block: cleanup bio_endio

Replace the while loop that unecessarily checks for a NULL bio in the fast
path with a simple goto loop.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@fb.com>

block/bio.c

@@ -1745,26 +1745,25 @@ static inline bool bio_remaining_done(struct bio *bio)
  **/
 void bio_endio(struct bio *bio)
 {
-	while (bio) {
-		if (unlikely(!bio_remaining_done(bio)))
-			break;
+again:
+	if (unlikely(!bio_remaining_done(bio)))
+		return;
 
-		/*
-		 * Need to have a real endio function for chained bios,
-		 * otherwise various corner cases will break (like stacking
-		 * block devices that save/restore bi_end_io) - however, we want
-		 * to avoid unbounded recursion and blowing the stack. Tail call
-		 * optimization would handle this, but compiling with frame
-		 * pointers also disables gcc's sibling call optimization.
-		 */
-		if (bio->bi_end_io == bio_chain_endio) {
-			bio = __bio_chain_endio(bio);
-		} else {
-			if (bio->bi_end_io)
-				bio->bi_end_io(bio);
-			bio = NULL;
-		}
+	/*
+	 * Need to have a real endio function for chained bios, otherwise
+	 * various corner cases will break (like stacking block devices that
+	 * save/restore bi_end_io) - however, we want to avoid unbounded
+	 * recursion and blowing the stack. Tail call optimization would
+	 * handle this, but compiling with frame pointers also disables
+	 * gcc's sibling call optimization.
+	 */
+	if (bio->bi_end_io == bio_chain_endio) {
+		bio = __bio_chain_endio(bio);
+		goto again;
 	}
+
+	if (bio->bi_end_io)
+		bio->bi_end_io(bio);
 }
 EXPORT_SYMBOL(bio_endio);