journal: make skipping of exhausted journal files effective again

Commit 668c965af "journal: skipping of exhausted journal files is bad if
direction changed" fixed a correctness issue, but it also significantly
limited the cases where the optimization that skips exhausted journal
files could apply.
As a result, some journalctl queries are much slower in v219 than in v218.
(e.g. queries where a "--since" cutoff should have quickly eliminated
older journal files from consideration, but didn't.)

If already in the initial iteration find_location_with_matches() finds
no entry, the journal file's location is not updated. This is fine,
except that:
 - We must update at least f->last_direction. The optimization relies on
   it. Let's separate that from journal_file_save_location() and update
   it immediately after the direction checks.
 - The optimization was conditional on "f->current_offset > 0", but it
   would always be 0 in this scenario. This check is unnecessary for the
   optimization.

1 files changed, 1 insertions, 2 deletions

diff --git a/src/journal/journal-file.c b/src/journal/journal-file.c
index 9b4967fb32..9c9a5483be 100644
--- a/src/journal/journal-file.c
+++ b/src/journal/journal-file.c
@@ -2013,8 +2013,7 @@ void journal_file_reset_location(JournalFile *f) {
         f->current_xor_hash = 0;
 }
 
-void journal_file_save_location(JournalFile *f, direction_t direction, Object *o, uint64_t offset) {
-        f->last_direction = direction;
+void journal_file_save_location(JournalFile *f, Object *o, uint64_t offset) {
         f->location_type = LOCATION_SEEK;
         f->current_offset = offset;
         f->current_seqnum = le64toh(o->entry.seqnum);