Update seq when merging deltas from partial log merge.

Two different clients can write delta's for totl indexes at the same
time, recording their changes. When merged, a reader should apply both
in order, and only once. To do so, the seq determines whether the delta
has been applied already.

The code fails to update the seq while walking the trees for deltas to
apply. Subsequently, when processing subsequent trees, it could
re-process deltas already applied. In case of a large negative delta
(e.g. removal of large amounts of files), the totl value could become
negative, resulting in quota lockout.

The fix is simple: advance the seq when reading partial delta merges
to avoid double counting.

Signed-off-by: Auke Kok <auke.kok@versity.com>

kmod/src/btree.c

@@ -2183,6 +2183,8 @@ static int merge_read_item(struct super_block *sb, struct scoutfs_key *key, u64
 		if (ret > 0) {
 			if (ret == SCOUTFS_DELTA_COMBINED) {
 				scoutfs_inc_counter(sb, btree_merge_delta_combined);
+				if (seq > found->seq)
+					found->seq = seq;
 			} else if (ret == SCOUTFS_DELTA_COMBINED_NULL) {
 				scoutfs_inc_counter(sb, btree_merge_delta_null);
 				free_mitem(rng, found);