f2fs: clean up the do_submit_bio flow

This patch introduces PAGE_TYPE_OF_BIO() and cleans up do_submit_bio() with it.
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

fs/f2fs/f2fs.h

@@ -350,6 +350,7 @@ enum count_type {
  *			with waiting the bio's completion
  * ...			Only can be used with META.
  */
+#define PAGE_TYPE_OF_BIO(type)	((type) > META ? META : (type))
 enum page_type {
 	DATA,
 	NODE,

fs/f2fs/segment.c

@@ -835,32 +835,35 @@ static void do_submit_bio(struct f2fs_sb_info *sbi,
 				enum page_type type, bool sync)
 {
 	int rw = sync ? WRITE_SYNC : WRITE;
-	enum page_type btype = type > META ? META : type;
+	enum page_type btype = PAGE_TYPE_OF_BIO(type);
+	struct bio *bio = sbi->bio[btype];
+	struct bio_private *p;
+
+	if (!bio)
+		return;
+
+	sbi->bio[btype] = NULL;
 
 	if (type >= META_FLUSH)
 		rw = WRITE_FLUSH_FUA;
-
 	if (btype == META)
 		rw |= REQ_META;
 
-	if (sbi->bio[btype]) {
-		struct bio_private *p = sbi->bio[btype]->bi_private;
+	p = bio->bi_private;
 	p->sbi = sbi;
-		sbi->bio[btype]->bi_end_io = f2fs_end_io_write;
+	bio->bi_end_io = f2fs_end_io_write;
 
-		trace_f2fs_do_submit_bio(sbi->sb, btype, sync, sbi->bio[btype]);
+	trace_f2fs_do_submit_bio(sbi->sb, btype, sync, bio);
 
 	if (type == META_FLUSH) {
 		DECLARE_COMPLETION_ONSTACK(wait);
 		p->is_sync = true;
 		p->wait = &wait;
-			submit_bio(rw, sbi->bio[btype]);
+		submit_bio(rw, bio);
 		wait_for_completion(&wait);
 	} else {
 		p->is_sync = false;
-			submit_bio(rw, sbi->bio[btype]);
-		}
-		sbi->bio[btype] = NULL;
+		submit_bio(rw, bio);
 	}
 }