Revert "block: cover another queue enter recursion via BIO_QUEUE_ENTERED"

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 698cef173983b086977e633e46476e0f925ca01e.

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

2 files changed, 10 insertions, 11 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index 1ccec27d20c3..3c5f61ceeb67 100644
--- a/block/blk-core.c
+++ b/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
diff --git a/block/blk-merge.c b/block/blk-merge.c
index d79a22f111d1..71e9ac03f621 100644
--- a/block/blk-merge.c
+++ b/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);