dm integrity: improve discard in journal mode

When we discard something that is present in the journal, we flush the
journal first, so that discarded blocks are not overwritten by the journal
content.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-integrity.c

@@ -1943,6 +1943,7 @@ static void dm_integrity_map_continue(struct dm_integrity_io *dio, bool from_map
 	unsigned journal_section, journal_entry;
 	unsigned journal_read_pos;
 	struct completion read_comp;
+	bool discard_retried = false;
 	bool need_sync_io = ic->internal_hash && dio->op == REQ_OP_READ;
 	if (unlikely(dio->op == REQ_OP_DISCARD) && ic->mode != 'D')
 		need_sync_io = true;
@@ -2059,6 +2060,21 @@ static void dm_integrity_map_continue(struct dm_integrity_io *dio, bool from_map
 			}
 		}
 	}
+	if (ic->mode == 'J' && likely(dio->op == REQ_OP_DISCARD) && !discard_retried) {
+		sector_t next_sector;
+		unsigned new_pos = find_journal_node(ic, dio->range.logical_sector, &next_sector);
+		if (unlikely(new_pos != NOT_FOUND) ||
+		    unlikely(next_sector < dio->range.logical_sector - dio->range.n_sectors)) {
+			remove_range_unlocked(ic, &dio->range);
+			spin_unlock_irq(&ic->endio_wait.lock);
+			queue_work(ic->commit_wq, &ic->commit_work);
+			flush_workqueue(ic->commit_wq);
+			queue_work(ic->writer_wq, &ic->writer_work);
+			flush_workqueue(ic->writer_wq);
+			discard_retried = true;
+			goto lock_retry;
+		}
+	}
 	spin_unlock_irq(&ic->endio_wait.lock);
 
 	if (unlikely(journal_read_pos != NOT_FOUND)) {