md/raid5: initialize next_checkpoint field before use

No initial operation was done to this field when we
load/recovery the log, it got assignment only when IO
to raid disk was finished. So r5l_quiesce may use wrong
next_checkpoint to reclaim log space, that would make
reclaimable space calculation confused.
Signed-off-by: Zhengyuan Liu <liuzhengyuan@kylinos.cn>
Signed-off-by: Shaohua Li <shli@fb.com>

drivers/md/raid5-cache.c

@@ -1096,6 +1096,8 @@ static int r5l_recovery_log(struct r5l_log *log)
 		log->seq = ctx.seq + 11;
 		log->log_start = r5l_ring_add(log, ctx.pos, BLOCK_SECTORS);
 		r5l_write_super(log, ctx.pos);
+		log->last_checkpoint = ctx.pos;
+		log->next_checkpoint = ctx.pos;
 	} else {
 		log->log_start = ctx.pos;
 		log->seq = ctx.seq;
@@ -1168,6 +1170,7 @@ static int r5l_load_log(struct r5l_log *log)
 	if (log->max_free_space > RECLAIM_MAX_FREE_SPACE)
 		log->max_free_space = RECLAIM_MAX_FREE_SPACE;
 	log->last_checkpoint = cp;
+	log->next_checkpoint = cp;
 
 	__free_page(page);