-off-by:

Filipe Manana <fdmanana@suse.com> Reviewed-by:

David Sterba <dsterba@suse.com> Signed-off-by:

David Sterba <dsterba@suse.com>

fs/btrfs/ctree.c

+13 −12

Original line number	Diff line number	Diff line
		@@ -341,7 +341,6 @@ void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
		struct rb_root *tm_root;
		struct rb_node *node;
		struct rb_node *next;
		struct seq_list *cur_elem;
		struct tree_mod_elem *tm;
		u64 min_seq = (u64)-1;
		u64 seq_putting = elem->seq;
		@@ -353,18 +352,20 @@ void btrfs_put_tree_mod_seq(struct btrfs_fs_info *fs_info,
		list_del(&elem->list);
		elem->seq = 0;

		list_for_each_entry(cur_elem, &fs_info->tree_mod_seq_list, list) {
		if (cur_elem->seq < min_seq) {
		if (seq_putting > cur_elem->seq) {
		if (!list_empty(&fs_info->tree_mod_seq_list)) {
		struct seq_list *first;

		first = list_first_entry(&fs_info->tree_mod_seq_list,
		struct seq_list, list);
		if (seq_putting > first->seq) {
		/*
		* blocker with lower sequence number exists, we
		* cannot remove anything from the log
		* Blocker with lower sequence number exists, we
		* cannot remove anything from the log.
		*/
		write_unlock(&fs_info->tree_mod_log_lock);
		return;
		}
		min_seq = cur_elem->seq;
		}
		min_seq = first->seq;
		}

		/*

Admin message