Revert "block: cover another queue enter recursion via BIO_QUEUE_ENTE…

…RED"

We can't touch a bio after ->make_request_fn(), for all we know it could
already have been completed by the time this function returns.

This reverts commit 698cef1.

Reported-by: syzbot+4df6ca820108fd248943@syzkaller.appspotmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-core.c

@@ -1083,18 +1083,7 @@ blk_qc_t generic_make_request(struct bio *bio)
 			/* Create a fresh bio_list for all subordinate requests */
 			bio_list_on_stack[1] = bio_list_on_stack[0];
 			bio_list_init(&bio_list_on_stack[0]);
-
-			/*
-			 * Since we're recursing into make_request here, ensure
-			 * that we mark this bio as already having entered the queue.
-			 * If not, and the queue is going away, we can get stuck
-			 * forever on waiting for the queue reference to drop. But
-			 * that will never happen, as we're already holding a
-			 * reference to it.
-			 */
-			bio_set_flag(bio, BIO_QUEUE_ENTERED);
 			ret = q->make_request_fn(q, bio);
-			bio_clear_flag(bio, BIO_QUEUE_ENTERED);
 
 			/* sort new bios into those for a lower level
 			 * and those for the same level

block/blk-merge.c

@@ -272,6 +272,16 @@ void blk_queue_split(struct request_queue *q, struct bio **bio)
 		/* there isn't chance to merge the splitted bio */
 		split->bi_opf |= REQ_NOMERGE;
 
+		/*
+		 * Since we're recursing into make_request here, ensure
+		 * that we mark this bio as already having entered the queue.
+		 * If not, and the queue is going away, we can get stuck
+		 * forever on waiting for the queue reference to drop. But
+		 * that will never happen, as we're already holding a
+		 * reference to it.
+		 */
+		bio_set_flag(*bio, BIO_QUEUE_ENTERED);
+
 		bio_chain(split, *bio);
 		trace_block_split(q, split, (*bio)->bi_iter.bi_sector);
 		generic_make_request(*bio);